bluuebunny/crossref_metadata_2025 huggingface dataset:
Considerations of ion channeling for semiconductor microstructure fabrication
Authors: Myers D. R. , Wilson R. G. , Comas J.
Published: July 2002

The performance of semiconductor devices becomes increasingly sensitive to details of the depth distribution of dopants as device dimensions are reduced. In this paper, limitations on the control of dopant distributions resulting from implantation into single-crystal silicon due to ion channeling are examined for a range of ion atomic numbers and energies characteristic of semiconductor device fabrication. Implantation profiles were obtained by 1 MHz differential capacitance–voltage profiling and by secondary ion mass spectroscopy for silicon substrates implanted at angles from accurately channeled alignment to ’’random equivalent’’ orientation. The critical angle as calculated from an existing computer fit to the Moliere continuum potential was used to scale the angular dependence of the implantation profiles. Ion channeling is seen to have important consequences not only for the deeply penetrating regions of the dopant profile but for the near-surface profile as well. The results of this study indicate that to minimize the extent of unintentional channeling, alignment of the ion beam to the nearest low-index crystallographic direction must be at angles exceeding twice the critical angle and that the angle required can exceed the commonly used seven degree tilt angle, especially for ions of large atomic number at low energy.
Phosphosilicate glass flow for integrated optics
Authors: Naumaan A. , Boyd J. T.
Published: July 2002

We have carried out an investigation of the use of phosphosilicate glass (PSG) flow for integrated optical circuits. PSG layers of thicknesses ranging from 4 to 22 μm were chemically vapor deposited on V-grooves in silicon substrates having a depth of 175 μm. The effect on the flow of (1) P2O5 concentration in PSG layers (5–10 mol %), (2) ambient during flow (dry O2, wet O2, POCl3, and wet N2), (3) temperature (1000°–1200°C) and (4) time (30–120 min) of the process has been determined. The extent of flow, as measured by curvature of the rounded corners, has been plotted against PSG layer thickness and reflow time. Radii of curvature up to 36 μm through 70° bends have been measured.
Analytic correction of edge effects in ion-beam sputtered depth profiles
Authors: Hoffman D. W. , Tsong I. S. T. , Power G. L.
Published: July 2002

A numerical integration procedure based on theoretical analysis of the crater geometry removes the edge effects from depth profiles obtained by sputtering with a static and nonuniform ion beam. Parameters characterizing the beam and the detector ensue from the depth profile of a standard sharp interface, e.g., a SiO2 film on silicon. These parameters then correct subsequent depth profiles of unknown interfaces sputtered by the same beam. The advantages of this approach are that no a priori knowledge of th beam current density distribution is required, and the mathematical treatment lends itself to computerization for on-line data processing. Examples of the correction performed on experiomental depth profiles obtained by sputter-induced optical emission and secondary ion mass spectrometry techniques illustrate its general applicability.
Chemical depth profiles of the GaAs/native oxide interface
Authors: Grunthaner P. J. , Vasquez R. P. , Grunthaner F. J.
Published: July 2002

The final-state oxidation products and their distribution in thin native oxides (30–40 Å) on GaAs have been studied using x-ray photoelectron spectroscopy in conjunction with chemical depth profiling. Extended room-temperature-oxidation conditions have been chosen to allow the native oxide to attain its equilibrium composition and structure. The work emphasizes the use of chemical depth-profiling methods which make it possible to examine the variation in chemical reactivity of the oxide structure. A minimum of two distinct regions of Ga2O3 with differing chemical reactivity is observed. Arsenic oxide species show one distinct phase at the outer oxide surface. Intensity analysis indicates an oxidized Ga to oxidized As composition ratio of 2:1 at the outer surface, which changes to approximately 10:1 at the oxide/GaAs interface. Chemical shift data indicate the presence of As2O3 in the oxide together with an elemental As overlayer at the interface. A change in relative charge transfer between oxygen and both arsenic and gallium–oxide species is observed in the region of the interface. The presence of mixed As/Ga oxides and different gallium oxide coordination environments is also discussed.
The thermal stability of thin layer transition and refractory metallizations on GaAs
Authors: Mukherjee S. D. , Morgan D. V. , Palmstrom C. J. , Smith J. G.
Published: July 2002

