bluuebunny/crossref_metadata_2025_split huggingface dataset:
Magneto‐optical Faraday effect in II–VI based semimagnetic semiconductor nanocrystals
Authors: Savchuk Andriy I. , Fediv Volodymyr I. , Stolyarchuk Ihor D. , Savchuk Tetyana A. , Perrone Alessio 
Published: March 2006

AbstractDifferent physical and chemical methods were used to prepare II–VI based semimagnetic semiconductor nanocrystals. A study of magneto‐optical Faraday effect in the nanocrystals revealed its enhancement as compared with bulk crystals. It is explained in framework of increase in the oscillator strength of exciton transitions and to the difference between these strengths in an external magnetic field. It was observed almost linear dependence of the Faraday rotation as function of magnetic field strength for nanocrystals at liquid helium temperature in contrast to the dependence with saturation in bulk case and changes in process of a transition of the semimagnetic nanocrystals from the paramagnetic state to a spin glass state. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Colloidal nanocrystals integrated in epitaxial nanostructures: structural and optical properties
Authors: Arens Ch. , Roussau N. , Schikora D. , Lischka K. , Schöps O. , Herz E. , Woggon U. , Litvinov D. , Gerthsen D. , Artemyev M. V. 
Published: March 2006

AbstractUsing the well established MBE process, we introduced colloidal nanocrystals (NCs) into monocrystalline semiconductor layers. CdSe nanorods (NRs) and CdSe(ZnS) core‐shell nanodots (NDs) with radii R between 2 and 4 nm on a ZnSe surface are capped by thin (d ∼ 2R ) and thick (d > 2R ) MBE‐grown ZnSe layers of a thickness d . This new growth technique does not rely on strain like the Stranski‐Krastanow growth of CdSe/ZnSe quantum dot layers, and thus offers additional degrees of freedom for choosing the NC composition, shape and size. In‐ and ex‐ situ characterisations of the samples are showing a ZnSe cap layer of high crystalline quality. After the growth of the cap layer the dots preserve their shape and emission spectrum. High‐resolution transmission electron microscope images show the direct connection of the NCs crystal lattice to the crystal lattices of the ZnSe buffer and the epitaxially grown cap layer. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of electric field on fine structure of exciton complexes in CdTe/ZnTe self‐assembled quantum dot
Authors: Kowalik K. , Kudelski A. , Golnik A. , Suffczyński J. , Krebs O. , Voisin P. , Karczewski G. , Kossut J. , Gaj J. A. 
Published: March 2006

AbstractWe report on micro‐photoluminescence (µ‐PL) measurements of CdTe/ZnTe self‐assembled quantum dots. Jumps in the line positions are observed and attributed to fluctuations of local electrostatic environment. We find that fine structures of exciton, biexciton and charged exciton originating from the same QD are correlated with line positions. We observe stronger influence of the field on the excitonic states of lower binding energy. The local field likely originates from charges localized at defects in the close vicinity of the QD, and correlations indicate that its direction is not completely random. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Acceptor doping in ZnO with group‐I elements
Authors: Sann Joachim , Hofstaetter Albrecht , Pfisterer Daniel , Stehr Jan , Meyer Bruno K. 
Published: March 2006

AbstractWe study the interaction of hydrogen donors and Lithium acceptors in bulk ZnO by electron paramagnetic resonance and photoluminescence. With increasing diffusion temperature the number of hydrogen donors increases whereas the number of deep Li acceptors decreases. In the temperature range between 450 and 600 °C a shallow Li related acceptor is formed. The very same defect is found in Li diffused ZnO, and in epitaxial ZnO thin films by in‐situ doping with Li. We suggest a tentative model for the shallow Li acceptor whereby hydrogen would be an essential part of the defect core. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Majority‐carrier mobilities in undoped andn‐type doped ZnO epitaxial layers
Authors: Makino T. , Segawa Y. , Tsukazaki A. , Ohtomo A. , Kawasaki M. 
Published: March 2006

AbstractTransparent and conductive ZnO:Ga thin films are prepared by laser molecular‐beam epitaxy. Their electron properties were investigated by the temperature‐dependent Hall‐effect technique. The 300‐K carrier concentration and mobility were aboutns∼ 1016cm–3and 440 cm2/V s, respectively. In the experimental ‘mobility vs concentration’ curve, unusual phenomenon was observed, i.e., mobilities atns∼ 5 × 1018cm–3are significantly smaller than those at higher densities above ∼1020cm–3. Several types of scattering centers including ionized donors and oxygen traps are considered to account for the observed dependence of the Hall mobility on carrier concentration. The scattering mechanism is explained in terms of inter‐grain potential barriers and charged impurities. A comparison between theoretical results and experimental data is made. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Oxygen in sputter‐deposited ZnTe thin films
Authors: Merita S. , Krämer T. , Mogwitz B. , Franz B. , Polity A. , Meyer B. K. 
Published: March 2006

