bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of Different Atmospheres on the Life Time of Porous Silicon Light-Emitting Devices
Authors: Jumayev B.R. , Tam H.L. , Cheah K.W. , Korsunska N.E. 
Published: April 2011

ABSTRACTIn present report, we investigated the degradation processes in porous silicon light-emitting devices (LED) in different atmospheres (O2, N2, air and vacuum) by photoluminescence (PL), electroluminescence (EL), lifetime (LT) and I-V characteristic measurements as well as by Energy Dispersive X-ray Spectroscopy (EDS). The contacts were made by evaporation of Au and Au/Cu alloy. The LEDs emit in visible range at forward and reverse bias. As a rule, full width at half maximum of EL spectrum is wider than that of PL spectrum. The bias direction of applied voltage during degradation change EL, PL, I-V characteristics, and LT of the LEDs. At forward bias, LT degradation is less than that in reverse bias.The degradation of LEDs during forward bias did not produce any change in the spectral shape of EL and PL. At reverse bias, degradation led to red shift in the peak of EL and PL. The results show that the lifetime of LEDs with Au contact is longer than Au-Cu. Operating in different atmospheres, the LT in vacuum is longest and is more than 100 hours in reverse bias at room temperature.Possible mechanisms of degradation of LEDs are discussed. It is proposed that degradation is connected mainly with two processes: oxidation and metal diffusion. It is shown that the oxygen and metal in ionic state can diffuse quickly. Hence, in forward bias, the diffusion of metal would dominate, and in reverse bias, diffusion of oxygen dominates.
Generation of Silicon Nanocolumns by Nanosecond Pulsed-Excimer Laser Irradiation and Their Field Emission Properties
Authors: Guan Yingfeng , Pedraza A. J. , Ellis E. D. , Baylor L. R. 
Published: April 2011

ABSTRACTLaser-generated silicon microcone arrays were used as templates for the growth of nanocolumns using laser irradiation as well. The formation mechanism of the microstructure is briefly reviewed, and the origin and growth of nanocolumns are discussed. The formation mechanism of nanocolumns requires highly localized melting, which explains why they fail to form on a flat surface but can grow atop the microcones. Field emission properties from both microcolumns and nanocolumns have been measured. The high aspect ratio (height/tip radius) of nanocolumns makes them suitable for various field emission applications.
Low-Cost, Large-Area Nanocrystalline TiO2 -Polymer Solar Cells on Flexible Plastics
Authors: Mandal Krishna C. , Smirnov Anton , Peramunage D. , David Rauh R. 
Published: April 2011

ABSTRACTThis paper describes our recent research on the development of fully flexible and low-cost dye-sensitized nanocrystalline TiO2 solar cells (DSSC). At EIC Laboratories, we have developed various large-area solid-state versions, which include both ionically, and hole-conducting allpolymer DSSCs made by continuous coating and lamination process. Various critical steps involve ∼10 micron thick nanocrystalline TiO2 film deposition on conducting PET plastics by various methods such as spraying, spin coating, and screen printing, a low temperature sintering (∼150°C) process, and polymer laminated electrolyte have been demonstrated as valuable active components. The photovoltaic (PV) performance presented in this paper show the fabricated solar cells of ∼1.2 cm2 area with reproducible AM1.5 (Air Mass 1.5) efficiencies of 4.7%. A prototype solar cell with a new hole conducting star polymer with AM 1.5 efficiency ∼2.12% has been thoroughly characterized and discussed.
Stimulated Opticaltransitions in Er-Doped Silicon Nanostructures
Authors: Kamenev B. V. , Emel'yanov V. I. , Timoshenko V. Yu. , Kashkarov P. K. , Lomonosov M.V. , Terukov E. I. , Kudoyarova V. Kh. 
Published: April 2011

ABSTRACTPhotoluminescence (PL) of Er3+ ions in nanocrystalline (amorphous) silicon matrix has been investigated under a high level of optical excitation. A superlinear increase of the PL intensity, a shortening of the PL decay time, and strong angular dependence were found at the excitation intensity above 200 kW/cm2. These effects are observed only in samples with presence of silicon nanocrystalls and explained by stimulated optical transitions.
Controlled Deposition and Applied Field Alignment of Single Walled Carbon Nanotubes for CNT Device Fabrication.
Authors: Smits Jan , Wincheski Buzz , Ingram JoAnne , Watkins Neal , Jordan Jeff 
Published: April 2011