The thermal stability of vacuum deposited thin metallic layers (namely Ta, Cr, Cr–Au, Mo, Mo–Au and W) on GaAs for short (1 h) and long (∠150 h) thermal anneals at temperatures up to 550°C have been studied using Rutherford backscattering of helium ions, scanning electron microscopy with energy and wavelength dispersive x-ray analysis, and secondary ion mass spectrometry. We attempt to generalize the nature of thermal reactions of the metals with GaAs and the competing oxidation reactions in a humid/oxidizing atmosphere in terms of simple physiochemical considerations.
High rate deposition of transparent conducting films by modified reactive planar magnetron sputtering of Cd2Sn alloy
Authors: Maniv S. , Miner C. , Westwood W. D.
Published: July 2002

A Cd2Sn alloy planar magnetron target has been dc sputtered in Ar/O2 mixtures. The variation of both sputtering pressure and discharge impedance indicated the formation of an oxide layer on the target surface at a critical oxygen flow, f2C, and its removal when the flow rate was reduced to f2D. For an average power of 375 W, the pressure increase at f2C was 0.4 Pa and the decrease at f2D was 0.16 Pa; for f2D<f2<f2C, the value of p in the presence of the oxide layer was 0.2 Pa lower than the value with the discharge off. For f2?f2C the film resistivity, ρ, and transparency, T, both increased with the ratio of oxygen flow to deposition rate of metal but the changes were too rapid for good reproducibility; T increased from zero to 80% with a 10% change in f2. The magnetron system was modified to increase the oxidation rate at the substrate relative to the target both by a geometric arrangement of slits and by application of an auxiliary rf discharge. The film properties were controlled by varying both the dc power to the target and the rf power. For a fixed dc voltage, T increased from 25% to 85% as the rf power to the substrate increased from 0 to 100 W. Transparent films with ρ as low as 4.4×10−4 Ωcm were obtained under optimum conditions without any heat treatment.
Silicon–refractory metal interfaces: Evidence of room-temperature intermixing for Si–Cr
Authors: Franciosi A. , Peterman D. J. , Weaver J. H.
Published: July 2002

Photoemission spectroscopy investigations of the Si–Cr interface using synchrotron radiation indicate metal–semiconductor intermixing during room temperature interface formation, in sharp contrast with the Si–V interface. The intermixed phase is 10–13 Å thick and is of definite metallic character. For higher metal coverage (≳20 monolayers) photoemission from Si 2p levels with variable surface sensitivity show Si segregation in the top layers of the Cr film.
A simple source cell design for MBE
Authors: Kubiak R. A. , Driscoll P. , Parker E. H. C.
Published: July 2002

A simple, low-cost, and easily-manufactured evaporation furnace, suitable for MBE, is described. The essential feature of the design is a composite heater-shroud and evaporation cell, machined from high-purity graphite. Good-quality silicon-doped gallium arsenide has been grown using this cell design.
Improvement of thermally formed nickel silicide by ion irradiation
Authors: Wieluński L. S. , Lien C-D. , Liu B. X. , Nicolet M-A.
Published: July 2002

A significant improvement of the lateral uniformity of thermally formed Ni2Si layers has been observed after low-dose (1013∠3×1014 ion/cm2) Xe irradiation of an As-deposited Ni film. Measurements have also been made on samples that contained a thin impurity layer formed intentionally between the silicon substrate and the evaporated nickel film. The impurity layer was thick enough to prevent thermal silicide formation in unirradiated samples, but in irradiated samples, the silicide formation was not prevented. Similar results were obtained for As implantations. We attribute this effect to ion mixing of the interfacial layer. These results demonstrate that a low-dose irradiation can render the process of silicide formation by thermal annealing more tolerant to interfacial impurities. The concept is of potential significance to VLSI technology.
Observation of Ge-induced electronic states at the Ge:GaAs(110) interface by means of polarization-dependent UPS
Authors: Zurcher P. , Lapeyre G. J. , Anderson J. , Frankel D.
Published: July 2002

