bluuebunny/crossref_metadata_2025_split huggingface dataset:
Growth and Electrical Properties of Fe doped (Ba,Sr)TiO3 Thin Films Deposited by Pulsed Laser Deposition
Authors: Yonezawa Yoshiyuki , Kato Megumi , Konishi Yoshinori , Yoshida Shizuyasu , Okuda Nobuhiro , Maeda Takahiko , Tanuma Ryohei , Ohsawa Michio , Matsuyama Hideaki , Ogino Shinji , Fujishima Naoto , Matsuda Akinori , Furusyo Noboru , Chikyow Toyohiro , Kawasaki Masashi , Koinuma Hideomi 
Published: April 2011

AbstractImpurity effects were investigated in (Ba,Sr)TiO3 (BST) systems in order to suppress leakage currents under relatively low oxygen pressure conditions by Pulsed Laser Deposition (PLD). We tried to dope transition metals, such as Mo, Mn, Cr, W and Fe into the BST target and used the targets to fabricate the films. By measuring electrical properties, we found Fe-doping had a significant effect on suppressing leakage current. Subsequently, we changed the amount of Fe doping from 0.1mol% to 6%. As a result, with post annealing, the sample with Fe:4% showed the lowest leakage current among those analyzed. Even without post annealing, the sample with Fe:6% showed the lowest leakage current. As for the dielectric constants, they decreased as the doping increased. At most, a 30% reduction was observed, compared with non-doped BST. XANES (X-ray Absorption Near Edge Structures) results indicated that the valency of the Fe ion was 3+ and located at the B-site of BST.
Erbium-Doped Barium Titanate Thin FilmWaveguides For Integrated Optical Amplifiers
Authors: Teren Andrew R. , Kim Seong-Soo , Ho Seng-Tiong , Wessels Bruce W. 
Published: April 2011

AbstractThe factors affecting optical gain were studied for Er-doped BaTiO3 thin film waveguides. Er-doped BaTiO3 with dopant concentrations of 0.3 – 9 at.% was deposited by metal-organic chemical vapor deposition. The luminescence efficiency was maximized by optimizing the growth temperature and erbium concentration as well as by post-deposition annealing. Stimulated emission was studied using the pump-probe technique over the spectral range of 1,520-1,550 nm. A maximum differential gain of 3 dB/cm was measured at 1,540 nm in an 8 mm long, 8 μm wide ridge waveguide.
Spin Polarization and Injection in ZnMnSe/ZnCdSe Heterostructures
Authors: Buyanova I.A. , Chen W.M. , Ivanov I.G. , Monemar B. , Toropov A.A. , Terent'ev Ya.V. , Sorokin S.V. , Lebedev A.V. , Ivanov S.V. , Kop'ev P.S. 
Published: April 2011

ABSTRACTMagneto-optical spectroscopy in combination with tunable laser excitation spectroscopy is employed to carry out a detailed study of spin alignment and spin injection in II-VI wide-bandgap semiconductor heterostructures, aiming at optimization of structural design for nano-scale spintronic applications. The use of tunable excitation is shown to provide a valuable opportunity to monitor separately spin relaxation and spin injection processes in the structures. Efficient spin alignment is achieved by using a diluted magnetic semiconductor (DMS) (a layer of ZnMnSe or a ZnMnSe/CdSe superlattice) as thin as 10 nm. The spin alignment efficiency is shown to depend critically on the ratio between the rates of spin relaxation and spin transport within the DMS layer. This allows the realization of spin alignment and spin switching functions by varying the structural design.
Spin Properties of Quantum wells Incorporating Semimagnetic Semiconductors
Authors: Malkova N. , Ekenberg U. , Thylen L. 
Published: April 2011

