bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrical Conductivity as a Function of Temperature of Diamond films Grown by Downstream Microwave Plasma Chemical Vapor Deposition
Authors: Stoner Brian R. , Windheim Jesko A. von , Glass Jeffrey T.
Published: March 2011

Electrical conductivity measurements were used to study the effects that sample distance from the plasma during growth has on the carrier transport properties of undoped CVD diamond. The films were grown by downstream microwave plasma chemical vapor deposition at distances from 0.5 to 2.0 cm from the edge of plasma glow. Electrical conductivity measurements were performed between room temperature and 1000 °C to gain a better understanding of the CVD growth process and the resulting electrical properties of the diamond film's. Room temperature electrical conductivity was found to vary by over 5 orders of magnitude with increasing growth distance from the plasma, and this is attributed to decreasing hydrogen incorporation efficiencies at further distances from the plasma.
Physical Property Characteristics of Pitch Materials
Authors: Anderson David P. , Wapner Philip G. , Curliss David B.
Published: March 2011

The two most important material properties for foam process modeling are liquid viscosity and surface tension. Several different pitches were examined including Ashland petroleum pitches and a synthetic mesophase pitch (Mitsubishi AR). Viscosities of isotropic pitch were measured at various temperatures above their softening points using an oscillating disk rheometer and found to be independent of shear rate and closely match the manufacturer's data. Only a very weak dependence of surface tension on temperature was found from calculations made from pendent drop measurements. The density of these materials, which was needed for the surface tension calculations, was measured using an elevated temperature mercury dilatometer. Transitions indicated by the volumetric results were also investigated by DSC.
Influence of Growth Orientation and Uniaxial Stress on the Electronic Properties of GaAs / GaAlAs Quantum Wells
Authors: Saidi N. , Zitouni K. , Kadri A.
Published: March 2011

Using the envelope function formalism and the effective mass thecry, we have studied the E(k) energy dispersion and the confinement energies of the lower lying conduction band and the higher lying valence bands states in GaAs /GaAlAs Single Qantum Well (SQW) structures grown on GaAs substrates with different orientations of the growth axis :(001),(111),and (113). Then, the valence subbands dispersions are calculated away from the zone center for a given well width and under uniaxial stress for the three different growth directions
Extended Pseudomorphic Limits Using Compliant Substrates
Authors: Lo Y. H. , Schaff W. J. , Teng D.
Published: March 2011

We propose a new approach, growth on compliant substrates, to achieve extended pseudomorphic limits. The compliant substrate can be approximately achieved with a corner supported membrane structure. Both thermal equilibrium model and dynamic model considering strain relaxation are used to analyze the relations between the extended critical thickness and the substrate thickness. Preliminary experimental results of InGaAs grown on GaAs membranes seem to support the theories.
Uniformity Control in Elemental Vapor Transport Epitaxy
Authors: Gurary A. I. , Tompa G. S. , Stall R. A. , Liang S. , Lu Y. , KUO H. C.
Published: March 2011

Elemental Vapor Transport Epitaxy (EVTE) is a novel technique for semiconductor manufacturing, which combines the advantages of Molecular Beam Epitaxy (MBE) and Vapor Phase Epitaxy (VPE). EVTE provides a high level of elemental flux control, scaling to large deposition areas, and elimination of elemental Ga source related oval defects. EVTE has been successfully applied to the deposition of III-V and II-VI thin films and heterostructures. Design considerations and evaluations of the novel EVTE elements: elemental flux regulating valve operating at temperatures >1250°C with demonstrated response times less than 1 second and elemental flux distribution manifold are presented. The calculated operational parameters for EVTE are in good agreement with the observed experimental results.
GaAs / AlGaAs SQW Optical Switch on Si
Authors: Yuasa T. , Nagashima Y. , Egawa T. , Jimbo T. , Umeno M.
Published: March 2011

We reported a waveguide-type optical switch fabricated on a Si substrate which utilized the Quantum Confined Stark Effect (QCSE). The prepared sample is an Al0.3Ga0.7As (cladding layer) / Al0.25Ga0.75As (guiding layer) double-heterostructure (DH) optical switch with a GaAs single quantum well (SQW) in the guiding layer by MOCVD. The absorption edge of the sample is measured by photocurrent method under reverse bias using a cw Ti: Sapphire laser for a light source. We measured about 10 nm shift of the absorption edge at -8 V from the sample with 8.3 nm SQW. This result demonstrates the Stark-shift effect of GaAs SQW on Si. A 2.5 μm-width ridge was formed by etching in the top cladding layer and the light traveling in the guiding layer was confined to a fundamental mode in vertical (parallel to growth direction) and horizontal direction. This switch showed 33.1 dB/mm modulation at 867 nm wavelength in -8 V bias.
Use of Low Temperature Si MBE Growth Techniques for High Performance SiGe/Si Electronics
Authors: Croke E. T. , Harrell M. J. , Mierzwinski M. E. , Plummer J. D.
Published: March 2011

