bluuebunny/crossref_metadata_2025 huggingface dataset:
An Evaluation of Simplified Models for Surface Kinetics in Movpe Processes
Authors: Tirtowidjojo Max , Pollard Richard
Published: March 2011

A general MOVPE model has been used to assess the applicability of simplified representations for surface kinetics. With the general model, predictions for GaAs deposition on (111 )Ga using trimethylgallium and arsine show excellent agreement with observed growth rates. However, if Langmuir-Hinshelwood kinetics is assumed, the model only matches the deposition rates over a narrow range of operating conditions, even when several rate-limiting steps are included. This limitation arises because combinations of equilibrium constants and local partial pressures often do not give reasonable approximations for the surface concentrations of reactive intermediates. The form of the Langmuir-Hinshelwood relation(s) and the parameter values can be fitted empirically to experimental data, but this could lead to erroneous conclusions concerning process behavior and the model would have limited predictive capabilities. An alternative approach is to use surface reaction probabilities, but they can only be applied in an empirical fashion and their magnitudes depend on gas flow rate, inlet composition, and reactor pressure as well as surface temperature.
Eqilibrium Analysis of the TMGa-TMA1-AsH3-H2 Mocvd Epitaxial Growth System
Authors: Moon Hyuk J. , Stoebe Thomas G. , Chadwick Brian K.
Published: March 2011

The thermodynamic equilibrium state of the Ga-Al-As-C-H system was determined theoretically by means of an iterative equilibrium constant method. This method of calculation is presented and discussed. With very little operator input, the program is capable of computing the partial pressures of the gas-phase species present in the equilibrated system.

In these calculations the system was considered to be saturated with solid-phase A1GaAs and included 58 plausible gas-phase intermediates which evolved from the initially present gas species; trimethylgallium, trimethylaluminum, arsine, and hydrogen. Temperature and total system pressure ranges investigated were 750–1100 K and 0.1 atm-1.0 atm, respectively. The effects of temperature and pressure variations, in addition to effects caused by changes in the appropriate atom ratios, have been delineated. The properties of this equilibrated system are compared with those from recent thermodynamic research efforts on AlGaAs systems consisting of only gaseous constituents.
Investigation of Ga Diffusion in (001) and (111) CdTe Layers Grown on (001) GaAs
Authors: Dubowski J. J. , Wrobel J. M. , Jackman J. A. , Becla P.
Published: March 2011

A secondary ion mass spectroscopy study of Ga diffusion in CdTe grown on (001) GaAs was carried out. The layers were grown by pulsed laser evaporation and epitaxy. Two characteristic regions with increased Ga concentration were found. The first was the CdTe/GaAs interface where the concentration of Ga decreases rapidly to the detection limit of −8 × 1014 cm−3. This region was usually less than 300 nm wide. The second was a surface region with a Ga accumulation of up to −1017 cm−3. Ion imaging revealed that in the (001) CdTe layers, Ga accumulates near the surface at localized spots, up to about 8 μm in diameter. This feature is less apparent in the (111) CdTe layers. Annealing at 500 °C for 1 h increased the Ga concentration in the whole layer to above 1016 cm−3. We also observe thermal annealing induced precipitation of Ga at the surface of bulk CdTe samples which were originally uniformly doped with Ga.
Oxidation Kinetics of Silicon Surfaces: Reactive Sticking Coefficient, Apparent Saturation Coverage and Effect of Surface Hydrogen
Authors: George S. M. , Gupta P. , Mak C. H. , Coon P. A.
Published: March 2011

The kinetics of the initial oxidation of silicon surfaces by O2 were studied using laser-induced thermal desorption (LITD), temperature programmed desorption (TPD) and Fourier Transform Infrared (FTIR) spectroscopy. The LITD results showed that the oxidation of Si(111)7×7 by O2 was characterized by two kinetic processes: an initial rapid oxygen uptake followed by a slower growth that asymptotically approached an apparent saturation oxygen coverage. The initial reactive sticking coefficient of O2 on Si(111)7×7 decreased with surface temperature. In contrast, TPD experiments on Si(111)7×7 and FTIR studies on porous silicon demonstrated that the apparent saturation oxygen coverage increased as a function of surface temperature. Experiments with preadsorbed hydrogen also revealed that silicon oxidation was inhibited as a function of increasing hydrogen coverage on the Si(111)7×7 surface.
Infrared Spectroscopy of Si(111) and Si(100) Surfaces After HF Treatment: Hydrogen Termination and Surface Morphology
Authors: Chabal Y. J. , Higashi G. S. , Raghavachari K.
Published: March 2011

The methodology for extracting structural information from surface infrared spectra is exemplified by considering the silicon-hydrogen stretching modes of flat and vicinal Si(111) and Si(100) surfaces obtained after HF treatment.
Surface Condition in the Plasma-CVD of a-Si:H,F from SiF4 and H2
Authors: Maruyama A. , Shen D. S. , Chu V. , Liu J. Z. , Jaroker J. , Campbell I. , Fauchet P. M. , Wagner S.
Published: March 2011

We present a detailed study of the growth of a-Si:H,F from SiF4 and H4. The growth surface appears to have a high density of surface states. These surface states can be thermally relaxed by keeping the films at growth temperature after the termination of growth, suggesting that the states were created during film growth. When frozen in, the surface state density is found to depend on the conditions during film growth. The density is related to the sharpness of the valence band tail as measured by the Urbach Energy. We believe that a reaction on the growth surface resulting in fluorine elimination creates these surface states and also affects the formation of the Si-network.
Kinetic and X-ray Photoelectron Spectroscopic Studies of the Thermal Nitridation of Si(100)
Authors: Peden C. H. F. , Rogers J. W. , Blair D. S. , Nelson G. C.
Published: March 2011