AbstractBandgap‐bowing has been observed in many of the zinc‐group‐VI compounds, when the anion is substituted with an isovalent element. Recently new results on the ZnO1–xSx and ZnO1–xSex system have been presented, but so far only one report on ZnO1–xTex is known. We examine the possibility of substituting tellurium by oxygen in sputter‐deposited polycrystalline ZnTe thin‐films and the effects on bandgap energy and crystal structure. A first approximation of the bowing curve with a lower limit of the bowing parameter of 2.7 eV is performed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth and characterization of ZnO nanostructures by remote plasma‐enhanced metal‐organic chemical vapor deposition
Authors: Zhang G. , Nakamura A. , Nakagawa S. , Aoki T. , Temmyo J. 
Published: March 2006

AbstractRemote plasma‐enhanced metal‐organic chemical vapor deposition was employed to grow ZnO nanostructure. The position of molecular O nozzle tip was optimized to improve the quality of the ZnO nanostructures based on photoluminescence measurement. The influence of the substrate orientation (a, c, and R‐plane sapphire) and growth temperature on the surface morphology for well‐assembled ZnO nanostructure was investigated. It is found that the surface morphologies appear as island and needle‐like crystals at low growth temperature (360 °C). With increasing temperature, faceted terraces are observed on c and R‐plane substrate and faceted needle‐like crystals were formed on a‐plane substrate. Regular terrace surface is achieved on R‐plane substrate and the step distance is increased with increasing growth temperature. The epitaxial relationship and optical property of the ZnO nanostructures were characterized by X‐ray diffraction and photoluminescence. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Luminescence and structural properties of defects in ion implanted ZnO
Authors: Monteiro T. , Soares M. J. , Neves A. J. , Carmo M. C. , Peres M. , Cruz A. , Alves E. , Wahl U. , Rita E. , Munoz‐SanJose V. , Zuniga‐Perez J. 
Published: March 2006

AbstractZnO substrates and films were intentionally implanted with rare earth and transition metal ions. The influence of the implantation and subsequent air thermal annealing treatments on the structural and optical properties of ZnO samples were studied by using Rutherford backscattering spectrometry and low temperature photoluminescence techniques. Intraionic Tm‐related emission was observed for bulk and ZnO films. Similarly, Eu and Tb‐doped ZnO films follow the same trend observed in bulk samples. No intraionic related emission was observed for Eu‐doped samples even being the ion in Zn sites and for the Tb‐doped samples ion segregation was observed for thermal annealing temperatures above 800 °C. For the Mn‐doped ZnO bulk samples the lattice recovery follows the same trend to that one observed for the Fe‐doped samples, starting near 800 °C being fully recovered at 1050 °C. Although Fe3+ was observed no intraionic Mn‐related emission was detected under the used conditions. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ultraviolet electroluminescence of ZnO based heterojunction light emitting diode
Authors: Jiao S. J. , Lu Y. M. , Shen D. Z. , Zhang Z. Z. , Li B. H. , Zhang J. Y. , Yao B. , Liu Y. C. , Fan X. W. 
Published: March 2006

AbstractZnO/GaN p‐i‐n heterojunctions light emitting diodes were fabricated by plasma‐assisted molecular beam epitaxy. We make use of high resistivity of nitrogen doped ZnO to fabricate n‐ZnO/i‐ZnO/p‐GaN heterojunction light emitting diode. The emission of i‐ZnO was obtained due to the limitation effect of i‐ZnO on electrons and holes. Moreover, n‐ZnO/i‐MgO/p‐GaN heterojunction light emitting diode was also fabricated. The limitation effect on electrons is increased in this heterojunction. The bright ultraviolet electroluminescence at 382 nm originating from the ZnO layer was observed in the room temperature electroluminescence spectrum. We hope to realize the stimulated emission of ZnO using these heterojunctions by the improvement of crystal quality and the optimization of device structure. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Temperature dependent band gap and homogeneous line broadening of the exciton emission in ZnO
Authors: Hauschild R. , Priller H. , Decker M. , Brückner J. , Kalt H. , Klingshirn C. 
Published: March 2006

