bluuebunny/crossref_metadata_2025_split huggingface dataset:
Terahertz Beams: Generation and Spectroscopy
Authors: Ralph Stephen E. , Grischkowsky D. 
Published: March 2011

ABSTRACTTeraHertz beams of ultrafast pulses of far infrared (λ=40–1000μm, v = 0.3x1012− 7.5×1012Hz) radiation generated via the induced dipole of photogenerated charge within a strong electric field in semiconductors are an emerging spectroscopic technique which incorporates ultrafast optical pulse generation, optoelectronics, and far infrared techniques. Recent results obtained using the trap enhanced field (TEF)[1] effect in the generation of THz beams demonstrate the extended frequency range of these sources and show their importance to time resolved infrared spectroscopy.The generation of collimated THz radiation within semi-insulating materials is dramatically improved by the extremely large field enhancement near the anode of an electrically biased metal/semi-insulator/metal structure. Our experimental results for semiinsulating GaAs establish an operational regime in which the applied potential is confined to a small region near the anode resulting from a space charge region which exists due to a dramatic change in the number of ionized EL2 traps. The effect, contrary to that observed in trap free or doped materials, is enhanced by optical injection of carriers near the anode, and can be exploited for the efficient generation of ultrafast THz radiation.Spectroscopy using THz beams allows both the static and dynamic properties, including refractive index, absorption, and photoconductivity, of materials and structures to be accurately measured. The energy range and time resolution of freely propagating subpsec THz pulses have not been previously available.
Rowth of Y-CUT LiNbO3 Layers on (1102) Al2O3
Authors: Robinson H. , Milledge H.J. , Pitf C.W. 
Published: March 2011

ABSTRACTIt has been found that y-cut LiNbO3 heteroepitaxial layers of good quality (as determined from X-ray diffraction patterns) can be obtained by radio frequency sputtering on noncrystallographic (vicinal) substrate surfaces approximating (1102) of Al2O3, in accord with the results concerning (100) Si growth on A12O3.Such material may find application in optical modulators monolithically integrated on to silicon-on-sapphire (SOS) circuits.
LOW-Temperature Epitaxial Growth of GaAs on Si Substrates by MBE
Authors: Chiang Ting-Yen , Liu En-Huery , Yiin Der-Hwa , Yew Tri-Rung 
Published: March 2011

ABSTRACTThis paper presents results of the low—temperature epitaxial growth of GaAs on Si substrates with orientation 1°—4° off (100) by molecular beam epitaxy (MBE). The epitaxial growth ·is carried out on Si wafers subjected to HF solution treatment by “spin-etch” technique before the wafer is transferred to the entry chamber of MBE system. Methods used for reducing defect density in the epitaxial layers are proposed. The characterization techniques include cross-sectional transmission electron microscopy (XTEM), plan-view transmission electron microscopy, scanning electron microscopy (S EM), and double crystal X-ray diffraction (DCXRD). Epitaxial films with a full width at half—maximum (FWHM) of about 310 arcsec measured by DCXRD are obtained without annealing.-
Initial Stage of Solid Phase Epitaxial Growth of GaAs Films on Vicinal Si (001) Substrate
Authors: Choo W.K. , Kim I. , Lee J.Y. , Cho K.I. , Lee J.-L. , Kim Y.J. 
Published: March 2011

ABSTRACTThe initial stage of solid phase epitaxial (SPE) growth of GaAs films on the vicinal Si (001) substrate was investigated by high resolution transmission electron microscopy (H-RTEM). Cross-sectional [110] and [110] HRTEM images show that the SPE growth of crystalline GaAs islands from the amorphous phase proceeds via the formation of three-dimensional islands at the initial stage and islands' size and spacing are not critically dependent on the substrate tilt direction. The average vertical and lateral dimensions of islands were found to be 9 nm and 14 nm respectively, and the average island spacing was 10 nm. Moreover, many internal stacking faults (and/or microtwins) and a few dislocations have been already formed at this initial stage of growth. In addition, the critical thickness for misfit dislocation formation is found to depend upon the islands' lateral dimensions as well as the heights.
Allotaxy: A New Method for Epitaxial Growth of Compound Thin Films
Authors: Mantl S. , Bay H. L. , Dieker Ch. 
Published: March 2011