The thermal nitridation of Si(100) by NH3 and N2H4 has been studied by X-ray photoelectron (XPS) and Auger electron (AES) spectroscopies. The pressure dependence of the rates as a function of reaction time has been measured. It has been found that the growth of the first monolayer (ML) of nitride is mediated by a surface reaction step. For subsequent growth, diffusion of one or more of the reacting species becomes an important process in determining the rate of reaction. Such species may be substrate Si diffusing to the vacuum/Si3N4 interface, or possibly network nitrogen diffusing into the Si substrate. The independence of the reaction rate on NH3 or N2H4 pressure at long reaction times rules out a mechanism involving molecular diffusion of the nitriding gas to the Si3N4/Si interface in a manner similar to the oxidation of Si by O2 or H2O. Careful analysis of the Si(2p) XPS spectra reveals the presence of a unique Si species with a Si(2p) binding energy intermediate between elemental Si and Si in Si3N4. Further, the relative intensity of the Si(2p) features due to this species, and the angular dependence of the XPS peaks indicate that they result from a ML of Si at the outermost surface layer, on top of the growing Si3N4 film.
Laser Studies of the SiH Radical/Surface Interaction During Deposition of a thin Film
Authors: Ho Pauline , Buss Richard J. , Breiland William G.
Published: March 2011

This paper presents a new method for studying the interaction of radicals with the surface of a depositing film using a combination of laser spectroscopy and molecular beam techniques. The reactivity of SiH molecules with the surface of a depositing a-Si:H film is measured to be at least 0.95, with no strong dependence on rotational state.
Dependence of PECVD Silicon Oxynitride Properties on Deposition Parameters
Authors: Helms Aubrey L. , Havrilla Robert M.
Published: March 2011

The properties of Plasma Enhanced Chemical Vapor Deposited (PECVD) silicon oxynitride thin films were determined for a variety of deposition conditions. The films were characterized with respect to stress, refractive index, deposition rate, hydrogen content, dielectric constant, and uniformity. The films were deposited in an Electrotech ND6200 parallel plate reactor using a silane - ammonia - nitrous oxide process gas chemistry. Deposition parameters which were investigated include process gas flow rate, power, and total pressure. The possible application of these films as both inter-layer and final passivation layers for use on GaAs ICs will be discussed.
The Effects of Surface Treatments for Low Temperature Silicon Dioxide Deposition on Cadmium Telluride.
Authors: Choi Seong S. , Kim S. S. , Tsu D. V. , Lucovsky G.
Published: March 2011

We have successfully deposited thin films of SiO2 on a cadmium telluride substrate at low temperature (Ts =100°C–300°C) by remote plasma enhanced chemical vapor deposition (Remote PECVD). The native oxide on the CdTe substrate has been removed, prior to deposition by either chemical etching in methanol and 1% bromine, or by dissolution in deionized water. After removal of the native oxide, the CdTe was inserted into a UHV-compatible deposition chamber and a He+ plasma treatment was performed prior to deposition of an SiO2 film. This treatment promotes strong adhesion between the deposited SiO2 film and the CdTe surface. We find that the initial oxide removal process does not influence SiO2 adhesion. The effect of the He+ plasma treatment on the CdTe surface has been studied by Auger electron spectroscopy(AES), and Reflection high energy electron diffraction (RHEED).
Controlled Mass Flow of Low Volatility Liquid Source Materials
Authors: Nolet Alan D. , Rhine Bruce C. , Logan Mark A. , Wright Lloyd , Monkowski Joseph R.
Published: March 2011

Chemical Vapor Deposition (CVD) of thin films for microelectronic devices has historically used source materials that are gases at room temperature [1]. The decision to use gases was largely a practical one based on the relative ease with which the flow of gaseous materials can be controlled. CVD of thin films plays a vital role in increased circuit density and performance of integrated circuits. Liquid sources offer alternative source composition, reaction kinetics and reaction mechanisms to optimize a given CVD process [2].

For example, CVD films of silicon dioxide (oxide) and oxide films modified to lower the glass transition temperature such a borophosphosilicate glass (BPSG) have traditionally used gaseous source materials such as silane, diborane and phosphine [3]. An all liquid system of tetraethylorthosilicate (TEOS), triethylborate (TEB) and triethylphosphine (TEPhine) has been found to offer superior conformality and overall safety [4]. However, from a practical standpoint, the all liquid system has historically suffered from reliable, reproducible mass flow control.
Aluminum Chemical Vapor Deposition Using Triisobutylaluminum: Mechanism, Kinetics, and Deposition Rates at Steady State
Authors: Bent Brian E. , Dubois Lawrence , Nuzzo Ralph G.
Published: March 2011

An important step in the chemical vapor deposition (CVD) of aluminum from triisobutylaluminum (TIBA) is the reaction between TIBA (adsorbed from the gas phase) and the growing aluminum surface. We have studied this chemistry by impinging TIBA under collisionless conditions in an ultra-high vacuum system onto single crystal Al(111) and Al(100) substrates. We find that when TIBA (340K) collides with an aluminum surface heated to between 500 and 600K, the aluminum atom is cleanly abstracted from this precursor with near unit reaction probability to deposit, epitaxially, carbon-free aluminum films. The gas phase products are isobutylene and hydrogen. From monolayer thermal desorption experiments, we have determined the kinetic parameters for the rate-determining step, a β-hydride elimination reaction by surface bound isobutyl ligands. Using these kinetic parameters and a Langmuir absorption model, we can predict the rate of aluminum deposition at pressures ranging from 10−6 to 1 Torr.
Epitaxial Growth of Al on Si By Gas-Temperature-Controlled CVD
Authors: Kobayashi Tsukasa , Sekiguchi Atsushi , Hosokawa Naokichi , Asamaki Tatsuo
Published: March 2011