Strong evidence for Ge-induced valence band states for ∠0.5 monolayer (ML) Ge on cleaved GaAs(110) is presented. Normal emission energy distribution curves have been measured for two different polarization [A⊥ mirror plane (MP) and A∥MP] for photon energies from hν = 14–27 eV at the University of Wisconsin Synchrotron Radiation Center. Four different kinds of Ge-induced features are observed: (i) attenuation of clean substrate transitions, (ii) energy shifts of substrate transitions, (iii) new transitions with hν dispersion, and (iv) new transition with no dispersion. The latter dispersionless transition observed for hν between 17 and 23 eV must originate from a two- dimensional structure, and we propose that it is due to a Ge:GaAs(110) interface state. With respect to the valence band maximum, its binding energy (EB) is 6.8 eV which compares to EB = 7.95 eV predicted for a coverage of 3 ML Ge by Mazur, Pollmann, and Schmeits for a Ge–Ga interface state. The observed interface state shows a relatively strong polarization dependence which implies that the initial state symmetry is odd. Strong Ge-induced transitions are observed with binding energies between 1 and 3 eV which show large dispersion. This means that the initial states must have a three-dimensional character. They are identified as GaAs(110) substrate transitions whose matrix elements are strongly enhanced by the chemisorption of Ge, making them observable in UPS.
Electronic correlation and the Si(100) surface: Buckling versus nonbuckling
Authors: Redondo Antonio , Goddard William A.
Published: July 2002

Theoretical cluster calculations for the Si(100) surface show that the use of doubly occupied orbital wavefunctions, such as the closed-shell Hartree–Fock (HF), lead to an asymmetric dimer description of the surface. The inclusion of electron correlation produces a symmetric dimer description with a ground state ∠1.0 eV below the minimum of the HF buckled dimer. There are two low-lying states of the symmetric dimer (a singlet and a triplet) with very different geometries. Energy minimization calculations indicate that a (2×1) structure is favored over a c(2×2) structure. We also report ionization potentials for surface and Si(2p) core electrons that are consistent with current experimental data.
Anodization of aluminum wire for ultrahigh vacuum electromagnetic coils
Authors: Barthel John R. , Hudson John B.
Published: July 2002

It was found that outgassing problems were eliminated when .020\ diam aluminum wires were anodized in a solution of 25 g oxalic acid per liter of water.
Disorder on GaAs(001) surfaces prepared by molecular beam epitaxy
Authors: Van Hove J. M. , Cohen P. I. , Lent C. S.
Published: July 2002

Measurable disorder exists on GaAs(001) surfaces during MBE even though these surfaces subsequently incorporate into exceedingly well-ordered bulk GaAs lattices. We have used reflection high energy electron diffraction (RHEED) to characterize this disorder. On the As stabilized surface obtained at 850 K, some of the fractional order beams are broadened indicating that there is antiphase disorder present on the surface. Models of this disorder are presented. In addition, if the growth is stopped by shuttering the Ga flux both integral and quarter order beams sharpen, indicating that a second type of disorder exists. From the lengths of the RHEED streaks we determine that during growth the long range order in the twofold direction is about 500 Å. About 10 min after growth is stopped, the extent of order in this direction increases to 3000 Å. At a given As flux the ordering process is slightly temperature dependent over the narrow range that this disordered 2×4 exists. At lower temperatures, the disordered structure switches to a C(4×4), at higher temperatures to a 1×4.
Fabrication of optically enhanced thin film a-SiHx solar cells
Authors: Deckman H. W. , Wronski C. R. , Witzke H.
Published: July 2002

