bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optically controlled magnetization of zero‐dimensional magnetic polarons in CdMnTe self‐assembled quantum dots
Authors: Mackowski S. , Gurung T. , Nguyen T. A. , Jackson H. E. , Smith L. M. , Kossut J. , Karczewski G. 
Published: February 2004

AbstractWe find strong optically induced magnetization of zero‐dimensional magnetic polarons confined to CdMnTe quantum dots. The spin alignment of magnetic ions at B = 0 T is created through circularly polarized resonant excitation and it is probed by polarization‐resolved photoluminescence. This observation clearly demonstrates that in the CdMnTe quantum dots the exciton spin relaxation time is significantly longer than the formation time of magnetic polaron. Importantly, the spatial confinement characteristic of quantum dots increases the stability of magnetic polarons so that significant polarizaton of the emission is observed for temperatures higher than 120 K. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Diluted ZnMnTe oxide: a multi‐band semiconductor for high efficiency solar cells
Authors: Yu K. M. , Walukiewicz W. , Wu J. , Shan W. , Scarpulla M. A. , Dubon O. D. , Beeman J. W. , Becla P. 
Published: February 2004

AbstractUsing oxygen ion implantation and pulsed laser melting, we have synthesized thin films of highly mismatched ternary (y= 0) and quaternary (y= 0.12) Zn1−yMnyOxTe1−xalloys with oxygen content in excess ofx∼ 0.01. We show that incorporation of a small amount of isoelectronic oxygen leads to the formation of a narrow, oxygen‐derived band of extended states located well below the conduction band edge of the Zn1−yMnyTe matrix. The structure of the conduction band is well described by the anticrossing interaction between O localized states and the extended states of the host semiconductor matrix. As a result the conduction band splits into two subbands with distinctly non‐parabolic dispersion relations. The three absorption edges of this material (∼0.73, 1.83 and 2.56 eV) cover the entire solar spectrum providing a material envisioned for the multi‐band, single junction, high efficiency photovoltaic devices. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Oxygen induced band‐gap reduction in ZnOxSe1−x alloys
Authors: Shan W. , Walukiewicz W. , Ager III J. W. , Yu K. M. , Wu J. , Haller E. E. , Nabetani Y. 
Published: February 2004

AbstractThe effect of alloying a small amount of ZnO with ZnSe on the electronic band structure has been studied. Optical transitions in MBE‐grown ZnOxSe1−x epitaxial films (0 ≤ x ≤ 0.0135) were investigated using photoreflectance and photoluminescence spectroscopies. The fundamental band‐gap energy of the alloys was found to decrease at a rate of about 0.1 eV per atomic percent of oxygen. The pressure dependence of the band gap was also found to be strongly affected by the O incorporation. Both effects can be quantitatively explained by an anticrossing interaction between the extended states of the conduction band of ZnSe and the highly localized oxygen states located at approximately 0.22 eV above the conduction band edge. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spin‐flip Raman scattering studies of antimony‐doped ZnSe
Authors: Davies J. J. , Wolverson D. , Aliev G. N. , Zeng S. , Wang J. F. , Isshiki M. 
Published: February 2004

AbstractSpin‐flip Raman scattering and photoluminescence studies of ZnSe crystals doped with antimony have provided evidence for the presence of (i) a shallow acceptor level at about 70 meV above the valence band and (ii) a previously unreported deep donor level at about 55 meV below the conduction band, with a g‐value of 1.81. As in ZnSe:N, it is possible that the formation of such deep‐donor states may be an inevitable consequence of high concentrations of p‐type dopants and the resulting compensation may be one of the reasons why attempts to obtain p‐type conductivity continue to be difficult. The deep donor g‐value fits well into the sequence of previously reported g‐values of 1.11, for shallow donor centres (at about 26 meV), of 1.38 for donors at about 45 meV and of 2.00 for deep donors at 90 meV. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Light scattering study on hybrid structures of Zn1−x−yCdxMnySe quantum wells with ferromagnetic Co wires
Authors: Sakuma M. , Hyomi K. , Souma I. , Murayama A. , Oka Y. 
Published: February 2004