Through the use of low temperature Si molecular beam epitaxy (MBE), we have fabricated high performance Si1−x Gex/Si heterojunction bipolar transistors (HBTs) and bipolar inversion-channel field effect transistors (BICFETs). Our growth method employs a high temperature Si-assisted desorption followed by MBE growth at a temperature only slightly in excess of the critical temperature for two-dimensional layer-by-layer growth. [1] At this temperature, segregation of Sb has previously been shown to be kinetically limited. [2] In addition, significantly more strain can be frozen into such an epitaxial layer as compared with those grown at higher temperatures.[3] Secondary ion mass spectroscopy (SIMS) data verify the abruptness of the Sb doping profiles in our device structures. High resolution x-ray diffraction (HRXRD) data are consistent with planar, coherently strained Si1−x Gex layers in our HBTs. A gain of 2690 (3210) is observed in our BICFETs at 300 K (7 K).
Growth of Ge-on-Si Structures using Remote Plasma-Enhanced Chemical Vapor Deposition
Authors: Qian Rong Z. , Kinosky D. , Mahajan A. , Thomas S. , Fretwell J. , Munguia P. , Banerjee S. , Tasch A.
Published: March 2011

Remote Plasma-enhanced Chemical Vapor Deposition (RPCVD) has been successfully used to grow GexSi1−x/Si (x = 0.1 – 1.0) heteroepitaxial structures at low temperatures (∼450°C). This technique utilizes a noble gas (Ar or He) r-f plasma to decompose reactant gases (SiH4 and GeH4) and drive the chemical deposition reactions in the gas phase as well as on the substrate surface. Growth of pure Ge on Si is of great interest because it provides a promising technique for making suitable low-cost substrates for thin-film Ge photodetectors as well as GaAs devices on Si substrates. The realization of these applications depends on the ability to grow high-quality epitaxial Ge layers on Si substrates. Since GaAs is lattice matched to Ge, growth of Ge layers on Si substrates with good crystalline perfection would permit the integration of GaAs and Si devices. Islanding was observed after the growth of pure Ge films directly on Si(100) for a wide range of plasma powers (7W ∼ 16W) in RPCVD. Cross-sectional TEM analysis showed that the islands have complicated facet structures, including {311} planes. Graded Gex Si1−x buffer layers with different Ge profiles have been used prior to the growth of Ge. It was found that uniform Ge films can be obtained using a buffer with an abrupt Ge profile, and the dislocation density in the Ge film decreases with increasing distance from the substrate.
Transport in High-Mobility Si1−xGex Heterostructures Grown by Molecular-Beam Epitaxy
Authors: Monroe Don , Xie Y.-H. , Fitzgerald E. A. , Silverman P. J.
Published: March 2011

We report Hall mobilities (at T = 4.2K) as high as 180,000cm2V−1 s−1 in modulation-doped Si layers in Si1−x Gex heterostructures grown by Molecular-Beam Epitaxy. These mobilities reflect dramatic improvements in the quality of relaxed Si1−xGex buffer layers (with x'30%) grown by gradual grading of composition at high temperature. The resulting moderate threading dislocation densities (< 106 cm−2 ) appear to cause no mobility degradation. The strong damping of Shubnikov de Haas oscillations, as well as the increase of mobility with carrier density, indicate predominantly small-angle scattering. This suggests that residual Coulomb scattering from background impurities limit the mobility, rather than interface-roughness scattering as for the Si/SiO2 interface. The reduced interfacial scattering, as well as the strain-induced splitting of the valley degeneracy to select the two low-effective-mass valleys, significantly enhance room-temperature transport as well, with μHall ' 2,100cm2 V−1 s−1. We also observe a small splitting of the remaining twofold valley degeneracy using the integral quantized Hall effect. As a further indication of the high sample quality, measurements to 17T at 0.3K show indications of the v = 2/3 fractional quantum Hall effect.
The Influence of Strain-Mediated Morphological Changes on the Structural and Optical Properties of MBE-Grown GeSi/Si
Authors: Perovic D. D. , Whitehurst J. , Noel J. P. , Rowell N. L. , Houghton D. C.
Published: March 2011

Recent studies on strained layer heteroepitaxy in high misfit systems (eg. Ge on Si) have clearly indicated the importance of elastic strain on a number of surface-mediated growth effects. In this work we consider the transition from ideal, 2-D layer-by-layer growth to the initial stages of a 3-D growth morphology as a precursor to misfit dislocation injection in GexSi1−x/Si heterostructures with x as low as 0.15. Experimentally, we have studied a wide range of MBE-and CVD-grown single and multilayer GexSi1−x/Si (x<0.5) structures using transmission electron microscopy and photoluminescence spectroscopy. Firstly, we describe a new mechanism for the heterogeneous nucleation of misfit dislocations in strained epitaxial layers, the ‘double half-loop’ source, which originates from atomic-scale (<1.5 nm) interfacial perturbations. Secondly, the atomic-scale dilatational perturbations, which can exist in areal densities up to ∼109 cm−2, have been identified as the origin of intense, broad-band PL from MBE-grown GexSi1−x/Si strained layers. The change in PL behaviour with increasing strained layer thickness has been used to study the effects of elastic strain-induced surface roughening at low misfits.
Single Crystalline / Porous Amorphous Superlattice Formation by the Etching of MBE Grown Si/Si1−x Gex Layers on Si Substrates
Authors: George T. , Pike W. T. , Fathauer R. W. , Jones E. W. , Ksendzov A.
Published: March 2011