ABSTRACTCarbon nanotubes (CNTs) offer great potential for advanced sensing devices due to their unique electronic transport properties. However, a significant obstacle to the realization of practical CNT devices is the formation of controlled, reliable and reproducible CNT to metallic contacts. In this work, a procedure for the deposition and alignment of CNTs onto metallic electrodes using chemically functionalized lithographic patterns is reported. This method uses photo and electron beam lithography to pattern simple Cr/Au thin film circuits on oxidized Si substrates. The circuits are then re-patterned with a self-assembled monolayer (SAM) of 3-aminopropyltriethoxysilane (APTES) to specify desired CNT locations between electrodes. The application of an electric field to the metallic contacts during the deposition of solution suspended single walled CNTs causes alignment of the CNTs in the field direction. This method consistently produces aligned CNTs in the defined locations.
Bio-inspired Self-Assembly of Micro and Nano-Structures for Sensing and Electronic Applications
Authors: McNally H. , Lee S. W. , Guo D. , Pingle M. , Bergstrom D. , Bashir R. 
Published: April 2011

ABSTRACTBio-inspired assembly, through the use of bio-molecules such as DNA and proteins, will play a critical role in the advancement of novel sensing techniques and for the realization of heterogeneous integration of materials. For many of these applications, such as antibody-based biosensor and the study of controlled cell growth, DNA and protein patterning techniques are crucial. We will present an update of our work on protein patterning techniques using microelectronic fabrication, DNA hybridization and biotin-streptavidin pairing. To show its application in biological inspired self-assembly, this technique was used successfully in the self-assembly of 20 nm streptavidin conjugated gold particles. In addition, the integration of nano-and micro-scale heterogeneous materials is very important for novel material synthesis and electro-optic applications. We will present an update on our work to assemble silicon electronic devices using DNA/charged molecules and electric fields. Devices are fabricated, released, charged with molecules, and subsequently manipulated in electric fields. The techniques described can be used to integrate the hybrid devices such as nano- or micro-scale resistors, PN diodes, and MOSFETs on silicon or other substrates such as glass, plastic, etc.
Phonon Frequencies and Thermal Expansion of III-V Compounds
Authors: Reeber Robert R. 
Published: April 2011

ABSTRACTThermal expansion is an important parameter for the design and manufacturing of dimensionally thermally stable opto-electronic integrated circuits and superlattices. In earlier work1, 2 we established the quantitative relationships between phonon frequencies and thermal expansion for Group IV semiconductors. In this paper we extend this approach to the III-V compounds GaAs, GaP, InP, GaSb, InAs, AlSb and InSb.
The compositional and optical characterizations of InGaAsN alloy semiconductor grown by MOVPE
Authors: Sanorpim Sakuntam , Nakajima Fumihiro , Katayama Ryuji , Onabe Kentaro , Shiraki Yashihiro 
Published: April 2011

ABSTRACTWe report on the compositional and optical investigation of InGaAs(N) alloy films grown on GaAs (001) substrates by low-pressure (60 Torr) metalorganic vapor phase epitaxy (MOVPE). The alloy films with the room-temperature photoreflactance (PR) signal (Eo transition) wavelength range of 0.98–1.36 m have been grown. The variation in PL characteristics of the InGaAs(N) alloy films has been investigated as a function of alloy composition, excitation power and temperature. At low temperatures (T<100K), the PL spectra with several sub-peaks include localization emission as well as near-band-edge emission. On the other hand, the room-temperature PL properties for InxGa1-xAs1-yNy (x = 10.5% and 17.0% and y < 2%) are excellent with a single near-band-edge emission peak corresponding to their own Eo transition. The evolution of PL spectra with excitation power and temperature led to an insight into the nature of the near-band-edge states. The temperature dependence of integrated PL intensity indicates the presence of a large density of non-radiative recombination centers, showing a behavior characterized by two activation energies. Our results suggest that the origin of localization in InGaAsN alloy films is the alloy inhomogeneities of both In and N, which may results in the characteristic carrier dynamics.
Process Control of Epi-Layers for SiGe:C Hetero-Structure Bipolar Transistors
Authors: Xie Qianghua , Duda Erika , Kottke Mike , Qin Wentao , Wang Xiang-Dong , Lu Shifeng , Erickson Martha , Kretzschmar Heather B. 
Published: April 2011