AbstractSub‐micron scale hybrid structures of Zn1−x−yCdxMnySe diluted magnetic semiconductor (DMS) quantum wells (QWs) with ferromagnetic Co wires have been fabricated for the purpose of applying local magnetic fields to the DMS‐QW. The wire of DMS‐QW with the width down to 100 nm was sandwiched between the Co wires. The magneto‐optical properties are studied by spin‐flip light scattering of paramagnetic Mn‐ions in the DMS. The application of uniform magnetic fields higher than 0.25 T has been attained from the Co wires to the DMS‐QWs. In addition, the field application from the Co to the DMS‐QWs is switched on by weak magnetic fields of 0.03 T due to the magnetic shape anisotropy of the Co wires, which can realize the switching behavior of the spin alignment of Mn‐ions in the DMS‐QW. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Pressure measurements of TO‐phonon anharmonicity in isotopic ZnS
Authors: Tallman R. E. , Ritter T. M. , Weinstein B. A. , Cantarero A. , Serrano J. , Lauck R. , Cardona M. 
Published: February 2004

AbstractWe have measured the dependence on pressure of the line‐widths of the TO and LO Raman phonons of β‐ZnS. In order to enhance the phenomena observed, and to eliminate possible effects of isotopic disorder, we have measured a nearly isotopically pure crystal, 68Zn32S. The strongly structured pressure effects observed are interpreted on the basis of anharmonic decay and the corresponding two‐phonon density of states. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Identification of bound exciton complexes in ZnO
Authors: Strassburg M. , Rodina A. , Dworzak M. , Haboeck U. , Krestnikov I.L. , Hoffmann A. , Gelhausen O. , Phillips M.R. , Alves H.R. , Zeuner A. , Hofmann D.M. , Meyer B.K. 
Published: February 2004

AbstractAn identification of shallow bound exciton centers in ZnO is presented based on magneto‐optical measurements and diffusion experiments. The thermalization behavior of the Zeeman split components confirms that the I4, I6, I8 and I9 exciton lines stem from donor bound exciton complexes. The results are supported by theoretical analysis of shallow bound exciton complexes revealing the Γ7 symmetry of the upper valence band. The presence of two‐electron satellites related to the respective transitions is further evidence for the donor bound complexes and enabled the determination of donor binding energies. Hydrogen, aluminum, gallium and indium were identified to origin the I4, I6, I8 and I9 lines by doping, diffusion and annealing experiments combined with photoluminescence and secondary ion mass spectrometry. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High‐quality ZnO epilayers grown on Zn‐polar ZnO substrates by plasma‐assisted molecular beam epitaxy
Authors: Kato Hiroyuki , Sano Michihiro , Miyamoto Kazuhiro , Yao Takafumi 
Published: February 2004

AbstractHigh‐quality ZnO epilayers have been grown on Zn‐polar ZnO substrates by plasma‐assisted molecular beam epitaxy. With increasing O/Zn flux ratio from the stoichiometric to the O‐rich, the growth mode changed from three‐ to two‐dimensional growth and the line widths of (0002) and (10–10) ω‐rocking curves showed dramatic narrowing from 471 to 42 arsec and from 1635 to 46 arcsec, respectively. These values are narrower compared to those of ZnO on sapphire and also those of device‐grade MOCVD‐grown GaN. Moreover, A‐, B‐excitons (FEA, FEB), and the n = 2 state of FEA at 3.378, 3.393, and 3.424 eV, respectively, were clearly observed in the low‐temperature (4.2 K) photoluminescence spectrum of ZnO grown under O‐rich flux conditions. Our results show that growth under high O‐rich flux conditions is required to produce high‐quality Zn‐polar ZnO films. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Extrinsic doping effect in the fabrication of CIGS and CIGSS thin film solar cells
Authors: Ramanathan K. , Pankow J. , Asher S. 
Published: February 2004

AbstractThis paper describes the effect of Cd and Zn impurities in the formation of photovoltaic junctions using CuInSe2‐based alloy thin‐film absorbers. We compare the properties of solar cells fabricated by using CdS window layers with those obtained by Cd or Zn treatment from the liquid or vapor‐phase environments. Efficient solar cells are obtained for the latter two cases, and their properties are comparable to those with CdS window layers. The results are interpreted in terms of the ability of Cd and Zn to produce n‐type doping in the surface region of the absorbers. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Development of CdxZn1−xTe alloy thin films for tandem solar cell applications
Authors: Dhere Ramesh , Gessert Tim , Zhou Jie , Pankow Joel , Asher Sally , Moutinho Helio 
Published: February 2004

