bluuebunny/crossref_metadata_2025 huggingface dataset:
Urbach's tail in the absorption spectra of CuIn5Se8 and CuGa3Se5 single crystals
Authors: Arushanov E. , Levcenko S. , Syrbu N. N. , Nateprov A. , Tezlevan V. , Merino J. M. , León M.
Published: August 2006

Optical absorption spectra of CuIn5Se8 and CuGa3Se5 single crystals grown by chemical vapour transport were investigated in the range of 10–300 K. The logarithmic variation of the absorption coefficient with photon energy observed in both compounds just below the fundamental absorption edge shows a linear dependence at different temperatures in agreement with Urbach's rule. The Urbach energy as well as the energy associated with the electron/exciton–phonon interaction related to Urbach's tail are estimated. The latter is found to be around 52 (41) meV for CuIn5Se8 (CuGa3Se5). It is lower than that {58 (60) meV} earlier reported for these compounds and confirms higher structural quality of samples studied. It is shown that the temperature of the Urbach energy can be modeled in CuIn5Se8 (CuGa3Se5) as an Einstein oscillator with the Einstein temperature equal to 222 (266) K. It is found that in the material studied structural disorder is dominant at 300 K. It may be caused by some compositional deviation from stoichiometry. The latter was observed in the studied samples by using the EDAX method. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fundamental absorption edge in CuIn5Se8 and CuGa3Se5 single crystals
Authors: León M. , Levcenko S. , Syrbu N. N. , Nateprov A. , Tezlevan V. , Merino J. M. , Arushanov E.
Published: August 2006

Optical absorption spectra of CuIn5Se8 and CuGa3Se5 single crystals have been investigated. The energy gap E g for CuIn5Se8 (CuGa3Se5) was found to be varied from 1.27 (1.79) to 1.21 (1.71) eV in the temperature range between 10 and 300 K. The temperature dependence of E g was studied by means of the Einstein model and the Pässler model. The Einstein temperature {222 (267) K}, the Debye temperature {310 (380) K}, a dimensionless constant related to the electron–phonon coupling {1.62 (2.65)} as well as an effective energy {20 (24) meV} and a cut‐off phonon energy {35 (39) meV} have been estimated for CuIn5Se8 (CuGa3Se5). It was also found that the major contribution of phonons to the shift of E g versus temperature in CuIn5Se8 (CuGa3Se5) is mainly from optical phonons. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic properties investigations of Mn substituted ABX2 chalcopyrites
Authors: Schorr S. , Hoehne R. , Spemann D. , Doering Th. , Korzun B. V.
Published: August 2006

Powder samples of Mn2x Cu1–x InS2 (x = 0.03) and Mn2x Cu1–x AlS2 (x = 0.01) were studied by X‐ray diffraction and magnetization measurements. With regard to the variation of structural parameters with Mn substitution it is evident, that Mn2+ is built into the chalcopyrit structure. For both samples the field dependence of the magnetization is characterized by a dominating linear behaviour with a positive and strongly temperature dependent susceptibility as expected for paramagnets. After subtraction of the linear part the almost no temperature dependent curves are s‐formed, ferromagnetic‐like loops with no hysteresis. In the sample with BIII = Al a magnetic transition is observed at about 48 K. We conclude that the dominating paramagnetism is superimposed by a small ferromagnetic part and speculate that the effect is of intrinsic nature. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic properties of intermetallic compounds La(Ni,Co,Cu)3
Authors: Tazuke Y. , Tanikawa H. , Okano A. , Miyaji T.
Published: August 2006

LaNi3 exhibited a metallic antiferromagnetic property with T N = 30 K. La(Ni1–x Cox )3 with x = 0.01, 0.03 and 0.05 exhibited ferromagnetic properties, T C increasing linearly with increasing x . La(Ni1–2z Coz Cuz )3 with z = 0.015 exhibited a ferromagnetic property with a small T C. A La(Ni1–y Cuy )3 sample with y = 0.01 exhibited a Pauli‐paramagnetic property; those with y = 0.02, 0.03 and 0.04 exhibited gradual metamagnetic behavior and that with y = 0.05 exhibited a ferromagnetic property. The gradual metamagnetic M –H variations are numerically simulated by using Landau‐type free energies. The results suggest that the gradual metamagnetic behavior occurs from an antiferromagnetic state to a ferromagnetic one. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Positive temperature variation of the bandgap energy in AgGaSe2
Authors: Ozaki Shunji , Sasaki Manabu , Adachi Sadao
Published: August 2006

Optical‐absorption, photoreflectance (PR), and photoluminescence spectra have been measured on the ternary chalcopyrite semiconductor AgGaSe2 at T = 15–300 K. The direct‐bandgap energy E 0A of AgGaSe2 determined from the optical absorption measurements shows unusual temperature dependence at low temperatures. The resultant coefficient ∂E 0A/∂T is positive at T < 70 K and negative above 70 K. The PR spectra also indicate positive temperature dependence of the bandgap energies, E 0A and E 0B, at T < 70 K. These results have been successfully explained by taking into account the negative lattice thermal expansion at low temperatures. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The optimization of CdSe nanoparticles synthesis in the apoferritin cavity
Authors: Iwahori Kenji , Morioka Takuya , Yamashita Ichiro
Published: August 2006