Epitaxial Al(111) film was deposited on Si(lll) by low-pressure chemical vapor deposition with the use of tri-isobutyl aluminum (TIBA) at the substrate temperature of 400 °C with the deposition rate of 0.9 μm/min. It was necessary for epitaxy to preheat the TIBA gas just before the deposition on the substrate. The preheat was made by gas-temperature-controller provided in the chamber. The film surface was so smooth that reflectance was higher than 90 % of Si and 20 ppm of O, C, and H. No hillock appeared on the film after 430 °C annealing for 40 min. The interface of Al and Si was rather stable so that no alloy penetration occured. The possibility of epitaxial growth of Al(100) on Si(100) was also shown.
Excimer Laser Photofragmentation of TMA on Aluminum: Identification of Photoproduct Desorption Dynamics
Authors: Orlowski T. E. , Mantell D. A.
Published: March 2011

New mechanistic details regarding aluminum deposition by ArF excimer laser photodecomposition of trimethylaluminum (TMA) adsorbed on aluminum covered SiO 2/Si substrates have been obtained using a time-of-flight quadrupole mass spectrometer. CH3 radicals and Al-(CH3)n (n = 1,2,3) species are efficiently photoejected from the surface with up to 0.22 eV of translational energy. Experiments at various TMA dosing levels reveal differences in desorbed fragment translational energy presumably associated with variations in surface site binding energy. No direct evidence is found for desorption of A1 from the surface indicating that A1 is more tightly bound than methyl-aluminum fragments. By carefully monitoring changes in fragment translational energy as an A1 deposit forms on the clean SiO2/Si substrate, we examine how the surface influences the onset of A1 growth. No evidence of ethane or methane desorption from the sample surface is found implying that radical recombination and hydrogen abstraction are primarily secondary gas phase reactions which are not surface initiated.
Syntheses of Metal Chalcogenides Using Organometallic Methods
Authors: Steigerwald Michael L.
Published: March 2011

The precursor method is being used increasingly in the preparation of solid state inorganic materials. Use of this general method allows the isolation of otherwise inaccessible phases and the preparation of known phases under much milder conditions. One approach which holds promise is the use of organometallic precursors for the preparation of both thin films and bulk samples of inorganic materials. In this paper I describe our syntheses of several metal chalcogenides from organometallic reagents.
The Effect of Metal Atoms and Ligand Combinations in Organometallics on Excimer Laser Photoproducts and Yields
Authors: Zhang Y. , Stuke M.
Published: March 2011

A systematic study to find the role of different metal atoms and ligand combinations on the yield of the photoproducts generated upon irradiation of gas phase organometallics (i.e. metalalkyls) by uv excimer laser radiation was performed using laser ionization mass spectrometry.
Chemical Vapor Deposition of Cobalt Silicide
Authors: West Gary A. , Beeson Karl W.
Published: March 2011

Cobalt silicide films have been deposited by chemical vapor deposition using Co2(CO)8or HCo(CO)4as the Co source and SiH4or Si2H6as the Si source. The Co:Si ratio of the films increases with the deposition temperature, and CoSi2stoichiometry is obtained at 300° C using SiH4or at 225° C when Si2H6is the Si precursor. Resistivities of films deposited in the range CoSi2.0to CoSi3.0. are typically 200 microohm-cm and drop to 30 – 40 microohm-cm upon annealing at 900° C.
Low-Temperature Organometallic Chemical Vapor Deposition of Transition Metals
Authors: Kaesz Herbert D. , Williams R. Stanley , Hicks Robert F. , Chen Yea-Jer Arthur , Xue Ziling , Xu Daqiang , Shuh David K. , Thridandamt Hareesh
Published: March 2011

A variety of transition-metal films have been grown by organometallic chemical vapor deposition (OMCVD) at low temperatures using hydrocarbon or hydrido-carbonyl metal complexes as precursors. The vapors of the metal complexes are transported with argon as the carrier gas, adding H2 to the stream shortly before contact with a heated substrate.

High-purity platinum films have been grown using (η5−C5H5)PtMe3 [1] or (η5−CH3C5H4)PtMe3 [2] at substrate temperatures of 180°C or 120°C, respectively. The incorporation of a methyl substituent on the cyclopentadienyl ligand decreases the melting point of the organoplatinum complex from 106°C [1] to 30°C [2] and increases the vapor pressure substantially. Film deposition also occurs at a lower substrate temperature. Analyses by X-ray diffraction (XRD), Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) indicate that the films are well crystallized and do not contain any observable impurities after sputter cleaning.

