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Journal Cover physica status solidi (c)
  [SJR: 0.392]   [H-I: 39]   [1 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1862-6351 - ISSN (Online) 1610-1642
   Published by John Wiley and Sons Homepage  [1580 journals]
  • Optical properties and electronic structures of CuSbS2, CuSbSe2, and
           CuSb(S1−xSex)2 solid solution
    • Authors: Takahiro Wada; Tsuyoshi Maeda
      Abstract: To clarify electronic structures of CuSbS2, CuSbSe2, and CuSb(S1−xSex)2 solid solutions, these powder samples were synthesized by a mechanochemical process and post-heating. CuSbS2 and CuSbSe2 have indirect and direct band gaps, of which the direct band gaps are a little wider than the indirect band gaps. The ionization energies of CuSb(S1−xSex)2 (0.0 ≤ x ≤ 1.0) powders were measured by photoemission yield spectroscopy (PYS). Energy levels of the valence band maximum (VBM) of the CuSb(S1−xSex)2 samples were estimated from the ionization energies. The electron affinity, energy level of conduction band minimum (CBM), of the CuSb(S1−xSex)2 samples could also be determined by adding the value of the optical band gap to the energy level of the VBM. The energy level of the VBM of the CuSb(S1−xSex)2 system monotonically increases from −5.45 eV for CuSbS2 (x = 0.0) to −5.15 eV for CuSbSe2 (x = 1.0). On the other hand, the energy levels of the indirect CBM of the CuSb(S1−xSex)2 system slightly decrease from −4.05 eV for CuSbS2 to −4.11 eV for CuSbSe2. The energy levels of the direct CBM also slightly decrease from −4.00 eV for CuSbS2 to −4.07 eV for CuSbSe2. We show the band alignment of CuSbS2 (CuSbSe2)-based solar cells with a standard device structure of ZnO/CdS/CuSbS2 (CuSbSe2) absorber.
      PubDate: 2017-03-30T04:10:43.579359-05:
      DOI: 10.1002/pssc.201600196
       
  • Preparation of CuIn(S,Se)2 films by PLD of precursor layers and
           post-annealing and their application to solar cells
    • Authors: Toshiyuki Kawabe; Tsuyoshi Maeda, Takahiro Wada
      Abstract: Cu-In-S precursor films were deposited at various substrate temperatures by pulsed laser deposition (PLD). CuIn(S,Se)2 films were prepared by post-annealing the Cu-In-S precursor films in H2S and Se atmosphere. CuIn(S,Se)2 solar cells with a device structure of Au/ITO/i-ZnO/CdS/CuIn(S,Se)2/Mo/soda-lime (SLG) glass were fabricated and characterized. Higher conversion efficiency was obtained for the CuIn(S,Se)2 solar cell with the precursor film deposited at room temperature. The phase and microstructure of the Cu-In-S precursor and the annealed CuIn(S,Se)2 films were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). We found that the quality of the CuIn(S,Se)2 films was strongly affected by the deposition temperature of Cu-In-S precursor films. We discuss the grain growth and sintering in CuIn(S,Se)2 films on the basis of the results of XRD and SEM. The highest conversion efficiency of 6.38% (Voc = 521 mV, Jsc = 22.6 mA cm−2, FF = 0.541) was obtained for the CuIn(S,Se)2 solar cell with the precursor film deposited at room temperature and post-annealed at 620 °C. The solar cell was analyzed by secondary ion mass spectroscopy (SIMS) and transmission electron microscopy (TEM).
      PubDate: 2017-03-30T04:03:31.487261-05:
      DOI: 10.1002/pssc.201600183
       
  • The doping mechanism and electrical performance of polyethylenimine-doped
           MoS­2 transistor
    • Authors: Seongin Hong; Geonwook Yoo, Dong Hak Kim, Won Geun Song, Ong Kim Le, Young Ki Hong, Kaito Takahashi, Inturu Omkaram, Do Ngoc Son, Sunkook Kim
      Abstract: Seongin Hong et al. (article no. 1600262) have investigated the polyethylenimine (PEI) doping mechanism and its effect on the electrical and optical properties of multilayer MoS2 field effect transistors (FETs). Density functional theory (DFT) calculation and X-ray photoelectron spectroscopy (XPS) measurement confirm that the PEI molecules were successfully doped and formed Mo–N bonds on the MoS2 channel, generating new energy states near the valence band. The strong n-doping changed the threshold voltage as well as the Schottky barrier width attributed to the induced interfacial dipoles. Therefore, the ON-current of the doped MoS2 FETs was improved in comparison with the pristine FETs. Furthermore, the PEI doping also enhanced the photoresponsivity of the MoS2 FETs from 0.14 A/W to 4.41 A/W. This study suggests that PEI molecular doping could be widely applicable to two-dimensional materials in order to improve the electrical and optical properties of respective devices.
      PubDate: 2017-03-27T12:48:21.570575-05:
      DOI: 10.1002/pssc.201770003
       
  • Issue Information
    • PubDate: 2017-03-27T12:48:21.42447-05:0
      DOI: 10.1002/pssc.201720003
       
  • XYO3 (X = K, Na; Y = Nb, Ta) based superlattices
           for photocatalysis
    • Authors: Guang-Zhao Wang; Xiao-Rui Chen, Hong-Kuan Yuan, An-Long Kuang, Hong Chen
      Abstract: The photocatalytic activities of XYO3 (X = K, Na; Y = Ta, Nb) and XYO3/X1Y1O3 (X, X1 = K, Na; Y, Y1 = Ta, Nb) systems are investigated by using hybrid density functional. All the XYO3 and XYO3/X1Y1O3 systems are indirect band gap semiconductors, and the band gap of KNbO3/KTaO3 is smaller than those of KNbO3 and KTaO3, while the band gaps of KNbO3/NaNbO3, KNbO3/NaTaO3, KTaO3/NaNbO3, KTaO3/NaTaO3, and NaNbO3/NaTaO3 are respectively between the band gaps of these two crystals which make up these superlattices. The electronic structure of KNbO3/NaTaO3 is the same as that of KTaO3/NaNbO3 since both have the same component and similar crystal structure. The band edges of all the considered superlattices are thermodynamically allowed for the water reduction and oxidation processes, and therefore, they could be used for photocatalytic water splitting.Band structures for (i) KNbO3/KTaO3, (ii) KNbO3/NaNbO3, (iii) KNbO3/NaTaO3, (iv) KTaO3/NaNbO3, (v) KTaO3/NaTaO3, and (vi) NaNbO3/NaTaO3 superlattices. The horizontal dashed lines represent the Fermi levels.
      PubDate: 2017-03-27T02:45:26.61124-05:0
      DOI: 10.1002/pssc.201700026
       
  • Gold-induced crystallization of amorphous germanium deposited on glass:
           Bilayer and multilayer films
    • Authors: Ismail Bouhadda; Lamia Laidoudi, Claude Simon, Sarah Bebiche
      Abstract: Gold-induced crystallization (GIC) of amorphous germanium (a-Ge) using bilayer and multilayer films was performed through electron beam evaporation on glass substrates. The GIC of a-Ge was studied while the post-annealing temperature was varied between 250 and 550 °C for a fixed annealing time. The structure of polycrystalline Ge films was investigated by employing X-ray diffraction (XRD), Raman spectra and scanning electron microscopy (SEM). In both the bilayer and multilayer films the crystallization of a-Ge took place from 250 °C. The amount of crystallization fractioning and film quality were improved as the annealing temperature increased. However, preferentially (220) oriented crystalline Ge was formed in the bilayer films, indicating a micro-crystalline structure of the Ge. In the multilayer configuration (111) oriented crystalline Ge was observed indicating a poly-crystalline structure of the Ge. Scanning electron microscopy (SEM) images clearly highlight the grain size difference between these structures, especially for annealing temperatures above 400 °C.
      PubDate: 2017-03-22T08:39:25.069434-05:
      DOI: 10.1002/pssc.201700083
       
  • Two-particle self-consistent analysis for the electron-hole asymmetry of
           superconductivity in cuprate superconductors
    • Authors: Daisuke Ogura; Kazuhiko Kuroki
      Abstract: In the hole-doped type cuprate superconductors, it is well-known that the superconducting transition temperature Tc exhibits a dome-like structure against doping. On the other hand, recent experiments unveil that Tc in the electron-doped compounds shows a monotonic increase with decreasing the doping, at least down to a very small doping rate. Our recent study for the three-band d–p model has unveiled that this asymmetric behavior can be explained as a combined effect of the intrinsic electron-hole asymmetry in systems comprising Cu3 d and O2 p orbitals and the band-filling-dependent vertex correction . In the present study, we study another compound Tl2 Ba2 CuO6 to show that this explanation can be applied to other cuprate superconductors with the small dz2 orbital mixture. By varying the d–p offset, we also study how the strength of the d–p hybridization controls the spin fluctuation and hence the pairing interaction.
      PubDate: 2017-03-20T02:10:43.14844-05:0
      DOI: 10.1002/pssc.201600157
       