AbstractWe report on an experimental study of the temperature dependent band gap shift and the homogeneous line broadening of the excitonic luminescence in ZnO. This data is derived from photoluminescence (PL) measurements at temperatures from T = 10–290 K and fitting the PL line shape with a theoretical model for the exciton line and its LO‐phonon replica. Additionally, transmission measurements are utilized to extend the data of the temperature dependent band gap into the temperature range from 290 K up to 800 K. The experimentally determined shift is compared with one that is obtained numerically from the phonon density of states, the pressure dependent band gap, the thermal expansion coefficient and the bulk modulus with only a single fit parameter. The interaction of excitons with phonons leads to a homogeneous broadening of the excitonic emission which reaches values of 40 meV at room temperature. This mechanism results in a substantially increased threshold for stimulated emission from every process involving excitons. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The exciton polariton model and the diffusion of excitons in ZnO analyzed by time‐dependent photoluminescence spectroscopy
Authors: Hauschild R. , Priller H. , Decker M. , Kalt H. , Klingshirn C. 
Published: March 2006

AbstractWe investigate the lineshape of the zero‐phonon luminescence of the A‐exciton polariton and of the LO‐phonon replicas in ZnO and their dynamics. The lineshape verifies details of the A‐exciton polariton model and confirms the inverted band structure (AΓ7, BΓ9, CΓ7). The dynamics give information on relaxation, diffusion and recombination processes. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of MBE grown ZnO on GaAs(111) substrates
Authors: Matsumoto Takashi , Nishimura Kazuto , Nishii Akito , Ota Atsuya , Nabetani Yoichi , Kato Takamasa 
Published: March 2006

AbstractZnO epitaxial layers grown on GaAs(111)B substrates by plasma assisted MBE with different O/Zn flux ratios are characterized by photoluminescence (PL), X‐ray diffraction (XRD) θ –2θ scan, ω scan, and reciprocal lattice mapping. Low temperature PL spectra are dominated by bound exciton bands at 3.360 eV and 3.330 eV. The 3.360 eV band is strong in samples grown under Zn‐rich cindition and the 3.330 eV band is strong in samples grown under O‐rich condition. The epitaxial orientation relationship is ZnO(0001)//GaAs(111) and ZnO[11‐20]//GaAs [01‐1] irrespective of the O/Zn flux ratio. The ZnO c‐axis tilts by 0.2° ∼ 0.3° from the GaAs [111] axis toward 〈1‐10〉 or 〈2‐1‐1〉 direction. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
p‐type ZnO and ZnMnO by oxidation of Zn(Mn)Te films
Authors: Przeździecka E. , Kamińska E. , Dynowska E. , Dobrowolski W. , Jakieła R. , Kłopotowski Ł. , Sawicki M. , Kiecana M. , Kossut J. 
Published: March 2006

AbstractZnO and ZnMnO doped with N and/or As layers were fabricated by thermal oxidation of ZnTe and ZnMnTe grown by MBE on different substrates. The Hall measurements demonstrated p ‐type conductivity with the hole concentration of ∼5 · 1019 cm–3 for ZnO:As and ZnO:As:N on GaAs substrates and ∼ 6 · 1017 cm–3 for ZnTe:N on ZnTe substrates. Optical study showed meaningful differences between samples with different acceptor, grown on different substrates. Magnetoptical experiment demonstration Zeeman splitting in ZnMnO samples. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A study of ZnMnO as a material for magneto‐ and spin‐electronics
Authors: Mofor A. C. , Reuss F. , El‐Shaer A. , Ahlers H. , Siegner U. , Bakin A. , Limmer W. , Eisenmenger J. , Mueller Th. , Ziemann P. , Waag A. 
Published: March 2006

AbstractDue to the large spin moment exhibited by the transition metal Mn, it is being extensively investigated as a candidate element for producing ferromagnetic ZnO for magnetoelectronic and spintronic applications. However, ferromagnetism in ZnMnO is being controversially discussed. We review our investigations on epitaxially grown ZnMnO layers and present findings on Mn‐implanted ZnO layers. The results of our investigations on the magnetic properties of the fabricated ZnMnO show that it is not trivial to confirm ferromagnetism in ZnMnO grown on sapphire because of ferromagnetic signal produced by the substrate. After a deduction of the substrate contribution to magnetisation data, both epitaxially doped ZnO layers and Mn‐implanted bulk and epitaxial layers show paramagnetic behaviour. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Aqueous chemical growth and patterning of ZnO nanopillars on different substrate materials
Authors: Kreye M. , Postels B. , Wehmann H.‐H. , Fuhrmann D. , Hangleiter A. , Waag A. 
Published: March 2006