Cadmium selenide nanoparticles (CdSe NPs) were synthesized in the cavity of the cage‐shaped protein, apoferritin, by designing a slow chemical reaction, which employs tetraamminecadmium ion and selenourea. The ammonia water concentration and solution pH were optimized and the suppression of the formation of selenium oxide was also studied by deoxydation of the reaction solution. At the concentration of 5 mM ammonia water and at pH 9.5, with N2 gas bubbling, the core formation ratio (CFR) of CdSe NPs reached 75% and yield of protein ratio (YPR) was as high as 98%. N2 gas bubbling of reaction solution was found to be critical for the high CFR and high YPR of the CdSe NPs synthesis in apoferritin cavity. Using this optimized conditions, high quality CdSe NPs were obtained by the bio‐template, apoferritin protein method. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermoelectric properties of Zn1–xMxSb2O6 (M = Al, In)
Authors: Katsui A. , Matsushita H.
Published: August 2006

In order to develop thermoelectric oxides, ZnSb2O6 with a high figure of merit and high reliability, Zn1–x Mx Sb2O6 (M = Al, In) ceramics have been prepared by using a solid phase reaction method. The phase identification during synthesis was investigated by using X‐ray diffraction measurement. The thermoelectric properties such as the Seebeck coefficient, electrical conductivity in the region from a room temperature to about 900 K were evaluated after heating for 2 h at 1073 K in air. The power factor of Zn0.95Al0.05Sb2O6 was the highest among all samples at x = 0 to 0.1 over a wide range of temperature. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structural properties of 2(ZnSe)x(CuInSe2)1–x crystals and thin films in the two‐phase region
Authors: Gremenok V. F. , Schorr S. , Wagner G. , Bente K. , Zaretskaya E. P. , Siarheyeva V. M.
Published: August 2006

This paper presents the results of the structural properties of 2(ZnSe)x (CuInSe2)1–x (ZCIS) crystals and thin films in the range 0.10 ≤ x ≤ 0.36. In this composition range the tetragonal phase (domains) within their surrounding cubic matrix coexists. The crystals were prepared by the solid‐state reaction of the elements, followed by controlled cooling at different rates. ZCIS thin films were prepared by selenization of sequentally evaporated ZnSe/(Cu + In) precursors. The selenization procedure was carried at various temperatures ranging from 300 to 540 °C. The morphology of the tetragonal domains and their orientation relationship to the cubic matrix were determined by selected area diffraction (SAD), transmission electron microscopy (TEM) and high resolution TEM (HRTEM). The results reveal that the compositions of domains and matrix within the thin films agree with those measured for polycrystalline bulk material, i.e. the extension of the two‐phase range mentioned above could be confirmed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
First‐principles study of nitridoaluminosilicate CaAlSiN3
Authors: Mikami Masayoshi , Uheda Kyota , Kijima Naoto
Published: August 2006

Atomic and electronic structure of nitridoaluminosilicate CaAlSiN3 (Cmc 21, No. 36), a distorted AlN‐based wurtzite superstructure with Al and Si disordered on 8b site and Ca occupying 4a site, has been investigated by first‐principles pseudopotential method based on density functional theory. The random distribution of Al/Si atoms is treated in two ways: (1) virtual crystal approximation (VCA) with a mixed Al/Si pseudopotential, (2) several assumptions of Al/Si distribution order in the primitive unit cell. Geometry optimization based on the aliovalent VCA reproduces the experimental orthorhombic structure as well as the bond lengths. The calculations of Al/Si‐ordered models lead to monoclinic structures that appear sufficiently close to the experimental structure, with the averages of the optimized Al–N/Si–N bond lengths corresponding to the experimental ones. Relative stability among the Al/Si‐ordered models appears consistent with Pauling's second crystal rule. The random Al/Si distribution leading to the experimental determination of the system as Cmc 21 can be explained by crystal symmetry, energetics among the ordered models, and configurational entropy effect. The electronic structure based on the VCA appears similar with those of the Al/Si‐ordered models. All the band structures indicate that the system has indirect band gap. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of Cu(In,Ga) (S,Se)2 thin films prepared by sequential evaporation from ternary compounds
Authors: Yamaguchi T. , Hatori M. , Niiyama S. , Miyake Y.
Published: August 2006

Cu(In,Ga) (S,Se)2 thin films were fabricated by sequential evaporation from CuGaSe2, CuInSe2 and In2S3 compounds for photovoltaic device applications. From XRF analysis, the Cu:(In + Ga):(S + Se) atomic ratio in all thin films was approximately 1:1:2. As the [In2S3]/([CuGaSe2] + [CuInSe2]) mole ratio in the evaporating materials increased, the S/(S + Se) atomic ratio in the thin films increased from 0 to 0.16 determined by XRF and to 0.43 by EPMA. XRD studies demonstrated that the prepared thin films had a chalcopyrite Cu(In,Ga) (S,Se)2 structure and the preferred orientation to the 112 plane. The SEM images demonstrated that Cu(In,Ga) (S,Se)2 thin films had large and columnar grains. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of water vapor introduction during Cu(In1–xGax)Se2deposition on thin film properties and solar cell performance
Authors: Ishizuka S. , Sakurai K. , Yamada A. , Matsubara K. , Shibata H. , Yonemura M. , Nakamura S. , Nakanishi H. , Kojima T. , Niki S.
Published: August 2006

The effects of water vapor introduction during the growth of Cu(In1–xGax)Se2, specifically CuInSe2(CISe), Cu(In,Ga)Se2(CIGSe), and CuGaSe2(CGSe) thin films were studied. We have developed thus far a novel technique to improve CIGSe (x∼ 0.5) cell performance by means of water vapor introduction during CIGSe deposition. In this study, we have examined the effectiveness of water vapor introduction for otherx‐compositions (CISe and CGSe). Variations in the electrical properties observed in CIGSe (x∼ 0.5), that is, increasing hole density and conductivity with water vapor introduction, were also observed in CISe and CGSe. Water vapor introduction affected solar cell performance as well; open circuit voltages, short circuit current densities, and efficiencies were improved. The improvements in cell performance are thought to be related to annihilation of donor defects arising from Se‐vacancies by incorporation of oxygen from the water vapor. In addition to this, the sodium content in the CIGSe layers was found to depend on the partial pressure of water vapor during deposition. This result suggests that the improvement mechanism is also related with the so‐called ‘Na‐effects'. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Prediction of solid‐state reactions for the formation of the chalcopyrites CuInS2, CuGaS2, CuAlS2 and CuAlSe2 starting from binary compounds
Authors: Hergert Frank , Jost Stefan , Hock Rainer , Purwins Michael
Published: August 2006