  • A space-charge-free CdS, and a new solar cell without pn-junction enabled
           by high-field domains
    • Authors: Karl W. Böer
      Abstract: A review of the electrical properties of a copper doped CdS as a model semiconductor describing three independent thermodynamic states depending on optical excitation and bias. These are the traditional ground state that, dependent of optical excitation renders it from an insulator to a highly conductive n-type semiconductor. With higher applied voltage, a high-field domain occurs that is locked-in, attached to the cathode. It presents the second thermodynamic stable state that is n-type with constant drift current limited by the carrier density at a blocking electrode nc. With further increased bias, the high-field domain becomes anode-adjacent. The CdS is in its third thermodynamic stable state. Here, the CdS has flipped into p-type conductivity with the current limited by the hole density at the blocking anode pa. In both states, the CdS is free of space charges within the domain that permits defect level spectroscopy without broadening influence of fluctuating electric fields. The minimum entropy production principle connects the work functions of blocking cathode and anode by the constant domain current, and permits the measurement of their values that depend on the optical excitation. A new solar cell is described that works without a pn-junction, with a thin, pure CdS layer replacing the junction. The CdS extracts the holes for tunneling into the base electrode. The CdS/CdTe to scale model is given as an example. It has substantial increased efficiency by preventing junction leakage and permits an increase of the open circuit voltage to approach the theoretical limit of the band gap of the emitter when extrapolated to 0 K. The solar cell is series resistance limited by the CdS and requires a thin planar deposition of CdS. Since CdS is photoelectrically passive, its Fermi-level at the base electrode is fixed. A Gallium doping of a thin layer pins the Fermi level within 0.05 V to the conduction band and increases Voc further. All properties of CdS with high-field domains are described quantitatively and the domains are made visible by the Franz–Keldysh effect.
      PubDate: 2017-03-20T02:05:43.710605-05:
      DOI: 10.1002/pssc.201700034
       
  • Characterization of high electron mobility transistor fabricated on
           hydride vapor phase epitaxy-grown GaN templates containing various Fe
           concentrations
    • Authors: K. Sugimoto; T. Nishihira, N. Arita, Y. Dempo, N. Okada, K. Tadatomo
      Abstract: An AlGaN/GaN high electron mobility transistor (HEMT) structure was grown on a semi-insulating (SI) GaN layer or substrate to suppress a leakage current and achieve a high breakdown voltage. Fe can be used as doping material to obtain SI-GaN. However, the relationship between the Fe concentration in the GaN layers and its influence on HEMT characteristics has not yet been investigated. In this study, we therefore investigated the influence of Fe concentration in the GaN layers on HEMT characteristics. The GaN layers containing several Fe concentrations were grown by hydride vapor phase epitaxy (HVPE). The Fe concentration was varied from 3 × 1017 to 3 × 1020 atoms cm−3. It was determined that the source-drain current (IDS) decreased as the Fe concentration increased. In the case of a low Fe concentration of 3 × 1017 atoms cm−3, IDS was almost the same as that of HEMT on the non-Fe-doped GaN template. Thus, HEMT characteristics deteriorated as the Fe concentration increased. The channel layer played a role in blocking the adverse effects of Fe doping on the two-dimensional electron gas concentration in AlGaN/GaN. Moreover, it was shown that the GaN channel layer must become thicker as the Fe concentration of the GaN layers increases.
      PubDate: 2017-03-20T02:05:30.282343-05:
      DOI: 10.1002/pssc.201600246
       
  • Annealing effects on Ga-doped ZnO thin films grown by atmospheric spray
           pyrolysis using diethylzinc solution
    • Authors: Kenji Yoshino; Himeka Tominaga, Akiko Ide, Kensuke Nishioka, Toshio Naka
      Abstract: Polycrystalline a-axis oriented Ga-doped ZnO thin film could be grown on glass substrate by a conventional atmospheric spray pyrolysis at 150 °C using diethylzinc-based solution. The n-type Ga-doped ZnO thin film had a resistivity of 1.5 × 10−3 Ω cm, a carrier concentration of 2.0 × 1020 cm−3 and a mobility of 20.0 cm2 (Vs)−1 at an optimal Ga content of 2 wt.% upon hydrogen annealing at 450 °C. It was assumed that an increase of the n-type carrier concentration is due to increase oxygen vacancies by reacting hydrogen and oxygen in ZnO from X-ray photoelectron spectroscopy.
      PubDate: 2017-03-17T07:15:29.80707-05:0
      DOI: 10.1002/pssc.201600177
       
  • Growth and annealing effect of SrTiO3 thin films grown by pulsed laser
           deposition using fourth harmonic Nd:YAG pulsed laser
    • Authors: Koji Takamura; Takumi Fujiwara, Akinobu Yokota, Motonori Nakamura, Ken'ichi Yoshimoto
      Abstract: SrTiO3 homoepitaxial films were grown by pulsed laser deposition (PLD) using a fourth harmonic Nd:YAG pulsed laser. The substrate temperature was kept constant at 600, 700, or 800 °C. The laser energy was set at 9–25 mJ on the polycrystal SrTiO3 target. Post-procedure annealing was performed in the air for 24 h. The X-ray diffraction measurement results showed that the lattice constant of the film was only 0.010 Å larger than that of the substrate and was not dependent on the annealing temperature. We demonstrated the possibility of growing near-stoichiometric SrTiO3 film by PLD using an Nd:YAG laser.
      PubDate: 2017-03-17T07:15:26.966421-05:
      DOI: 10.1002/pssc.201600190
       
  • Plasma-assisted self-formation of nanotip arrays on the surface of
           Cu(In,Ga)Se2 thin films
    • Authors: Sergey P. Zimin; Egor S. Gorlachev, Valery F. Gremenok, Klaus Bente, Dmitry A. Mokrov, Ildar I. Amirov, Viktor V. Naumov, Woo Y. Kim
      Abstract: In this paper, we report on the phenomenon of nanostructure self-formation on the surface of Cu(In,Ga)Se2 (CIGS) thin films during inductively coupled argon plasma treatment with its duration varied from 10 to 120 s. The initial films were grown on glass substrates using the selenization technique. During the CIGS film surface treatment in the high-density low-pressure radio-frequency inductively coupled argon plasma there took place a formation of arrays of uniform vertical nanostructures, which shape with increasing processing duration changed from nanocones to nanorods and back to nanocones. A model of the nanotip plasma-assisted self-formation associated with the implementation of micromasking and vapor–liquid–solid mechanisms involving metallic In-Ga (In-Ga-Cu) liquid alloy droplets is proposed.
      PubDate: 2017-03-16T06:51:20.145264-05:
      DOI: 10.1002/pssc.201600135
       
  • Surface enhanced Raman scattering of whole human blood on nanostructured
           ZnO surface
    • Authors: Oktay K. Gasymov; Oktay Z. Alekperov, Arzu H. Aydemirova, Nigar Kamilova, Rasim B. Aslanov, Ayaz H. Bayramov, Afet Kerimova
      Abstract: Surface enhanced Raman spectroscopy (SERS) owing to the greatly enhanced sensitivity is widely utilized to study biological molecules in various states. However, the enhancement in SERS is not uniform throughout the spectra. As a result, the strong enhancement of some transitions in SER overshadows weak Raman peaks that are very important to characterize the molecules. Here we show the SERS investigation for whole human blood on a nanostructured ZnO surface. The result indicates that despite the moderate enhancement (20–30 fold), all spectral components of the blood demonstrated in regular Raman are detected in SERS on ZnO. Moreover, SERS on ZnO identifies some components of the blood that are not easily accessible to regular Raman spectroscopy. Data indicate that SERS on ZnO is a valuable tool to investigate the whole blood for diagnosis of various human diseases.
      PubDate: 2017-03-16T06:51:07.779409-05:
      DOI: 10.1002/pssc.201600155
       
  • Preparation of Zn2SiO4:Mn2+ films by electrical discharge pulse method
    • Authors: Makoto Hattori; Yuya Suzuki, Akihiro Goto, Minoru Dohi
      Abstract: The use of electrical discharge pulses is a new method to prepare thin films. The conventional phosphor thin film preparation technology uses rf sputtering or vacuum vapor deposition. However, thin films prepared by conventional methods are formed in amorphousness on the substrates. In contrast, this new method uses the electrical discharge energy between an electrode and a conductive substrate. When an electrical pulse is discharged between the electrode and the substrate, the electrode material, which is zinc and phosphor, moves to the substrate. Consequently, this new method can be used to produce light-emitting devices. In this study, we used the phosphor Zn2SiO4:Mn2+. We were able to prepare luminescent Zn2SiO4:Mn2+ films using a discharge currant of 10 A, at a voltage of 80 V and weight ratio of zinc to Zn2SiO4:Mn2+ of 6:4. We evaluated the resultant films with scanning electron microscopy (SEM) and X-ray diffraction (XRD).
      PubDate: 2017-03-15T09:30:40.638565-05:
      DOI: 10.1002/pssc.201600179
       
  • Intergranular barrier height fluctuations in polycrystalline
           semiconductors
    • Authors: C. Buono; F. Schipani, M. A. Ponce, C. M. Aldao
      Abstract: The punctual character and random nature of the impurity positions in depletion regions lead to inhomogeneities that can significantly affect the potential intergranular barriers at polycrystalline semiconductors and, in general, of potential barriers at any semiconductor interface. This would reflect in Arrhenius plots for the electrical conductivity that become curved due to fluctuations of the intergranular barrier heights. Experimental results for polycrystalline tin oxide can be fitted assuming thermionic emission conduction at grain boundaries with a Gaussian distribution of barrier height fluctuations. However, resorting to a computational numerical model, we found that spatial fluctuations in barrier heights due to the discreteness of the donors and their statistical distribution at the depletion region differ from a Gaussian distribution. The type of obtained fluctuations, considering thermionic emission conduction, cannot explain the Arrhenius plots for the electrical conductivity found experimentally, especially at low temperature. Conversely, the tunneling contribution to conduction, without resorting to fluctuations, presents the observed trends.
      PubDate: 2017-03-15T09:30:27.688647-05:
      DOI: 10.1002/pssc.201700069
       