Fabrication methods used to produce the first optically enhanced thin film solar cells are described. Optically enhanced 0.6–1 μm thick a-SiHx solar cells have been fabricated which yield short circuit currents ∼3 mA/cm2 greater than comparable unenhanced cells. This respresents a ∼20% improvement in the short circuit current and is due to trapping of weakly adsorbed photons in the semiconductor that have been scattered by textured surfaces within the cell. Texturing of the cell must be such that light is efficiently scattered, and the roughness must not produce shorting of the front surface transparent conductor with the rear electrical contact. To produce the required texture, thin film solar cells are deposited on the surface of substrates patterned with microstructures created using a new lithographic method (natural lithography). Other considerations for fabrication of enhanced PIN a-SiHx cells include (1) production of reflector geometrics which minimize parasitic optical absorption and (2) creation of a carrier collection width nearly equal to the cell thickness.
Study of cleaved, oxidized, etched, and heat-treated CdTe surfaces
Authors: Häring J.-P. , Werthen J. G. , Bube R. H. , Gulbrandsen L. , Jansen W. , Luscher P.
Published: July 2002

The chemical compounds present on the surface of CdTe have been investigated after different surface preparations and correlated with the properties of junctions formed by Cr on the CdTe. X-ray photoelectron spectroscopy (XPS) analysis indicates that four different surface compositions result from five different treatments. Cleaving leaves a stoichiometric surface whereas oxidation in air leads to the formation of TeO2. Bromine-in-methanol etch leaves a Te-enriched surface and chromate etch leaves a surface containing both TeO2 and excess Te. Hydrogen heat treatment of an etched CdTe surface restores a stoichiometric cleavedlike surface from that disrupted by the etching process. Effects on the properties of subsequently formed junctions are evidenced by a decrease in the diode saturation current from 2×10−5 for a bromine-etched surface to 2×10−8 A/cm2 for a cleaved surface.
Solid-state quaternary phase equilibrium diagram for the Hg–Cd–Te–O system
Authors: Rhiger David R. , Kvaas Robert E.
Published: July 2002

For the Hg–Cd–Te–O system an approximate three-dimensional diagram of quaternary phase equilibrium at room temperature has been constructed for the first time, to aid in the study of Hg1−xCdxTe surface oxides. Thermodynamic calculations based on standard Gibbs energies of formation were performed to determine which phases are mutually stable. Stability relationships were checked by reaction experiments in mixtures of bulk reference compounds, using Raman spectroscopy for analysis. Elemental Hg is shown to coexist in equilibrium with all of the oxide and telluride phases. Thus, it is likely to be present whenever oxidation is incomplete. CdTeO3 is shown to be stable with respect to the other oxides and tellurides. Several instabilities are indicated, in which an oxide can react with the Hg1–xCdxTe to release elemental Hg or Te, or HgTe.
Growth of low dislocation density CdTe films on hydroplaned CdTe substrates by molecular beam epitaxy
Authors: Myers T. H. , Schetzina J. F. , Magee T. J. , Ormond R. D.
Published: July 2002

A systematic study of CdTe film growth by molecular beam epitaxy (MBE) on hydroplaned (111)A and (111)B CdTe substrates is discussed. Substrate preparation prior to growth involved chemical etching techniques, rather than sputtering in UHV, in order to maintain the integrity of the hydroplaned surface. A range of substrate temperature during growth was investigated. X-ray diffraction, UV reflection, and transmission electron diffraction measurements were employed to evaluate the structural quality of the CdTe films. Bright and dark field transmission electron microscopy was used to determine film dislocation densities. An entirely different film growth morphology was observed on the (111)A versus (111)B substrate surfaces for the range of temperatures and growth rate employed. Growth of high quality, low dislocation density, twin-free CdTe films was achieved on hydroplaned (111)A CdTe substrates at 250 °C.
Horizontal slider LPE of (Hg,Cd)Te
Authors: Wood R. A. , Hager R. J.
Published: July 2002

We report the epitaxial growth of single and double layers of Hg1−xCdxTe on 2×3 cm single-crystal CdTe substrates, using liquid phase epitaxy (LPE) from tellurium solution in an atmospheric pressure horizontal slider apparatus. The layers are found to be extremely uniform in composition (x) across individual layer areas and in layer-to-layer reproducibility (standard deviation 0.002). We report our observations of the morphological, compositional and crystalline quality of the layers, and measurements of the electrical parameters of the layers.
Device physics and technology of III–V compounds
Authors: Wieder H. H.
Published: July 2002