ABSTRACTThe SiGe:C hetero-structure bipolar transistor (HBT) has turned into a key technology for wireless communication. This paper describes the metrology tools for SiGe epitaxy process control. Two types of analysis are critical, (1) routine control of SiGe base and Si cap thicknesses, location and thickness of the doping layer, doping dose, Ge composition profile, and their uniformity across the wafer; and (2) root-cause analysis on non-routine problems. This is achieved by developing a transmission electron microscopy (TEM) technique allowing a thickness measurement with a reproducibility better than 3 Å. Charge-compensated low-energy secondary ion mass spectrometry (SIMS) using an optical conductivity enhancement (OCE) allows a Ge composition measurement to a required precision of 0.5 at. %.
High Efficiency Bulk Crystalline Silicon Light Emitting Diodes
Authors: Zhao Jianhua , Wang Aihua , Trupke Thorsten , Green Martin A. 
Published: April 2011

ABSTRACTA high power conversion efficiency above 1% from a bulk crystalline silicon (c-Si) light-emitting diode (LED) has been demonstrated at near room temperature. These devices are based on normally weak one- and two-phonon assisted sub-bandgap light emission processes. Their improved performance results from device designs that take advantage of enhanced light absorption by a light trapping scheme which was developed for high efficiency silicon solar cells, and from reducing scope for parasitic non-radiative recombination within the diode. Each feature individually is shown to improve efficiency by a factor of ten, accounting for an improvement by factor of one hundred compared to baseline devices.Also demonstrated is a greatly improved band-edge light emission and detection using bulk c-Si diodes. A bulk c-Si LED is combined with a similar diode used as a detector that collects the light emitted with a high quantum collection efficiency of 33%, to produce a silicon to silicon optically coupled system that demonstrates 0.18% coupling quantum efficiency. The crystalline silicon LED demonstrates similarly high performance at very low power levels, where it has even higher power efficiency than a high efficiency GaAlAs LED.
Effect of Growth Temperature and Annealing on ZnO
Authors: Cai A. L. , Muth J. F. , Reed M. J. , Porter H. L. , Jin C. , Narayan J. 
Published: April 2011

ABSTRACTA series of epitaxial single crystal ZnO samples were grown by Pulsed Laser Deposition (PLD) on c-axis, double-side polished sapphire at temperatures ranging from 600°C to 800°C. A comprehensive optical study, consisting of cathodoluminescence (CL) and transmission spectroscopy measurements, was performed before and after annealing the samples in air and oxygen environments. The structural characteristics of the films were observed by x-ray diffraction and transmission electron microscopy (TEM). Using these measurements, the data revealed that annealing significantly improved the luminescence and exciton line-width of the better material grown at the higher end of the temperature range. In lower quality samples grown at the lower end of the temperature range, the optical quality of the material was degraded. In the samples grown at higher temperatures, annealing improved the optical qualities. An increase in the below band-gap, green band emission was also observed under some annealing conditions.
Novel resistance reduction and phase changes of contacts to n-type InP by rapid thermal annealing
Authors: Huang J.S. , Nguyen T. , Bar-Chaim N. , Vartuli C.B. , Anderson S. , Shearer J. , Fisher C. 
Published: April 2011

ABSTRACTWe studied the influence of n-metal alloy on the long wavelength InP device performance. Various alloy schemes of rapid thermal annealing (RTA) were experimented to obtain the optimized contact resistance for the n-InP/AuGe/Ni/Au/Cr/Au metallization systems. Significant resistance reduction was achieved at 390°C for 45sec with wafer flattening step at 310°C. Using scanning transmission electron microscopy (STEM) and Auger electron spectroscopy (AES) analyses, we showed that resistance was correlated with interfacial reaction at the n-InP/metal. For the high resistance devices, little interfacial reaction between n-InP and Au occurred. For the low resistance devices, significant out-diffusion of P in the bottom Au and Ni layers occurred, forming Au-P and Ni-P metallic compounds. In addition, accumulation of Ge in the Ni layer was also detected. We suggest that Ni-P is very critical in obtaining low contact resistance for n-InP.
A Differential Scanning Calorimetry (DSC) Study on The Pyrolysis Mechanism of Zinc Oxide CVD Precursor, Zinc Acetylacetonate
Authors: Chang Yuneng , Hsieh Junhsuan , Wang Chonan , Hong Liting 
Published: April 2011