In a recent work we have described the importance of epitaxy for the formation of CuInSe2 and CuGaSe2. In this article we identify epitaxial relations between binary selenide compounds serving as educts for the formation of the title compounds. From this we derive a set of possible chemical reaction equations for those solid‐state reactions, which will preferably take place. By exploiting these reactions the chalcopyrite compounds can be synthesised smartly in short annealing processes at relatively low temperatures. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical and magnetic properties of c ‐oriented ZnCoO films
Authors: Zhou Huijuan , Knies Christoph , Hofmann Detlev M. , Stehr Jan , Volbers Niklas , Meyer Bruno K. , Chen Limei , Klar Peter , Heimbrodt Wolfram
Published: August 2006

We investigated ZnCoO thin films prepared via sol‐gel methods and dip‐coating techniques. The Co concentrations range from 0.5% to 5%. The films show the wurtzite crystal structure of ZnO and are highly c ‐axis oriented grown on the quartz substrates. They have a typical grain size of 20 to 50 nm and a thickness between 300 nm and 1 µm. The fine structures of the Co (3d7) internal absorptions are well resolved, all zero‐phonon lines (ZPL) and phonon replica related to the 4T1(F) → 4A2 are observed, demonstrating the good crystalline quality of the layers and the incorporation of the Co2+ on Zn2+ lattice sites. The films show paramagnetic behaviour. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Luminescence properties of YAl3(BO3)4 substituted with Sc3+ ions
Authors: Yoshida Hisashi , Fujikawa Kazuhiro , Toyoshima Hiroaki , Watanabe Shinta , Ogasawara Kazuyoshi
Published: August 2006

Luminescence properties of YAl3(BO3)4 (YAB) and Y1–x Scx Al3(BO3)4 (YSAB) have been investigated under vacuum ultraviolet (VUV) light excitation. In YAB, two emission bands peaking at 3.2 and 3.9 eV are observed. On the other hand, there appear two emission bands at 3.2 eV and about 4.1 eV in YSAB. The origins of these emission bands are ascribed to two kinds of BO3 atomic groups. We suppose that the shift of the peak around 4 eV band is deeply related to the fact that one kind of BO3 atomic groups of YSAB are significantly distorted compared to that of YAB. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Band structure and dielectric function of TlInTe2
Authors: Wakita K. , Shim Y. , Orudzhev G. , Mamedov N. , Hashimzade F.
Published: August 2006

The band structure of ternary chain TlInTe2 was calculated with allowance for non‐locality of ionic pseudo‐potentials. The dielectric function, as well as the effective masses of holes and electrons, the effective number of valence electrons, and the function of characteristic losses were determined. The results of comparison between the calculated dielectric function and the one obtained ellipsometrically in the spectral range from 0.85 to 6 eV are quite favorable. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
InxGa1–xAs single crystal growth by dispersing local misfit stress
Authors: Miyata Hiroaki , Adachi Satoshi , Ogata Yasuyuki , Tsuru Tetsuya , Muramatsu Yuji , Kinoshita Kyoichi , Odawara Osamu , Yoda Shinichi
Published: August 2006

We succeeded in growing a single crystal by dispersing the misfit stress around an initial solid‐liquid interface in In0.3Ga0.7As ternary bulk crystal growth. We gradually increased concentration of indium arsenide so that the local misfit stress could be smaller than critical resolved shear stress. The traveling lqiuidus‐zone (TLZ) method was applied for growing crystals. To grow a single In0.3Ga0.7As crystal, an In0.1Ga0.9As single crystal region was grown first on a GaAs seed. Then the concentration of indium arsenide was gradually increased up to In0.3Ga0.7As by lowering temperature at the interface. As a result, In0.3Ga0.7As single crystals of 2 mm in thickness, 10 mm in width and more than 25 mm in length were successfully obtained. Mean value of full width half maximum (FWHM) of X‐ray rocking curves in the In0.3Ga0.7As grown crystal was 0.116°. It is not small enough but it will be improved by increasing compositional homogeneity. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
P‐type conductive CuYO2 phosphor Co‐doped with Eu, Tb or Tm rare‐earth cation and Ca acceptor cation
Authors: Tsuboi Nozomu , Hoshino Takanobu , Kobayashi Satoshi , Kato Keizo , Kaneko Futao
Published: August 2006

In delafossite‐type oxides of CuRx Y1–x O2 (R = Eu, Tb or Tm) and CuRx Cay Y1–x –y O2 prepared through the conventional solid state reactions, the lattice constant dependence on the composition implies doping with the Tb3+, Eu3+ and Tm3+ cations on the Y3+ site. Noticeable sharp emission lines due to the f–f transitions of Eu3+, Tb3+ and Tm3+ are observed at room temperature in CuRx Cay Y1–x –y O2 as well as CuRx Y1–x O2. P‐type conductivity of CuRx Cay Y1–x –y O2 increases with increasing Ca concentration, indicating the increase of hole concentration caused by doping with Ca2+ acceptor cation on the Y3+ site. These results indicate the controllability of the luminescence and conductivity in delafossite‐type CuYO2 oxides by co‐doping with Eu, Tb or Tm rare‐earth cation and Ca acceptor cation on the Y3+ sites. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ferromagnetism in short‐period GaGdN/GaN superlattices grown by RF‐MBE
Authors: Choi S. W. , Zhou Y. K. , Kim M. S. , Kimura S. , Emura S. , Hasegawa S. , Asahi H.
Published: August 2006