AbstractWe report our development efforts for CdxZn1−xTe alloy thin films for tandem solar cells. We used three aspects of CdTe solar cell fabrication considered key to high performance: high‐temperature deposition, post‐deposition CdCl2 heat treatment, and use of O2 ambient during device processing. We used bilayers of CdTe and ZnTe as the basis for the formation of CdxZn1−xTe alloy. Use of oxygen at any stage of the processing proved to be problematic due to the formation of ZnO, which resulted in two‐phase mixture of CdTe and ZnO. These results can explain the poor performance of CdxZn1−xTe alloy thin‐film solar cells reported by several groups. We carried out oxygen free processing of the bilayer stacks and post‐deposition heat treatments. Heat treatment in the presence of CdCl2 vapor resulted in the interaction between ZnTe and CdCl2 and the loss of Zn in the form of ZnCl2. Heat treatments of the stack in He ambient resulted in the interdiffusion of the two layers. The composition profiles of the intermixed alloy region were influenced mainly by temperature and the time of the treatment. It is possible to obtain either uniform or graded alloy profiles by adjusting the two parameters. It is possible to adjust the composition of the resuting alloy by adjusting the thickness ratio of CdTe and ZnTe layers. We discuss suitability of the alloy formation using the CdTe/ZnTe bilayers for the top cell fabrication of two‐junction tandem solar cells. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of undoped ZnO layers grown by molecular beam epitaxy towards biosensing devices
Authors: Ogata K. , Komuro T. , Hama K. , Koike K. , Sasa S. , Inoue M. , Yano M. 
Published: February 2004

AbstractUndoped ZnO layers grown by molecular beam epitaxy (MBE) were investigated aiming at biosensing devices based on organic/inorganic hybrid structures. Clear observation of free exciton emission in low temperature photoluminescence (PL) spectra and electron mobility as high as 114 cm2/Vs at room temperature indicate that the quality of the ZnO layers is applicable for biosensors. Surface bonding of the ZnO the layers, which is one of the key issues for hybridization, was examined by means of xray photoelectron spectroscopy (XPS). The XPS spectra of O 1s revealed that formation and desorption of hydroxyl (OH) bonds can be controlled by air exposure and thermal treatments. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dephasing of interacting σ+ and σ− excitons in a ZnSe single quantum well
Authors: Wagner H. P. , Tripathy S. 
Published: February 2004

AbstractWe investigate coherences between σ+ and σ− exciton states in a 10 nm thick ZnSe/ZnMgSe single quantum well by spectrally resolved three‐pulse degenerate four‐wave mixing using circularly polarized 100 fs pulses. Intensity dependent measurements are performed to study the influence of exciton–exciton scattering on their dephasing rates. The experiments reveal nearly equal zero‐density dephasing rates for coherences between σ+ and σ− heavy‐ and/or light‐hole exciton states as compared to the dephasing rate of the interband coherence between these states and the ground state. The measurements also demonstrate that exciton‐exciton scattering destroys the coherence between heavy‐ and light‐hole excitons about three times more effectively than the coherence between σ+ and σ− heavy‐hole excitons. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetotransport and magnetic properties of p‐Zn1− xMnxTe:N – Carrier‐induced ferromagnetism
Authors: Nam K.‐T. , Kuroda S. , Kumekawa T. , Ozaki N. , Takita K. 
Published: February 2004

AbstractThe magnetic properties of nitrogen‐doped p‐Zn1− xMnxTe grown by MBE were studied through the magnetotransport measurements. In a sample of p‐Zn1− xMnxTe with x = 0.034 and p = 4.7 × 1019 cm−3, a hysteresis loop was observed below 2.5 K in the Hall resistance and the magnetoresistivity, which indicates the ferromagnetic transition. From the plot of (RHall/Rsheet)2 against B/(RHall/Rsheet) at several temperatures, which corresponds to the so‐called Arrott plot, we can estimate the Curie temperature (Tc) of the sample as about 3 K, suggesting that this sample has the higher Tc than ever reported. We also demonstrated, by means of light irradiation, that the strength of ferromagnetic interactions can be controlled by changing the hole concentration. An increase of the ferromagnetic behaviours such as a small increase of the coercive field was observed under light irradiation. This result strongly supports that the ferromagnetic transition in Zn1− xMnxTe is the carrier‐induced one. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Confinement‐induced enhancement of spin interactions in Mn‐doped II–VI semiconductor nanocrystals
Authors: Bhattacharjee A. K. , Pérez‐Conde J. 
Published: February 2004