ABSTRACTThe electronic band-edge spectrum of magnetic semiconductor quantumwells containing a diluted magnetic semiconductor as one of the constituents is studied within the envelope-function formalism. Quantum wells with normal and mutually inverted band arrangements are considered. The sp – d hydribization between the bare sp-electron states and the d-states of the Mn atoms is shown to lead to a spin-splitting effect. The spin-splitting effect is studied as a function of external magnetic field, well width, valence band offset and fraction of magnetic atoms. The results have bearing on the perspective for using the magnetic semicondutor structures in spin electronics.
Spin-Memory Loss in Metallic Multilayers
Authors: Pratt W. P. , Gu J.Y. , Bass J. 
Published: April 2011

ABSTRACTWe review the results of measurements of spin-memory loss (spin-flipping) at cryogenic temperatures in sputtered or electrodeposited ferromagnetic and non-magnetic metals and alloys, and at metallic interfaces, using the current perpendicular to plane (CPP) geometry.
Transport in Metallic Multilayers with Both Specular and Diffuse Scattering at Interfaces
Authors: Shpiro Asya , levy Peter M. , Zhang Shufeng 
Published: April 2011

ABSTRACTBy using a rather simple model potential we calculate the influence of specular and diffuse scattering at interfaces on the resistance for currents perpendicular to the plane of the layers (CPP) in multilayered metallic structures. We find that if one maintains the same interfaces between layers, their contribution to the total resistance of the system depends on the thickness of the intervening layers. Their contribution is constant only if the distance between interface is larger than the electron mean free path in the bulk of the layers. The error incurred by neglecting the dependence of the interface resistance on layer thickness depends on the amount of diffuse scattering at interfaces and the height of the potential step at the interface. For a Fe-Cr or Co-Cu multilayer consisting of three or five layers with realistic interfaces where both specular and diffuse scattering may occur, the error reaches 15-20%; this exceeds the experimental error. We suggest systems where this effect may be observed.
Circular Photogalvanic Effect in SiGe Semiconductor Quantum Wells
Authors: Ganichev Sergey D. , Kalz Franz-Peter , Rössler Ulrich , Prettl Wilhelm , Ivchenko Eugenius L. , Bel'kov Vasily V. , Neumann Robert , Brunner Karl , Abstreiter Gerhard 
Published: April 2011

ABSTRACTThe photogalvanic effects, which require a system lacking inversion symmetry, become possible in SiGe based quantum well (QW) structures due to their built-in asymmetry. We report on observations of the circular and linear photogalvanic effects induced by infrared radiation in (001)-and (113)-orientedp–Si/Si1–xGex QW structures and analyse these observations in view of the possible symmetry of these structures. The circular photogalvanic effect arises due to optical spin orientation of free carriers in QWs with band splitting in k-space which results in a directed motion of free carriers in the plane of the QW. We discuss possible mechanisms that give rise to spin-splitting of the electronic subband states for different symmetries.
The use of NiMnSb Heusler alloy in MBE Grown Tunnel Junction
Authors: Turban Pascal , Andrieu Stéphane , Tagliaferri Alberto , Nadai Céline De , Brookes Nike 
Published: April 2011

ABSTRACTIn this paper, the structural, magnetic and electronic properties of single-crystalline NiMnSb thin films grown by molecular beam epitaxy are presented. The growth process and surface morphology were studied by RHEED and STM. The structural quality of the films was investigated by EXAFS and HRTEM. For the optimized growth conditions, the expected NiMnSb C1b structure was obtained. Moreover, the most stable surface was found to be 4x1 reconstructed. The magnetic and electronic properties were studied by X-ray magnetic circular dichroïsm and spin-resolved x-ray photoemission spectroscopy experiments. The magnetization was observed to be essentially due to Mn, in agreement with theory. The surface was not found to be fully polarized but a polarization near 50% at room temperature was observed. Finally, the preparation of fully epitaxial NiMnSb/MgO/NiMnSb(001) trilayers is presented.
Photo-Assisted MOVPE Growth of ZnMgS on (100) Si
Authors: Rodriguez Angel , Shattuck Jeremy , Zhang Xiaoguang , Li Peng , Parent David , Ayers John , Jain Faquir 
Published: April 2011