GaGdN single layers and GaGdN/GaN short‐period superlattices (SLs) were grown on Al2O3(0001) substrates by radio frequency molecular beam epitaxy (RF‐MBE) and their magnetic and structural properties were investigated. Both types of samples exhibited ferromagnetic characteristics at both 10 and 300 K. Clear hysteresis and clear saturation were observed in the magnetization vs. magnetic field curves at both temperatures. The GaGdN/GaN short‐period SL samples showed significantly higher saturation magnetization than the GaGdN single layer samples. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Surface potential of chalcopyrite films measured by KPFM
Authors: Sadewasser S.
Published: August 2006

Atomic force microscopy is widely used to characterize the surface topography of a variety of samples. Kelvin probe force microscopy (KPFM) additionally allows determining images of the surface potential with nanometer resolution. The KPFM technique will be introduced and studies on surfaces of chalcopyrite semiconductors for solar cell absorbers will be presented. It is shown that operation in ultra‐high vacuum (UHV) is required to obtain meaningful work function values. Different methods for obtaining UHV‐clean surfaces are presented and KPFM studies on these are compared. Surfaces where prepared by in‐vacuum deposition, inert‐gas transfer, in‐vacuum decapping of a protective Se‐cap and a peel‐off method. Finally, a sputter‐annealing cycle also allows to obtain well‐suited surfaces for KPFM studies. Employing KPFM, variations in the local surface potential at grain boundaries of polycrystalline CuGaSe2 films were observed. A potential drop indicates the presence of charged defects at grain boundaries. Furthermore, different electronic activity was found for different grain boundaries, as concluded from studies under illumination. Using laterally resolved surface photovoltage, a Cu2–x Se impurity phase could be observed in CuGaSe2. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermoelectric properties of Fe‐doped Ca3Co2O6 single crystals with a pseudo‐one‐dimensional structure
Authors: Takahashi Junichi , Shimada Masahiko , Yamane Hisanori
Published: August 2006

Columnar single crystals of Fe‐doped Ca3Co2O6 with a pseudo‐one‐dimensional structure were synthesized by a flux method using K2CO3. Seebeck coefficient (S ) and electrical resistivity (ρ ) of an Fe‐doped Ca3Co2O6 single crystal along the elongated direction were measured in the temperature range from room temperature to over 1000 K in air. The single crystal showed p‐type semiconducting behaviour and the Fe doping augmented the S, ρ, and the power factor (S 2ρ –1). (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
MBE growth and properties of GaMnAs with high level of Zn acceptor incorporation
Authors: Asubar J. T. , Sato S. , Jinbo Y. , Uchitomi N.
Published: August 2006

GaMnAs epitaxial films with high Zn incorporation level were prepared by molecular beam epitaxy. Our results indicate an increasing hole concentration p accompanied by decreasing Curie temperature T C and transition towards metallic behavior of the epitaxial film properties with increasing level of Zn incorporation. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of Cu(In,Ga)Se2 thin films by time‐resolved photoluminescence
Authors: Shimakawa Shin‐ichi , Kitani Kimihiko , Hayashi Shigeo , Satoh Takuya , Hashimoto Yasuhiro , Takahashi Yasuhito , Negami Takayuki
Published: August 2006

Cu(In,Ga)Se2(CIGS) films were characterized by time‐resolved photoluminescence (TRPL) on performances of solar cells. Open circuit voltage and efficiency of the solar cells increased with increasing the TRPL lifetimes meausred at 77 K and room temperature. The results at 77 K show that the CIGS films with the TRPL lifetime of over 30 ns achieve an efficiency of exceeding 15% of the solar cells. Dependence of the TRPL lifetime on the photon energy was observed on the CIGS film with high efficiency at both temperatures. This dependence is discussed on localization of exited carriers and non‐radiative centres. The minority carrier lifetime which dominates the solar cell performances can be characterized by not only the TRPL lifetime but its dependence on the photon energy. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A comparative study of thermoelectric properties in (Pr,Y)Ba2Cu3O7 and PrBa2Cu3O7–Ag percolative systems
Authors: Mori Natsuki , Okano Hiroyuki , Furuya Akio
Published: August 2006

Measurements of the temperature‐dependent thermoelectric power S (T ) and resistivity ρ (T ) were performed to characterize two kinds of polycrystalline systems (Pr1–x Yx )Ba2Cu3O7 and Ag‐doped PrBa2Cu3O7, each of which exhibits percolative behaviour at a certain doping level. At room temperature, Jonker plots of the thermoelectric power against logarithm of the conductivity in both systems show a similar tendency that two different fitting lines are intercrossed at the percolation thresholds. The ρ (T ) behaviour below 100 K in each system with low dopant content obeys the variable‐range‐hopping conduction. Variations of S (T ) in both systems could be reconciled with the Boson–Fermion theory based on the resonating‐valence‐bond model with reasonable dependences of fitting parameters upon doping. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
MBE growth and TEM analyses in Mn–Ge–P compounds
Authors: Minami K. , Bouravleuv A. D. , Sato Y. , Ishibashi T. , Kuwano N. , Sato K.
Published: August 2006

