bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rotation‐domains suppression and polarity control of ZnO epilayers grown on skillfully treated c‐Al2O3 surfaces
Authors: Yoshikawa Akihiko , Wang Xinqiang , Tomita Yosuke , Roh Ok‐Hwan , Iwaki Hiroyuki , Ishitani Yoshihiro 
Published: February 2004

AbstractRotation domains are easily and often introduced into ZnO epilayers grown on c‐Al2O3 substrate, resulting in degraded epilayer quality. In this paper, effects of the sapphire surface properties on the epitaxy of ZnO were studied; the surface was carefully treated by high temperature thermal cleaning (TC), atomic hydrogen (H*), oxygen radical (O*) treatments, decoration by a few monolayers gallium and nitridation, and then the ZnO epilayers grown on these surfaces were characterized. Three kinds of rotation domains were observed in total and the sub‐domains were completely suppressed by Ga decoration and sapphire nitridation. The effect of the above treatments on polarities of ZnO epilayer was also studied. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of CdSe/ZnSSe quantum dot ordering by grazing incidence small angle X‐ray scattering
Authors: Schmidt Th. , Clausen T. , Falta J. , Bernstorff S. , Alexe G. , Passow T. , Hommel D. 
Published: February 2004

AbstractThe spatial correlation of CdSe quantum dots in stacked CdSe/ZnSSe quantum dot layers has been investigatedusinggrazing incidence small angle X‐ray scattering. Lateral and vertical ordering has been found by the presence of satellite spots, and its dependence on the number of quantum dot layers and on the spacer layer thickness has been studied. Significant ordering occurs, if the number of quantum dot layers is not too small, and if the ZnSSe spaces thickness is not too large. These findings are interpreted in terms of a strain‐driven, self‐organized ordering process. In addition, an anisotropy of two‐fold symmetry has been observed, with the weakest correlation signal along 〈110〉. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic field switching of spin injection and spin coherence in magnetic quantum structures
Authors: Ghali M. , Kossut J. , Janik E. , Teppe F. , Scalbert D. 
Published: February 2004

AbstractWe report on spin injection and spin dynamics of free carriers in II–VI hybrid magnetic quantum structures. As a model structure for spin injection, a MBE‐grown Cd0.96Mn0.04Te/Cd0.98Mg0.02Te/CdTe QW was studied. The Cd0.96Mn0.04Te acts as a spin aligner while a thick intermediate spacer (1000 Å) of Cd0.98Mg0.02Te can be also used to detect the carrier spins just right after their crossing the interface (in contrast to usual detection done at the QW optical transition wavelength). All‐optical CW and time‐resolved techniques were used to monitor the spin transport and spin relaxation in our structure. By tuning the spin aligner‐spacer layer band offset with an external magnetic field, we demonstrate that spin injection into the non‐magnetic CdMgTe region may be switched on and off by the field. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Quantum structures in Zn–Se–Te system containing submonolayer quantities of Te
Authors: Kuskovsky Igor L. , Gu Y. , van der Voort M. , Neumark G. F. , Zhou X. , Muñoz M. , Tamargo M. C. 
Published: February 2004

AbstractIn this paper we show that a multilayer Zn‐Se‐Te system, grown by molecular beam epitaxy in such a way as to contain sub‐monolayer quantities of Te (so‐called delta‐doped ZnSe:Te), exhibits optical properties consistent with the presence of quantum size centers. We present results of excitation intensity and temperature dependent cw photoluminescence (PL) as well as time‐resolved PL measurements that explicitly show that the ensemble of type‐II quantum islands is formed in this system. Specifically, for the 2.46–2.51 eV PL we show that (1) its maximum shifts as a cube root of excitation intensity; (2) its full‐width‐at‐half‐maximum decreases with the temperature while its maximum undergoes a red shift in the temperature interval where the integrated PL intensity stays approximately constant; (3) the PL decay is non‐exponential at high excitation intensities and a single exponential decay at low excitation intensities; (4) the PL life‐time initially increases with temperature from of 86 ns at T = 15 K to 143 ns at T = 115 K before deceasing due to non‐radiative processes. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ferromagnetic phase in II–VI semiconductors controlled by carriers
Authors: Cibert J. , Boukari H. , Bertolini M. , Pacuski W. , Ferrand D. , Tatarenko S. , Kossacki P. , Gaj J.A. 
Published: February 2004