AbstractThis paper presents for the first time photo-assisted Metalorganic vapor phase epitaxial (MOVPE) growth of ZnMgS on Si (100) substrates. The growth was done using dimethylzinc (DMZn), bismethylcyclo-pentadienyl-magnesium ((MeCP)2Mg), and diethylsulfhide (DES) as zinc, magnesium, and sulfur precursors. Epitaxial characterization by X-ray Photoelectron Spectroscopy (XPS), and low - angle X-ray Diffraction (XRD) results are presented. Mg solid phase incorporation is estimated to vary from 0 to 60 percent. The epitaxial nature of the ZnMgS layers has been verified using the low-angle X-ray diffraction eliminating any interference from the Si substrate. It can be shown with this technique that the change in the ZnMgS peak position changes from 27.35 degrees to 26.5 degrees with an increase in Mg incorporation, compared with a Si control sample peak at 27.4 degrees. XRD results obtained have been verified with XPS data. Chlorine doping of the ZnMgS layer was also studied. Concentrations up to 3 × 1015 cm−3 were observed in the ZnMgS layer. Results of the n (ZnMgS:Cl) – p (Si) diodes fabricated are also presented.
Optical Vibrational and Structural Properties of Ge1−xSn x alloys by UHV-CVD
Authors: Taraci Jennifer , Zollner S. , McCartney M. R. , Menendez Jose , Smith D. J. , Tolle John , Bauer M. , Duda Erika , Edwards N. V. , Kouvetakis J. 
Published: April 2011

AbstractUHV-CVD growth based on a deuterium stabilized Sn hydride and digermane produces Ge-Sn alloys with tunable bandgaps. The Ge1−xSnx (x=2–20 at.%) alloys are deposited on Si (100) and exhibit superior crystallinity and thermal stability compared with MBE grown films. Composition, crystal and electronic structure, and optical and vibrational properties are characterized by RBS, low energy SIMS, high resolution electron microscopy TEM, x-ray diffraction, as well as Raman and IR spectroscopies. TEM studies reveal epitaxial films with lattice constants between those of Ge and Sn. X-ray diffraction shows well-defined (004) peaks and rocking curves indicate a tightly aligned spread of the crystal mosaics. Resonance Raman indicate a E1 bandgap reduction relative to Ge, consistent with a decrease of the E2 critical point observed in spectroscopic ellipsometry. IR transmission spectra indicate an increase in absorption with increasing Sn content consistent with a decrease of the direct bandgap.
Near-field photoluminescence spectroscopy of localized states in InGaAsN alloys
Authors: Mintairov A. M. , Blagnov P. A. , Kosel T. , Merz J. L. , Ustinov V. M. , Vlasov A. S. , Cook. R. E. 
Published: April 2011

AbstractWe used near-field magneto-photoluminescence scanning microscopy to study structural and optical properties of quantum-dot-like compositional fluctuations in GaAsN and InGaAsN alloys. We show that these fluctuations manifest themselves by the appearance of narrow emission lines (halfwidth 0.5−2 meV) at temperatures below 70K. We estimated the size, density, and nitrogen excess of individual compositional fluctuations (clusters), revealing phaseseparation effects in the distribution of nitrogen in GaAsN and InGaAsN. We found a dramatic difference in the Zeeman splitting of cluster lines between GaAsN and InGaAsN, indicating a strong effect of In on the exciton g-factor.
Quantum dots of InAs/GaSb type II superlattice for infrared sensing
Authors: Razeghi M. , Wei Y. , Gin A. , Brown G. J. 
Published: April 2011