  • Analysis of low-temperature data of Hall-effect measurements on Ga-doped
           p-Ge on the basis of an impurity-Hubbard-band model
    • Authors: Yasutomo Kajikawa
      Abstract: The low-temperature data of Hall-effect measurements on Ga-doped p-Ge reported by Fritzsche (Phys. Rev. B 99, 406 [1955]) have been analyzed on the basis of an impurity-Hubbard-band model. It is shown that the complicated behavior of the temperature dependence of the Hall coefficient can be well fitted by assuming the hopping drift mobility expressed as μb = μ0b(T0b/T)1/3 exp[−(T0b/T)1/2] and the hopping Hall factor expressed as Ab = A0b(T0b/T)2/3 exp[(1 − ν¯)(T0b/T)1/2] with ν¯ = (3/2)1/2 − 1 for the bottom Hubbard band while assuming μt = μ0t(E2/kBT)3/2 exp(−E2/kBT) and At = (kBT/Jt)exp(KHtE2/kBT) for the top Hubbard band. The deduced values of Eb for the activation energy of carriers in the bottom Hubbard band is proved to obey the relation of Eb = Ib[1−(NA/Nb)1/2], where Ib is the ionization energy of isolated Ga impurities, NA is the acceptor concentration, and Nb = 1.0 × 1017 cm−3. The deduced values of T0b is proved to obey the relation of T0b = T00(1 − NA/Nc), where Nc = 1.86 × 1017 cm−3 and T00 = 2.8e2/(4πϵ0ϵsa0) with a0 = ℏ/2mlhIb and mlh being the effective mass of light holes. It is also shown that KHt increases with E2.
      PubDate: 2017-03-15T05:45:31.776854-05:
      DOI: 10.1002/pssc.201700071
       
  • Note on the Coulomb blockade of a weak tunnel junction with Nyquist noise:
           Conductance formula for a broad temperature range
    • Authors: Antónia Mošková; Martin Moško
      Abstract: We revisit the Coulomb blockade of the tunnel junction with conductance much smaller than e2/ℏ. We study the junction with capacitance C, embedded in an Ohmic electromagnetic environment modeled by a series resistance R which produces the Nyquist noise. In the semiclassical limit, the Nyquist noise charges the junction by a random charge with a Gaussian distribution. Assuming the Gaussian distribution, we derive analytically the temperature-dependent junction conductance G(T) valid for temperatures kBT≳(RK/2πR)Ec and resistances R≳RK, where RK=h/e2 and Ec=e2/2C is the single-electron charging energy. Our analytical result shows the leading dependence G(T)∝e−Ec/4kBT, so far believed to exist only if (RK/πR)Ec≪kBT≪Ec and R≫RK. The validity of our result for kBT≳(RK/2πR)Ec and R≳RK is confirmed by a good agreement with the numerical studies which do not assume the semiclassical limit, and by a reasonable agreement with experimental data for R as low as RK. Our result also reproduces various asymptotic formulae derived in the past. The factor of 1/4 in the activation energy Ec/4 is due to the semiclassical Nyquist noise.
      PubDate: 2017-03-13T02:30:59.473932-05:
      DOI: 10.1002/pssc.201700029
       
  • The doping mechanism and electrical performance of polyethylenimine-doped
           MoS­2 transistor
    • Authors: Seongin Hong; Geonwook Yoo, Dong Hak Kim, Won Geun Song, Ong Kim Le, Young Ki Hong, Kaito Takahashi, Inturu Omkaram, Do Ngoc Son, Sunkook Kim
      Abstract: We present a systematic investigation of polyethylenimine (PEI) doping mechanism and its effects on the multilayer MoS2 field effect transistors (FETs). The threshold voltages of MoS2 FETs before (i.e., pristine) and PEI doping are observed at 3.7 and 0.72 V, respectively. This negative threshold voltage shift clearly reveals that the PEI molecules effectively act as n-type dopants. The electrical properties are improved by absorption of PEI molecules onto MoS2 channel because the width of Schottky barrier (SB) is narrowed by the induced interfacial dipole between PEI molecules and MoS2 layers. Through the density function theory (DFT) calculation and X-ray photoelectron spectroscopy (XPS) analysis, we confirm that formation of MoN bond generates new energy state into the bandgap. Consequently, the hole carriers can easily tunnel through the barrier under negative gate voltage. Furthermore, PEI doping improve photoresponsivity and time-resolved photo-switching characteristics because of the new energy state. Our studies demonstrate the PEI doping method has a great potential for improving electrical and optical properties of MoS2-based devices.
      PubDate: 2017-03-08T09:55:32.571032-05:
      DOI: 10.1002/pssc.201600262
       
  • Effect of surface treatment on the Cu2ZnSnS4 thin films using a cationic
           surfactant
    • Authors: Hisashi Miyazaki; Masami Aono, Hiroaki Kishimura, Kazuo Jimbo, Hironori Katagiri
      Abstract: Cu2ZnSnS4 (CZTS) is one of the promising materials for high efficiency thin film solar cells. Here we report on the chemical and structural characterization of the CZTS thin films after the surface treatment by using 1% Br2-methanol etchant with and without cationic surfactant, oleylamine. Raman scattering spectroscopy results showed that the etching with surfactant of oleylamine did not affect the bulk structural characterization. Cu, Zn, and S chemical composition ratio decreases after etching process without surfactant of oleylamine. However, in the case of the sample etched by using surfactant of oleylamine, the surface composition changes to only Cu-poor composition. Moreover, we report the first time that the oleylamine additive is possible of selective etching of Cu-related compounds of CZTS.
      PubDate: 2017-03-08T09:55:31.168698-05:
      DOI: 10.1002/pssc.201600176
       
  • Effect of surface treatment by hydrogen peroxide solution on Cu2ZnSnS4
           thin films
    • Authors: Hisashi Miyazaki; Masami Aono, Hiroaki Kishimura, Kazuo Jimbo, Hironori Katagiri
      Abstract: Cu2ZnSnS4 (CZTS) is one of the promising materials of absorber layer used in thin film solar cells. In this paper, we revealed the effects of surface treatment by hydrogen peroxide solution on the chemical and structural properties of CZTS thin films in order to improve the conversion efficiency. On the Raman spectra, the full width at half maximum (FWHM) of A1 peak at around 338 cm−1 is not affected by H2O2 solution treatment. However, Raman scattering spectroscopy results showed that the existence of not only CZTS but also oxide was confirmed by the H2O2 solution treatment. From the XPS spectra, Zn, and S were dissolved by H2O2 solution. The surface oxidation takes place in a very short period of time. The sulfate phase is existence on the CZTS surface by H2O2 surface treatment.
      PubDate: 2017-03-08T09:55:26.267388-05:
      DOI: 10.1002/pssc.201600175
       
  • Effect of nano-porous SiNx interlayer on propagation of extended defects
           in semipolar (112¯2)-orientated GaN
    • Authors: Morteza Monavarian; Natalia Izyumskaya, Marcus Müller, Sebastian Metzner, Peter Veit, Saikat Das, Ümit Özgür, Frank Bertram, Jürgen Christen, Hadis Morkoç, Vitaliy Avrutin
      Abstract: Semipolar orientations of GaN have attracted considerable attention as potential platforms for high brightness light-emitting devices. The heteroepitaxy of semipolar GaN layers results in high densities of threading dislocations (TDs) and basal-plane stacking faults (BSFs). Various defect reduction methods have been employed to improve the crystal quality of the semipolar substrates, among which the in situ epitaxial lateral overgrowth (ELO) is of great importance due to its relatively simple procedure, low cost, and high effectiveness in reducing density of TDs. We have shown that in situ deposited nano-porous SiNx could act as a blocking layer preventing both TDs and BSFs from penetrating to overgrown semipolar (112¯2) GaN layers. In this contribution, we present microscopic study of interaction of extended defects (TDs and BSFs) with nano-porous SiNx in (112¯2)-oriented GaN layers grown by MOCVD on m-sapphire substrates. Cross-sectional scanning transmission electron microscopy-cathodoluminescence (STEM-CL) reveals reduction of BSF density by about 50% for dual insertion of SiNx interlayers. It is also shown that the integrated CL intensity is enhanced by about two orders of magnitude indicating that the majority of TDs are blocked by the interlayers. The interaction of TDs and BSFs with nano-porous SiNx and defect distribution in GaN nuclei are briefly discussed.
      PubDate: 2017-03-06T04:50:37.707813-05:
      DOI: 10.1002/pssc.201700024
       
  • Fabrication of perovskite solar cells by reaction between spin-coated
           precursor films and CH3NH3I vapor
    • Authors: Hinako Ebe; Shohei Sasagawa, Hideaki Araki
      Abstract: The organic–inorganic hybrid perovskite CH3NH3PbI3 thin-films were obtained by reaction between spin-coated PbI2 precursor thin-films on a porous-TiO2 layer and CH3NH3I vapor. The dependence of the photovoltaic properties of solar cells fabricated with these films on the CH3NH3I powder source temperature and reaction time was investigated. The obtained thin-films were characterized using X-ray diffraction and scanning electron microscopy. The best power conversion efficiencies (PCEs) for each heating condition were 160 °C for 30 min, 150 °C for 45 min, and 140 °C for 60 min. The presence of PbI2 and CH3NH3PbI3 layers, and a flatter and more compact morphology, led to relatively high PCE. The perovskite thin-films were annealed in a N2 atmosphere and the effect of annealing temperature on the photovoltaic performance was also investigated. The PCE for a solar cell fabricated using CH3NH3PbI3 thin-films annealed in the range from 130 to 150 °C for 1 h was over 4%.
      PubDate: 2017-03-03T14:10:34.751589-05:
      DOI: 10.1002/pssc.201600192
       