AbstractOne main interest of carrier‐induced ferromagnetism in diluted magnetic semiconductors, is that it allows an active and sometimes reversible control of the magnetic properties, simply by manipulating the carrier density or carrier distribution using the usual techniques of semiconductor technology. We shall give two examples realised in (Cd,Mn)Te quantum wells: (i) control of the magnitude of the magnetisation by changing the carrier density; (ii) control of the magnetic anisotropy by changing the light‐hole/heavy‐hole splitting by strain and confinement in a quantum well. We will also shortly discuss the peculiarities of the II–VI quantum wells with respect to systems based on other diluted magnetic semiconductors. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic resonant tunnelling diodes as voltage‐controlled spin selectors
Authors: Gould C. , Slobodskyy A. , Slobodskyy T. , Grabs P. , Becker C. R. , Schmidt G. , Molenkamp L. W. 
Published: February 2004

AbstractWe study the transport characteristics of all II–VI semiconductor resonant tunneling diodes made from the (Zn,Mn,Be)Se material system and with a quantum well of dilute magnetic material. The current–voltage characteristics of these devices exhibit a normal resonant tunneling diode resonance at zero external magnetic field. When a field is applied, the resulting spin splitting of the levels in the quantum well splits the transmission resonance into two separate peaks that move apart with increasing field. We interpret this as evidence that the tunneling is taking place through spin polarized levels. This device could therefore be viewed as a first step towards the demonstration of a voltage controlled spin filter. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
X‐ray, photo‐ESR and optical spectroscopy studies of ZnSxSe1−x solid solutions doped with Co
Authors: Surkova T. P. , Galakhov V. R. , Godlewski M. , Świątek K. 
Published: February 2004

AbstractExperimental studies of X‐ray photoelectron and Co Lα X‐ray emission spectra of the ZnS:Co semiconductor were carried out. It was established that Co ions are in a Co2+ configuration and that the Co 3d impurity states are localized above the top of the valence band by 1.0 ± 0.2 eV. It was found that the covalency reduction factor for Co2+ defect changes through the alloy from 0.62 in ZnSe lattice to 0.59 in ZnS. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
CdSe‐based nanostructures: growth, properties, lasers
Authors: Ivanov S. V. , Toropov A. A. , Shubina T. V. , Sorokin S. V. , Kyutt R. N. , Sitnikova A. A. , Solnyshkov D. D. , Nekrutkina O. V. 
Published: February 2004

AbstractPaper presents an overview of recent results on novel CdSe quantum dot (QD) fabrication techniques with the main impact on a stressor‐controlled self‐organization process resulting in nucleation of real CdSe QDs optically active up to room temperature, with a narrower size distribution, a higher density and a high Cd content. The main idea of the stressor‐controlled epitaxy is an intentional introduction of a super‐strained fractional monolayer of the much higher lattice‐mismatch compound – stressor – to create strong local stress fields on the growth surface which govern self‐assembling of the main QD material. The studies are performed on a type‐II non‐common atom CdSe/BeTe system, where CdTe (Δa/a ∼ +14%) and BeSe (Δa/a ∼ −10%) interface bonds play a role of intrinsic stressors. Both experimental data (growth, structural and optical characterization) and Monte Carlo simulation of the growth process are presented. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
InAs/Zn(Mn)Te/Cd(Mn)Se pseudomorphic quantum well structures for spintronic applications
Authors: Toropov A. A. , Terent'ev Ya. V. , Shubina T. V. , Sorokin S. V. , Sedova I. V. , Kaygorodov V. A. , Solov'ev V. A. , Mel'tser B. Ya. , Ivanov S. V. , Kop'ev P. S. , Buyanova I.A. , Chen W. M. 
Published: February 2004

AbstractZn(Mn)Te/Cd(Mn)Se quantum well heterostructures have been grown pseudomorphically on InAs(001) substrates using original InAs surface preparation techniques. The structures demonstrated bright PL in the 1‐1.3 eV range and the effect of giant Zeeman splitting in the external magnetic field. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Giant polarized optical properties in type‐II ZnTe/CdSe multiple quantum wells induced by interface chemical bonds
Authors: Chen Y. F. , Su W. S. , Ya M. H. , Chiu Y. S. 
Published: February 2004