ABSTRACTA new method for the growth of epitaxial compound thin films, termed allotaxy, is proposed and the fabrication of the silicide heterostructure Si/CoSi2/Si(100) Is demonstrated. Allotaxy is a two. step process. In our example, Si is deposited on a heated Si substrate and then Co is coevaporated at varying rates such that a peaked Co-depth profile in Si is generated. At appropriate deposition conditions CoSi2 precipitates embedded in single crystalline Si are formed. These precipitates coarsen and coalesce into a buried, uniform, epitaxial CoSi2 layer during the second processing step, a high temperature anneal. Allotaxy should allow not only the epitaxial growth of silicides but also that of other binary, precipitates forming systems.
Formation of Heterogeneous Thickness Modulations During Epitaxial Growth of LPCVD-Si1−xGex/Si Quantum Well Structures
Authors: Vescan L. , Jäger W. , Dieker C. , Schmidt K. , Hartmann A. , Lüth H. 
Published: March 2011

ABSTRACTTransmission electron microscopy and photoluminescence studies were performed to determine the critical thickness for generation of misfit dislocations in Sil-xGex layers grown by low pressure chemical vapor deposition. Above a certain Ge content the transition from two dimensional to three-dimensional growth occurs before generation of misfit dislocations. For instance, for x ∼0.3 and a substrate temperature around 700°C island formation was observed to start at 1.8 nm. The formation of islands is attributed to the preferential growth of SiGe in areas with less lattice strain. Islands were observed to broaden the exciton photoluminescence of the quantum well structures.
Observation of the Ordered CoPt3 Alloy in Co-Pt Multilayers
Authors: Toney M.F. , Farrow R.F.C. , Marks R.F. , Harp G. , Rabedeau T.A. 
Published: March 2011

ABSTRACTWe report results of a synchrotron X-ray diffraction study of Co-Pt multilayers, with Pt[111] as the growth axis. The multilayers were grown by MBE on Pt seedfilms on basal-plane sapphire substrates at growth temperatures of 100 and 200ºC.The multilayers comprised 15 periods of Co 3Å, Pt 15Å and both exhibited perpendicular anisotropy. Grazing-incidence radial- and phi-scans revealed a set of {110{ peaks indicating doubling of real space periodicity consistent with the presence of the ordered alloy CoPt3. This supports the results of other studies which indicate interdiffused interfaces in Co-Pt multilayers and shows that chemical ordering can occur at much lower temperatures than in bulk alloys where annealing times of several days at ∼ 700ºC are required to stimulate ordering.
Atomic Structure of Interfaces in Epitaxial NiSi2 on (001) Silicon
Authors: Chen W.J. , Chen F.R. , Chen L.J. 
Published: March 2011

ABSTRACTHigh resolution transmission electron microscopy (HRTEM) has been applied to study the atomic structure of NiSi2 /(001)Si interface. Previous HRTEM result suggested that Ni atoms in the boundary core are six-fold coordinated and Si atoms are everywhere tetrahedrally coordinated. In this work, high resolution imaging technique and computer image simulation were used to study the atomic structure of NiSi2 /(001)Si interfaces and a new interface structure was found. For the new interface structure, Ni and Si atoms are also six-fold and tetrahedrally coordinated, respectively, with an extra layer of fourfold planar bonded Si atoms present at the interface.
Relationship between Self-Texture and Interfacial Restriction on the Epitaxy of (Ca,Sr)CuO2 Thin Films
Authors: Nagai Satoshi , Tanaka Hideaki , Fujimura Norifumi , Ito Taichiro 
Published: March 2011