AbstractThroughout the past years, significant progress has been made in Type II (InAs/GaSb) photovoltaic detectors in both LWIR and VLWIR ranges. BLIP performance at 60K for 16μm photovoltaic type II detectors has been successfully demonstrated for the first time. The detectors had a 50% cut-off wavelength of 18.8 μm and a peak current responsivity of 4 A/W at 80K. A peak detectivity of 4.5×1010cm·Hz1/2/W was achieved at 80K at a reverse bias of 110mV. Detectors of cutoff wavelength up to 25μm have been demonstrated at 77K. The great performance of single element detectors appeals us to lower dimensional structures for both higher temperature performance and possible wavelength tunability. Simple calculations show that quantum effects will become significant when the lateral confinement is within tens of nanometers. The variation of applied gate voltage will move the electron and hole energy levels unevenly. The cutoff wavelength of the superlattice will vary accordingly. Auger recombination will also decrease and higher temperature operation becomes possible. In this talk, the latest results will be discussed.
Electroluminescence and Spectral Shift of CdS Nanoparticles on Si Wafer
Authors: Liang Eih-Zhe , Lin Ching-Fuh , Shih Sheng-Ming , Su Wei-Fang 
Published: April 2011

AbstractPreparation of CdS nanoparticles, devices fabrication, and electroluminescence properties at room temperature of CdS nanoparticles on silicon substrates are reported. A spectral shift of 86-meV of free exciton transition was observed that was due to the passivation of p-hydroxyl thiophenol molecules around nanoparticles. Controlled process conditions such as heat treatment and/or with oxygen-rich environment are experimented and found to have significant influences on emission spectra. Radiative recombination corresponding to oxygen-impurity level, 273 meV below bandgap energy, presents in samples prepared in oxygen-rich environment. In addition to such mechanism, coalescence of nanoparticles into bulk form also exists and contributes to enhanced luminescence.
InAs quantum dots in AlAs/GaAs short period superlattices: structure, optical characteristics and laser diodes
Authors: Tokranov Vadim , Yakimov M. , Katsnelson A. , Dovidenko K. , Todt R. , Oktyabrsky S. 
Published: April 2011

AbstractThe influence of two monolayer - thick AlAs under- and overlayers on the formation and properties of self-assembled InAs quantum dots (QDs) has been studied using transmission electron microscopy (TEM) and photoluminescence (PL). Single sheets of InAs QDs were grown inside a 2ML/8ML AlAs/GaAs short-period superlattice with various combinations of under- and overlayers. It was found that 2.4ML InAs QDs with GaAs underlayer and 2ML AlAs overlayer exhibited the lowest QD surface density of 4.2×1010 cm-2 and the largest QD lateral size of about 19 nm as compared to the other combinations of cladding layers. This InAs QD ensemble has also shown the highest room temperature PL intensity with a peak at 1210 nm and the narrowest linewidth, 34 meV. Fabricated edge-emitting lasers using triple layers of InAs QDs with AlAs overlayer demonstrated 120 A/cm2 threshold current density and 1230 nm emission wavelength at room temperature. Excited state QD lasers have shown high thermal stability of threshold current up to 130°C.
Radiative recombination processes of thermal donors in silicon
Authors: Pizzini S. , Binetti S. , Leoni E. , Donne A. Le , Acciarri M. , Castaldini A. 
Published: April 2011

AbstractThere is a recent, renewed attention on the possible development of optical emitters compatible with silicon microelectronic technology and it has been recently shown that light emitting diodes could be manufactured on dislocated silicon, where dislocations were generated by plastic deformation or ion implantation. Among other potential sources of room temperature light emission, compatible with standard silicon-based ULSI technology, we have studied old thermal donors (OTD), as the origin of their luminescence is still matter of controversy and demands further investigation.In this work we discuss the results of a spectroscopical study of OTD using photoluminescence (PL) and Deep Level Transient Spectroscopy (DLTS) on standard Czochralsky (Cz) silicon samples and on carbon-doped samples.We were able to show that their main optical activity, which consists of a narrow band at 0.767 eV ( P line), is correlated to a transition from a shallow donor level of OTD to a deep level at EV+0.37 eV which is tentatively associated to C-O complexes. As we have shown that the P line emission persists at room temperature, we discuss about its potentialities to silicon in optoelectronic applications.
Field emission enhancement of DLC films using triple-junction type emission structure
Authors: Paik Namwoong , Martin Michael , Kim Daeil , Kim Sungjin , Kim Steven , Song Kie Moon 
Published: April 2011