AbstractThe effects of sp–d exchange interactions on the optical properties of quantum dots containing a single Mn ion are investigated within the effective mass formalism. The quantum‐mechanical eigenvalue problem of an electron‐hole pair in interaction with the Mn spin is solved analytically. In zinc‐blende semiconductors such as CdTe the fundamental absorption line splits into six components, whose relative intensities strongly depend on the Mn spin orientation with respect to the polarization of light, suggesting the possibility of optical detection of spin. In a magnetic field the splitting between the strong components of the σ− and σ+ spectra rapidly attains a saturation value close to the overall zero‐field splitting, which is inversely proportional to the nanocrystal volume. Typically, it is an order of magnitude larger than the saturation Zeeman splitting in the corresponding bulk diluted magnetic semiconductor. The numerical results for ZnSe:Mn nanocrystals show a good agreement with the published experimental data. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Zinc oxide thin films synthesized by metal organic chemical reactions
Authors: Yasuda Takashi , Segawa Yusaburo 
Published: February 2004

AbstractHigh quality ZnO films on sapphire substrates were synthesized using metal organic chemical reactions, such as metal organic chemical vapour deposition (MOCVD) and metal organic decomposition (MOD) method. Stable solid source of Zn‐acetylacetonate was used for MOCVD, and the sol‐gel method from Zn‐acetate, 2‐methoxyethanol and 2‐aminoethanol, and a commercial MOD source from Symetrix Co. were used for MOD. Dominant excitonic emission was obtained from these layers synthesized by these simple and economical methods, which are expected to develop powerful techniques for functional oxide fabrications. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Slow mode degradation mechanism of ZnSe based white LEDs
Authors: Adachi Masahiro , Ando Koshi , Abe Tomoki , Tsutsumi Sueyuki , Inoue Noboru , Kasada Hirofumi , Katayama Koji , Nakamura Takao 
Published: February 2004

AbstractThis paper presents slow mode degradation mechanism of ZnSe‐based white LEDs, which is induced by point defect. The white LEDs are very high quality devices, of which the optical power at a forward current of 20 mA is 8.3mWand the luminous efficiency is 28 lm/W, which is comparable to GaN‐based white LEDs in the market. It is proven that microscopic point defects in the devices, detected as deep hole traps of the H1 center (Ev + 0.6 eV) and H0 center (Ev + 0.8 eV) in p‐type ZnMgSSe cladding layer, are responsible for the slow‐mode degradation. These point defects, related to nitrogen complex centers, are very electrically active under device operation. An important insight of the H0 center are found that the mobility of the defect is extremely high, and then it induces marked interaction with macroscopic defects. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Time‐ and bias‐dependent effects in ZnCd(Mg)Se blue and red quantum well light emitting diodes studied by cathodoluminescence
Authors: Nikiforov A. Yu. , Cargill III G. S. , Guo S. P. , Tamargo M. C. 
Published: February 2004

AbstractLuminescence variations in MBE‐grown blue and red ZnCd(Mg)Se/InP QW LEDs have been studied by time‐resolved and bias‐dependent cathodoluminescence (CL) spectroscopy. CL from the red LED reversibly increased under forward bias and decreased under negative bias during several complete biasing cycles. CL from blue LEDs was bias dependent only during the first few cycles. The irreversible effects were QW CL intensity decreases after electron bombardment for the red LED and QW CL intensity enhancements seen as bright regions in CL images and dark regions in SE micrographs for blue LEDs. For the red LED, the bombarded regions were dark in CL images and had a dark dot and halo contrast in SE micrographs. The enhancements of CL intensity in the blue LEDs may result from buildup of internal fields due to persistent charge trapping in preexisting or electron bombardment created defects. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Exciton localization in MgxZnyCd1−x−ySe alloy
Authors: Maksimov O. , Wang W. H. , Samarth N. , Muñoz M. , Tamargo M. C. 
Published: February 2004

AbstractWe report photoluminescence and reflectivity measurements of MgxZnyCd1−x−ySe epitaxial layers (0 < x < 0.53) grown by molecular beam epitaxy on InP (100) substrates. Significant emission line broadening, increase in activation energy and Stokes shift are monitored with increasing Mg content. For MgxCdyZn1−x−ySe samples with large Mg content (x > 0.3), we observe an anomalous temperature dependence of both the emission energy and line broadening. This behavior is assigned to the emission from localized states. Different mechanisms of carrier localization are discussed and exciton localization on statistical CdSe clusters is proposed to be the most likely one. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
CBD‐Cd1−xZnxS thin films and their application in CdTe solar cells
Authors: Zhou J. , Wu X. , Teeter G. , To B. , Yan Y. , Dhere R. G. , Gessert T. A. 
Published: February 2004