Novel porous amorphous/crystalline superlattices were produced by the etching of mesas containing superlattices of alternating layers of Si and Si1−xGex. These layers were grown by molecular beam epitaxy on (100) Si substrates and etched in an aqueous HF:HNO3 solution. Preferential attack and amorphization of the Si1−x Gex layers was observed, leading to the formation of alternating layers of single crystal Si and porous amorphous Si1−xGex. The etchant is highly selective and it was possible to etch extremely thin (5nm) Si0.7Ge0.3 layers between 30nm Si layers. Complete conversion of the Si0.7Ge0.3 layers to the porous amorphous state was seen in lμm wide mesas. The role of composition and thickness of the Si1−xGex layers was studied. The variation in the lateral etch depths of the Si1−xGex layers in the superlattices demonstrates that lattice strain in these layers is an important factor in the selectivity of the etch process. As the thickness of the Si1−xGex layers is decreased, transport of the etchant to and the etch products from the reaction front is reduced, limiting the penetration of the etching process. The porosities of these etched Si1−xGex layers were determined to be comparable to measured values for thick etched alloy layers.
Transmission Electron Microscopy of Nitrogen Doped ZnSe/GaAs
Authors: Kuo L. H. , Salamanca-Riba L. , Depuydt J. M. , Cheng H. , Qiu J.
Published: March 2011

Transmission election microscopy studies show that nitrogen doping changes the misfit dislocation structure in ZnSe films and decreases the density of threading dislocations. There appears to be a critical N doping concentration of ∼ 1.5 × 1018/cm3 above which the density of threading dislocations increases again. Samples with high N doping concentrations (> 1019/cm3 ) also show compensation or decrease in the carrier density of the films. Our TEM observations show that N doping can produce low energy nucleation sites for the 60° misfit dislocations at or close to the ZnSe/GaAs interface.
Fabrication of Short Period ZnSe-GaAs Superlattices by MOVPE
Authors: Funato Mitsuru , Fujita Shizuo , Fujita Shigeo
Published: March 2011

The growth condition and the structural properties of short period ZnSe-GaAs superlattices grown by metalorganic vapor phase epitaxy (MOVPE) are described. First, the growth condition was investigated. Superlattices (SLs) grown at 450°C have better structural property than those grown at 500°C. The thickness fluctuation of each constituent layer was investigated by means of the X-ray diffraction analysis, and it was indicated that the fluctuation in the fabricated structure was within 1 and 2 monomolecular layers for GaAs and ZnSe, respectively. Further optimization for growing thinner layers successfully brought SL with 25Å well and 140Å barrier layers. X-ray diffraction analysis and transmission electron microscopy (TEM) observation showed its good structural properties; high crystalline quality, high degree of lateral uniformity, well defined interfaces and strong periodicity. Another SL with 100 periods of ZnSe (33Å) / GaAs (25Å), which have smaller layer thickness and much larger number of periods compared with the SL mentioned above, could be also fabricated and the crystalline quality was found to be excellent by X-ray diffraction measurement.
Trapping and Luminescence Mechanism Studies in SrS:Eu2+, Sm3+ Thin Films at Various Temperatures
Authors: Hua Susan Z. , Salamanca-Riba L. , Wuttig M. , Soltani P. K.
Published: March 2011

The temperature dependence of photoluminescence in SrS singly and doubly doped with Eu2+, Sm3+ was studied with different excitation energies. Different energy transfer mechanisms, namely, phonon-assisted energy transfer and electron transfer through energy bands, depending on the excitation energy, are proposed to take place in SrS:Eu2+, Sm3+ thin films. We estimate that under UV light excitation 10% of Eu2+ emission originates from electronic transitions between Eu2+ and Sm3+ through the conduction and valance bands. In contrast, direct inter-ionic transitions take place for 2.84 eV excitation energy via a phonon assistance mechanism.
Exciton Magnetoluminescence Studies in Ordered and Disordered In0.48Ga0.52P Semiconductor Alloys
Authors: Jones E. D. , Follstaedt D. M. , Lyo S. K. , Schneider R. P.
Published: March 2011

We report the observation of magnetic-field dependent excitonic photoluminescence energies and linewidths in ordered and disordered In0.48Ga0.52P alloys (lattice matched to GaAs). The photoluminescence measurements were made at 1.4 K and the applied magnetic field ranged between 0 and 13.6 tesla. With increasing magnetic fields, we observe increasing photoluminescence linewidths for disordered alloys and decreasing photoluminescence linewidths for the ordered alloys. The magnetic field dependence of the photoluminescence peak-energy shifts for all samples (ordered and disordered) is in good agreement with theoretical considerations. The presence of CuPt-type ordering was confirmed by transmission electron microscopy.
Optical Properties and Band Offset of PbTe/Pb1−xEuxTe Diluted Magnetic Semiconductor Multiquantum Wells Studied by Transmission and Photoconductivity Measurements
Authors: Yuan Shu , Krenn H. , Springholz G. , Bauer G. , Kriechbaum M.
Published: March 2011

From transmission experiments in the mid infrared region the optical interband transitions between electric subbands in the valence and conduction band of the PbTe wells embedded in Pb1−xEuxTe barriers (x = 2.6% to 3.0%) were determined and compared with calculations based on the envelope function approximation. The frequency dependence of the absorption constant α was calculated, taking the in-plane dispersion of the multiquantum well band structure into account. The frequency dependence of the refractive index n(ω) was derived from α(ω) using a Kramers-Kronig transformation and it exhibits several extrema which coincide with the onset of the various interband transitions. Experimentally the onset of these transitions was also observed in photoconductivity experiments. The changes in n(ω) are as large as 15 % and therefore important for the optical confinement in quantum well lasers grown with these materials.
Growth of Single Crystal Si/NiSi2/Si(100) and Si/CoSi2/Si(100) Structures by Molecular Beam Epitaxy and Furnace Annealing
Authors: Tung R. T. , Eaglesham D. J. , Schrey F. , Sullivan J. P.
Published: March 2011