ABSTRACTIn this study, we used differential scanning calorimetry (DSC) to study pyrolysis kinetics of zinc acetylacetonate (Zn(acac)2) in chamber ambient simulating real CVD condition, with heating rate from 10 to 20 °C/min. For Zn(acac)2 heated in pure N2, inert environment, DSC showed three endothermic peaks locating at 91–106 °C, 121–128 °C, and 135–142 °C, with peak area being 88 KJ/mol, 14 KJ/mol, and 18 KJ/mol, respectively. The DSC residuals analyzed by IR indicated all peaks might be originated from physical phenomena, since no compositional change observed. Further study by temperature programmed polarized optical microscope (POM) showed these peaks might be related to dehydration, phase transition, and melting of Zn(acac)2 and its hydrates. DSC in oxygen-containing ambient with O2 concentration from to 13 to 40 % showed three endothermic peaks and two additional exothermic broad peaks at higher temperature, 209–236 °C, and 330–400 °C. These exothermic peaks are assigned to oxidative decomposition of Zn(acac)2 and releasing of ligands. When oxygen concentration increased, peak area grew. Positions of these peaks depend on heating rate. Increasing the heating rate caused every peak to shift toward higher temperatures, with the first two endothermic peaks merged into one broad one.
Formation of Defects in MBE Re-Grown GaAs Films on GaAs/AlGaAs Heterostructures
Authors: Lamberti M. , Tokranov V. , Moore R. , Yakimov M. , Katsnelson A. , Oktyabrsky S. 
Published: April 2011

ABSTRACTIn the present work, we examine the formation of defects on the sidewall slope in 1 μm - thick GaAs layers regrown on GaAs/AlGaAs heterostructures. Site-specific TEM specimens of sidewall slopes are obtained using focused ion beam combined with lift-out method. TEM analysis shows planar defects, such as stacking faults and microtwins, dislocations and large twinned areas, nucleating on the AlGaAs surfaces. SIMS and EDX reveal an increase in carbon and oxygen at the interface. The defect density increased with Al content exceeding 1010 cm-2 on Al0.4Ga0.6As. The defect formation is related to the oxidation of Al-containing surfaces.
Electronic Properties of n-type AlXGa1-XAs Alloys
Authors: Ferreira da Silva A. , Pepe I. , Haratizadeh H. , Holtz P.O. , Persson C. , Ahuja R. , Souza de Almeida J. , de Oliveria A.G. 
Published: April 2011

ABSTRACTWe have investigated, theoretically and experimentally, the reduced and optical bandgap shift of Si-doped AlXGa1-XAs alloys as a function of both the Al composition and the Si concentration. The calculations were carried out within a framework of the many particle random phase approximation with the Hubbard local-field correction, considering electron populations in the conduction minima located at the Γ, X and L-points of the Brillouin zone. The experimental data have been obtained by means of photoluminescence spectroscopy. The theoretical predictions are found to be in good agreement with the experimental results.
Optical and EPR Study of Defects in Cadmium Germanium Arsenide
Authors: Bai Lihua , Garces N. Y. , Yang Nanying , Schunemann P. G. , Setzler S. D. , Pollak T. M. , Halliburton L. E. , Giles N. C. 
Published: April 2011

ABSTRACTBulk crystals of CdGeAs2 have been characterized using photoluminescence (PL), optical absorption, Hall effect, and electron paramagnetic resonance (EPR) techniques. An absorption band near 5.5 microns at room temperature is observed in all of the p-type samples we have studied. A correlation between the magnitude of this optical absorption and the excess hole concentration at room temperature is established. Also, an EPR signal is found to correlate with the strength of this absorption band. PL data are consistent with an increased concentration of shallow acceptors being present in high-absorption samples. From the EPR data, we suggest that a model for the paramagnetic defect associated with the absorption at 5.5 microns may be an acceptor on an anion site.
Spectral Response Modification Of Quantum Well Infrared Photodetector By Quantum Well Intermixing
Authors: Shin J. C. , Choi W. J. , Han I. K. , Park Y. J. , Lee J. I. , Kim E. K. , Kim H. J. , Choi J. W. 
Published: April 2011