Ternary MnGeP2 thin films have been grown on GaAs substrate using MBE technique. The films prepared at 435 °C showed ferromagnetism at room temperature. TEM observation revealed a segregation of MnP tile‐shaped grains. Films grown at 585 °C showed no trace of ferromagnetic secondary phases in XRD profiles and were found to show no ferromagnetic behaviors down to 77 K. This is consistent with theoretical prediction that stoichiometric MnGeP2 is antiferromagnetic, and our previous experimental results that the MnGeP2 layer existing at the top of ZnGeP2:Mn has no contribution to ferromagnetic properties of the latter. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical properties of TlInGaAs/TlInP/InP laser diodes
Authors: Fujiwara A. , Matsumoto T. , Krishnamurthy D. , Hasegawa S. , Asahi H.
Published: August 2006

TlInGaAs/TlInP/InP separate confinement heterostructures (SCHs) were grown by gas‐source molecular‐beam epitaxy and metal stripe laser diodes (LDs) were fabricated. Temperature variation of electroluminescence peak wavelength was as small as 0.06 nm/K due to the reduced temperature variation of band gap energy of TlInGaAs. Pulsed laser operation was achieved at 77–297 K. Threshold current density for the TlInGaAs/TlInP/InP SCH LD (0.6 kA/cm2 at 77 K) was smaller than that for the TlInGaAs/InP double heterostructure LD (0.8 kA/cm2 at 77 K), which is due to the increased refractive index for TlInP and the improved optical confinement. Temperature variation of main peak wavelength in the lasing spectra was as small as 0.07 nm/K, which is much smaller than those for the InGaAsP/InP Fabry–Perot LDs (0.4 nm/K) and distributed feed‐back LDs (0.1 nm/K). (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ab initio study of spinodal decomposition in (Zn, Cr)Te
Authors: Fukushima T. , Sato K. , Katayama‐Yoshida H. , Dederichs P. H.
Published: August 2006

The spinodal decomposition in (Zn, Cr)Te is simulated by using first principles calculations and Monte Carlo simulation. It is found that the chemical pair interaction between Cr atoms in (Zn, Cr)Te is attractive interaction and leads to spinodal decomposition. Curie temperatures in decomposed situation are estimated by the random phase approximation with taking the magnetic percolation effect into account. This decomposed phase makes the random pattern of high concentration regions which connect each other and have possibility to realize high Curie temperature. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of co‐doping of Ce3+ and alkaline metals on the photoluminescence in CaGa2S4 and SrGa2S4 hosts
Authors: Hidaka Chiharu , Miura Kazutaka , Oikawa Shinya , Takizawa Takeo
Published: August 2006

Ce3+ doped alkaline‐earth thiogallates represented as MIIGa2S4 (MII = Ca, Sr, Ba) are known as blue phosphors with high brightness and good purity of color. However the Ce concentration is limited below about 1 mol% in the process of the single crystal growth, presumably due to the charge imbalance of the dopant. Here in order to increase Ce3+ concentration, alkaline metals and Ce ions are codoped in the alkaline earth thiogallates and the effect of co‐doping on the photoluminescence is studied. More than 15 mol% Ce doping is achieved, and PL intensity in Na codoped Ca and Sr thiogallates becomes three and five times stronger than that of the only Ce3+ 1 mol% doping case, respectively. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Composition‐dependent behavior of Co(d7) optical transitions in Cd1–xCoxGa2S4 mixed crystals
Authors: Kim Young‐San , Park Hyun , Hyun Seung‐Cheol , Jin Moon‐Seog , Park Gye‐Choon , Kim Chang‐Dae , Jang Kiwan , Choi In‐Hwan , Kim Wha‐Tek
Published: August 2006

The optical transitions due to the cobalt transition metal impurity centers with composition x in Cd1–k Cox Ga2S4 mixed crystals were investigated by optical absorption spectroscopy. The optical absorption spectra showed three crystal‐field transitions between the ground state 4A2(4F) and the excited states 4T2(4F), 4T1(4F), and 4T1(4P) of substitutional Co2+ ions that were similar for all the investigated compositions. The crystal‐field parameter (Dq ) and the Racah parameter (B ) obtained from the observed absorption bands showed a composition dependence such that the Dq parameter increases; on the other hand, the B parameter decreases with increasing composition x, which implies that the Racah parameter (B ) depends strongly on the host crystal. Also, the total splitting between the highest and the lowest states of the 4T1(4P) state split due to spin–orbit coupling showed a composition dependence varying from 1576 cm–1 to 1232 cm–1 with increasing x . The spin–orbit coupling parameter γ varied from 394 cm–1 to 308 cm–1 with composition x . (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Low‐temperature wet chemical syntheses of nanocrystal phosphors with surface modification and their characterization
Authors: Isobe T.
Published: August 2006

We report photoluminescence (PL) and chemical properties of nanocrystal phosphors synthesized by low‐temperature wet chemical processing. YAG:Ce3+ nanocrystals were synthesized from aluminium isopropoxide, yttrium(III) acetate tetrahydrate and cerium(III) acetate monohydrate in the mixed solvent of 1,4‐butylene glycol and polyethylene glycol (PEG) in an autoclave at 300 °C to discuss roles of PEG surface modification on PL enhancement. We also discuss roles of a lauryl phosphate surface modifier on PL enhancement in two systems of LaPO4:Ce3+,Tb3+ nanocrystals synthesized at 140 °C in the autoclave and ZnS:Mn2+ nanocrystals synthesized by a reverse micelle method. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical characterization of CuInSe2 single crystals prepared by travelling heater method
Authors: Shirakata Sho , Miyake Hideto
Published: August 2006