AbstractPhotoluminescence (PL) and photoconductivity (PC) spectra were studied in type‐II ZnTe/CdSe multiple quantum wells. It was found that the PL spectrum exhibits a strong in‐plane polarization with respect to 〈011〉 axis with polarization degree up to 30%. The degree of polarization does not depend on the excitation intensity and temperature, which excludes extrinsic mechanisms related to the observed in‐plane anisotropy. The underlying mechanism of the observed polarization dependence of the optical properties was attributed to the inherent property of the orientation of chemical bonds in ZnTe/CdSe heterostructures with no common atom. In addition, the PC spectra also display a strong polarization dependence. We therefore point out that polarized PL and PC spectroscopies provide a unique way to probe the effects of the orientation of interface chemical bonds on semiconductor heterostructures. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
How to avoid non‐radiative escape of excitons from quantum dots?
Authors: Robin I. C. , André R. , Dang Le Si , Mariette H. , Tatarenko S. , Gérard J. M. , Kheng K. , Tinjod F. , Bartels M. , Lischka K. , Schikora D. 
Published: February 2004

AbstractWe investigated the transition between two different exciton recombination regime in quantum dots depending on temperature. When temperature is raised above a threshold value that we determine experimentally non‐radiative recombination channels, characterized by their activation energy, dominate over radiative recombination. The analyses of time resolved photoluminescence spectroscopy versus temperature shows that the maximum temperature for dominant radiative recombination scales linearly with the activation energy of the non‐radiative channels over a large range of values (10–60 meV) measured for various kind of II–VI‐based quantum dots: CdTe/ZnTe, CdTe/ZnMgTe, CdSe/ZnSe. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magneto‐photoluminescence study on magnetic/non‐magnetic semiconductor coupled quantum dots
Authors: Lee S. , Shin D. Y. , Titova L. , Kutrowski M. , Dobrowolska M. , Furdyna J. K. 
Published: February 2004

AbstractMagneto‐photoluminescence experiments were carried out on self‐assembled quantum dots (QDs) fabricated in the form of two adjacent QD layers separated by a thin barrier. A strong PL peak is observed in this double‐layer QD system, which is identified as the ground state transition. The PL peak exhibits a large Zeeman shift, characteristic of structures involving diluted magnetic semiconductors (DMSs) when an external magnetic field is applied. However, the dependence of the PL intensity on magnetic field shows an entirely unexpected behavior in this double‐layer QD structure. In contrast to typical behavior of many low‐dimensional DMS systems, where the application of a magnetic field B dramatically increases the PL intensity, in double‐layer structures described above we observe a striking decrease of the PL intensity as a function of B. This effect indicates carrier tunneling from CdSe to CdMnSe dots as the band edges of CdMnSe are Zeeman‐shifted, thus increasing the exciton probability in the DMS QDs. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamical properties of atom‐like emissions from single localized states in ZnCdS ternary mesa‐shaped structures
Authors: Kumano H. , Hitaka Y. , Suemune I. 
Published: February 2004

AbstractDynamical properties of exciton localization into spatially isolated localized states with atom‐like density of states caused by alloy potential fluctuations were examined. Submicron‐sized mesa‐shaped structures were prepared to resolve the contribution of single localized states to the optical spectra, which makes it possible to observe atom‐like emission lines and to discuss the dynamical properties of exciton energy relaxations by employing micro‐time‐resolved PL measurements. It will be shown that in the samples with high exciton energy transfer efficiency, photogenerated excitons can relax into the spatially isolated localized centers with strong zero‐dimensional nature, which leads to the limited number of atom‐like emission lines. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
P‐type doping and devices based on ZnO
Authors: Look D. C. , Claflin B. 
Published: February 2004

AbstractBoth n‐type and p‐type ZnO will be required for development of homojunction light‐emitting diodes (LEDs) and laser diodes (LDs). It is easy to obtain strong n‐type ZnO, but very difficult to create consistent, reliable, high‐conductivity p‐type material. The most natural choice of an acceptor dopant is N, substituting for O, and indeed several groups have been able to obtain p‐type material by such doping. Surprisingly, however, other groups have also been successful with P and As, elements with much larger ionic radii than that of O. Although ZnO substrates are now available, most of the epitaxial p‐type layers so far have been grown on sapphire, or other poorly‐matched materials. The lowest p‐type resistivity obtained up to now is about 0.5 Ω‐cm, which should be sufficient for LED fabrication. In spite of the present availability of p‐type ZnO, very few homojunction LEDs have been reported so far, to our knowledge; however, several good heterojunction LEDs have been demonstrated, fabricated with p‐type layers composed of other materials. One such structure, with fairly strong 389‐nm emission at 300 K, involves n‐type ZnO and p‐type AlGaN, grown on an SiC substrate. Also, an N+‐ion implanted ZnO layer, deposited by chemical vapor deposition on Al2O3, exhibits 388‐nm emission at 300 K and could be economical to produce. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Contactless electroreflectance studies of II–VI nanostructures grown by molecular beam epitaxy
Authors: Muñoz Martín , Lu Hong , Guo Shiping , Zhou Xuecong , Tamargo Maria C. , Pollak Fred H. , Huang Y. S. , Trallero‐Giner C. , Rodríguez A. H. 
Published: February 2004