Uniform, single crystal Si/NiSi2/Si(100) and Si/CoSi2/Si(100) structures were fabricated by molecular beam epitaxy and furnace annealing. A Si template technique and a post-growth anneal at ∼960°C led to high quality buried NiSi2 layers with thickness ∼1000Å. The conditions for fabricating high quality buried CoSi2 layers by the recently proposed allotaxy process were studied and discussed. The endotaxial growth of buried CoSi2 layers in Si(100) was also studied.
Electrical and Structural Properties of Cobalt Annealed on Silicon-Germanium Epilayers
Authors: Sarcona G. , Lin F. , Hatalis M. K. , Cserhati A. F. , Austin Eva , Greve D. W.
Published: March 2011

The structural and electrical properties of cobalt annealed on heteroepitaxial, strained-layer silicon-germanium were studied by transmission electron microscopy, four-point-probe and four-terminal resistor resistivity measurements, and junction diodes. The I50nm thick epitaxial p-Si0.87Ge0.13 was grown by UHV-CVD at 590°C. Cobalt was deposited by DC magnetron sputtering. The cobalt was rapid-thermally annealed at various temperatures in forming gas.

The cobalt film and the SiGe layer reacted, as illustrated by changes in their film thicknesses, and increased interfacial roughness. The roughness and reacted-film thickness increased with increasing temperature. The sheet resistances of the samples were dependant on the anneal temperature and time. Films formed by annealing at 700°C, 3 min, were 80nm thick, and had 2.8ω/sq sheet resistivity, corresponding to 20μω-cm resistivity. The contact was ohmic, with contact resistivity of l.6×10−4ω-cm2. SiGe/ Si heterojunction diodes contacted by the reacted film, containing Co, Si, and Ge, were compared to diodes contacted by aluminum.
Electrical and Structural Properties of Ti Contacts on an Atomically Clean N-Type GaAs Surface
Authors: Lin X. W. , Liliental-Weber Z. , Swider W. , McCants T. , Newman N. , Spicer W. E. , Washburn J. , Weber E. R.
Published: March 2011

Using current-voltage measurements and high-resolution electron microscopy (HREM), we have studied the electrical and structural properties of Ti contacts on an atomically clean n-type GaAs (110) surface. The Ti/n-GaAs diodes are formed at room temperature in ultrahigh vacuum and in situ isochronally (10 min) annealed at temperatures ranging from 200 to 450°C. We find that the Schottky barrier height of the diodes increases by ≈0.10 eV upon annealing at 200°C and remains basically stable for higher-temperature anneals. HREM investigation reveals that Ti reacts with GaAs in its as-deposited state to form an amorphous interlayer ≈1.5 nm thick. After anneals to 450°C, extensive reactions occur at the interface, resulting in the formation of a layered structure Ti/Ga3Ti2/TiAs/GaAs, with TiAs protruding into the GaAs substrate.
Structure of Chalcogen-Stabilized GaAs Interface
Authors: Takatani Shinichiro , Nakano Asao , Ogata Kiyoshi , Kikawa Takeshi , Nakazawa Masatoshi
Published: March 2011

A photo chemical vapor deposited silicon dioxide - gallium arsenide interface treated by a selenium(Se)-molecular beam is investigated using extended X-ray absorption fine structure (EXAFS) analysis. The Se K-edge EXAFS shows the presence of Ga2Se3-related compound at the SiO2/GaAs interface, indicating that the Ga2Se3 layer formed by the Se-treatment is preserved after the deposition of the SiO2film. The effective coordination number of the Se atoms is found to depend on the direction of the polarizing vector with respect to the crystal orientation. An attempt is made to interpret this dependence using a simple atomic layer model.
X-Ray Studies of Gasb/Sb Heterostructure and Multilayers: A New Semimetal/Semiconductor System
Authors: Vigliante A. , Chow P. C. , Moss S. C. , Dura J. A. , Wang W. C. , Golding T. D.
Published: March 2011

A substantial research effort has been devoted to the growth of metals on semiconductors [1], motivated in part by the necessity of electrical contacts and interconnects in semiconducting devices and by the possibility of new physical phenomena and devices derived from the combination of electronic properties of the two materials. Semimetals provide an alternative for applications involving electrical contact, for which their unique transport, optical, and nonlinear properties make them attractive in hybrid devices.
Effect of as Overpressure on Mn-Induced Layer Disordering in AlGaAs-GaAs Superlattices: An Investigation of the Mn Diffusion Mechanism
Authors: Wu C. H. , Maun J. I. , Hseh K. C.
Published: March 2011

Data are presented showing the effect of As overpressure on the diffusion of Mn into an AlGaAs-GaAs superlattice (SL) using MnAs as the diffusion source. Arsenic overpressure has been shown to play a significant role in both impurity-induced layer disordering (IILD) and the microstructure of the Mn-diffused samples. The degree to which layer disordering occurs decreases as As overpressure increases. Furthermore, dislocation loops are observed for the diffusion of Mn under Ga-rich conditions at prolonged diffusion times. Both results, in addition to the effect of As overpressure on the Mn diffusion profile, indicate that Mn diffusion into GaAs or GaAs-AlGaAs heterostructures takes place by an interstitial-substitutional mechanism involving column III vacancies under As-rich conditions and a “kick-out” mechanism involving column III interstitials under Ga-rich conditions.
Heteropolytype Growth of Beta Silicon Carbide on Alpha Silicon Carbide by Low Pressure Chemical Vapor Deposition at 1150 C
Authors: Irvine K. J. , Spencer M. G. , Dmitriev V. A.
Published: March 2011