Temperature dependences of photoreflectance (PR), photoluminescence (PL), and time‐resolved PL have been determined for bulk CuInSe2 single crystals grown by a travelling heater method. The PR spectra exhibited excitonic AB (1.04 eV) and C (1.27 eV) transitions, and their temperature dependence has been determined. PL exhibited an exciton peak at 1.036 eV at 8 K. Other PL peaks at 0.99 eV and 1.01 eV quenched at 40 K and 100 K, respectively. For 50–200 K, exciton PL exhibited thermal quenching with an activation energy (ΔE ) of 16 meV. Further increase in temperature (200 K < T < 300 K) leads to a strong broadening of PL, an abrupt PL energy decrease, and a negative thermal quenching (ΔE = –89 meV). With increase in temperature, the PL lifetime decreases for 80 K < T < 160 K, while it increases for 180 K < T < 300 K. These results suggest a change of the recombination mechanism at about 200 K. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth of high‐quality CuGaSe2 thin films using ionized Ga precursor
Authors: Miyazaki H. , Miyake T. , Chiba Y. , Yamada A. , Konagai M.
Published: August 2006

We have fabricated high‐quality CuGaSe2 thin films using ionized Ga precursors. The films were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy. The grain size and the crystallinity of CuGaSe2 films using ionized Ga precursors were larger than those of the films using unionized Ga precursors. It was found from the experiments that the migration energy of Ga precursors played an important role in the crystal growth for high‐quality CuGaSe2 films. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Doping induced structural changes in CuInS2 thin films and the effects on optical and electrical properties
Authors: Enzenhofer T. , Unold T. , Schock H. W.
Published: August 2006

The systematical study of the admixture of small amounts of group‐II elements (<1 at%) with Raman and photoluminescence spectroscopy reveal an increase in the Raman response of the cation‐anion vibration modes accompanied with the generation of a new broad emission band at 1.35 eV in the PL spectra of the chalcopyrite system Cu–In–S. Intensity dependent PL measurements indicate that this emission band is strongly influenced by a high degree of compensation in contrast to the commonly found donor‐acceptor pair recombination in undoped CuInS2 samples. From temperature dependent conductivity measurements an increased concentration of acceptors and donors in doped CuInS2 thin films is found. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Epitaxial growth and optical investigations of ZnTeO alloys
Authors: Nabetani Y. , Okuno T. , Aoki K. , Kato T. , Matsumoto T. , Hirai T.
Published: August 2006

We have grown zincblende‐structured ZnTeO alloy semiconductors on GaAs substrates by molecular beam epitaxy using RF‐excited O. O concentrations measured by secondary ion mass spectroscopy were found to increase with the increase of O2 flow rate supplied during the growth, while the change of lattice constant measured by X‐ray diffraction does not follow Vegard's law. It is considered that the O atoms are incorporated not only into group‐VI sites but also as interstitials. Formation of other compounds such as ZnTeO3, Zn2Te3O8, and TeO2 was not detected. Optical reflectance spectroscopy revealed the increase of the band‐gap energy with O concentration that can be interpreted as the repulsive interaction between the energy states originated in the localized states of O and the conduction‐band edge of host ZnTe. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Low temperature growth of transparent conducting ZnO films by plasma assisted deposition
Authors: Nishii A. , Uehara T. , Sakano T. , Nabetani Y. , Akitsu T. , Kato T. , Matsumoto T. , Hagihara S. , Abe O. , Hiraki S. , Fujikawa Y.
Published: August 2006

Transparent conducting ZnO films are deposited by plasma assisted deposition technique on glass and plastic substrates at temperatures 60 ∼ 300 °C using metallic Zn, metallic Ga and plasma‐excited oxygen as source materials. Deposited films were characterized by X‐ray diffraction (XRD), optical transmittance in the visible and infrared region, Raman scattering, and Hall measurements. Film properties are controlled by substrate temperature, oxygen source/zinc source supply ratio, and Ga doping. 350 nm‐thick Ga‐doped ZnO films deposited at 290 °C showed low resistivity (∼2 × 10–4 Ω cm) and high transmittance in the visible region (∼85%). (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fabrication of Cu(In,Ga)Se2 thin films by a combination of mechanochemical and screen‐printing/sintering processes
Authors: Wada T. , Matsuo Y. , Nomura S. , Nakamura Y. , Miyamura A. , Chiba Y. , Yamada A. , Konagai M.
Published: August 2006

We prepared fine Cu(In,Ga)Se2 (CIGS) powder suitable for screen printing using a mechanochemical process. Particulate precursors were deposited in a thin layer by a screen‐printing technique, the remaining organic solvent was removed from the screen‐printed CIGS film and finally the porous precursor layer was sintered into a dense polycrystalline film by atmospheric‐pressure firing. The crystal structure of the film was analyzed by X‐ray diffraction and the microstructure was observed in a SEM. The thickness of the film was 5–10 μm with a grain size of about 2 μm. The films were also observed in a TEM. The grain size of the as‐prepared powder was less than 1 μm; however, it enlarged to 2–3 μm after firing at 575 °C under a Se ambient. Preliminary CIGS solar cells with our standard Al grid/B‐doped ZnO/i‐ZnO/ CdS/CIGS/Mo/soda‐lime glass structure were fabricated. An efficiency of 2.7%, a V oc of 0.325 V, a J sc of 28.3 mA/cm2 and a FF of 0.295 was obtained. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Non‐stoichiometry and properties of SnTe〈Cd〉 semiconducting phase of variable composition
Authors: Rogacheva E. I. , Nashchekina O. N.
Published: August 2006