ABSTRACTThe Orientation control of (Ca,Sr)CuO2 film has been investigated under various sputtering conditions from the view point of controlling the “self-texture” and epitaxy. The films with (001), (110) and (101) orientations were able to be obtained by changing partial gas pressure during sputtering. These orientations were observed on glass and MgO(100) single crystal substrates. The cohesive energy between the film and the MgO single crystal substrate was calculated to evaluate the change in orientation on glass and MgO substrates.
Growth and Characterization Of GexSi1−x/ Si Multiple Quantum Well Structures
Authors: Greve D.W. , Misra R. , Capano M.A. , Schlesinger T.E. 
Published: March 2011

ABSTRACTWe report on the growth and characterization of multiple quantum well structures by UHV/ CVD epitaxy. X- ray diffraction is used to verify the expected layer periodicity and to determine the quantum well thickness. Photoluminescence measurements show peaks which we associate with recombination of excitons in the quantum wells. The measurements are consistent with high quality layers with small variation in quantum well thickness across a wafer.
Dependence on MOCVD Growth Temperature of The Photoluminescence Properties of ZnSe, ZnTe, and ZnSe(1-x)Te(x) Alloys and ZnSe/ZnTe Superlattices
Authors: Ponga B.E. , Calas J. , Averous M. , Cloitre T. , Briot O. , Gil B. , Aulombard R.L. 
Published: March 2011

ABSTRACTIt has been recently shown that high quality ZnSe and ZnTc filns can be grown on GaAs using low temperature growth techniques such as Metal-Organic Chemical Vapor Deposition ( MOCVD). All samples: ZnSe, ZnTe, ZnSc(l−x)Tc(x) epilayers and ZnSe/ZnTc superlattices were grown using a novel zinc precursor, the Tri-Ethyl-Amine Di-Methyl-Zinc, while we used the classical precursors H2Se and Di-Isopropyl-Tellurium for selenium and tellurium. Investigation of the photoluminescence (PL) properties of ZnSc and ZnTe single layers enabled us to optimize the growth conditions of these compounds. The crystal growth conditions for mixed alloys and superlattices were determined by direct comparison to the aspect of low-temperature PL features. Strong PL spectra were obtained from these materials, suggesting us that tellurium has the ability to behave like an iso-clectronic center. At low concentration of tellurium in ZnSe, an interesting physical situation is observed, which we have interpreted in terms of extrinsic exciton “self-trapping” mechanism.
Anisotropic Electron Mobility of Two-Dimensional-Electron-Gas in Modulation Doped Inx.Ga1−y As/InyAl1−yAs Heterostructures
Authors: Chen Jianhui , Fernandez J.M. , Wieder H.H. 
Published: March 2011

ABSTRACTWe have investigated the electrical properties of the two-dimensional-electron-gas (2DEG) present in strain relaxed heterojunctions with InxGa1−xAs channels (x<0.4). These were grown by molecular beam epitaxy on misoriented (001) GaAs substrates using compositionally step graded buffer layers, … x' = 0.1 per step, each step 0.3 µm thick. The 2DEG is produced by modulation doping using lattice matched InyAl1−yAs as the carrier supply layer. We find typical electron densities and mobilities, for x=0.3, of ns(300 K) = 1.3 × 1012 cm−2 and µH(300 K) = 9300 cm2/V-s; and for ns(1.6 K) = 1.2 × 1012 cm−2, µH(1.6 K) = 37800 cm2/V-s. While the room temperature electron mobility shows negligible anisotropy, an <110>-orientation dependent low temperature electron mobility of the 2DEG is observed and attributed to dislocation scattering.
Strain Relief Mechanisms in The Growth of GexSi1−x/Si(110) Heterostructures
Authors: Hull R. , Bean J.C. , Weir B. , Peticolas L.J. , Bahnck D. , Feldman L.C. 
Published: March 2011