We report on the low temperature growth of heteropolytype junctions of 3C-SiC on 6H-SiC by low pressure chemical vapor deposition. In this work we have observed the epitaxial layers to be single crystal below a critical thickness limit which depends on growth temperature. Films thicker than this limit are polycrystalline. At 1150 C we have found the critical thickness to be approximately 2500 angstroms.
Surface States at LT GaAs-n+ GaAs Interfaces
Authors: Verma Ashlsh K. , Smith J. S. , Weber Eicke R.
Published: March 2011

GaAs grown using Molecular Beam Epitaxy at below normal substrate temperatures (∼ 220 °C) has found many potential applications in GaAs MESFET devices. These so-called Low Temperature (LT) layers were originally used between the MESFET substrate and active region to eliminate backgating effects.[1] More recently, LT layers have been incorporated into MESFET gate structures to improve gate breakdown characteristics.[2] [3] When used in this capacity, the quality of the LT GaAs - n+ GaAs interface becomes an important issue: a large number of traps at the interface will result in channel mobility degradation. Furthermore, it is desirable to develop a method by which the interface quality can be evaluated through simple electrical measurements.
An Overview of Plasma Processing
Authors: Szekely Julian
Published: March 2011

An overview is presented of the plasma processing of materials. The principal components of this overview include the definition and classification of plasmas of interest in materials processing, the methods of plasma generation and the basic engineering principles that govern plasma phenomena. Here emphasis is placed on both plasma theory and on the experimental verification of the models. This is followed by a brief description of principal plasma applications, including thermal plasmas used in melting, refining, plasma deposition and plasma synthesis and low pressure plasmas used in synthesis and in the processing of electronic materials.

The review is concluded by a brief discussion of future prospects for plasma technology, where the main developments envisioned are in the area of improved coatings, the processing of electronic materials, melting and refining of refractory metals and superalloys and finally the possibility of more widespread use for plasma systems in extractive metallurgy.
Heat Transfer Analysis of the Plasma Sintering Process
Authors: Pfender E. , Lee Y.C.
Published: March 2011

In the process of r.f. plasma sintering of Al2O3 at reduced pressure, a number of puzzling observations have been reported. They include higher heating rates and higher maximum temperature of a sample at increased propagation velocities of the sample through the plasma and a sudden temperature drop of approximately 700°C if the sample motion in the plasma is stopped. An analysis of the sintering process indicates that the change of che surface area and of the catalytic properties of the sample surface during sintering seem to be responsible for these observations. The change from an initially negatively charged co an essentially non-charged surface causes a drastic decrease of the heat transfer from the plasma to the sample. A simulation of the plasma sintering process based on a r.f. argon plasma provides a semi-quancicative explanation of all the observed phenomena.
Plasma Spray Processing of Ceramic Oxides
Authors: Ravi Shankar N. , Herman H. , Mac Crone R. K.
Published: March 2011

We report some measurements of unique physical properties that arise in plasma-sprayed alumina. It is suggested their origin is the O- species formed on the surface of the particles during the fabrication process.
Multiple Arc Discharges for Metallurgical Reduction or Metal Melting
Authors: Harry J.E. , Knight R.
Published: March 2011

Multiple arc discharges enable more than one arc to be operated in close proximity supplied from the same supply. This enables reduced individual electrode current to be used. Multiple electrodes may be used in d.c. arc furnaces and d.c. plasma furnaces for melting, liquid-phase smelting and particulate phase processes. Non-consumable multiple electrodes may be used to replace graphite electrodes in arc furnaces. Other applications include high temperature gas heating and in flight plasma reactions.
Plasma Arc Carbide Coatings on Titanium
Authors: Shull R. D. , Boyer P. A. , Ives L. K. , Bhansali K. J.
Published: March 2011

The plasma transferred arc (PTA) process has been traditionally used to deposit wear resistant coatings on iron base alloy substrates, but has not been employed to coat lightweight alloys due to processing problems. In the current study, use of the PTA process to deposit TiC, WC, and Cr3C2 coatings on titanium substrates has been explored. The resistance of these coatings to dry abrasive wear has been measured and compared to that of the base metal. The variation in wear resistance of these coatings is discussed in terms of the carbide particle size and the microstructure of the deposit. A comparison is also made to coatings prepared by a laser surface melting and carbide particle injection process.
Modelling of Plasma Processes
Authors: Boulos Maher I.
Published: March 2011

A review is made of some of the mathematical modelling work carried out over the last few years with the objective of computing the flow and temperature fields for different thermal plasma systems. Typical results are given for d.c. plasma jets, transfered and non-transfered arc plasma reactors and for inductively coupled plasma torches. This is followed by a brief discussion of the important problem of plasma-particle heat transfer.
Electrical and Optical Properties of Yb, Er doped GaAs
Authors: Benyattou T. , Seghier D. , Brémond G. , Moneger S. , Kalboussi A. , Marrakchi G. , Guillot G. , Lhomer C. , Lambert B. , Toudic Y. , Le Corre A.
Published: March 2011

In this paper we report results from electrical and optical measurements carried out on GaAs:Yb, Er.