AbstractAqueous chemical growth (ACG) is a low‐temperature approach that is only weakly influenced by the substrate and allows for the growth of ZnO nanopillars on various substrates. ACG is an efficient way to generate wafer‐scale and densely packed arrays of ZnO nanopillars even on polymer materials. Photoluminescence (PL) characterisation clearly shows a comparatively strong band‐edge luminescence even at room temperature that is accompanied with a rather weak visible luminescence in the yellow / orange spectral range. We introduce a rather simple postgrowth lithographic technique. Patterning of ZnO nanopillars even on layered conducting and flexible substrate materials using ACG as a low‐temperature growth technique is demonstrated. The economical potential for future applications and devices using ZnO nanopillar arrays is discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Epitaxial growth of nonpolar ZnO by MOVPE
Authors: Moriyama Takumi , Fujita Shizuo 
Published: March 2006

AbstractEpitaxial growth characteristics of nonpolar (M‐ and A‐plane) ZnO on M‐ and R‐plane sapphire substrates were investigated. The growth of ZnO along the c‐axis direction, which aligns parallel to [2‐1‐10] and [01‐11] directions of M‐ and R‐plane sapphire, is achieved under lower growth temperature and/or VI/II ratio, and this growth direction is preferable for smooth lateral growth. Increasing the growth time, the surface becomes rough on M‐plane, while is significantly improved on R‐plane sapphire. The growth behaviour on R‐plane sapphire can be attributed to the small lattice mismatching along the ZnO c‐axis direction and enhanced lateral growth characteristics. From photoluminescence measurements, the appearance of peak at 3.383 eV, which is at higher energy compared to well‐known impurity‐ and/or defect‐related peaks, at 10 K suggests the residual strain in ZnO films. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Impurity segregation in CdZnTe by photoluminescence mapping
Authors: Horodyský P. , Franc J. , Grill R. , Hlídek P. , Höschl P. 
Published: March 2006

AbstractLow temperature photoluminescence (PL) mapping is employed to retrospectively monitor the processes taking place during crystal growth. Time evolution of the solidification of the melt is derived from zinc concentration map, which is calculated from energy gap obtained from free‐exciton (FX) reabsorption in the PL spectra. Investigation of the distribution of PL intensities of specific defects shows that at least relative segregation coefficients can be calculated. This method has a potential application in preparation and characterization of pure and homogeneous CdZnTe wafers and also in identification of unknown defects. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of BexCd1–xSe alloys by contactless electroreflectance
Authors: Huang P. J. , Sitarek P. , Huang Y. S. , Maksimov O. , Tamargo M. C. , Firszt F. , Męczyńska H. 
Published: March 2006

AbstractWe present characterization of a Bridgman‐grown wurtzite‐type Be0.075Cd0.925Se mixed crystal and a zinc‐blende Be0.09Cd0.91Se epilayer grown by MBE on InP substrate using contactless electroreflectance in the temperature range of 15 to 400 K. Various interband transitions, originating from the band edge and spin‐orbit splitting critical points, of the samples have been observed. The parameters that describe the temperature dependence of the fundamental and spin split‐off band gaps are evaluated. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth and optical properties of graded band‐gap CdHgTe and CdMnHgTe structures
Authors: Zakharuk Z. I. , Rybak E. V. , Rarenko H. I. , Koval'chuk M. L. , Tal'yanski E. B. , Fochuk P. M. 
Published: March 2006

AbstractThe present paper deals with the technology of CdTe, Cd1–yMnyTe substrates and CdxHg1–xTe, CdxMnyHg1–x–yTe graded band‐gap structures (GBS). Investigation results of structural quality, IR‐radiation transmission and optical density of the GBS are represented. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Determination of the thermophysical parameters of Zn1–xBexSe mixed crystals by means of photothermal techniques
Authors: Zakrzewski J. , Maliński M. , Pawlak M. , Firszt F. , Łęgowski S. , Męczyńska H. , Strzałkowski K. 
Published: March 2006

AbstractThis paper presents the results of the studies of a thermal diffusivity of a series of mixed Zn1–xBexSe crystals by means of the piezoelectric technique. For determination of a thermal diffusivity of samples the method based on the measurement of the phase of the piezoelectric signal, in the rear configuration, as a function of a frequency of modulation was chosen. This method enabled analysis of the influence of Be concentration and the process of annealing of crystals on the values of their thermal diffusivities. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of growth temperature conditions on electric properties of CdTe:Ge crystals
Authors: Nikonyuk Ye. , Zakharuk Z. , Rarenko A. , Rybak Ye. , Kuchma M. , Shlyakhoviy Vya. , Fochuk P. 
Published: March 2006