ABSTRACTWe have studied the change of the spectral response in a quantum well infrared photodetector (QWIP) by using the impurity-free vacancy disordering (IFVD) to change the bandgap of the GaAs/AlGaAs multiple quantum well absorption layer. IFVD process has been carried out with PECVD-grown SiO2 capping on the MOCVD-grown QWIP structure, whose absorption region consists of 25 periods of 3.6nm thick Si-doped GaAs well and 50nm thick Al0.24Ga0.76As barrier. The PL peak of MQW decreased with the increase of annealing temperature and time from 802 nm to 700 nm at 15 K. The fabricated QWIP whose absorption region was intermixed at 850 °C by IFVD technique showed the maximum change in spectral response from 8 to 10 um when compared to a QWIP without intermixing. This result implies that the intermixing technology can be used to make multicolor QWIP without growing multiple IR absorption regions.
Micromagnetic Simulation of Thermal Effects in Magnetic Nanostructures
Authors: Dittrich Rok , Schrefl Thomas , Tsiantos Vassilios , Forster Hermann , Suess Dieter , Scholz Werner , Fidler Josef 
Published: April 2011

ABSTRACTA path finding method and a stochastic time integration scheme for the simulation of thermally activated magnetization processes are introduced. The minimum energy path and the saddle points for the thermally induced transitions between the ground states of NiFe magnetic nano-elements are calculated.
Simulations of the Domain State Model
Authors: Nowak U. , Misra A. , Usadel K. D. 
Published: April 2011

ABSTRACTThe domain state model for exchange bias consists of a ferromagnetic layer exchange coupled to an antiferromagnetic layer. In order to model a certain degree of disorder within the bulk of the antiferromagnet, the latter is diluted throughout its volume. Extensive Monte Carlo simulations of the model were performed in the past. Exchange bias is observed as a result of a domain state in the antiferromagnetic layer which develops during the initial field cooling, carrying a remanent domains state magnetization which is partly irreversible during hysteresis. A variety of typical effects associated with exchange bias like, e. g., its dependence on dilution, positive bias, temperature and time dependences as well as the dependence on the thickness of the antiferromagnetic layer can be explained within this model.
A Small Angle Polarized Neutron Scattering Investigation of Magnetic Correlations in Nanocrystalline Fe89Zr7B3Cu1
Authors: Agosti Enrico , Moze Oscar , Cadogan John , Suzuki Kiyonori , Heinemann Andre , Hoell Armen 
Published: April 2011

ABSTRACTThe technique of small angle neutron scattering (SANS) is ideally suited for determining the length scale of magnetic correlations in nanocrystalline materials. The additional use of polarized neutrons also allows for a clear separation between magnetic and non-magnetic scattering. The temperature dependence of the SANS cross-section from a two-phase alloy, consisting of both amorphous and nano-crystalline parts, Fe89Zr7B3Cu1, has been measured in the temperature range from 293 to 500 K. The SANS measurements are accompanied by bulk magnetization and Mössbauer transmission data. In this range of temperatures, the magnetic contrast between the nanocrystalline and amorphous phases, which are both magnetic, changes dramatically. This phase contrast increases up to 380 K, which is the proposed decoupling temperature for the inter-granular exchange stiffness. Above this temperature, the contrast levels off slowly, being totally dominated by the decreasing magnetization of the nanocrystalline phase.
Real-time x-ray scattering study of homoepitaxial growth of SrTiO3 by sputtering
Authors: Lee Hsin-Yi , Hsu C.-H. , Hsieh Y.-W. , Liang K. S. 
Published: April 2011

ABSTRACTThe real-time x-ray scattering measurements under in-situ sputtering conditions were employed to study the growth behavior of sputter-deposited SrTiO3 films on SrTiO3 (001) substrate. A condition for conformal growth between deposited layers and substrate was found by observing the oscillation fringe in the diffuse scattering of measured reflectivity. The azimuthal scan around surface Bragg peak of the film peak shows that the epitaxial relationship between film and substrate can be achieved by sputtering.
Study of Surface Morphological Evolution by Cluster Ion Irradiation on Solid Targets
Authors: Aoki Takaaki , Nakai Atsuko , Matsuo Jiro , Takaoka Gikan 
Published: April 2011

ABSTRACTSmoothing effect by large gas cluster ion irradiation was studied. Ar cluster ion beams were irradiated on rough Si surface with various ion dosage. 100×100μm2 AFM image was measured for each surface. These AFM images were treated with fast Fourier transform in order to examine the change of surface morphologies with cluster ion irradiation. Power spectra analysis showed that the intensity at each wave number (the inverse number of wavelength) exponentially decreases with ion dose. The relationship between smoothing rate and wave number was derived. The surface smoothing process was modeled with the use of this wave number dependence on decreasing rate. The calculated and the experimental surface profiles are in good agreements. With this model, roughness of cluster-irradiated surface can be calculated from initial surface images.