ABSTRACTWe describe a detailed quantitative theoretical and experimental analysis of strain relief mechanisms in GexSi1−x/Si(110). For this interface, both partial and total glide dislocations may effect strain relief. Detailed comparison between experimental measurement and theoretical prediction of the regimes in which the two types of dislocations are observed allows a very accurate determination of the stacking fault energy in GexSi1−x alloys.
Properties and Strain Relaxation below Room Temperature of Epitaxial Pbse and Pb(Se,Te) on Fluoride-Covered Silicon Substrates
Authors: Maissen C. , Zogg H. , Blunier S. , Sultan A. , Teodoropol S. , Richmond T. , Tomm J.W. , Kostorz G. 
Published: March 2011

ABSTRACTNarrow-gap PbSe and PbSe1−xTex films were grown by MBE on 3n-Si(111) wafers. The layers are used for IR-sensor array applications. Epitaxy was achieved by using an intermediate CaF2/BaF2 bilayer to overcome the large difference in lattice constants (14%) and thermal expansion coefficients (700%). While PbSe is rather soft, the hardness increases with x (x<0.5) in PbSe1−xTex. Thermal stresses are relieved by dislocation glide on (100)-planes, leading to slip lines on the surface. The surface morphology and step heights were studied with the scanning tunneling microscopy technique, and a model for the resulting (111)-surface structure is presented. The value of the remaining strain was determined with precision Rutherford backscattering spectrometry absolute angle measurements, X-ray diffraction and photoluminescence in the temperature range down to 10 K. It is found that no appreciable strain builds up even at cryogenic temperatures and after many temperature cycles. In contrast to PbSe, ternary PbSe1−xTex layers are strained elastically below room temperature owing to solid solution strengthening, and plastic deformation occurs only at higher temperatures.
Quaternary Alloys InxAlyGa1−x-yAs Grown on GaAs with A Compositionally-Step-Graded Buffer
Authors: Fan C. , Shih D. W. , Hansen M. W. , Chen J. , Lee P. Z. , Esener S. C. 
Published: March 2011

ABSTRACTFundamental bandgaps and Schottky barrier heights of strain-relaxed quaternary InxAlyGa1−x-yAs alloys with 0 < x < 0.35 and 0 < y < 0.30 were studied. The alloys were grown on GaAs substrates by molecular beam epitaxy. The lattice mismatch (up to 2.5%) and mismatch strain were accommodated by a compositionally-step-graded buffer. A residual compressive strain of less than 0.5% was determined by x-ray diffraction. Measured Schottky barrier heights v.s. bandgap deviate from the values predicted by the “commonanion” rule. This behavior is attributed to the compositional inhomogeneities and chemical reactivity of the air-exposed InAlGaAs surfaces.
X-Ray Diffraction Determination of Critical Thickness of InAs and InP on GaAs Grown by Atomic Layer Molecular Beam Epitaxy
Authors: Mazuelas A. , Gonzalez L. , Tapfer L. , Briones F. 
Published: March 2011

ABSTRACTTwo series of samples consisting in a strained layer of InAs (InP) of different thickness, InAs N monolayers (ML) with N=1,2,3, and 4, and, InP M ML with M=2,3,4,5,6 and 7, covered by a GaAs cap layer of 200 nm were grown by Atomic Layer Molecular Beam Epitaxy (ALMBE).The samples have been characterized by X-ray diffraction in order to measure the critical thickness of InAs and InP on GaAs.Computer simulation using dynamical theory of X-ray diffraction is used to fit the experimental patterns. In this way we determine the composition, thickness, and strain both in the strained layer of InAs or InP and in the cap layer of GaAs.A disagreement between simulated and experimental curves is reached at a thickness where the beginning of relaxation takes place (i.e. critical thickness). We have found that the critical thickness of InAs on GaAs(001) is 2.3 ML (0.75 nm) and the critical thickness of InP on GaAs(001) is 5.6–5.7 ML (1.71-1.74 nm), both grown by ALMBE.
Tem Study of Temperature Influence on The Crystalline Quality of InGaAs/Si Epilayers
Authors: Vila A. , Cornet A. , Morante J.R. , Westwood D.I. 
Published: March 2011