AbstractA model of Ge incorporation into CdTe lattice based on the analysis of temperature influence of post‐growth crystal annealing on CdTe:Ge electric properties is proposed. Ge impurity is mainly placed in Te sublattice in crystals fast cooled from high temperatures. GeTe defect is an acceptor defining the electric and photoelectric properties at T ≤ 290 K. GeCd donors and deep (GeCdVCd)/ acceptors are generated in lesser amount. Long‐term ingot thermal treatment at T < 1090 K causes germanium atom relocalization chiefly into cadmium sublattice. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
MOVPE growth optimisation of CdTe epitaxial layers for p‐i ‐n diode X‐ray detector fabrication
Authors: Traversa M. , Marzo F. , Prete P. , Tapfer L. , Cappello A. , Lovergine N. , Mancini A. M. 
Published: March 2006

AbstractWe report on the atmospheric pressure metalorganic vapour phase epitaxy of both nominally undoped and iodine (I) donor doped CdTe layers on high resistivity (111)B CdTe substrates, as a preliminary step towards the fabrication of p‐i‐n diode X‐ray detectors. CdTe epilayers were grown at 330 °C after in‐situ H2 heat treatment of the substrate for surface oxide removal. We show that the homoepitaxy of CdTe critically depends on in‐situ heat treatment temperature (TA), best epilayer morphology and reduced surface roughness being obtained for TA = 350 °C. Secondary ion mass spectrometry analysis of I‐doped samples shows good dopant incorporation, which increases for Te:Cd precursor molar flow ratios in the vapour below unity. I‐doped samples grown under the latter conditions have room temperature resistivity three orders of magnitude lower than for undoped layers and electron concentrations ∼1016 cm–3. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
HgTe segregation process in HgCdTe studied by E1 reflectance peak positions
Authors: Pociask M. , Pukowska B. , Kisiel A. , Sheregii E. M. , Berchenko N. N. 
Published: March 2006

AbstractLong term diffusion processes near the Cd1–xHgxTe surface influences the electronic structure as is shown in this paper. Measurements of reflectivity and surface characterisation by means of scanning electron microscopy (SEM) were performed for samples with x = 0.4 and x = 0.62. The optical results were compared with the reflectivity spectra obtained 22 years ago using the same samples. We discuss the observed dramatic changes in the optical changes upon the SEM and comparative analysis. E 1 + Δ reflectance peak position corresponds to binary HgTe in both recently investigated samples. That method reflection is sensitive to no more than 120 µm the upper depth of investigated samples. The measurements of the E 1 reflectance peak has proven to be a helpful and convenient tool for mercury telluride segregation near the HgCdTe surface and may be used to determine composition and age of HgCdTe. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
CdTe native point defects under Cd saturation
Authors: Fochuk Petro , Panchuk Oleh 
Published: March 2006

AbstractThe high temperature point defect (PD) structure of undoped CdTe under well‐defined Cd vapour pressure was studied. The single crystals were grown by different techniques (vapor phase, THM, classical and high pressure Bridgman methods). By using in situ Hall effect measurements it was established that the native double charged PDs $ {\rm Cr}^{2+}_{\rm i} $ and $ {\rm V}^{2+}_{\rm Te} $ are the dominant donors at t > 500 °C. The formation enthalpies of these PDs were determined from [e–] temperature dependencies (Δ$ {\rm H}_{ {\rm V}^{2+}_{\rm Te} } $=1.3 eV; Δ$ {\rm H}_{ {\rm Cr}^{2+}_{\rm i} } $=2.5 eV). The PD structure modelling demonstrated satisfactory agreement with experimental results both for temperature and Cd vapor pressure dependencies. It showed that $ {\rm V}^{2+}_{\rm Te} $ dominates at low temperatures and $ {\rm Cr}^{2+}_{\rm i} $ begins to prevail at t > 930 K. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photoluminescence characterization of cubic CdS epilayers
Authors: Yu Young‐Moon , Choi Yong Dae 
Published: March 2006

AbstractCubic CdS epilayers were grown on (100) GaAs substrates by hot‐wall epitaxy and their photoluminescence (PL) characteristics were studied. A heavy hole free exciton peak was observed even at room temperature and a light hole free exciton peak was observed at 30–100 K. The temperature dependence of the free excitonic emission intensity was demonstrated using a two‐step quenching mechanism. The excitation power dependence showed that the PL peak at 2.367 eV is due to the free‐to‐bound transition. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)