The science and technology of III–V compound semiconducting films and epitaxial layers is at the confluence of subdisciplines which cut across conventional demarcation lines of solid state physics and chemistry, surface science and high vacuum techniques, device physics and electronics. A retrospective of the past two decades shows that a strong feedback loop links emergent technological advances to new tools and techniques developed for the synthesis and characterization of thin layers which in turn influences the context of fundamental studies on III–V compound surfaces and interfaces. These theoretical and experimental investigations provide a framework for the evolution of a planar integrated circuit insulated gate field effect transistor technology which, it is hoped, will emulate that of the MOS silicon IC technology while taking advantage of the specific high electron velocities of the III–V compound binary and ternary alloys.
Noble metal interactions with the InP(110) surface
Authors: Petro W. G. , Kendelewicz T. , Babalola I. A. , Lindau I. , Spicer W. E.
Published: July 2002

We present details of the interfacial chemical reactions and intermixing observed for Cu, Ag, and Au overlayers on the clean cleaved InP(110) surface using soft x-ray photoemission spectroscopy (SXPS). Analysis of the P 2p and In 4d core levels and the P LVV Auger line reveals a range of chemical interactions: Cu–P metallic bonding with phase segregation of metallic In for Cu overlayers, Ag islanding with a small amount of In segregation for Ag overlayers, and elemental P precipitation with Au–In alloying for Au overlayers. Deconvolution of the substrate and reacted layer components of the core level spectra is used to determine the Fermi level pinning positions for Ag and Au on n- and p-type InP, and these values are compared to theoretical calculations of native defect energy levels.
LEED and AES characterization of the GaAs(110)–ZnSe interface
Authors: Tu D.-W. , Kahn A.
Published: July 2002

In this paper, we study the composition and structure of epitaxial ZnSe films grown by congruent evaporation on GaAs(110) at a rate of 2 Å/min. We find that the films grown on 300 °C GaAs are nearly stoichiometric and form an abrupt interface with the substrate. Films grown at higher temperature (T>350–400 °C) are Se rich. The crystallinity of films grown at 300 °C is good and their surface atomic geometry is identical to that of a ZnSe crystal. The GaAs–ZnSe interface geometry seems to be dominated by the Se–substrate bonds. The adsorption of Se, during the formation of very thin ZnSe films (2–3 Å), produces a (1×2) LEED pattern and modifications of the LEED I–V profiles, which probably indicate a change in the substrate atomic relaxation.
Comment on misfit dislocations in abrupt Hg1−xCdxTe heterojunctions
Authors: Schoolar Richard B.
Published: July 2002

The misfit dislocations and dangling bond densities of abrupt (111) Hg1−xCdxTe heterojunctions have been calculated based on a mathematical model for epitaxial crystal growth. For unstrained heterojunctions with alloy composition difference Δx≥0.10, the minimum density of dangling bonds is ≥1011 cm−2. Such large dangling bond densities may produce high interface recombination velocities or band bending at the interface.
Quantitative chemical surface, in-depth, and bulk analysis by secondary neutrals mass spectrometry (SNMS)
Authors: Müller K.-H. , Seifert K. , Wilmers M.
Published: July 2002

An SNMS/SIMS apparatus is described that allows measurements in three different modes: SNMS direct bombardment mode (DBM), SNMS separate bombardment mode (SBM), and SIMS, with the sample remaining in the same positions. A novel geometrical arrangement that guarantees optimum performance in each operating mode was chosen for this combination. A postdescription of the two SNMS modes is given. From the presented results it could be deducted that direct quantification is possible; the sensitivity is in the ppm range for all elements; in in-depth-profiling high resolution and high speed can be obtained simultaneously; and conductors, semiconductors, and insulators can be analyzed. The results show that the combination of two SNMS modes and SIMS promises to become a valuable tool for surface, interface, and bulk analysis.
Electrical characteristics of fast radiatively processed titanium silicides thin films
Authors: Wei C. S. , Van der Spiegel J. , Santiago J.
Published: July 2002