The substrate temperatures for the first appearance of other transition-metal films from organometallic precursors are as follows (°C): Rh(η3−C3H5)3 (120/Si), Ir(η3-C3H5)3 (100/Si), HRe(CO)5 (130/Si) and Ni(η5−CH3C5H4)2 (190/glass, 280/Si). These films are essentially amorphous and contain trace oxygen impurities (< 2%), except for the Re film, which was 10% oxygen and 20%carbon.
The Deposition of Metallic and Non-Metallic Thin Films Through the Use of Boron Clusters.
Authors: Zhang Zhongju , Kim Yoon-Gi , Dowben P. A. , Spencer James T.
Published: March 2011

New borane clusters and their corresponding transition and rare earth metal complexes are currently being investigated in our laboratories for their utility as unique source materials for the formation of both metallic and non-metallic thin films. These borane cluster complexes exhibit highly favorable properties for use in OMVPE processes, such as; (1) relatively high volatility, (2) anticipated high stability of the ligand itself to provide clean ligand-metal dissociations, (3) high temperature stabilities of the complexes, (4) readily preparable in significant quantities, and (5) availability of theoretical and spectroscopic probes of structure-reactivity relationships. In this work, we have prepared both non-metallic thin films, including materials such as boron nitride, and metallic thin films (both the transition and rare earth metals) through the use of these unique cluster materials.

Boron nitride has been investigated as a potential hard coating for use as an insulating electrical layer and protective coating. We have investigated plasma enhanced chemical vapor deposition and pyrolytic deposition of boron nitride from readily available and easily handled borane clusters. Auger electron spectroscopy was used to show that the film was high purity boron nitride of uniform composition.

The deposition of transition and rare earth metal thin-film materials of controlled stoichiometry has recently received considerable interest. We have discovered the borane cluster-assisted deposition (CAD) of metallic thin-films involving both transition and rare earth metal materials. Through the use of this unprecedented borane cluster chemical transport process, films ranging in thickness from 100 nm to several microns have been straightforwardly and systematically prepared for numerous metal and mixed-metal boroncontaining systems with controlled composition at relatively low temperatures. These new materials have been characterized by SEM and other techniques.
Polyalkylsilynes: Synthesis and Properties of “Two-Dimensional” Silicon-Silicon Bonded Network Polymers.
Authors: Biancon Patricia A. , Weidman Timothy W. , Schilling Frederic C.
Published: March 2011

The synthesis of the first soluble silicon-silicon bonded network polymers, the polyalkylsilynes [RSi]n was accomplished using high-intensity ultrasound to effect the reductive condensation of alkyltrichlorosilanes with liquid sodium-potassium alloy. The resulting polymers remain hydrocarbon-soluble and may be cast into transparent films. Spectroscopic data indicate a structure consisting of tetrahedral alkylsilicon units assembled via silicon-silicon bonds into amorphous networks. Films or solutions of the polysilynes exhibit an intense UV absorption which tails into the visible, blue-shifted but similar in shape and intensity to that of amorphous silicon. The photoreactivity and pyrolysis properties of these materials will be described.
New Precursors for the Organometallic Chemical Vapor Deposition of Aluminum Nitride
Authors: Gladfelter Wayne L. , Boyd David C. , Hwang Jen-WeI , Haasch Richard T. , Evans John F. , Ho Kwok-Lun , Jensen Klavs F.
Published: March 2011

Organometallic aluminum azides have been found to be effective precursors for the low temperature chemical vapor deposition of thin films of aluminum nitride. Quantitative analysis of the gas phase products of the reaction are used to develop an understanding of the reaction. Rate studies of the deposition were performed in the temperature range from 400 to 800°C. Below 525°C, an activation barrier of 26.4 kcal/mol was found, while above 525°C, a value of 5.23 kcal/mol was obtained. The effects of the presence of N-C bonds and the type of Al-N interaction within the precursor are evaluated.
The Use of Tris(Trimethylsilyl)Arsine to Prepare AlAs, GaAs and InAs. The X-Ray Crystal Structure of (Me3Si)3AsAlCl3.C7H8.
Authors: Wells Richard L. , Pitt Colin G. , Mcphail Andrew T. , Purdy Andrew P. , Shafieezad Soheila , Hallock. Robert B.
Published: March 2011

The reactions of (Me3Si)3As with group III halides have been utilized to prepare AlAs, GaAs and InAs. The adduct (Me3Si)3AsAlCl3 has been isolated as an intermediate in the formation of AlAs from (Me3Si)3As and AICI3. The crystal structure of its toluene solvate has been determined.
Adhesion of Metals to Mixed Oxide Coatings (Al & Cr, Mo, OR W) Prepared by Spray Pyrolysis of Organometallics.
Authors: Burlitch James M. , Demott Gerard J. , Kohlstedt David L.
Published: March 2011

Spray pyrolysis of the mixed metal organometallics, Al[M(CO)3C5H5]3 (M is Cr, Mo or W), prepared in tetrahydrofuran from the mercury analogues and aluminum metal, gave mixed oxide gels on heated alumina substrates. Air was used as the propellant for M = Cr, whereas oxygen was used for M = Mo or W. Mixtures of Al[Cr(CO)3C5 H5]3 and Al(O-i-C3H8)3 having a Cr/Al ratio of 0.02 to 0.93 were used to prepare gels with intermediate dopant concentrations. When calcined at 500 °C, the gels produced amorphous coatings of two-component oxides that were characterized by SEM and EDS methods. The strength of adhesion of a E-beam evaporated chromium metal overlayer to the coating, as measured by a continuous microindentation method, increased in the order Cr < Mo ≅ W; adhesion was found to be directly proportional to the effective free energy of formation of the oxide mixture.
Surface Reactions Leading to Contamination of Metal Films Photochemically Deposited from the Hexacarbonyls
Authors: Singmaster K. A. , Houle F. A. , Wilson R. J.
Published: March 2011