  • Comparison of buffer layers on SnS thin-film solar cells prepared by
           co-evaporation
    • Authors: Aimi Yago; Shohei Sasagawa, Yoji Akaki, Shigeyuki Nakamura, Hiroto Oomae, Hironori Katagiri, Hideaki Araki
      Abstract: The binary compound SnS consists of elements that are non-toxic, inexpensive, and abundant in the Earth's crust. It is a p-type semiconductor with a band gap energy of 1.3 eV and an absorption coefficient of 104 cm−1, and is therefore a potential candidate for use as a solar cell absorber material. In this study, SLG/Mo/SnS/CdS/ZnO:Al/Al and SLG/Mo/SnS/ZnO/ZnO:Al/Al SnS thin-film solar cells with different buffer layers were fabricated using a co-evaporation method. The dependence of the photovoltaic properties of the SnS thin-film solar cells with CdS or ZnO as the buffer layer was investigated. We demonstrate that the device with a ZnO buffer layer exhibited higher conversion efficiency and short-circuit current density compared to the device with a CdS buffer layer.
      PubDate: 2017-03-03T14:05:26.71713-05:0
      DOI: 10.1002/pssc.201600194
       
  • Synthesis and characterization of Cu2Sn1−xGexS3
    • Authors: Hideaki Araki; Masaki Yamano, Genki Nishida, Akiko Takeuchi, Naoya Aihara, Kunihiko Tanaka
      Abstract: Cu2SnS3 (CTS) is a promising compound for use as an absorber layer in thin-film solar cells because it is made up of low-cost and abundant elements. However, the band gap energy of 0.94 eV for monoclinic Cu2SnS3 is less than the optimal value for absorber layers in single-junction solar cells. On the other hand, the band gap energy of Cu2GeS3 (CGS) is approximately 1.5–1.6 eV. Therefore, in this study, we carried out the synthesis of Cu2Sn1−xGexS3, which is a solid solution of Cu2SnS3 and Cu2GeS3. The structure of the prepared samples was investigated using X-ray diffraction and Raman analyses. Diffuse reflectance spectra were obtained using a UV–Vis–NIR spectrometer and used to estimate the band gap energy. In X-ray diffraction patterns from the synthesized compounds, the diffraction peaks were found to shift to higher 2θ values with increasing x, indicating a decrease in the lattice constants. In addition, the estimated band gap energy increased from 0.86 to 1.53 eV with increasing x. Cu2Sn1 − xGexS3 is, therefore, a potential candidate for use as the absorber layer in thin film solar cells because its band gap energy can be adjusted simply by varying its composition.
      PubDate: 2017-03-03T14:05:25.482374-05:
      DOI: 10.1002/pssc.201600199
       
  • Effect of sulfur vapor pressure on SnS thin films grown by sulfurization
    • Authors: Shuntaro Mikami; Tsubasa Yokoi, Hiroki Sumi, Satoru Aihara, Ishwor Khatri, Mutsumi Sugiyama
      Abstract: Tin monosulfide (SnS) films were grown by sulfurization of sputtered Sn thin films. The effect of S vapor pressure (PS), which varied from 10 to 105 Pa, was analyzed through depth profiling of SnS films. S atoms were diffused into the surface regions of the SnS layer to approximately 100 nm at PS = 10 Pa. The activation energy for S diffusion in the Sn thin films was 1.4eV. At PS = 103 Pa, on the other hand, S atoms were diffused into the SnS layer to a depth of approximately 700 nm. Accordingly, the activation energy was 1.1 eV. The experimentally obtained crystallite size was found to increase from 12 to 35 nm with the increase of S vapor pressure. Furthermore, by varying the sulfurization temperature range, a similar tendency was likewise observed. Under the photovoltaic properties with a structure of Al/ZnO:Al/ZnO/CdS/SnS/Mo/SLG, a current density of 6.2 mA cm−2 was obtained when the SnS crystallite size was 35 nm.
      PubDate: 2017-03-03T08:35:24.154367-05:
      DOI: 10.1002/pssc.201600160
       
  • Fabrication and electrical response of flexible supercapacitor based on
           activated carbon from bamboo
    • Authors: N.A. Echeverry-Montoya; J.J. Prías-Barragán, L. Tirado-Mejía, C. Agudelo, G. Fonthal, H. Ariza-Calderón
      Abstract: We present the fabrication and electrical response of a flexible prototype supercapacitor based on activated carbon electrodes obtained from bamboo (Guadua angustifolia Kunth) as precursor. The supercapacitor prototype was fabricated by using a multilayer configuration method; activated carbon electrodes were impregnated with 0.5 M H2SO4 as electrolyte and filter paper was used as separator. Carbon activation was performed by using NaOH and KOH solutions. Activated carbon electrodes were characterized by adsorption isotherms, cyclic voltammetry, and SEM techniques. Electrical response was found by using charge-discharge curves. Through adsorption isotherms analysis, we found a surface area of 408 and 309 m2 g−1 for the activated carbon with NaOH and KOH, respectively. From the electrical characterization analysis of the supercapacitor device, we obtained 0.92 F for the maximum capacitance value by using 0.5 V as fixed value in the bias voltage. Also, we proposed an equivalent electrical circuit for the supercapacitor prototype. This capacitance value is comparable with the capacitance values exhibited by rigid commercial supercapacitor, such as Dinacap and capacitor Capattery Gold, among others. Finally, these results suggest that the activated carbon from bamboo can be used in flexible electronic applications.
      PubDate: 2017-03-01T08:00:25.417713-05:
      DOI: 10.1002/pssc.201600258
       
  • Observation of the c-f hybridization effect in valence-transition system
           EuPtP
    • Authors: Hiroaki Anzai; Katsuya Ichiki, Eike F. Schwier, Hideaki Iwasawa, Masashi Arita, Hitoshi Sato, Kenya Shimada, Hirofumi Namatame, Masaki Taniguchi, Akihiro Mitsuda, Hirofumi Wada, Kojiro Mimura
      Abstract: We study the electronic structure of EuPtP, which exhibits two first-order valence transitions at T1 = 247 K and T2 = 201 K, using angle-resolved photoemission spectroscopy. Below T2, we observe an energy gap at the crossing point of the bulk Eu 4f and conduction bands. The shape of band dispersions is described by a hybridization-band picture based on the periodic Anderson model. Our results demonstrate the c-f hybridization effect in the low-temperature phase of EuPtP.
      PubDate: 2017-03-01T07:40:29.466483-05:
      DOI: 10.1002/pssc.201600185
       
  • Cross-plane thermal conductivity of tungsten diselenide
    • Authors: Payam Norouzzadeh; David J. Singh
      Abstract: The cross-plane thermal conductivity of WSe2 is investigated using reverse nonequilibrium molecular dynamics (RNEMD) and a recently developed Stillinger-Weber potential. It is found that the cross-plane thermal conductivity of WSe2 is strongly size dependent and saturates around 80 layers. Moreover, it is shown that even at 1000 K, ordered crystalline WSe2 does not reach the phonon glass-like limit in the cross-plane direction.
      PubDate: 2017-03-01T07:40:24.394237-05:
      DOI: 10.1002/pssc.201700078
       
  • Fabrication of ternary and quaternary chalcogenide compounds based on Cu,
           Zn, Sn and Si for thin film photovoltaic applications
    • Authors: Guy Brammertz; Bart Vermang, Hossam ElAnzeery, Sylvester Sahayaraj, Samaneh Ranjbar, Marc Meuris, Jef Poortmans
      Abstract: We investigated the use of ternary and quaternary chalcogenide compounds based on Cu, Zn, Sn and Si for use as high band gap absorber layers in thin film photovoltaics. We have investigated the fabrication of Cu2Zn(Sn,Si)Se4, Cu2Si(S,Se)3 and Cu8Si(S,Se)6 thin film layers. Whereas, Cu2Zn(Sn,Si)Se4 and Cu2Si(S,Se)3 appeared to be difficult to fabricate, because the Si did not intermix well with the rest of the elements at the typical process temperatures used for glass substrates, Cu2ZnSiSe4 and Cu8Si(S,Se)6 could be formed. The fabricated layers were polycrystalline with a typical thickness of about 1 μm. We also fabricated solar cells with the different absorber materials, using a standard Mo back contact and CdS/ZnO buffer layer combination, but despite very bright photoluminescence response of the Cu8SiS6 and Cu8SiSe6 layers at an energy of about 1.84 and 1.3 eV respectively, the measured efficiencies remained below 0.1% due to particularly low photocurrents.
      PubDate: 2017-02-27T06:45:30.159611-05:
      DOI: 10.1002/pssc.201600162
       
  • Electrical conductivity improved Cu2SnS3 thermoelectrics
    • Authors: Shigeyuki Nakamura; Hiroyuki Funabiki, Shinya Shiga
      Abstract: Cu2SnS3 is an attractive earth abundant material for not only solar cells but also thermoelectrics because high thermoelectric performance is predicted by the first principle calculation. In our previous work, Cu2SnS3 is successfully synthesized by solid phase reaction with binary compounds and obtained a high Seebeck coefficient and a low thermal conductivity. However, a low electric conductivity results in a low figure of merit (ZT) of less than 0.1. In this work, CuS and In2S3 are added to starting materials to enhance the electrical conductivity and it has been improved by one order of magnitude.CuS and In2S3 addition enhance electrical conductivities.
      PubDate: 2017-02-27T06:45:22.605794-05:
      DOI: 10.1002/pssc.201600172
       
  • Local structure analysis of Cu(In,Ga)Se2 by X-ray fluorescence holography
    • Authors: Sho Shirakata; Yuma Kitamura, Naohisa Happo, Shinya Hosokawa, Kouichi Hayashi
      Abstract: X-ray Fluorescence Holography (XFH) study of Cu(In,Ga)Se2 single crystals has been performed using an inverse mode. Energies of incident X-ray are from 9.2 to 13.2 keV. The Cu-Kα X-ray fluorescence hologram has been constructed, and atomic images were reconstructed using Barton's algorithm. Dependence of fluorescent X-ray, either Cu or Ga, on the reconstructed atomic images of CuIn0.2Ga0.8Se2 was examined. The atomic image of CuIn0.2Ga0.8Se2 was compared with that of CuIn0.8Ga0.2Se2. The reconstructed atomic images of the cation (Cu, Ga, and In) plane and that of the anion (Se) plane are discussed in terms of the alloy composition.
      PubDate: 2017-02-23T09:10:23.957426-05:
      DOI: 10.1002/pssc.201600171
       