AbstractNegative Electron Affinity (NEA) of Diamond-like-Carbon (DLC) films has made DLC films a favorable candidate for field emission display (FED). It was suggested that triple-junction type structure could enhance the field emission characteristics. A triple junction is defined as the intersection of a semiconductor surface with a metal substrate in vacuum. In this study, field emission enhancement in triple junction type structures was investigated. As a metal substrate 5000 of Mo films were deposited. Then, 3000–4000 of DLC film was deposited as a semiconductor material. Thin film layers were made using a negative ion beam source. After the deposition, using an excimer laser, we removed the DLC layer and made circular shaped triple junction trenches with a diameter of 25–250 μm. The field emission characteristics such as I–V characteristics turn on voltage and emission lifetime data were obtained for a diode type field emission measurement system. Overall results show significantly enhanced performance of field emission characteristics such as uniform emission over patterned area, reduced turn on voltages and longer lifetimes can be achieved.
Depth Profiling of SiC Lattice Damage Using Micro-Raman Spectroscopy
Authors: Muntele Iulia C. , Ila Daryush , Muntele Claudiu I. , Poker David B. , Hensley Dale K. 
Published: April 2011

AbstractDepth profiling for the amount of lattice damage using a Confocal Micro-Raman (CMR) spectrometer is demonstrated in this paper. Samples of n-type silicon carbide were implanted with 2 MeV He and O ions at both room temperature and 500 °C, and fluences between 1015 and 1017 ions/cm2. Post-implantation annealing at 1000 °C was also performed in order to study the damage evolution. Optical Absorption Spectrophotometry (OAS) was used for establishing the opacity (and therefore the probing depth) of the damaged layer to the 632.8 nm wavelength of the He-Ne laser used for CMR throughout this study. The methodology used and the results obtained are presented herein. Total dissipation of amorphous carbon islands was observed even at low annealing temperatures of the RT implanted samples, along with an increase in the size of the amorphous silicon islands.
High-Performance InAs/GaAs Quantum Dots Infrared Photodetector With/Without Al0.2Ga0.8As Blocking Layers
Authors: Ye Zhengmao , Campbell Joe C. , Chen Zhonghui , Baklenov O. , Kim E. T. , Mukhametzhanov I. , Tie J. , Madhukar A. 
Published: April 2011

AbstractInAs/AlGaAs quantum dot infrared photodetectors based on bound-to-bound intraband transitions in undoped InAs quantum dots are reported. AlGaAs blocking layers were employed to achieve low dark current. The photoresponse peaked at 6.2 μm. At 77 K and –0.7 V bias the responsivity was 14 mA/W and the detectivtiy, D*, was 1010 cmHz1/2/W.
Effects of Ion Bombarding and Nitrogenation on the Properties of Photovoltaic a-CNx Thin Films
Authors: Zhou Z. B. , Cui R. Q. , Hadi G. M. , Pang Q. J. , Jin C. Y. , Ding Z. M. 
Published: April 2011