A systematic study of the origin of contaminants in metal films photochemically deposited from the group VI hexacarbonyls is described. Background gas present in the cell during deposition, exposure to air and incomplctc removal of CO groups from the surface of the growing film all affect C and O incorporation. The data are compared to results of recent experiments examining surface photoproducts of the metal carbonyls.
Molecular Beam Study of the KrF* Laser Photodissociation of Cr(CO)6 and Mo(CO)6
Authors: Tyndall George W. , Jackson Robert L.
Published: March 2011

The one-photon and sequential two-photon KrF* laser (248 nm) photodissociation of Cr(CO)6 and Mo(CO)6 were studied in a molecular beam using mass spectrometry to detect the photoproduct molecular ions. For Cr(CO)6, the major one-photon product, Cr(CO)4, undergoes secondary photodissociation to give predominantly Cr(CO)2. The photodissociation cross section of Cr(CO)4 is found to be 1.6 × higher than that of Cr(CO)6 at 248 nm. For Mo(CO)6, the major one-photon products, Mo(CO)5 and Mo(CO)4, undergo secondary photodissociation to give predominantly Mo(CO)3.
The Direct Photo-CVD of Silicon Dioxide from Si2H6 and N2O3
Authors: Bhatnagar Yashraj K. , Milne W. I.
Published: March 2011

The direct photo-CVD of silicon dioxide on c-Si substrates has been achieved using a new combination of Si2H6 and N2O3 gases, with an external deuterium lamp as the VUV source. The variation of the deposition rate and the refractive index with process parameters is reported. FTIR studies on these oxides show that the oxide is very nearly stoichiometric with no Si-N bonds and only trace amounts of Si-H bonds. C-V, I-V and breakdown measurements made on these films are reported. a-Si:H thin film transistors have also been fabricated using this oxide as the gate dielectric.
Pyrolytic and Laser Photolytic Growth of Crystalline and Amorphous Germanium Films from Digermane (Ge2H6)
Authors: Eres Djula , Lowndes D. H. , Tischler J. Z. , Sharp J. W. , Geohegan D. B. , Pennycook S. J.
Published: March 2011

High-purity digermane (Ge2H6, 5% in He) has been used to grow epitaxially oriented crystalline Ge films by pyrolysis. Amorphous Ge:H films also have been deposited by pyrolysis and ArF (193 nm) laser-induced photolysis. The amorphous-to-crystalline transition and the film's morphology was studied as a function of deposition conditions. The film's microstructure, strain and epitaxial quality were assessed using x-ray diffraction curves and scanning and transmission electron microscopy. It was found that commensurate, coherently strained epitaxial Ge films could be grown pyrolytically on (100) GaAs at low (0.05–40 m Torr) Ge2H6 partial pressures, for substrate temperatures above 380°C.
Hydrogen Ion Beam Smoothening of Oxygen Roughened Ge(001) Surfaces
Authors: Horn K. M. , Chason E. , Tsao J. Y. , Picraux S. T.
Published: March 2011

A smooth Ge(001) surface can be severely roughened by chemical etching with oxygen gas and then returned to its original smoothness by exposure to hydrogen. The rate of recovery of the surface depends strongly on temperature, as well as on whether the hydrogen is introduced as a low energy ion beam or simply as a gas. The roughness induced in the surface by etching is “locked-in” after removal of the oxygen gas through pinning of ledges by residual contamination. This pinning prevents the surface from smoothening thermally. The introduction of hydrogen to the surface promotes a chemical reaction which frees the pinned sites and allows thermal smoothening to proceed.
Electrical Behavior of Spin-on Silicon Dioxide (SOX) in a Metal-Oxide-Semiconductor Structure
Authors: Lifshitz N. , Smolinsky G. , Andrews J. M.
Published: March 2011

We studied the behavior of mobile charges, which we believe are hydrogen ions, in a novel spin-on oxide, SOX. Our analysis is based on the Triangular Voltage Sweep (TVS) technique, which is normally used to detect the presence of mobile alkali ions in silicon dioxides. We found that the TVS traces of protons exhibit several unique features that allow us to distinguish a proton signal from that of other common contaminants, such as sodium. We suggest a model to explain these unique features. We show that the presence of hydrogen in the SOX material is due to the high water retention of this porous oxide.
Catalysis of Electroless Copper Plating using Pd+2/Poly(Acryilc Acid) TIIIN Films
Authors: Jackson Robert L.
Published: March 2011

A new method is described for initiating electroless copper deposition onto dielectric substrates. The method employs a thin poly(acrylic acid) film, applied to the substrate by dip-coating, to bind Pd+2 from PdSO4 solution. Uptake of Pd+2 takes place by H+/Pd+2 ion exchange at the carboxylic acid sites of the polymer. Upon immersion of a substrate treated with Pd+2/poly(acrylic acid) into an electroless copper plating bath, reduction of Pd+2 to Pd0 takes place, forming an active catalyst for the initiation of electroless copper plating.
Low Temperature Transformation of the Surface of Copper Oxide Filled Ptfe Via Treatment in a Hydrogen Plasma
Authors: Goldman Dov B.
Published: March 2011

The surface conductivity of PTFE-copper oxide filled composites containing between 10 and 25% of the oxides increases significantly after treatment in a low pressure hydrogen plasma at temperatures below 100°C. The plasma-reduction of copper oxides (CuO and CuO/Cu2O mixture) was investigated and compared with thermal reduction at different hydrogen partial pressures.
Degradation of the Polyimide/Copper Interface
Authors: Chakravorty K. K. , Loebs V. A. , Chambers S. A.
Published: March 2011