It was established that the dependences of microhardness, hole concentration, electrical conductivity, and the Seebeck coefficient on composition in the Sn0.984Te–Cd and Sn0.984Te–CdTe solid solutions based on non‐stoichiometric tin telluride exhibit non‐monotonic behavior. The effects connected with the interaction between intrinsic and impurity defects and with critical phenomena accompanying a transition to the impurity continuum were isolated. The results obtained in this work represent another evidence for our proposition about the universal character of critical phenomena accompanying the transition from an impurity discontinuum to an impurity continuum in solid solutions. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Synthesis and impurity doping of GaN powders by the two‐stage vapor‐phase method for phosphor applications
Authors: Hara K. , Okuyama E. , Yonemura A. , Uchida T. , Okamoto N.
Published: August 2006

The analysis of particle formation and the doping of luminescent impurities during the two‐stage vapor‐phase synthesis of GaN powder were carried. GaN particles were grown very fast during the second stage of this method, and the increment in particle size was larger for higher reaction temperature in the region between 800 and 1000 °C. The analysis on the behaviour of particle growth based on the reaction kinetics suggested that the growth almost finishes in a few seconds with an extremely high rate at the early stage at 1000 °C, whereas the growth lasts with relatively low rates for a time longer than the actual growth duration for the case of lower temperature synthesis. GaN powders doped with various impurity atoms were synthesized by supplying impurity sources with GaCl during the second stage. The samples doped with Zn, Mg and Tb showed emissions characteristic for each doped impurity. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Third‐harmonic generation in a quantum well with adjustable asymmetry under an electric field
Authors: Yıldırım H. , Tomak M.
Published: August 2006

We study third‐harmonic generation in a quantum well represented by a Pöschl–Teller confining potential under an applied electric field. This potential is well suited for such purposes as it can easily become asymmetrical by a correct choice of its parameter set. We calculate the third harmonic generation within the density matrix formalism. Numerical results for a typical GaAs quantum well are presented. We investigate the third‐harmonic generation for several values of asymmetry parameters under small electric fields. It is found to be enhanced with the increasing electric field. While the resulting third‐harmonic generation peak is promising it is still quite smaller than that observed in similar quantum well systems. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Confinement of magnetoexcitons in GaAs quantum well with a superconducting disk on top of the well
Authors: Koinov Z. G. , Collins G. , Mirassou M.
Published: August 2006

We study the confinement of magnetoexcitons in quantum wells in the presence of a strong external homogeneous magnetic field and a cylindrical symmetric inhomogeneous magnetic field created by a superconducting disk, placed on the top of the well. We calculate numerically the trapping energy and the corresponding center‐of‐mass wave function of magnetoexcitons in a GaAs single quantum well. The calculations clearly indicate the formation of bound exciton states with nonzero values for the center‐of‐mass exciton wave function only in a sufficiently small area. This effect of exciton trapping can be used to design new functional nanoelectronic devices. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Theoretical study of pressure shift for R line of Cr3+ ion in lanthanum lutetium gallium garnet
Authors: Zhou Yi‐Yang
Published: August 2006

The pressure shifts for R line (2E → 4A2 transition) of Cr3+ luminescence spectra in lanthanum lutetium gallium garnet (LLGG:La3Lu2Ga3O12) are studied by a molecular orbital model. The obtained pressure dependence of R line is in qualitative agreement with experiments, this is an attempt to overcome the theoretical difficulty for the R line pressure shifts of Cr3+:LLGG within the crystal‐field approximation. The anticrossing model and the assumed nephelauxetic effect for Cr3+ ions in gallium garnets are mentioned. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Gas phase interaction of zinc ion with purine and pyrimidine DNA and RNA bases
Authors: Marino T. , Mazzuca D. , Toscano M. , Russo N. , Grand A.
Published: August 2006

The interaction of uracil, thymine, cytosine, adenine, and guanine with zinc ion was studied at the density functional B3LYP/6‐311+G(2df,2p) level. Different binding sites allowing both mono‐metal and bi‐metal coordination were considered for the different low‐lying tautomers of nucleic acid bases. Zinc ion forms stable compounds with all nucleobases. Except for cytosine, mono‐coordination appears to be less favored than bi‐coordination in the other pyrimidines. Instead, the preferred sites in the case of adenine and guanine were found to be the N7 and O6 and N7 and N6 pairs of atoms, respectively. Zinc ion affinity was evaluated for all the complexes and compared with values previously obtained for other transition metal ions. In the present case, the following order of metal ion affinity (MIA) was found: G>A>C>T>U. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007
On the Reconstruction of Diagonal Elements of Density Matrix of Quantum Optical States by on/off Detectors
Authors: Brida Giorgio , Genovese Marco , Gramegna Marco , Paris Matteo G. A. , Predazzi E. , Cagliero E.
Published: August 2006

We discuss a scheme for reconstructing experimentally the diagonal elements of a density matrix representing quantum optical state. Applications to PDC heralded photons, multi-thermal and attenuated coherent states are illustrated and discussed in more detail.
Tomography in Abstract Hilbert Spaces
Authors: Man'ko V. I. , Marmo G. , Simoni A. , Ventriglia F.
Published: August 2006

The tomographic description of a quantum state is formulated in an abstract infinite-dimensional Hilbert space framework, the space of the Hilbert-Schmidt linear operators, with trace formula as scalar product. Resolutions of the unity, written in terms of over-complete sets of rank-one projectors and of associated Gram-Schmidt operators taking into account their non-orthogonality, are then used to reconstruct a quantum state from its tomograms. Examples of well known tomographic descriptions illustrate the exposed theory.
Quantum Correlations in a Generalized Spin Star System
Authors: Palumbo Francesca , Napoli Anna , Messina Antonio
Published: August 2006