ABSTRACTA Transmission Electron Microscopy (TEM) study of In0.53Ga0.47As Molecular Beam Epitaxy films grown at different temperatures onto misoriented Si (100) substrates is presented. The evolution of the density of the different kind of defects is discussed as a function of the growth temperature in the range between 200 and 500° C. The results are compared with the characterization techniques of Double Crystal X-Ray Diffraction and Hall effect.
The Chemical Interaction of Disilane on Ge(100)
Authors: Lapiano-Smith D. A. , McFeely F. R. 
Published: March 2011

ABSTRACTThe room temperature chemisorption of disilane on Ge(100) and subsequent reaction at elevated temperatures was investigated by core level photoemission spectroscopy. At room temperature Si2H6 chemisorbs dissociatively on Ge(100) forming a surface populated largely by Si-H groups. Annealing the sample to 300°C effectively reduces the Si-H species to elemental Si. An additional anneal to 580°C promotes the diffusion of Si into the bulk and restores the Ge surface to an atomically clean state.
VLPCVD Heteroepitaxial Growth of Very Thin GE-Layers on Si-Substrates
Authors: Caymax Matty R. , Poortmans J. , Ammel A. Van , Nus J. , Vandervorst W. , Vanhellemont J. , Brus B. 
Published: March 2011

ABSTRACTBy Pulsed Gas CVD-growth, heteroepitaxial growth of pure Ge-layers from pure GeH4 has been accomplished at 650 °C on Si-substrates without intermediate Si1−xGex-bufferlayers. The material has been studied by means of RBS, SEM, ECP, XRD and cross-sectional, highresolution and plan-view TEM. The thickness of the Ge-layers varied between 2 and 24 monolayers. From 5 monolayers on, some part of the Ge appears to be fully relaxed. Uptill 12 monolayers, the growth is fully 2-dimensional and results in specular, flat surfaces; for thicker layers islanding starts (Stranski-Krastanow growth). The material is completely defect-free. According to XRD-measurements, the perpendicular strained Ge-cell dimension is 5.748 Å, which is very reproducible for all layer-thicknesses. Nevertheless, from linear elastic theory considerations, it should be 5.83 Å. The Ge-layers so formed appear to be suitable for use in short-period (SinGem)p-superlattices.
Uni-Directional Shrinkage Sintering for Ceramic Packaging Substrates with Low Dimensional Tolerances
Authors: Kodama Hironori 
Published: March 2011

AbstractUni-directional shrinkage sintering technology was studied to fabricate ceramic packaging substrates which meet requirements of very low dimensional tolerances (high dimensional accuracy). Three methods were considered. The first method used laminating of long fiber sheet materials and showed restraining effects on X, Y-directional (plane dimensional) shrinkage. However, the restricting ability was not sufficient for thicker laminates of the green sheets. The second method incorporated short fibers with a planar arrangement in green sheets, and some constraining effects on X, Y-directional shrinkage were observed with increasing short fiber content and modification of the fiber mixing method. But there was concurrent lowering of densification. The third method applied pressure lightly during sintering without using a mold. Control of the sintering shrinkage was relatively easy and X, Y-directional shrinkage of less than 0.1% was achieved by selecting a suitable pressure for the process. This method is very simple and easy to control, ensuring products of high dimensional accuracy.
Characterization of Polyimide Thin Films on Metals
Authors: Lu Jiong-Ping , Nagarkar Pradnya V. , Volfson David , Jensen Klavs F. , Senturia Stephen D. 
Published: March 2011