  • A closer look into metastable effects of Cu(In,Ga)Se2 solar cells
    • Authors: Tetiana Lavrenko; Thomas Walter, Balázs Plesz
      Abstract: In this contribution, metastabilities of Cu(In,Ga)Se2 (CIGS)/CdS thin films are discussed based on photoluminescence (PL) imaging and complementary vibrating Kelvin probe (VKP) measurements. It has been shown that thermal treatment of CIGS/CdS thin films leads to the PL intensity quenching and a change in a surface band-bending as deduced from VKP measurements under illumination. The impact of white light soaking has the opposite effect as compared to heat treatment: elevated temperatures enhance surface band-bending whereas illumination leads to at least a partial band-flattening. Furthermore, it has been found that etching away the CdS buffer layer reduces the previously measured band-bending significantly pointing out the importance of the buffer layer deposition process. Moreover, the investigation of P1 scribes revealed that surface potentials in the vicinity of the patterning lines differ from the surface potentials measured on cells what is also reflected in the PL images as differences in the intensity between the bulk of the cells and P1 scribes. This observation suggests that the influence of P1 scribing parameters on electrical characteristics of CIGS solar cells has to be studied additionally as they can significantly affect the overall efficiency of the cell.
      PubDate: 2017-02-23T08:10:27.177047-05:
      DOI: 10.1002/pssc.201600197
       
  • Demonstration of wafer-level white light emitting diode with
           92,000 lm luminous flux
    • Authors: Yibin Zhang; Jianwei Xu, Desheng Zhao, Hongjuan Huang, Mingdi Ding, Zhenlin Miao, Yanming Wang, Peng He, Baoshun Zhang, Yong Cai
      Abstract: A high-power phosphor-converted white wafer-level LED with 92,000 lm was demonstrated. The high-power white LED was manufactured by utilising a blue single wafer-level LED chip coated with a 60-µm-thick thin film phosphor layer. The electrical and optical characteristics of the LED were measured. Results show that the luminous flux and luminous efficacy reach to 92,000 lm and ∼89 lm/W at an input electrical power of 1035 W, respectively. The view angle is about 133°.
      PubDate: 2017-02-22T08:30:26.574335-05:
      DOI: 10.1002/pssc.201600244
       
  • Quenching interface recombination in wide bandgap Cu(In,Ga)Se2 by
           potassium treatment
    • Authors: Setareh Zahedi-Azad; Roland Scheer
      Abstract: In this contribution, we report on the increase of the output voltage for wide bandgap (Eg > 1.4 eV) Cu(In,Ga)Se2 films by doping potassium via post-deposition treatment of the grown absorber layer. Also the carrier collection is improved by Potassium fluoride treatment (KF). The difference between KF-treated and untreated samples is investigated using J–V parameters, external quantum efficiency (EQE), and VOC(t) transients under red illumination. Statistics shows an increased activation energy of saturation current and a trend toward a positive dVOC/dt. Thus the increased VOC can be explained through partially quenched recombination at the interface of buffer/absorber layer.
      PubDate: 2017-02-22T07:55:36.592167-05:
      DOI: 10.1002/pssc.201600203
       
  • New applications of chalcopyrite crystals in nonlinear optics
    • Authors: Valentin Petrov
      Abstract: The properties of chalcopyrite crystals relevant to nonlinear optics are considered comparing existing representatives. The applications of such birefringent noncentrosymmetric crystals for laser frequency up- and down-conversion in the mid-IR are reviewed with emphasis on the newly developed LiGaTe2 and CdSiP2.
      PubDate: 2017-02-22T07:55:35.305814-05:
      DOI: 10.1002/pssc.201600161
       
  • Microwave synthesis and magnetic properties of Laves-type Ti2M3Si
           (M = Mn, Fe, Co, Ni)
    • Authors: Christin M. Hamm; Léopold V.B. Diop, Hongbin Zhang, Oliver Gutfleisch, Christina S. Birkel
      Abstract: Fast and energy-efficient synthesis methods become increasingly important aspects in the experimental high throughput searching of functional materials. Particularly high-temperature solid-state preparation techniques typically require large amounts of energy due to extended heating cycles. Therefore, we have utilized a time and energy-efficient synthesis method using a commercial microwave oven in order to prepare intermetallic Laves-type phases. Ti2M3Si with M = Mn, Fe, Co, Ni can be prepared within only 10 min of microwave heating based on this convenient one-step procedure. These compounds are of interest because of their potentially useful magnetic properties and therefore contribute to the ongoing search for rare earth-free alternatives to state-of-the-art magnetic materials.Transition metal-based Laves phase compounds Ti2M3Si were prepared by time- and energy-efficient microwave heating and their structural and magnetic properties studied.
      PubDate: 2017-02-22T07:50:38.576515-05:
      DOI: 10.1002/pssc.201700027
       
  • Structural analysis of co-evaporated In2S3 and In2S3:V for solar cell
           absorber applications
    • Authors: Leonard A. Wägele; Diana Rata, Galina Gurieva, Roland Scheer
      Abstract: In this study we use co-evaporation to grow In2S3 thin films on glass substrates and X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) to analyse the structural properties of annealed In2S3 and V-doped In2S3 for intermediate band solar cell application. We find co-evaporated In2S3 to be polycrystalline on float glass and with improved crystallinity after annealing in S-atmosphere. We confirm that excessive incorporation of vanadium into the host structure is possible without formation of secondary crystalline phases. The analysis indicates a reduced crystalline quality after V doping.
      PubDate: 2017-02-22T07:50:35.867652-05:
      DOI: 10.1002/pssc.201600204
       
  • Recovery current characteristics of diode mode operation in GaN gate
           injection transistor bi-directional switch
    • Authors: Toshihide Ide; Mitsuaki Shimizu, Xu-Qiang Shen, Hidetoshi Ishida, Masahiro Ishida, Nobuyuki Otsuka, Tetsuzo Ueda
      Abstract: The recovery current characteristics of the GIT bi-directional switches in the diode mode are investigated. The recovery current waveforms are only dependent on the gate bias condition of the switching transistor, and not dependent on the gate bias of the GIT bi-directional switch. The products of the recovery current peak and the recovery time estimated by the switching waveforms are almost constant in spite of changing the turn-on voltage, and these values agree well with the charge at the diode shown by the integral of the diode capacitance and S2-S1 voltage of the GIT bi-directional switch. From these results, it is found that the independence of the gate bias of the GIT bi-directional means that the influence of the hole injection is slight, and the diode operation of the GaN GIT bi-directional switch is likely to be operated as schottky barrier diode.
      PubDate: 2017-02-22T07:50:32.015967-05:
      DOI: 10.1002/pssc.201600245
       
  • Magnetoelectric effect in two-layered self-biased composites
           Tb0.12Dy0.2Fe0.68/epoxy − PbZr0.53Ti0.47O3
    • Authors: A.V. Kalgin; S.A. Gridnev, I.I. Popov
      Abstract: Direct magnetoelectric (ME) effect in two-layered Tb0.12Dy0.2Fe0.68/Epoxy − PbZr0.53Ti0.47O3 composites containing magnetostrictive layers of the epoxy with distributed in it Tb0.12Dy0.2Fe0.68 granules and piezoelectric layers of the PbZr0.53Ti0.47O3 ceramics was studied. It was found, that the gradient distribution of Tb0.12Dy0.2Fe0.68 granules in magnetostrictive layers induces the internal (self-biased) magnetic field. This field leads to the increase in ME responses in composites with the gradient distribution of Tb0.12Dy0.2Fe0.68 granules in magnetostrictive layers as compared with ME responses in composites with the random distribution of Tb0.12Dy0.2Fe0.68 granules in magnetostrictive layers, which does not induce the internal magnetic field. We revealed the possibility of controlling and determining values of the internal magnetic field in composites and conditions for obtaining optimal ME responses.
      PubDate: 2017-02-22T07:50:27.376912-05:
      DOI: 10.1002/pssc.201600231
       
  • Ultraviolet and visible micro-Raman and micro-photoluminescence
           spectroscopy investigations of stress on a 75-mm GaN-on-diamond wafer
    • Authors: B. Logan Hancock; Mohammed Nazari, Jonathan Anderson, Edwin Piner, Firooz Faili, Seajin Oh, Daniel Francis, Daniel Twitchen, Samuel Graham, Mark W. Holtz
      Abstract: Investigations of stress distributions and material quality across a 75-mm wafer consisting of device-quality GaN integrated with a diamond substrate are presented. Stress in the GaN are mapped both over the full wafer and across the layer along the growth direction. Ultraviolet (UV) and visible micro-Raman and UV photoluminescence (PL) spectroscopy from both sides of the wafer reveal an unexpected gradient between the tensile stress at the free GaN surface (∼0.86–0.90 GPa) and the GaN/diamond interface (∼0.05–0.23 GPa). The stresses obtained exhibit good cross-wafer uniformity. The stress gradient is understood through variations in the material along the growth direction of the layers due to the presence of threading dislocations which result in local stress relaxation. Transmission electron microscopy confirms the presence of extended defects to be greater near the interface with diamond, corresponding to the initial GaN growth regime, and diminished toward the surface where transistors would be fabricated in a full device technology. Finite element (FE) simulations describing the observed stress dependence along with TEM imaging of the GaN cross-section support the relaxation interpretation.
      PubDate: 2017-02-22T07:45:27.070459-05:
      DOI: 10.1002/pssc.201600247
       