A comparative investigation of polyimide/Cu interface degradation has been carried out for ultrathin photosensitive, non-photosensitive, and preimidized polyimide precursor films cured while in contact with a Cu substrate. The role of curing byproducts and environmental conditions on interface degradation has been elucidated by means of X-ray photoelectron spectroscopy. Immediately after curing, we observed some oxidation of the Cu in contact with non-photosensitive and photosensitive polyimide overlayers. On the other hand, only negligible oxidation was observed for the preimidized polyimide/Cu interface. Experiments in which samples were stored in vacuum, air and a humidity chamber show a dependence of the oxidation kinetics on air/moisture exposure. Preimidized and photosensitive polyimide/Cu interfaces, stored in air, became more extensively oxidized with time relative to identical samples stored in vacuum. Moreover, all three polyimide/Cu interfaces exhibited significantly more oxidation after 3 days in a humidity chamber than after 19 days of storage in air. Taken together, these data clearly demonstrate that absorbed water and its interaction with curing byproducts are key factors in the extent of Cu oxidation at the interface.
Interaction of an Aromatic Molecule with a Surface
Authors: Vidali G. , Karimi M.
Published: March 2011

The interaction between an aromatic molecule and the graphite basal plane is constructed using a Lennard-Jones 6–12 potential. The corrugation of the potential across the surface, the binding energies and vibrational frequencies of the aromatic molecules on the basal plane have been calculated and compared with experimental data. We have also calculated the interaction between a rare-gas atom and an aromatic molecule using two independent models, one based on the pairwise sum of the Lennard-Jones potential and the other on the Effective Medium Theory (EMT) for the repulsive part and a Van der Waals dispersion term for the attractive part. Our results are then compared with available experimental data.
New Organotellurium Precursors for the Pyrolytic and Photolytic Deposition of Hg1-xCdxTe
Authors: Gedridge Robert W. , Higa Kelvin T. , Nissan Robin A.
Published: March 2011

Organometallic precursors with low decomposition temperatures are essential in the fabrication of high performance mercury cadmium telluride (Hg1-xCdxTe) infrared detectors by pyrolytic and photolytic metal-organic chemical vapor deposition (MOCVD). Film growth temperature is governed by the relative stability and/or reactivity of the organotellurium precursor, which is determined by the strength of the Te-C bonds. Since the rate-determining step in the pyrolysis of organometallic compounds involves bond breaking and free radical formation, we have concentrated on the synthesis of a variety of organotellurium precursors with substituents that possess low activation energies for the formation of hydrocarbon free radicals. The synthesis, characterization, and properties of methylallyltelluride, ethylallyltelluride, isopropylallyltelluride, tertiarybutylallyl-telluride, methylbenzyltelluride, and methylpentadienyltelluride are reported. These unsymmetrical tellurides were characterized by 1H, 13 C, and 125Te NMR spectroscopy. The potential applicability of these organotellurium precursors to lower film-growth temperatures in MOCVD is discussed.
The Synthesis of InP drom Indium Halides and Tris(Trimethylsilyl)Phosphine
Authors: Healy Matthew D. , Laibinis Paul E. , Stupik Paul D. , Barron Andrew R.
Published: March 2011

InP has been prepared by the reaction of InX3 (X = Cl, Br, I) with P(SiMe3)3. The intermediates and product have been characterized by XPS, elemental analysis and X-ray powder diffraction.
Coherent Anti-Stokes Raman Scattering Measurements of Group V Hydride and Trimethylgallium Decomposition in Organometallic Vapor Phase Epitaxy
Authors: Löckerath R. , Koss H. J. , Tommack P. , Richter W. , Balk P.
Published: March 2011

The thermal decomposition of AsH3 and TMG is measured insitu under different experimental conditions. Simultaneously the production of H2, CH4 and C2H6 is observed. The data indicate a situation where AsH3 is only partially decomposed at the GaAs surface. The hydrogen released removes additional CH3 groups from the trimethyl-gallium (TMG) molecule, enhances the decomposition of TMG, and thereby forms methane.
Properties of Transparent Silica Gel - Pmma Composites
Authors: Pope Edward J. A. , Asami Minuo , Mackenzie John D.
Published: March 2011

Transparent silica gel - polymer composites have been prepared by the impregnation of porous silica gels with fluid organic monomer followed by in situ polymerization. These materials constitute an entirely new class of transparent composites.
Magnetic Properties Of Iron/Silica Gel Nanocomposites
Authors: Shull Robert D. , Ritter Joseph J. , Shapiro Alexander J. , Swartzendruber Lydon J. , Bennett Llawrence H.
Published: March 2011

Homogeneous gelled composites of iron and silica containing 5–30 wt. % Fe have been prepared by low temperature polymerization of aqueous solutions of ferric nitrate, tetraethoxysilane, and ethanol (with an HF catalyst). X-ray diffraction data, characterized by the presence of a diffuse scattering peak centered at 20≈24 degrees and the absence of any strong Bragg scattering from the iron-containing regions, indicates that these bulk materials are comprised of nanometer-sized regions of iron compounds embedded in a silica gel matrix. Scanning electron microscopy observations show that this matrix is characterized by the presence of many interconnected pores and that the size of these pores is related to the particle size of the Fe-containing regions. The paramagnetic nature of these materials at room temperature, as well as the small size of the iron-containing regions, is indicated by the appearance in many of the samples of only a high intensity central doublet in the 57Fe M6ssbauer spectra. The Mössbauer effect data demonstrates that the form of the iron can be changed by a subsequent treatment in an atmosphere of ammonia or hydrogen at elevated temperatures: for a 10 wt. % Fe sample treated with ammonia, only a central doublet was observed but with a much larger quadrupole splitting and isomer shift. Both of these subsequently treated materials became superparamagnetic at room temperature. In addition, magnetic susceptibility measurements indicate that the hydrogen treated material becomes a spin glass at low temperatures.
Synthesis, Characterization, and Properties of Nanophase Ceramics
Authors: Siegel R. W. , Eastman J. A.
Published: March 2011