AbstractWe describe an approach using thin films on metals as models to study interfacial interactions. Thin films of biphenyl-tetracarboxylic dianhydride (BPDA) - p-phenylene diamine (PPD) based polyimide on Cr and Au surfaces have been investigated using infrared reflection absorption spectroscopy (IRRAS) and x-ray photoelectron spectroscopy (XPS). IRRAS was used for in-situ monitoring of polymer curing processes. Cured polyimide thin films on metals were characterized ex-situ by both XPS and IRRAS. Anhydride was observed to be an intermediate during chemical transformation of polyamic acid to polyimide. Imidization processes were found to be completed after curing at 250°C for thin films. Strong chemical modification of polyimide thin films resulting from interaction with Cr substrates were observed by infrared spectroscopy. These observations were consistent with angle-resolved XPS data showing a different C 1s emission spectrum of polyimide-Cr interfacial region, compared to the polyimide spectrum.
Waxd Study of Low TCE Polyimide Films Formed from Polyamic Acid Blends and Copolymers.
Authors: Nunes Thomas L. , Sachdev Krishna G. 
Published: March 2011

AbstractLow TCE polyimides, typically BPDA-PDA and related materials are well known for their special properties which include low in-plane TCE, up to 3X higher elastic modulus and ultimate tensile strength, and lower moisture uptake relative to the commonly known flexible chain polyimides [1]. These differences are due to the rod-like orientation and highly organized molecular structure of the polyimides that are derived from linear-planar precursors resulting in more anisotropic properties such as the X-Y vs Z-direction TCE [2], and optical as well as dielectric properties.In the present study, we have measured the WAXD patterns of polyimide films formed from BPDA-PDA and BTDA-PDA polyamic acid mixtures and BPDA-BTDA-PDA random copolyamic acids. In order to examine the effect of a highly flexible chain segment on the molecular anisotropy of rod-like polyimides, preliminary WAXD patterns were recorded for films of BPDA-BDAF and a BPDA-PDA-BDAF copolyimide.An in-plane and an out-of-plane crystallinity index, measures of molecular order within the polyimide films studied were estimated from the WAXD patterns. The data are correlated with the various blends and copolymer compositions and discussed in terms of structural implications.
Chemistry Of Solid/Solid Interfaces
Authors: Opila R. L. 
Published: March 2011

AbstractThe chemistry that occurs at buried interfaces often determines the performance and reliability of multi-chip modules (MCM's). For example, chemical reactions between sputter deposited metals and polymers may ultimately determine the interlayer adhesion of multilevel metallizations for MCM's. Both destructive and non-destructive probes can used to study these interfaces, and the interfaces may be studied as they are formed or as they age. Complicating the interpretation of any of the results of these techniques is the inherent complexity of the chemistry and, often, the non-planarity of the interface. Several examples of complex interfaces will be described along with strategies for elucidating the chemistry and their reliability.
Characterization and Use of Polyfluorosiloxanes in Automotive Applications
Authors: Polak Anthony 
Published: March 2011

AbstractPolysiloxanes are routinely used in the semiconductor industry as die encapsulants. Thermal analysis, NMR, ion chromatography, and dielectric spectroscopy was used to characterize these polymers. The dielectric loss spectrum was found to be directly related to the long term electrical stability of the encapsulated die, and was also found to be a more sensitive technique for determining the concentration of electronically active impurities than GC/MS, and ion chromatography. Dielectric spectroscopy was also used to study the diffusion of acids, and water, through these polymers. While the solubility of acids and water in these materials is low, their diffusion constants are high, on the order of 10−4 cm2/s. In addition, the interaction of the encapsulant with the silicon nitride passivation used on the die surface was found to have an effect on the long term stability of the device. This is believed to be due to the formation of a conductive layer at the silicon nitride/polymer interface which ultimately forms a leakage path between the bond pads, or into the silicon nitride passivation layer.