  • Secondary ion mass spectrometry as a tool to study selenium gradient in
           Cu2ZnSn(S,Se)4
    • Authors: Sigbjørn Grini; Nils Ross, Thomas Neset Sky, Clas Persson, Charlotte Platzer-Björkman, Lasse Vines
      Abstract: Secondary ion mass spectrometry (SIMS) has been utilized to study compositional gradients in compound-sputtered and annealed Cu2ZnSn(S,Se)4 (CZTSSe). SIMS image depth profiling shows a non-uniform spatial distribution of selenium and supports a mechanism where selenization is accompanied by grain growth rather than substitution of selenium for sulfur. Furthermore, SIMS depth profiles of S and Se using O2+ primary ions and detecting molecular ions of the MCs+ type using Cs+ primary ions have been compared, where a linear relationship between the sulfur and selenium concentration suitable for compositional analysis is observed for concentrations with an Se/(S+Se) ratio in the range from 0.25 to 0.65.3D image of the spatial Se distribution in a 20 × 20 μm2 grid measured with SIMS image depth profiling.
      PubDate: 2017-02-21T09:46:20.797461-05:
      DOI: 10.1002/pssc.201600187
       
  • Yb valence state in Yb5Rh4Ge10
    • Authors: Hitoshi Sato; Yuki Utsumi, Kenichi Katoh, Kojiro Mimura, Shigenori Ueda, Hitoshi Yamaoka, Awabaikeli Rousuli, Masashi Arita, Kazunori Umeo, Kenya Shimada, Hirofumi Namatame, Masaki Taniguchi
      Abstract: Temperature- and pressure-dependent Yb valence state in Yb5Rh4Ge10 has been investigated by means of Yb 3d hard X-ray photoemission spectroscopy (HAXPES) and Yb L3 absorption spectroscopy (XAS). The mean Yb valence derived from the Yb 3d HAXPES is estimated to be ∼2.78 at 300 K and decreases to ∼2.74 at 20 K. On the other hand, the Yb valence deduced from the Yb L3 XAS at 300 K is almost constant with ∼2.81 in the pressure range between 9.2 and 34.7 GPa.
      PubDate: 2017-02-21T09:45:58.549549-05:
      DOI: 10.1002/pssc.201600164
       
  • Site selective doping of Zn for the p-type Cu(In,Ga)Se2 thin film for
           solar cell application
    • Authors: Sho Shirakata
      Abstract: Selective doping of a Zn impurity at the group III site in a Cu(In, Ga)Se2 (CIGS) film was performed by the doping of Zn at the first stage of the three-stage method. The p-type CIGS:Zn film was obtained, which is in contrast to the n-type CIGS:Zn film obtained by the Zn impurity doping at the second and third-stages. Based on excitation intensity dependence of photoluminescence (PL) at low-temperature, the change in the acceptor level was observed. The enhancement of carrier concentration as a result of Zn-doping in the p-type CIGS:Zn film was observed. The CIGS:Zn solar cells exhibited η of 14.5% and Voc of 0.658 V, which are higher than that of the corresponding solar cells using the undoped CIGS films
      PubDate: 2017-02-21T09:01:06.239851-05:
      DOI: 10.1002/pssc.201600170
       
  • Ionization effects on Cu(In, Ga)Se2 thin-film solar cells
    • Authors: Shirou Kawakita; Mitsuru Imaizumi, Shogo Ishizuka, Hajime Shibata, Shuichi Okuda
      Abstract: Cu (In, Ga) Se2 (CIGS) solar cells were irradiated with 60, 100, and 250 keV electrons to reveal the characteristics of radiation induced defects. Electrons with less than 200 keV energy cannot generate any displacement defects in CIGS materials. In addition, a low amount of the electrons can improve the roll-over behavior in current-voltage characteristics of CIGS solar cells. However, the deterioration of the electrical performance in CIGS solar cells irradiated with a high amount of electrons was observed. The deterioration rate on the cells irradiated with lower-energy electrons was higher than that induced by electrons with higher-energy. The degradation curve of JSC based on the ionizing dose estimated from the ionizing energy loss model does not depend on the energy of electrons. Therefore, it implies that the electrons can degrade CIGS solar cells due to the ionization effect.
      PubDate: 2017-02-21T08:56:10.496381-05:
      DOI: 10.1002/pssc.201600168
       
  • Phase transformation during simultaneous chalcogenization of CuIn(S,Se)2
           thin films using metalorganic sources
    • Authors: Ryuki Shoji; Yoshiki Kayama, Shigefusa F. Chichibu, Mutsumi Sugiyama
      Abstract: Simultaneous chalcogenization of CuIn(Sy,Se1-y)2 (CISSe) thin films has been demonstrated using organometallic sources such as diethylselenide [(C2H5)2Se] and ditertiarybutylsulfide [(t-C4H9)2S] to obtain homogeneous CISSe pseudobinary alloys with controlled amounts of Se and S species. Low-temperature chalcogenization at 300 °C resulted in the formation of Cu-SSe and In-SSe alloys diffused into the Cu11In9 metallic precursor. On the other hand, high-temperature chalcogenization produced CISSe thin films without additional phases. The obtained results can be used for elucidating the mechanism of simultaneous chalcogenization and development of high-performance and cost-effective commercial applications.
      PubDate: 2017-02-21T08:51:03.580264-05:
      DOI: 10.1002/pssc.201600159
       
  • Correcting for interference effects in the photoluminescence of
           Cu(In,Ga)Se2 thin films
    • Authors: Max Hilaire Wolter; Benjamin Bissig, Patrick Reinhard, Stephan Buecheler, Philip Jackson, Susanne Siebentritt
      Abstract: Photoluminescence (PL) measurements are performed on high-quality Cu(In,Ga)Se2 (CIGS) thin films with the intention of investigating their electronic structure. Due to the nature of the CIGS absorbers, notably their smooth surface and a graded band gap, the measured PL spectra are distorted by interference effects, limiting thus the information that one can gain. Here we show that, by varying the entrance angle of the laser light and the detection angle of the emitted PL, we are able to correct for interference effects. As a result, we receive interference-free PL spectra that enable us to determine quantities such as band gap energies and quasi-Fermi level splittings (QFLS). Furthermore, we show that it is possible to measure the QFLS even without correcting for interference effects and we compare the QFLS to the open circuit voltage for a particular sample.
      PubDate: 2017-02-21T08:46:04.895504-05:
      DOI: 10.1002/pssc.201600189
       
  • Activation energies of the InSi-Sii defect transitions obtained by carrier
           lifetime measurements
    • Authors: Kevin Lauer; Christian Möller, Christopher Teßmann, Dirk Schulze, Nikolay V. Abrosimov
      Abstract: Light-induced degradation (LID) is investigated in indium doped silicon by time and temperature dependent carrier lifetime measurements. Different transitions rates and activation energies were measured and interpreted within the ASi-Sii defect model. The case of indium acceptors is compared to the case of boron. Results are discussed within the frame of a comparison between ASi-Sii and ASi-Fei defects. It was found that reported dependencies of the transitions rates of the ASi-Sii defect on the hole density support defect models which are based on defect configuration changes. An in-depth explanation of the ASi-Sii defect model is given and possible errors related to the measurement of transition rates are discussed.
      PubDate: 2017-02-21T07:21:06.427731-05:
      DOI: 10.1002/pssc.201600033
       
  • Synthesis and characterization of Cu2ZnSnS4 bulk polycrystalline
    • Authors: Akiko Takeuchi; Koichiro Oishi, Naritoshi Aoyagi, Genki Nishida, Wataru Shimizu, Masato Nakagawa, Makoto Yamazaki, Hironori Katagiri
      Abstract: Cu2ZnSnS4 bulk polycrystalline were synthesized by pressureless sintering (PLS) method in vacuum and spark plasma sintering (SPS) method. It was confirmed that there were no the secondary phases in a sample sintered by SPS method at 750 °C from the results of powder X-ray diffraction (XRD) patterns and Rietveld refinement. The Raman spectrum of the sample showed the strongest peak at 338 cm−1 with a shoulder at 350–370 cm−1, and the weaker peaks at about 255 and 289 cm−1, which originated from Cu2ZnSnS4. The FWHM of the strongest peak of 7.4 cm−1 was narrower than other samples. The photoluminescence (PL) spectrum measured at 15 K were observed a broad emission band with the maximum at 1.26 eV. Also, the measured photoluminescence excitation (PLE) for the band-edge emission was originated the energy transfer from the band-to-band excitation.The obtained activation energy was 62 ± 9 meV.
      PubDate: 2017-02-21T05:41:09.416373-05:
      DOI: 10.1002/pssc.201600188
       
  • Morphology of multiple-selenized Cu2ZnSn(S,Se)4 absorber layers
    • Authors: Markus Neuwirth; Jasmin Seeger, Heinz Kalt, Michael Hetterich
      Abstract: The impact of multiple-selenization of wet-chemical precursors for kesterite-type Cu2ZnSn(S,Se)4 solar cells is reported. The absorber forms a compact layer with mostly big grains. Gaps between the big grains are filled with smaller grains. Also the absorber lacks the common trilayer/multilayer structure. As a result the layer thickness is more homogeneous and the morphology is more evened out. This is the basis for a more homogeneous device parameter distribution across large samples and a better reproducibility of CZTSSe solar cells.
      PubDate: 2017-02-21T05:37:23.794821-05:
      DOI: 10.1002/pssc.201600163
       