Ultrafine-grained ceramics have been synthesized by the production of ultrafine (2–20 nm) particles, using the gas-condensation method, followed by their in-situ, ultra-high vacuum consolidation at room temperature. These new nanophase ceramics have properties that are significantly improved relative to those of their coarser-grained, conventionally-prepared counterparts. For example, nanophase rutile (TiO2) with an initial mean grain diameter of 12 nm sinters at 400 to 600°C lower temperatures than conventional powders, without the need for compacting or sintering aids. The sintered nanophase rutile exhibits both improved microhardness and fracture characteristics. These property improvements result from the reduced scale of the grains and the increased cleanliness of the particle surfaces and the subsequently-formed grain boundaries. Research completed on the synthesis, characterization, and properties of nanophase ceramics is reviewed and the potential for using the nanophase synthesis method for engineering new and/or improved ceramics and composites is considered.
Ultrafine Composite Synthesis by Laser-Reactions and Rapid Condensation
Authors: Chow Gan-Moog , Strutt Peter R.
Published: March 2011

A new approach in ultrafine composite synthesis involves rapid condensation of metallic and non-metallic species, produced by laser-induced evaporation. A heated tungsten filament is simultaneously employed for codeposition of W via chemical transport mechanisms. This process occurs in a reducing environment of hydrogen gas, where evaporated species were produced by a laser-induced plume. Composite layers were formed on a Ni alloy substrate surface, at a rate of about 1Pm/sec. The matrix of the composite films was either Al or W, and the dispersed phase was amorphous silica fibers. The diameter of the fibers was between 25nm and 120nm, depending on the interaction times. Various analytical techniques have been employed to characterize the as-synthesized layers. Experimental evidences do not support the Vapor-Liquid-Solid model for fiber growth. An alternative fiber growth mechanism is proposed.
Fabrication of Ferromagnetic Fe/Mullite Composite Materials Via Sol-Gel Processing
Authors: Yamato Deanne P. , andis Abraham L. , Kuan Teh S.
Published: March 2011

The sol-gel technique was used to fabricate α-Fe/mullite composite materials with iron concentrations ranging from 20–60 wt.% Fe. Microscopy studies showed the microstructure to consist of particulate α-Fe dispersed uniformly throughout a mullite matrix. Iron particle size, estimated by TEM, ranged from 20–500 nm. The materials exhibited ferromagnetic hysteresis with saturation magnetization Ms values as high as 115 EMU/g.
Material with Novel Compositions and Fine Microstructljres Produced Via the Mixalloy Process
Authors: Lee Arthur K. , Sanchez-Caldera Luis E. , Chun Jung-Hoon , Suh Nam P.
Published: March 2011

A new processing method, the Mixalloy process, has been developed to process alloys with novel microstructures and compositions. In this process, microstructural control is achieved through the use of turbulent mixing of liquid metals in addition to controlling solidification rate and chemical composition. Boride dispersion strengthened copper alloys were produced using the Mixalloy process. Thermally stable and fine (average less than 100 nm) boride dispersoids were formed by in-situ chemical reaction in the copper alloy matrices during mixing. The uniform mixture of the matrix and dispersoids was then rapidly solidified to maintain the fine microstructure. The consolidated material shows exceptional thermal stability and an excellent combination of strength, ductility, and electrical conductivity. Furthermore, the flexibility of the process allows the matrices of these dispersion strengthened coppers to be easily alloyed to fulfill specific needs. The versatility and simplicity of the Mixalloy process provide an economical alternative to other processing means in the manufacturing of high performance alloys such as dispersion strengthened alloys.
Alloy Modeling and Experimental Correlation for Ductility Enhancement in NiAl
Authors: Darolia R. , Lahrman D. F. , Field R. D. , Freeman A. J.
Published: March 2011

Single crystals of stoichiometric NiAl and NiAl+V alloys were tested in compression and tension from room temperature to 871°C to determine deformation behavior. The dislocations were predominately <100> in the plastically deformed specimens. Attempts to ductilize NiAl by the addition of vanadium are described. The lowering of the anti-phase boundary energy by vanadium addition to NiAl, believed to promote the formation of <111> dislocations, was predicted by the all electron self consistent total electron band structure calculations. The vanadium additions caused considerable solid solution strengthening in NiAl, rendering the ternary alloys more brittle than stoichiometric NiAl.
Surface Energies of Planar Defects and Dislocation Processes in Al3Ti and Tial
Authors: Hug G. , Douin J. , Veyssiere P.
Published: March 2011

Information on APB energy in ordered alloys is important not only to understand their mechanical properties but also to analyse conditions for phase transformation. APB surface energies are determined from dissociation distances of superdislocations both in TiAl and Al3Ti Medium and high APB energy anisotropies are found in TiAl and Al3Ti respectively. These results are consistent with phase diagram studies which predict that the APB energy vanishes in the (001) plane near the Al3Ti composition. Examples of decompositions of perfect dislocations into perfect dislocations are discussed.
Examination of Dislocation Cores in Ni3Al Using High Resolution Electron Microscopy
Authors: Crimp Martin A. , Hazzledine P. M.
Published: March 2011