AbstractAmorphous carbon nitride films (a-CNx) were synthesized by using single ion beam sputtering of a graphite target in argon and nitrogen sputtering gases. This thin film could be used as a novel photovoltaic material. The films were characterized with the technique of laser Raman, spectroscopic ellipsometry and electron spin resonance spectrometer (ESR). In this paper we report the effects of ion impacting and nitrogenation on the microstructure, density of defect states, bonding character, optical and photovoltaic properties. Effective decreasing of intensity of the ESR signal and formation of C-N bonding were observed, which could be attributed to the increment of the impinging ions on the growing films. The nitrogenation of a-CNx films could decrease the Tauc optical gap (0.62∼0.86eV) and the intensity of ESR signal, increase photon absorption coefficient of the films (106∼104cm−1).The primary photovoltaic values of the devices having Schottky structure of ITO/CNx/Al are Isc 1.56 μ A/cm2 and Voc 250 mV, respectively, when exposed to AM1.5 illumination ( 100mW/cm2, 25°C).
Third Order Mode Optically Pumped Semiconductor Laser for an Integrated Twin Photon Source in Quantum Optics
Authors: Semaltianos N. G. , De Rossi A. , Berger V. , Vinter B. , Chirlias E. , Ortiz V. 
Published: April 2011

AbstractLasing action on a third order waveguide mode is demonstrated at room temperature under optical pumping, in a specifically designed quantum well laser structure. The AlGaAs heterostructure involves barriers which ensure that the third order mode has a higher overlap with the single quantum well emitter than the fundamental mode. Third order mode operation of a laser structure opens the way to modal phase matched parametric down conversion inside the semiconductor laser itself. It is a first step towards the realization of semiconductor twin photon laser sources, needed for quantum information experiments.
Preparation of CdS/ZnO Core/shell Structured Nanoparticles by Hydrothermal Method
Authors: Yan Chunhua , Sun Lingdong , Fu Xuefeng , Liao Chunsheng 
Published: April 2011

AbstractCdS and ZnO capped CdS (CdS/ZnO) semiconductor nanoparticles were synthesized via hydrothermal method by thermal decomposition of the cysteine-cadmium and Zn(OH)42− complex precursors. Both of the photoluminescence properties and structure characterization confirmed the core/shell structure as expected. Compared to CdS nanoparticles, the band-gap emission of CdS/ZnO was greatly improved, that means the capping layer of ZnO modified the surface of CdS and reduced the surface defects effectively. ED and XRD confirmed the formation of hexagon phased CdS and the TEM image indicated the size of CdS/ZnO was about 20 nm.
Oxidation Kinetics and Microstructure of Wet-Oxidized MBE-Grown Short-Period AlGaAs Superlattices
Authors: Todt René , Dovidenko Katharine , Katsnelson Alexei , Tokranov Vadim , Yakimov Michael , Oktyabrsky Serge 
Published: April 2011

AbstractThe kinetics of the wet oxidation process of MBE-grown high-Al-content AlAs/Al0.6Ga0.4As short-period superlattices (SPSLs) was investigated and compared to AlGaAs alloys and pure AlAs. We found that alloys and superlattices (SLs) have different oxidation characteristics. These differences were attributed to traces of the superlattice structure in the oxidized material. The microstructure and chemistry of SPSLs with an equivalent composition of Al0.98Ga0.02As was studied, using transmission electron microscopy, energy-dispersive x-ray spectroscopy, Rutherford backscattering, and nuclear reaction analysis for hydrogen-profiling. We also report on the mechanical stability of oxidized SPSL layers in optoelectronic device structures.
Atomistic Modeling of III-V Semiconductors: Thermodynamic Equilibrium and Growth Kinetics
Authors: Grosse Frank , Carter-Barvosa William , Zinck Jennifer J. , Gyure Mark F. 
Published: April 2011

AbstractGrowth kinetics and thermodynamic equilibrium can both be determining factors at different stages of III-V semiconductor heteroepitaxy. We study their interplay, employing kinetic Monte Carlo simulations for the InAs(001) surface. The simulation contains atomistic details of both species, including the stability of different reconstructions and their kinetics. The behavior of the surface in thermodynamic equilibrium, including different reconstructions, is determined exclusively by extensive total energy calculations employing ab initio density functional theory. The continuous phase transition between the α?(2×4) and β?(2×4), predicted by theory, is confirmed by experiment. At full layer coverage, a recovery of the stable reconstruction is observed. The different time scales associated with As2 and In are discussed with respect to equilibrium and kinetics.