  • Improvement of photoelectric conversion efficiencies of dye-sensitized
           solar cells consisting of hemispherical TiO2 films
    • Authors: Shogo Izumi; Ayame Mizuno, Naoki Ohtani
      Abstract: To improve the photoelectric conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs), we fabricated hemispherical TiO2 films using a poly(dimethylsiloxane) mold and improved the light harvesting efficiency in DSSCs by a large light-scattering effect caused by the hemispherical structure. In addition, the amount of the adsorption density of the dye in TiO2 increased due to the larger surface area of the hemispherical structure. Consequently, the short-circuit current of DSSCs containing hemispherical TiO2 film increased even though the open-circuit voltage was not changed. As a result, the overall PCE value was improved to about 1.2 times larger than a DSSC containing a flat TiO2 film.In addition, polyethylene glycol-doping in TiO2 effectively improved the DSSC performance comprised of hemispherical TiO2 films.
      PubDate: 2017-02-21T05:36:50.700637-05:
      DOI: 10.1002/pssc.201600186
       
  • Chemical composition dependence of photoluminescence from Cu2ZnSnS4 thin
           films with potential fluctuations
    • Authors: Kunihiko Tanaka; Yoshiharu Takamatsu, Shinya Miura
      Abstract: The temperature and excitation intensity dependence of photoluminescence (PL) spectra from Cu2ZnSnS4 (CZTS) thin films with various chemical compositions was investigated. Three types of CZTS thin films were examined: Zn-rich (group A), Cu- and Zn-poor (group B), and Cu-rich and Zn-poor (group C). Groups A, B, and C gave PL spectra with peaks at around 1.2, 1.30, and 1.45 eV, respectively. These spectra exhibited large peak energy shifts to higher energies as the excitation intensity increased by more than 10 meV/decade due to potential fluctuations. The PL spectra of groups A and B can be attributed to band-to-impurity luminescence, and the origin of the spectra was found to be CuSn and VZn or [VZn + SnZn], respectively. The potential fluctuations were estimated from the lower energy side of the PL spectra, and the Cu-poor samples exhibited smaller potential fluctuations.
      PubDate: 2017-02-21T05:25:41.120508-05:
      DOI: 10.1002/pssc.201600138
       
  • Optical and magnetic properties of some XMnSb and Co2YZ Compounds: ab
           initio calculations
    • Authors: Selami Palaz; Husnu Koc, Haci Ozisik, Engin Deligoz, Amirullah M. Mamedov, Ekmel Ozbay
      Abstract: In present work, our research is mainly focused on the electronic structures, optical, and magnetic properties of XMnSb (X = Ni, Cu, Pd), Co2YZ (Y = Ti; Z=Si, Ge, Sn), and Co2YZ (Y =Mn; Z=Al, Ga, Si) Heusler compounds by using ab initio calculations within the generalized gradient approximation. The calculations are performed by using the Vienna ab initio simulation package based on the density functional theory. The band structure of these Heusler alloys for majority spin and minority spin were calculated and the majority spin states cross the Fermi level and thus have the metallic character, while the minority spin states open the band gaps around the Fermi level and thus have the narrow-band semiconducting nature. We also find that these Heusler compounds have the indirect band gaps in the minority spin channel. The real and imaginary parts of dielectric functions and hence the optical functions such as energy-loss function, the effective number of valance electrons and the effective optical dielectric constant for XMnSb and Co2YZ compounds were also calculated. In addition, we also show the variations of the total magnetic moment per f.u. and minority spin gap width of these compounds with optimized lattice constants: minority spin gap width decreases with increasing the lattice constants.
      PubDate: 2017-02-20T07:25:28.336014-05:
      DOI: 10.1002/pssc.201600182
       
  • Temperature dependence of low-frequency polarized Raman scattering spectra
           in TlInS2
    • Authors: Raul Paucar; YongGu Shim, Kojiro Mimura, Kazuki Wakita, Oktay Alekperov, Nazim Mamedov
      Abstract: In this work, we examined phase transitions in the layered ternary thallium chalcogenide TlInS2 by studying the temperature dependence of polarized Raman spectra with the aid of the Raman confocal microscope system. The Raman spectra were measured over the temperature range of 77–320 K (which includes the range of successive phase transitions) in the low-frequency region of 35–180 cm−1. The optical phonons that showed strong temperature dependence were identified as interlayer vibrations related to phase transitions, while the phonons that showed weak temperature dependence were identified as intralayer vibrations.
      PubDate: 2017-02-20T07:25:24.966134-05:
      DOI: 10.1002/pssc.201600214
       
  • Nanostructured CdS thin films deposited by spray pyrolysis method
    • Authors: A. Kerimova; E. Bagiyev, E. Aliyeva, A. Bayramov
      Abstract: Influence of solution pH on the structural and optical properties of CdS films deposited by conventional spray pyrolysis technique was studied. X-Ray Diffraction (XRD), Atomic Force Microscopy (AFM), Photoluminescence spectroscopy (PLS), and Spectroscopic Ellipsometry (SE) methods were used for the characterization of the deposited films. PL spectrum of the film deposited from the solution with pH = 10.2 shows broad-band PL emission located at 460 nm (2.7 eV), which can be attributed to the quantum size effect at grain sizes of
      PubDate: 2017-02-20T07:25:21.128414-05:
      DOI: 10.1002/pssc.201600144
       
  • AIBIIICVI2 (A = Cu, Ag; B = Ga, In; C = S, Se, Te) based
           photonic crystal superlattices: Optical properties
    • Authors: Sevket Simsek; Selami Palaz, Chingiz Akhundov, Amirullah M. Mamedov, Ekmel Ozbay
      Abstract: In this study, we present an investigation of the optical properties and band structures for the photonic structures based on AIBIIICVI2 with a Fibonacci sequence that can act as a multi-wavelength birefringent filter. The filtering wavelengths are analyzed by the indices concerning the quasi-periodicity of a Fibonacci sequence and the average lattice parameter. The transmittances of filtering wavelengths can be tuned by varying structure parameters such as the lengths of poled domains, filling factor, and dispersion relation. In our simulation, we employed the finite-difference time domain (FDTD) technique, which implies a solution from Maxwell equation.
      PubDate: 2017-02-20T07:20:39.538532-05:
      DOI: 10.1002/pssc.201600156
       
  • Annealing behaviour of photoluminescence spectra on Cu2ZnSnS4 single
           crystals
    • Authors: Satoru Seto; Hideaki Araki
      Abstract: We have measured photoluminescence (PL) spectra at 10 K for Cu2ZnSnS4 (CZTS) single crystals grown by the iodine transport method and explored the anneal changes of PL spectra under a Zn and S-saturation. All the crystals showed S- and Zn-poor composition, and nearly stoichiometric composition of Cu/(Zn + Sn). The observed PL spectra are divided into two groups; one is PL band with a peak at ∼1.3 eV (1.3-eV band), and another is PL band with a peak at ∼1.35 eV (1.35-eV band). It was found from SEM observations that the 1.35-eV band was observed in crystals with a mirror-like facet and, on the other hand, the 1.3-eV band was seen in the crystals with some small dark areas where the composition is Cu-poor. The Zn-saturated annealing at 600 °C caused the PL peak shift of ∼0.1 eV, from 1.295 to 1.185 eV. The S-saturated annealing at 550 °C caused a disappearance of PL emission. The implications of these annealing behaviour are discussed.
      PubDate: 2017-02-20T07:20:37.003253-05:
      DOI: 10.1002/pssc.201600158
       
  • The influence of phonon focusing on density of states and the Knudsen
           phonon gas flow in nanowires with different types of anisotropy of elastic
           energy
    • Authors: I. I. Kuleyev; S. M. Bakharev, I. G. Kuleyev, V. V. Ustinov
      Abstract: The influence of elastic energy anisotropy on phonon density of states (PDOS) and phonon mean free paths for acoustic modes in nanowires of cubic crystals with positive (Ge, Si, LiF, GaSb, GaAs, and GaN) and negative (CaF2, SrF2, and PbS) anisotropy of the second order elastic moduli has been investigated. The proposed calculation method allows one to determine angular distributions of the PDOS of fast and slow quasi-transverse modes in elastically anisotropic crystals for phonon focusing and defocusing regions. It has been shown that the PDOS and the phonon mean free paths in the cubic crystals take maximum and minimum values in the directions of phonon focusing and defocusing, respectively. Moreover, the anisotropy of the crystals differs qualitatively: the maxima values for the type-I crystals correspond to the minima for the type-II crystals. The heat flux directions that provide the maximum and minimum phonon thermal conductivity in the nanowires have been identified.
      PubDate: 2017-02-17T09:20:56.183386-05:
      DOI: 10.1002/pssc.201600263
       
  • Composition-ratio control of CZTS films deposited by PLD
    • Authors: Masahiro Kotani; Hiroki Miura, Yong-Gu Shim, Kazuki Wakita
      Abstract: The control of the composition of the CZTS polycrystals has been examined. CZTS poly-crystal, ZnS, and SnS powders were mixed for adjusting the composition and were sintered at temperature of 400 °C. We evaluated polycrystal with the molar ratios of Cu/(Zn+Sn) = 0.79, Zn/Sn = 1.04, and S/(Cu+Zn+Sn) = 0.95. Then, we prepared CZTS film by PLD method using the CZTS polycrystal as a target. Composition content of the film was also evaluated to be the molar ratios of Cu/(Zn+Sn) = 1.14, Zn/Sn = 1.04, and S/(Cu+Zn+Sn) = 0.69. The film indicats slightly Cu-rich, and S-poor compositions, and no change of Zn/Sn rate. Definitely, we successfully performed composition control and improvement of composition uniformity for polycrystals by using the source materials of CZTS, ZnS, and SnS. Additionally, we prepared homogeneous CZTS film with either a kesterite or a stannite structure by PLD method.
      PubDate: 2017-02-17T09:20:53.672332-05:
      DOI: 10.1002/pssc.201600212
       