For GaAs:Yb electrical experiments such as photoconductivity (PC) and Photo Induced Current Transient Spectroscopy (PICTS) show that there is a level at 0.65eV related to Yb. This explains why no Yb3+ photoluminescence (PL) emission is detected, the recombination energy of the trapped excitons is too low (≈ 0.6eV) to excite the Yb3+ internal transition(≈ 1.24eV). We also present results on Er doped GaAs materials. From PL experiments we deduce an estimate of 10−19cm2 for the stimulated emission cross section. By PICTS and PC, we have evidenced a trap at 0.67eV related to Er ions in GaAs. And we think that in this case, the rare earth ions are excited via formation of bound excitons.
Luminescence of TM3+ in Gallium Arsenide Grown by Metal-Organic Vapor Phase Epitaxy
Authors: DÖrnen Achim , Pressel Klaus , Hiller Christoph , Haase Dieter , Weber JÜrgen , Scholz Ferdinand
Published: March 2011

We investigate the excitation mechanism of the characteristic 4f luminescence 3H5 →3H6 of Tm3+ in GaAs by photoluminescence excitation spectroscopy. This luminescence transition is also used to study the incorporation of thulium into the GaAs lattice by angular dependent Zeeman spectroscopy.
Correlation of the Location in Crystal Lattice and Optical Activity of the Yb Impurity in 111-V Compounds
Authors: Kozanecki Adrian
Published: March 2011

Rutherford backscattering (RBS) and channeling measurements have been applied to study lattice location of the Yb atoms implanted into III-V compounds. It has been found that the Yb atoms locate in the lattice positions only in InP and its alloys with Ga and As, while in gallium compounds the substitutional fraction of Yb atoms could not be detected. The intra- 4f-shell luminescence of the Yb3+ ions in different crystalline matrices have been studied. It has been shown that the ability of efficient excitation of the atomic-like luminescence of Yb3+ ions is associated with their substitutiontl location in the lattice. The intracentre emission from substitutionally located Yb3+ ions may serve as a probe of the local alloy disorder in GaInP and InPAs crystals.
Praseodymium Dioxide Doping of In1−xGaxAsyP1−y Epilayer Grown with Liquid Phase Epitaxy
Authors: Hjelt Kari T. , Sopanen Markku A. , Lipsanen Harri K. , Tuomi Turkka O. , HasenÖhrl Stanislav
Published: March 2011

Praseodymium dioxide (PrO2) -doped In0.69Ga0.31As0.67P0.33 layers are grown on semiinsulating In P substrates with liquid-phase epitaxy. The PrO2 doping of the growth solution varies from 0 to 0.32 wt %. The quaternary In0.69Ga0.31As0.67P0.33 layer composition determined with two-crystal X-ray diffraction and photoreflectance is found to be independent of the PrO2 concentration in the melt. The photoluminescence spectra measured at 12 K show both exciton and donor-acceptor peaks, the magnitudes of which depend on the PrO2 doping. The carrier concentration of the n-type quaternary layer decreases and the mobility increases with increasing PrO2 concentration and reaches the values of 8.3.1015 cm−3 and 7300 cm2/Vs, respectively, at about 0.1 wt% at 77 K. The experiments show that PrO2 has an impurity gettering effect in the growth process.
Eu and Yb Excitation Mechanisms in ZnS, CaS, SrS and InP
Authors: Godlewski M. , Światek K. , Monemar B.
Published: March 2011

The role of the excitonic excitation mechanism of the rare earth (RE) intra-shell emission is discussed. Two cases are analyzed. For Yb ion in InP 4f-4f emission of Yb3+ is induced by energy transfer from bound exciton state to the RE core state. For Eu in CaS and SrS RE emission is induced by carrier trapping directly to the excited state of Eu2+ ion. Also in this case the intermediate excitonic state may participate in RE excitation, as suggested by some experimental results.
Electronic Structure of Si Doped by Rare-Earth Yb3+
Authors: Ren Shang Yuan , Dow John D.
Published: March 2011

The electronic structure of Yb3+-doped Si is elucidated in terms of level repulsion between the Si vacancy's deep levels (and spectral density) and the Yb3+ levels, both for bulk Si and for small clusters. The 2F5/2 level of Yb3+ splits into a Γ8 level and a Γ6 level, with the Γ6 repelled most, by the nearby Γ6 (A1) level of the Si vacancy. The level-repulsion is either upwards or downwards in energy, depending on whether the Al-like vacancy level lies below or above this Yb3+ level. The 2F7/2 Yb 3+ level is split into Γ6, Γ7, and Γ8 sub-levels, all moving downwards in energy, with Γ6 moving most, again due to strong level repulsion from the nearby Al-like vacancy level, while the more-distant, higher-energy T2-like (Γ7 and Γ8) vacancy level produces a weaker repulsion. In small clusters, the Si-vacancy's wavefunctions and deep level energies are sensitive to cluster-size, and changes in them alter the level repulsion experienced by the Yb 3+ levels, even though the 4f electrons are localized.
Simple Model for Rare-Earth Impurities in the Compound Semiconductors
Authors: Ilyin Nicolas P. , Masterov Vadim F.
Published: March 2011

A model of the ground state for a rare-earth element in a binary semiconductor is suggested and illustrated for ytterbium in InP. It is shown that the charge state of Yb3+ with 4f13 shell is more stable than the state of Yb2+ with f 14 shell.
Growth of Er Doped si Films by Electron Cyclotron Resonance Plasma Enhanced Chemical Vapor Deposition
Authors: Rogers Jim L. , Varhue Walter J. , Adams Edward
Published: March 2011

Thin Si films doped with Er have been grown at low temperature by plasma enhanced chemical vapor deposition. The Er gas source is a sublimed organo-metallic compound fed into the process chamber. High doping concentrations without precipitation are possible because of the low deposition temperatures. The process relies on the beneficial effects of low energy ion bombardment to reduce the growth temperature. The ions as well as reactive chemical species are produced by an electron cyclotron resonance (ECR) plasma stream source. A hydrogen plasma stream is used to perform an in-situ pre-deposition clean to remove oxide from the Si surface. Film crystallinity and impurity concentration are determined by Rutherford backscattering spectrometry.
Monocrystal Dislocationless Si :Ge, Grown from The Melt With Gd Impurity.
Authors: V.V. Borschensky , D.I. Brinkevich , V.V. Petrov , V.S. Prosolovch
Published: March 2011