High resolution electron microscopy has been used to study the core structure of a/2[101] and a/3<112> dislocations in Ni3Al deformed in the range of increasing strength with temperature. a/3<112> coupled SISFs were found to lie on (111) and their structure agreed well with theoretical predictions. a/2[101] superpartials were always dissociated on (111) or (111) planes while the APB plane was found to be (010). Computer simulation of dislocation core structures were found to agree well with the observed dissociations. The APB width was found to increase significantly with increasing deformation temperature near the peak yield strength temperature.
Deformation Twinning in Ordered Intermetallic Compounds
Authors: Yoo M. H. , Fu C. L. , Lee J. K.
Published: March 2011

Mechanistic understanding of deformation twinning in ordered superlattice structures is reviewed, and the inter-relationships between twinning and generalized plastic flow or fracture toughness are discussed. While general discussions refer to all the fcc-based and bcc-based cubic and noncubic ordered intermetallic alloys, specific calculations of the energetic and kinetic aspects of deformation twinning are made for TiAl. The importance of the twin-slip conjugate relationship on high temperature mechanical properties is emphasized. Discussion is given of possible effects of macro- and micro-alloying on twinning propensity.
The Effect of Prestrain on Deformation of Ni3Al Single Crystals
Authors: Dowling W. E. , Gibala R.
Published: March 2011

Prestrain of bcc metals at temperatures T>0.2Tm decreases the flow stress at lower temperatures (T<O.15Tm) where the yield strength has a large negative temperature dependence. This investigation has examined the influence of prestrain on the flow stress of Ni3A1, for which the yield strength has a large positive temperature dependence above 25°C. Nickel-rich Ni3Al single crystals with axial orientations near <001> or <123> were prestrained in compression up to 20% shear strain at -196°C and subsequently compression tested at 550°C. Specimens near the <123> axial orientation were also prestrained at 550°C and then tested at -196°C. The initial flow stress of samples prestrained at - 196°C and tested 550°C was reduced up to 50% compared to samples solely compression tested at 550°C. The magnitude of the reduced flow stress and its extent as a function of plastic strain were dependent upon the amount of prestrain and orientation. Prestraining at 550°C and subsequent testing at -196°C increased the flow stress by as much as 60% over samples solely tested at -196°C. Dislocation substructures obtained from selected samples coupled with arguments based on dislocation dynamics and obstacle strengthening are used to explain the results.
Electron Microscopy Study of Fatigue Crack Initiation in Ni3Al Single Crystals
Authors: Hsiung L. M. , Stoloff N. S.
Published: March 2011

Transmission electron microscopy of single-slip oriented Ni3Al single crystals cyclically deformed at room temperature revealed a high density of dislocation dipoles and point defect clusters. The majority of the defect clusters were identified by weak-beam TEM to be of vacancy type. The observations of circular perfect dislocation loops, Frank loops, and spherical voids revealed the evidence of vacancy condensation during fatigue cycling at room temperature. Together with SEM observations of surface topography, it is suggested that fatigue crack initiation in Ni3Al single crystals can be rationalized by formation of microvoids at PSB/matrix interfaces.
The Creep Behavior of Cr Modified Ni3 Al Single Crystals
Authors: Hsu S. E. , Tong C. H. , Lee T. S. , Liu T. S.
Published: March 2011

Ni-Al-Cr single crystals with 4 at% Cr and different levels of aluminum content are grown in a directional solidification facility. The crystals are creep tested at temperatures from 760°C to 860°C. Steady state, as well as transient, creep rates are measured. The results show that Cr modified Ni3 A1, when tested along the <100> direction, exhibit remarkably high values of activation energy for creep. Along with evidence from dislocation structures, it is likely that there is a change in the dislocation core structure upon Cr addition.
Fracture Modes in Ll2 Compounds
Authors: Briant C. L. , Taub A. I.
Published: March 2011

This paper reports a study of grain boundary segregation and fracture modes in Ll2 intermetallic compounds. Data obtained on Ni3A1, Ni3Si, Ni3Ga, Ni3Ge, and Pt3Ga will be presented. It will be shown that the amount of boron segregation and its ability to improve cohesion depends on the total composition of the compound. The beneficial effects of boron can be counteracted by the presence of borides on the grain boundaries. Carbon additions also produce some improvement in ductility in Ni3Si.
Ductility and Fracture Behavior of Single Crystalline Ni3Al with Boron Additions
Authors: Heredia F. E. , Pope D. P.
Published: March 2011

Low and high temperature tensile tests were performed on single crystals of pure Ni3Al and Ni3Al+B in order to determine the effect of B additions on the ductility and fracture behavior. Tests were carried out in air at a constant strain rate of 1.3 × 10−3 s−1. The orientations tested were [001] for which the yield stress in tension is always greater than in compression, and those for which the tension/compression asymmetry is zero ([T=C]) for each particular composition. At room temperature, the results show a positive effect of B additions on both the fracture stress and on the ductility. The ductility at 800K appears to decrease monotonically with B additions. The largest ductilities are found for [T=C] at room temperature where an improvement of about 26% (resolved strain) for an addition of 0.2 at% B was obtained. However, the most dramatic increase in ductility occurs for the [001] oriented samples at room temperature where a 55% improvement was measured over that of pure Ni3Al. Fracture surfaces show a combination of massive slip, some cleavage, and heavily dimpled areas. These observations show that B additions not only increase the ductility of polycrystalline Ni3Al, as has been previously observed by many investigators, but also that of the already-ductile single crystalline material, indicating that a “bulk effect” should be added to the grain boundary strengthening effect of B when explaining the improvement in ductility of polycrystalline Ni3Al due to B additions.