  • Low band-gap CuIn(S,Se)2 thin film solar cells using molecular ink with
           9.5% efficiency
    • Authors: Yajie Wang; Xianzhong Lin, Lan Wang, Tristan Köhler, Martha Ch. Lux-Steiner, Reiner Klenk
      Abstract: Vacuum free, solution based routes to the preparation of chalcopyrite absorbers for solar cells promise options in device design and manufacturing that are not provided by the standard vacuum based approaches. In order to fully exploit these options, the precursor should contain neither nanoparticles nor hazardous chemicals, and it should be stable under ambient conditions. In this contribution we report on CuIn(S,Se)2 thin film preparation based on spin coating of an air stable molecular ink containing metal chlorides and thiourea in organic solvents. Several key parameters directly influencing the performance of the resulting solar cells have been identified. Wetting of the glass/Mo substrate has been adjusted by varying the concentration of ethylene glycol butyl ether in the ink. Before annealing in Ar/Se at atmospheric pressure, several cycles of ink deposition and drying can be used to increase the thickness of the precursor stack. Careful balancing of ink concentration, number of precursor deposition cycles, and annealing temperature profile will transform the multi-layer precursor into a sufficiently thick, continuous, large grained film as required for high quantum efficiency, and good red response of the cells. These optimizations aimed at high photo current have already led to an efficiency of 9.5%.
      PubDate: 2017-02-17T09:20:49.645152-05:
      DOI: 10.1002/pssc.201600169
       
  • Trusting STEM Experts and Authorities in the Age of “Fake
           News”
    • Authors: Raymond A. Heitger; Andrea R. Milner
      Pages: 89 - 91
      PubDate: 2017-04-19T05:05:54.976714-05:
      DOI: 10.1111/ssm.12216
       
  • Promoting Equitable Biology Lab Instruction by Engaging All Students in a
           Broad Range of Science Practices: An Exploratory Study
    • Authors: Anna M. Strimaitis; Sherry A. Southerland, Victor Sampson, Patrick Enderle, Jonathon Grooms
      Pages: 92 - 103
      Abstract: This study examines what students enrolled in the honors and general sections of a high school biology course offered at the same school learn when they have an opportunity to participate in a broad or narrow range of science practices during their laboratory experiences. The results of our analysis suggest that the students enrolled in the general sections of the course made similar or larger gains than the students enrolled in the honors section of the course in their abilities to plan and carry out an investigation, argue from evidence, and write a science-specific persuasive essay when these students had an opportunity to participate in a broad range of science practices. These findings suggest that laboratory experiences that give students an opportunity to participate in a broad range of science practices, although considered challenging by many teachers, have the potential to help all students become more proficient in science. The article concludes with a discussion of the implications of this study for classroom instruction and educational policy.
      PubDate: 2017-04-19T05:05:54.564556-05:
      DOI: 10.1111/ssm.12212
       
  • Strategies Toward the Inclusion of Environmental Education in Educator
           Preparation Programs: Results from a National Survey
    • Authors: Courtney Crim; Christine Moseley, Blanche Desjean-Perrotta
      Pages: 104 - 114
      Abstract: A national study was conducted to investigate the inclusion of environmental education (EE) into educator preparation programs across the United States. Responses from teacher educators in institutions of higher education indicated that the infusion of EE into educator preparation programs is limited and varies greatly across the nation. Findings also identified more barriers than supports for the inclusion of EE, and there exists minimal knowledge and use of the North American Association for Environmental Education Guidelines for the Preparation and Professional Development of Environmental Educators by teacher educators for programmatic development and assessment. The results also indicated that most state licensure programs have few or no requirements related to environmental education, and in the majority of educator preparation programs, environmental education is not institutionalized.
      PubDate: 2017-04-19T05:05:54.13473-05:0
      DOI: 10.1111/ssm.12211
       
  • Examining Secondary Mathematics Teachers' Opportunities to Develop
           Mathematically in Professional Learning Communities
    • Authors: Matthew P. Campbell; Hollylynne Stohl Lee
      Pages: 115 - 126
      Abstract: To make progress toward ambitious and equitable goals for students’ mathematical development, teachers need opportunities to develop specialized ways of knowing mathematics such as mathematical knowledge for teaching (MKT) for their work with students in the classroom. Professional learning communities (PLCs) are a common model used to support focused teacher collaboration and, in turn, foster teacher development, instructional improvement, and student outcomes. However, there is a lack of specificity in what is known about teachers’ work in PLCs and what teachers can gain from those experiences, despite broad claims of their benefit. We discuss an investigation of the work of secondary mathematics teachers in PLCs at two high schools to describe and explicate possible opportunities for teachers to develop the mathematical knowledge needed for the work of teaching and the ways in which these opportunities may be pursued or hindered. The findings show that, without pointed focus on mathematical content, opportunities to develop MKT can be rare, even among mathematics teachers. Two detailed images of teacher discussion are shared to highlight these claims. This article contributes to the ongoing discussion about the affordances and limitations of PLCs for mathematics teachers, considerations for their use, and how they can be supported.
      PubDate: 2017-04-19T05:05:55.187302-05:
      DOI: 10.1111/ssm.12209
       
  • The Influence of an Internet-Based Formative Assessment Tool on Primary
           Grades Students’ Number Sense Achievement
    • Authors: Drew Polly; Chuang Wang, Christie Martin, Richard G. Lambert, David K. Pugalee, Catharina Win Middleton
      Pages: 127 - 136
      Abstract: This study examined primary grades students’ achievement on number sense tasks administered through an Internet-based formative assessment tool, Assessing Math Concepts Anywhere. Data were analyzed from 2,357 students in teachers’ classrooms who had participated in a year-long professional development program on mathematics formative assessment, 1,427 students from teachers who had participated in the program in the year prior, and 9,783 students whose teachers had not participated at all. Analyses indicated that all students in the treatment group demonstrated growth, and that student achievement was influenced by the number of times the assessment was used to collect data and make instructional decisions. Further, there was a relationship between districts’ socioeconomic status and growth, meaning students from impoverished backgrounds grew more than their peers.
      PubDate: 2017-04-19T05:05:55.924072-05:
      DOI: 10.1111/ssm.12214
       
  • University−Urban High School Partnership: Math and Science
           Professional Learning Communities
    • Authors: mutindi ndunda; Meta Van Sickle, Lindsay Perry, Alison Capelloni
      Pages: 137 - 145
      Abstract: This study focused on science and math professional learning communities (PLCs) that were implemented through a university-urban high school partnership. These PLCs were part of mandated school-wide, content-based PLCs implemented as part of the reform efforts initiated in an urban school to address the school's failure to meet Adequate Yearly Progress (AYP) for four years consecutively and low graduation rate (less than 25%) for male students. The key issues were (a) students had continually earned low test scores; (b) there was continuous principal turnover; (c) faculty morale was at an all-time low, and the quality of teaching was very poor; and (d) the students were not effectively disciplined. The study examined the impact that university faculty-led mandated PLCs have on teachers' practices and students' learning and achievement. Analysis of data revealed practices that were effective in developing and implementing these successful math and science PLCs. Three themes emerged: ethics of care, teacher agency, and aesthetics of professional interactions. Each theme contained key features that appeared to contribute to the implementation of a successful PLC.
      PubDate: 2017-04-19T05:05:56.255852-05:
      DOI: 10.1111/ssm.12215
       
  • Students’ and Teachers’ Conceptual Metaphors for Mathematical
           Problem Solving
    • Authors: Sean P. Yee
      Pages: 146 - 157
      Abstract: Metaphors are regularly used by mathematics teachers to relate difficult or complex concepts in classrooms. A complex topic of concern in mathematics education, and most STEM-based education classes, is problem solving. This study identified how students and teachers contextualize mathematical problem solving through their choice of metaphors. Twenty-two high-school student and six teacher interviews demonstrated a rich foundation for these shared experiences by identifying the conceptual metaphors. This mixed-methods approach qualitatively identified conceptual metaphors via interpretive phenomenology and then quantitatively analyzed the frequency and popularity of the metaphors to explore whether a coherent metaphorical system exists with teachers and students. This study identified the existence of a set of metaphors that describe how multiple classrooms of geometry students and teachers make sense of mathematical problem solving. Moreover, this study determined that the most popular metaphors for problem solving were shared by both students and teachers. The existence of a coherent set of metaphors for problem solving creates a discursive space for teachers to converse with students about problem solving concretely. Moreover, the methodology provides a means to address other complex concepts in STEM education fields that revolve around experiential understanding.
      PubDate: 2017-04-19T05:05:56.557716-05:
      DOI: 10.1111/ssm.12217
       
  • Investigating Changes in Preservice Teachers’ Conceptions of STEM
           Education Following Video Analysis and Reflection
    • Authors: Jeffrey Radloff; Selcen Guzey
      Pages: 158 - 167
      Abstract: Nationally, there is a steadily increasing emphasis on the improvement of STEM education. This includes the integration of STEM subjects that have been traditionally taught separately, making it critical that prospective STEM educators are equipped to teach using integrated STEM approaches. Connected, an important challenge is providing preservice STEM teachers with experiences in which they can develop an understanding of how to optimize learning through integrated STEM instruction. A potentially effective way to foster this conceptualization is through video analysis of integrated STEM practices. To investigate this possibility, here we present a semester-long study focused on engaging preservice STEM teachers with observing, analyzing, and reflecting about instructional STEM practices through a video-based intervention. Findings suggest that viewing and reflecting on integrated STEM practices may enhance preservice STEM teachers' conceptions of integrated STEM approaches, representing a practical method of preservice STEM teacher professional development.
      PubDate: 2017-04-19T05:05:55.562661-05:
      DOI: 10.1111/ssm.12218
       
  • Problems Section
    • Authors: Ted Eisenberg
      Pages: 168 - 168
      PubDate: 2017-04-19T05:05:55.125242-05:
      DOI: 10.1111/ssm.12219
       
  • Problems Section
    • Authors: Ted Eisenberg
      Pages: 169 - 169
      PubDate: 2017-04-19T05:05:55.86923-05:0
      DOI: 10.1111/ssm.12220
       
 
 
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