The properties of Si grown from the melt having impurities of germanium and gadolinium have been studied by IR-absorption and Hall effect methods.It was stated that Ge and Gd are effective getters for technological impurities of oxygen and carbon in silicon melt. It has been shown that the combined doping by rare earth and isovalent impurities allows to increase the thermostability of dislocationless monocrystals of silicon.
Epitaxial Layers Si:(Sn,Yb) Produced by The Crystallization From The Melt-Solution On The Basis Of Sn.
Authors: Brinkevich D.I. , Kazuchits N.M. , Petrov V.V.
Published: March 2011

Epitaxial layers (EL) Si:Sn doped with Yb in the process of liquid phase epitaxy were studied by optical microscopy and photoluminescence (PL) methods.At low concentration of lanthanoid (0,01 < Nyb < 0,1 weight %) the good planarity of the interface and high quality of the surface are detected. At NYb > 0,1 weight % microirregularities are presented.

In EL Si:(Sn, Yb) irradiated by 4,5 MeV-electrons the suppression of the generation of radiaton defects, responsible for G- and C-lines of PL, has been found. This effect has been explainedwithin the score of the model takeng into the consideration gettering propering ofYb in reference to the impurities of 0 and 0 as deformation fields, attributed to the presence of Sn atoms.
Microstructure Based Modelling of Stress Migration and Electromigration Induced Failure Distributions
Authors: Børgesen P. , Korhonen K. A. , Brown D. D. , Li C.-Y.
Published: March 2011

Stress and current induced degradation of the interconnects may well define the ultimate limits on device density and total on-chip power in microelectronic circuits. The two damage mechanisms are found to be mutually interdependent in a fashion determined by the line microstructure, as well as by design features such as W-studs and refractory metal back up layers. We have developed a comprehensive model for the synergistic effects of stress migration and electromigration, taking such factors into account. The present work reviews the modelling of the statistical failure distributions, with emphasis on the temperature and current density dependencies, for the case of ‘near-bamboo’ submicron lines.
Observation and Modelling of Electromigration-Induced Void growth in Al-Based Interconnects
Authors: Kraft O. , Bader S. , Sanchez J.E. , Arzt E.
Published: March 2011

Accelerated electromigation tests on unpassivated, pure aluminum interconnects were performed. The failure mechanisms were observed by interrupting the tests and exanming the conductor lines using an SEM. Because the metal thin film was subjected to a so-called laser reflow process before patterning, grain boundaries were visible in the SEM as thermal grooves. Voids were observed to move along the line and to grow in a transgranular manner, and a characteristic asymmetric void shape was identified which seems to be related to the failure mechanism. It is argued that substantial progress in modelling and understanding of electromigration failure can be made by consideration of such void shape effects.
Analysis of Stresses at Singular Points of Patterned Structures
Authors: Chouaf A. , Loppin O. , Ignat M. , Terriez J.M.
Published: March 2011

An iterative method describing the stress state at the vicinity of singularity point is presented here. This approach is based on concepts of rupture mechanics, uses classical solutions from finite element calculations and concerns plane problems. Through this approach, the stress state at the vicinity of several types of singular points in a patterned structure were analysed. The obtained results can be discussed according to failure mecanisms.
X-RAY Determination and Analysis of Residual Stresses in Uniform Films and Patterned Lines of Tungsten
Authors: Maniguet L , Ignat M. , Dupeux M. , Bacmann J.J. , Normandon Ph.
Published: March 2011

The determination by X-ray diffraction of the elastic strain tensors and the corresponding stress tensors in uniform films and patterned lines of tungsten was used to investigate the effect of line width. The stresses were found to increase with increasing line width. These experimental results are discussed with respect to the values obtained from a model using a distributed force in the line. The results of the calculations are in agreement with the X-ray measurements. The edge effects appear to be significant for tungsten lines.
Empirical Modeling of Electromigration Early Resistance Changes
Authors: Niehof J. , de Graaff H.C. , Verwey J.F.
Published: March 2011

An empirical model for electromigration-induced early resistance changes is given. The basis olthe model are two coupled partial differential equations, one for vacancies, and one for mobile atoms. These equations are then solved numerically. For model verification purposes model calculations are compared with experimentally obtained resistance change curves.
Comparison Between I/F Noise, High-Resolution Resistometric, and Lifetime Electromigration Studies of AL and AL(SI)
Authors: Kraayeveld J.R. , Verbruggen A.H. , Radelaar S.
Published: March 2011

To compare the results obtained by 1/f noise, high-resolution resistance and electromigration lifetime measurements, the effect of annealing at 400 °C in forming gas of Al and AI(Si) thin films has been studied. All samples of a given composition have been fabricated simultaneously. Upon annealing, the 1/f noise measured at room temperature decreases by a factor of two whereas the lifetime increases by a factor 3 to 6. The activation energies derived from the 1/f noise and the high-resolution resistance measurements during and after stressing with a DC current are closely correlated and compare well to values reported for lifetime measurements. Comparing the data of the different experiments suggest that the lifetime experiments predominantly probe the presence of weak spots in the films whereas the noise measurements respond more to local disorder.
Theory of Microstructure Evolution in Heterogeneous Materials
Authors: Pantelides Sokrates T.
Published: March 2011