AbstractThe interband transitions of a single quantum well structure of Zn0.53Cd0.47Se/Zn0.27Cd0.23Mg0.50Se, lattice matched to InP, and of a capped CdSe quantum dot structure have been investigated using contactless electroreflectance. From a comparison of the quantum well optical transitions with those calculated using the envelope function approximation we determined the band offsets for this system. The electroreflectance spectrum of the quantum dot structure shows transitions originating from all the portions of the sample including the quantum dots and the wetting layer. Assuming a lens shape geometry and that the effective height‐to‐radius ratio observed in uncapped quantum dots is preserved, the size of the capped quantum dots was determined using the observed electroreflectance transitions, and the effective mass approximation. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
14% sputtered thin‐film solar cells based on CdTe
Authors: Compaan A. D. , Gupta A. , Drayton J. , Lee S‐H. , Wang S. 
Published: February 2004

AbstractPolycrystalline II–VI semiconductor materials show great promise for thin‐film photovoltaic cells and modules. Large‐area deposition of these II–VI semiconductors such as CdTe is possible by a variety of methods but the use of a plasma‐based method such as magnetron sputtering can have significant advantages. Here we present recent results in the fabrication of CdS/CdTe cells using rf magnetron sputtering and discuss some of the advantages that appear possible from the use of sputtering methods in this class of materials. Some of these advantages are particularly relevant as the polycrystalline thin‐film PV community addresses issues related to the challenges of fabricating high efficiency tandem cells with efficiencies over 25%. Our best results have been obtained with sputtered ZnO:Al to achieve a CdTe solar cell with 14.0% efficiency at one sun for an air‐mass‐1.5 global spectrum. In addition, we have studied reactive sputtering of ZnTe:N which shows promise for use as a transparent back contact or recombination junction for alloyed II–VI‐based top cells in a tandem solar‐cell configuration. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Exchange induced Zeeman splitting in resonant tunnelling diodes
Authors: Estanislau J. F. , Bittencourt A. C. R. , Marques G. E. 
Published: February 2004

AbstractWe have studied effects of symmetry on spin dependent transport in CdTe‐Cd1−xMnxTe magnetic tunneling diodes. The tunneling and shot‐noise currents may give complementary information on charging processes of the resonant levels. Optimized sample design can explore the exchange induced Zeeman splitting to obtain efficient spin‐filters. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Near band edge emission of MBE grown ZnO epilayers: identification of donor impurities and O2 annealing effects
Authors: Morhain C. , Teisseire‐Doninelli M. , Vézian S. , Deparis C. , Lorenzini P. , Raymond F. , Guion J. , Neu G. 
Published: February 2004

AbstractPhotoluminescence (PL) and selective photoluminescence (SPL) experiments have been carried out to analyse the near band edge emission (NBE) spectra of unintentionally doped ZnO epilayers. It is shown that the different NBE transitions involve donor centres only. The lines can be divided into two groups. Those lying on the low energy side consist of recombinations of neutral‐donor bound exciton complexes, while those lying just below the A free excitonic emission correspond to donor‐to‐valence band transitions. One of the donors is identified as indium. The emission energy of the In‐donor bound exciton, the spectra of the bound exciton excited states, the In‐related D0h transition energy, and the electronic spectrum of the In‐donor are established. The binding energies of another three donor centres are evaluated. The occurrence of two of these centres is shown to depend on the stoechiometry, as revealed by annealing experiments in an O2 atmosphere. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Formation of ohmic contacts to p‐type ZnO
Authors: Kurimoto Makoto , Ashrafi A. B. M. Almamun , Ebihara Masato , Uesugi Katsuhiro , Kumano Hidekazu , Suemune Ikuo 
Published: February 2004