AbstractComposition, optical properties, structure properties, and surface morphology of thin films of Cd1−xZnxS (x ≤ 10%) prepared by chemical bath deposition (CBD) are reported. The best cell efficiency was 15.7%. It used a Cd1−xZnxS window layer, was confirmed by NREL (Voc = 840.1 mV, Jsc = 24.81 mA/cm2, and FF = 75.55%), and had a CTO/ZTO/Cd0.92Zn0.08S/CdTe cell structure. The use of low zinc concentration in the Cd1−xZnxS layer and interdiffusion between Cd1−xZnxS and CdTe layers were assumed to be the reasons for maintaining high Voc and FF. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magneto‐optical spectroscopy of gated p‐doped CdMnTe quantum wells
Authors: Boukari H. , Bertolini M. , Ferrand D. , Cibert J. , Tatarenko S. , Kossacki P. , Gaj J. A. 
Published: February 2004

AbstractWe describe the magneto‐photoluminescence of (Cd,Mn)Te/(Cd,Zn,Mg)Te quantum wells containing a 2D hole gas . The hole population can be tuned either optically in p‐i‐p structures, by above barrier illumination, or electrically by applying a bias voltage of a few volts on a p‐i‐n structure. We identify the photoluminescence at low field as due to the positively charged exciton X+, which is destabilized at a given value of the Zeeman splitting, due to its crossing with a state involving a triplet configuration of the trion hole pair. The X+ looses its intensity in favor of a double line which exhibits features associated to band‐to‐band transitions at k = 0 and k = kF (wave vector at Fermi energy). (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Time resolved photoluminescence studies of Zn–Se–Te nanostructures with sub‐monolayer quantities of Te grown by molecular beam epitaxy
Authors: Gu Y. , Kuskovsky Igor L. , van der Voort M. , Neumark G. F. , Zhou X. , Muñoz M. , Tamargo M. C. 
Published: February 2004

AbstractWe investigate triple‐delta‐doped ZnSe:Te samples grown with different Te/Zn flux ratios using time‐resolved photoluminescence (TRPL). We show that the properties of the TRPL of both samples are consistent with the presence of quantum islands with a type‐II band alignmrnt. Moreover, from the comparison of the PL, we show that higher Te/Zn flux ratio during the growth leads to the formation of larger quantum islands. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
ZnTe single crystal growth by the liquid encapsulated pulling method
Authors: Asahi T. , Yabe T. , Sato K. 
Published: February 2004

AbstractLarge diameter ZnTe single crystals were grown by the liquid‐encapsulated pulling method using a double crucible. Crystals of around 80 mm in diameter and 40 mm in length were reproducibly obtained by this method. Both 〈100〉 and 〈110〉 crystals were successfully grown. The strong facet growth was observed when the shoulder part of the bulk was formed. Rectangular facet growth was observed in 〈100〉 growth and hexagonal facet growth was observed in 〈110〉 growth. The etch pit density of the grown crystal was lower than 10000 cm−2 and the strain in the crystal was lower than that of modified liquid encapsulated Kyropoulos method. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
ZnCdSe quantum structures by (110)‐cleaved‐edge overgrowth: MBE growth and μ‐PL characterization
Authors: Titova L. V. , Cywiński G. , Kutrowski M. , Wojtowicz T. , Liu X. , Furdyna J. K. , Dobrowolska M. 
Published: February 2004

AbstractCleaved edge overgrowth has been used to fabricate zero‐ and one‐dimensional ZnCdSe nanostructures in a ZnSe matrix. Polarization‐dependent micro‐photoluminescence results indicate that 0‐D structures (quantum dots) are present in the entire overgrowth region due to (110) interface roughness, while 1‐D structures (quantum wires) appear only in the region where quantum wells grown on (001) and (110) surfaces intersect. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical spin injection and tunneling in asymmetric coupled II–VI quantum wells
Authors: Nawrocki M. , Kłopotowski Ł. , Suffczyński J. 
Published: February 2004

AbstractWe give an overview of recent results concerning exciton and carrier tunneling and relaxation in II–VI asymmetric double quantum wells structures with semimagnetic (diluted magnetic) wells or barriers. We undertake the issue of the spin relaxation and injection in the tunneling process and we discuss the dependence of the tunneling efficiency and spin injection on the energy detuning between the initial and final state of the process. The fast tunneling of excitons as whole entities was observed with efficiency strongly dependent on the barrier width, exciton detuning and the relation between detuning and optical phonon energy. In the energy transfer processes an important role of the charged excitons formation is observed. As a result of high sensitivity of energy levels in semimagnetic semiconductor to magnetic field, the thermodynamical redistribution of neutral and charged excitons dependence in magnetic field is observed and must be taken into account in the analysis. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)