The problem of detecting quantum signatures in the correlations formed in dynamical evolution of quantum bipartite systems receives a lot of attention in current literature. Generally speaking, the occurrence of correlations between two observables of a system does not necessarily reflect nonclassical behaviour. In this paper, the exact dynamics of a pair of uncoupled spins 1/2 interacting with a common spin 1/2 bath is investigated. Starting from a separable initial condition, the ability of the system to develop purely quantum correlations is brought to light. Physical interpretation of the concurrence function as well as a suggestion on how to measure it are given.
What Constitutes a Good Childbirth? A Qualitative Study of Pregnant Finnish Women
Authors: Melender Hanna‐Leena
Published: August 2006

The aim of this study was to describe pregnant Finnish women's perceptions of a good childbirth. Data were collected through semistructured interviews in maternity health care clinics and maternity hospitals. Data interpretation was based on content analysis. A purposive sample of 24 pregnant women aged 19 to 45, half of them expecting their first child, were interviewed. Five main issues were seen by informants as important in the course of childbirth: 1) unhurried atmosphere, 2) normality, 3) reasonable duration of labor, 4) security, and 5) control. Participants did not expect much from their birth companions, although some mentioned various tasks for them. The three main issues considered important for the role of staff were the professionals'1) personal characteristics, 2) attitudes toward the childbearing woman, and 3) way they acted. The question about the physical environment was found quite irrelevant by some women, and only a few had special wishes related to the birthing environment. None of the participants voiced opposition to obstetric interventions, but some were willing to avoid them if possible. Informed consent for interventions was seen as very important. These results suggest that health care providers are challenged to provide individualized care for every woman.
Attitudes, Perceived Ability, and Knowledge About Depression Screening: A Survey of Certified Nurse‐Midwives/Certified Midwives
Authors: Sanders Lorraine B.
Published: August 2006

A survey of certified nurse‐midwives/certified midwives (CNMs/CMs) attending the 2004 American College of Nurse‐Midwives (ACNM) annual meeting was undertaken to describe the depression screening practices of CNMs/CMs and to examine factors associated with depression screening. A relationship was found between attitude, perceived ability, knowledge, education level, and depression screening, with attitude and perceived ability having the strongest positive relationship to screening. Attitude, perceived ability, knowledge, and education accounted for 20% of the variance in depression screening conducted by CNMs/CMs. These findings suggest that the management of depression is not fully integrated into the practice of many CNMs/CMs. Further research is needed to assess screening methods, interventions for the treatment of depression, and evaluation of institutional barriers to depression screening.
An Exploration of Negative Thoughts as a Normal Phenomenon After Childbirth
Authors: Hall Pauline L. , Wittkowski Anja
Published: August 2006

The period following the birth of a child brings many transitions into a woman's life, which can effect major psychological and social changes, including feelings of loss. If new mothers experience negative thoughts at this time, when societal expectations are of happiness, this may lead to feelings of unacceptability and guilt. This study aimed to investigate the prevalence of negative thoughts after childbirth in nondepressed mothers. Following the identification of negative thoughts experienced by women who had suffered postnatal depression, a quantitative survey was conducted, which asked nondepressed mothers to indicate how often they experienced the negative thoughts or images identified by depressed mothers. One hundred and fifty‐eight returned questionnaire packs were included in the analyses. The 158 nondepressed mothers acknowledged experiencing all but one of the 54 negative cognitions. Negative cognitions usually associated with postnatal depression are also experienced by mothers who are not considered depressed. This information provides evidence for reassuring new mothers that negative thoughts after childbirth are common. This, in turn, may help to reduce feelings of guilt associated with experiencing negative thoughts in the postpartum period.
Conference Proceedings: Abstracts From Research Forums Presented at the ACNM 51st Annual Meeting 2006
Authors: Hanson Lisa
Published: August 2006

The American College of Nurse‐Midwives Division of Research, International Committee, and the Journal of Midwifery and Women's Health are pleased to present the abstracts from the 2006 Research Forum podium presentations. The podium presentations were selected in a blinded peer review process in the winter of 2005, and presented at the Annual Meeting in Salt Lake City, Utah. Only abstracts of completed research were eligible for publication. The abstracts presented here demonstrate the breadth and quality of research being conducted about midwifery and women's health by midwifery researchers and our colleagues.

Holly Kennedy, Chair,

Division of Research

Lisa Hanson,

Division of Research

Linda Walsh,

International Committee
Tenderly Lift Me: Nurses Honored, Celebrated, and Remembered
Authors: Battalora Elizabeth
Published: August 2006

Tenderly Lift Me: Nurses Honored, Celebrated, and Remembered, Jeanne Bryner, 2004, softcover, 181 pp $18
Lasers: The Perioperative Challenge
Authors: Freeman Karen
Published: August 2006

Lasers: The Perioperative Challenge, Kay A. Ball, third edition, 2004, softcover, 475 pp $40 (member)/$50 (nonmember)
Writing Research: Transforming Data into Text
Authors: Osborne Sonya
Published: August 2006

Writing Research: Transforming Data into Text, Judith Clare, Helen Hamilton, 2003, paperback, 222 pp $29.95
Keeping the People Who Keep You in Business: 24 Ways to Hang On to Your Most Valuable Talent
Authors: Phillips Susan S.
Published: August 2006

Keeping the People Who Keep You in Business: 24 Ways to Hang On to Your Most Valuable Talent, Leigh Branham, 2000, hardcover, 338 pp $27.95
Telecommunications for Nurses: Providing Successful Distance Education and Telehealth
Authors: Lagueux Donna
Published: August 2006

Telecommunications for Nurses: Providing Successful Distance Education and Telehealth, Myrna L. Armstrong, Shari Frueh, second edition, 2002, hardcover, 304 pages $44.95