AbstractFormation of ohmic contacts to p‐type zinc oxide (ZnO) was studied. The p‐type ZnO samples were grown by metalorganic molecular‐beam epitaxy with diethylzinc, deionized water vapor and monomethylhidrazine and were annealed under oxygen gas ambient at 650 °C or 700 °C for 20 min to activate doped nitrogen acceptors. Although the current‐voltage characteristics measured through gold p‐contacts were not perfectly ohmic, they showed perfectly ohmic properties after rapid thermal annealing (RTA) in the temperature range of 300 to 520 °C for 2 min. The ohmic contact resistivity was measured with the transmission‐line measurement method and it was decreased to approximately 1/64 with increasing the RTA temperature. The minimum contact resistivity of 3.15 × 10−3 Ω cm2 was observed with RTA at 520 °C for 2 min. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
ZnS‐based photonic crystal phosphors fabricated using atomic layer deposition
Authors: King J. S. , Neff C. W. , Blomquist S. , Forsythe E. , Morton D. , Summers C. J. 
Published: February 2004

AbstractThe infiltration by atomic layer deposition of three‐dimensional opal structures has been investigated as a means of fabricating photonic crystal phosphors. ZnS:Mn infiltrated and inverse opals have been demonstrated with filling fractions >95%. Characterization of these structures by scanning electron microscopy, specular reflectance, and photoluminescence is reported. Specular reflectance measurements confirm successful infiltration, and demonstrate modification of the electromagnetic density of states consistent with calculated photonic (111) pseudo band gaps. Photoluminescence measurements reveal modification of emission by the photonic crystal consistent with angular dependent specular reflectance measurements. These results reveal a flexible and convenient route for fabricating high performance photonic crystal structures and optical microcavities. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Epitaxial ZnO growth and p‐type doping with MOMBE
Authors: Suemune Ikuo , Ashrafi ABM. Almamun , Ebihara Masato , Kurimoto Makoto , Kumano Hidekazu , Seong Tae‐Yeon , Kim Bong‐Joong , Ok Young‐Woo 
Published: February 2004

AbstractControl of ZnO and CdO crystalline structures and p‐type doping in ZnO were studied. Formation of zincblende ZnO layers as well as zincblende CdO/ZnO short‐period superlattices (SPSL) are demonstrated and bright luminescence was observed even at room temperature from the CdO/ZnO SPSL. p‐Type conductivity observed in N‐doped ZnO is studied and the relation to the photoluminescence peaks is discussed. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Determination of the dielectric functions of MBE‐grown Zn1−xMgxTe II‐VI semiconductor alloys
Authors: Franz A. J. , Peiris F. C. , Liu X. , Bindley U. , Furdyna J. K. 
Published: February 2004

AbstractWe have explored the dielectric functions of ternary Zn1−xMgxTe thin films using a variable angle spectroscopic ellipsometer for samples between x = 0 and x = 0.52. We obtained values for the complex dielectric function for Zn1−xMgxTe in both the transparent and absorption regions by incorporating a threelayer model to simulate the experimental data. To this end, we also used the previously published relations of the dispersion of the indices of refraction (in the transparent region) of Zn1−xMgxTe measured using a combination of prism coupler and reflectivity. We have fitted the second derivatives of both the real and the imaginary parts of the dielectric function to obtain the critical point parameters corresponding to the higher order electronic transitions in the lattice. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Quantum Hall ferromagnetism in II–VI based alloys
Authors: Jaroszyński J. , Andrearczyk T. , Karczewski G. , Wróbel J. , Wojtowicz T. , Papis E. , Kamińska E. , Piotrowska A. , Popović Dragana , Dietl T. 
Published: February 2004

AbstractThe article reviews our recent studies on quantum Hall ferromagnetism (QHF) in diluted magnetic semiconductors. We carried out magnetoresistance studies on modulation‐doped, gated heterostructures of (Cd,Mn)Te/(Cd,Mg)Te:I.We put into evidence the formation of Ising quantum Hall ferromagnet with Curie temperature TC as high as 2 K. QHF is manifested by anomalous magnetoresistance maxima. Moreover, magnitude of these spikes depends dramatically on the history of the sample, shows hysteresis when either magnetic field or gate voltage are swept, stretched‐exponential time evolution characteristic of glassy systems, and strong Barkhausen noise. Our study suggests that these metastabilities stem from the slow dynamics of ferromagnetic domains. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)