This paper summarizes the main ingredients of a general theory for a quantitative description of dynamical processes in heterogeneous materials under stresses, thermal cycling, or current. The theory is derived analytically from the atomic scale using the principles of quantum mechanics and statistical mechanics, without any empirical postulates. The equations describe the cross-coupled phenomena of stress-induced diffusion, diffusion-induced stress, electromigration, void growth, dislocation climb, and slip. The laws of continuum mechanics are recovered as a subset of the general equations. All constitutive relations can be constructed by a general and systematic procedure.
Theoretical Studies of Electromigration in Polycrystalline Metal Stripes
Authors: Maroudas Dimitris , Pantelides Sokrates T.
Published: March 2011

A systematic analysis is presented of the mesoscopic mechanisms that govern the structural evolution of polycrystalline conductors under the action of applied electric fields. A recently derived set of general dynamical mesoscopic equations is specialized to study the behavior of microstructural building blocks. Scaling analysis is presented for the dynamics of the corresponding transport and micromechanical processes associated with a wide range of time scales. Results of numerical simulations are presented for vacancy migration along grain boundaries, evolution of current-induced stresses, surface diffusion, and void stability and growth. The calculated dependence of characteristic times on current density is discussed.
The Microstructural Nature of Electromigration and Mechanical Stress Voids in Integratedcircuit Interconnect
Authors: Rose Jamie H. , Spooner Terry
Published: March 2011

It is well known that stress and electromigration induced voiding is of major concern for integrated circuit interconnect reliability. However, there has been little systematiccharacterization of void morphology and crystallography in ever more technologically important narrow, “near-bamboo” conducting lines. Prior reports indicate thatvoids are typically wedge or slit shaped, with failure often associated with slit voids.Void face habit plane is most often reported to be {111}. Wedge and slit void morphology and crystallography have been studied in comb/serpentine and parallel line array test structures. In virtually all cases, void faces are {111} oriented. In contrast to earlier studies, intragranular wedge stress voids have been observed. All electromigration opens were due to slit voids; these were typically intragranular, in contradiction to current theories of void formation, and likely are mechanical fractures. Under accelerated test conditions, non-grain boundary diffusion paths appear to operate at distances of tens of micrometers. Relative displacement between wedge voids and attached grain boundaries occurs where a wedge face lies on a near common {111} plane for the two grains. It is suggested that slit voids are intragranular under both stress and electromigration conditions and likely associated with local interconnect depassivation. Based solely on appearance and crystallography, no void can uniquely be identified as due to stress alone or electromigration alone.
Characterization of the Degradation Processes in SiO2-Si Structure by Means of Electrolyte-Insulating-Semiconductor Systems
Authors: Bota S.A. , Morante J.R. , Baraban A.P. , Bulavinov V.V. , Konorov P.P.
Published: March 2011

A non destructive method to characterize the properties of SiO2 films in SiO2-Si structures and analyze their variations under different external actions is presented and discussed. The method is based on the properties of the Electrolyte-SiO2 contact under polarization which allows us to study the SiO2 film in different injection conditions, in a hole injection zone, in a predominant electron injection zone, and finally, in a region of electron heating as a result of the electric field action before to reach the oxide breakdown. Moreover, using this method, higher electric field values than in the metal-SiO2-Si system can be applied.

The characterization of hole traps, electron traps and defect precursors states in SiO2 films are carried out as well as their evolution and influence on the SiO2-Si structure degradation and electrical behaviour. Results measured on SiO2-Si structures obtained from different technological processes and submitted to different treatments are reported in order to discuss the possibilities of this method as a power tool to assess the stability and quality of insulating layer on semiconductors.
Mechanical Stability of Passivation Films Deposited on Aluminium Substrates
Authors: Scafidi P. , Ignat M. , Dupeux M.
Published: March 2011

The damage of films of two different passivation materials deposited on aluminium substrates was investigated. These systems were subjected to uniaxial stretch in an in situ tensile testing device adapted to a scanning electron microscope. Successive stages of crack development were observed: the failure is first in the film, then at the interface. The presence of a thermally grown aluminium oxide interlayer delays the decohesion process. The substrate surface roughness weakens the systems. The evolution of the crack density with the longitudinal strain was analysed and then fitted with a model based on a Weibull distribution function.
Formation of Oriented Conductive SrVO3-x(SVO) Films on Si(100) Substrates by Evaporation in Low-Pressure Hydrogen
Authors: Hayashi Tsunemasa , Ishiwara Hiroshi
Published: March 2011

Conductive SrVO3-x films are deposited directly on Si(100) substrates by vacuum evaporation method using SrVO3-x as a source material. It has been found that the conductive film was strongly oriented to only <100> direction on Si(100). By introducing hydrogen, the resistivity of the SrVO3-x film decreases to 0.57mΩcm, which is smaller than those of samples deposited without hydrogen.
Strained Layer Growth: how do 3d Islands Relax Strains?
Authors: Priester C. , Lefebvre I. , Allan G. , Lannoo M.
Published: March 2011

We study the elastic strain relaxation in highly strained layers deposited on a [001] substrate induced by coherent 3D islanding. We first calculate the elastic strain distribution within several pyramidal 3D islands with different faces (the observed ones being usually [114] or [014]). For this, we use a valence force field (VFF) description. Our calculation includes interactions between islands, which appear to be a key parameter. We study how the shape of the island modifies the strain relaxation which is proved to vary within the island. Very simple considerations on surface tension indicate why pyramidal islands are the most stable.