A fast radiative processing technique using quartz-halogen tungsten lamps is employed for the formation of titanium silicides on either high purity single crystal or undoped polycrystalline Si substrates. Characterization techniques such as four-point probe, x-ray diffraction, SEM, and backscattering spectrometry (BS) show complete TiSi2 formation after 17 s exposure to 18 W/cm2 radiation. Electrical characterization was performed by galvanomagnetic measurements. The results show a metallic and highly conductive silicide whose resistivity varies linearly with temperature in the temperature interval from 80 to 300 K. Films grown on (111) oriented single crystals and (110) textured polycrystalline Si showed both electrons and holes, with the holes as the predominant carriers at low temperature.
Effects of biased cosputtering on resistivity and step coverage in tungsten silicide films
Authors: Choi K. W. , Ahn K. Y.
Published: July 2002

Electrical resistivity and step coverage on thick oxide steps of various slopes were examined in tungsten silicide films sputter deposited by multilayering of W and Si utilizing magnetron targets. The desired composition was obtained by adjusting power levels to the targets and bias voltage. A broad minimum in electrical resistivity was obtained with bias voltage ranging from −40 to −80 V. Typical resistivity in films of 2500 Å thickness after annealing at 1000 °C was 52–66 μΩ cm when deposited on poly-Si substrates. The effect of bias was found to produce films with much lower levels of impurity such as N, O, C, and H and the sputtering gas Ar. Proper bias voltage (−50 V) was necessary to achieve good step coverage on thick oxide step with various slopes. Zero-bias sputtering provided minimum step coverage, while too high bias (−100 V) led to poor step coverage and formation of rounded corners and faceting.
Ion bombardment induced changes in silicon dioxide surface composition studied by x-ray photoelectron spectroscopy
Authors: Thomas John H. , Hofmann S.
Published: July 2002

A model for the quantitative analysis of silicon oxide using x-ray photoelectron spectroscopy (XPS) peak intensities is developed. This model is shown to have a precision of <5% in predicting the O/Si ratio within the XPS sampled volume. He+, Ne+, Ar+, and Xe+ bombardment of SiO2 are studied using this model. Results indicate that oxygen is preferentially depleted as a result of sputtering. Although elemental Si was not spectrally detected due to measurement noise and overlayer contamination, an equivalent upper limit to the elemental Si thickness of ∼2 Å is determined for Ne+, Ar+, and Xe+; He+ results in about 4 Å of elemental Si.
Hydrogen vibrational population distributions and negative ion generation in tandem high density hydrogen discharges
Authors: Hiskes J. R. , Karo A. M. , Willmann P. A.
Published: July 2002

The tandem high-density hydrogen negative-ion-source system is optimized to identify the largest possible ion concentrations and extracted ion currents. The optimization includes varying the length of the second chamber, varying neutral gas and electron densities, and varying the ratio of atomic to molecular density. Vibrational excitation occurs via high-energy electron excitation (E–V process) and H+2 surface neutralization (s–V process). These processes are considered separately and acting in parallel. The solutions are presented in terms of a dimensional scale factor R. For a system scale length R=1 cm, optimum extracted current densities are in the range 50 to 100 mA cm−2. A single-chamber s–V system with the high-energy electron component suppressed can provide larger ion concentrations than a tandem E–V, s–V system.
Lattice relaxation in aluminum monolayers
Authors: Batra Inder P.
Published: July 2002

A self-consistent pseudopotential technique based on the density functional formalism is used for calculating the electronic structure and total energy of an unsupported monolayer of aluminum in the [001] orientation. The results are presented for a number of values of the lattice constant and the equilibrium value is determined by an energy minimization criterion. One significant result of our study is that the lattice constant in a monolayer is contracted by about 10% with respect to the bulk lattice constant. This result is similar to the one recently reported by Wimmer for the two-dimensional Cs layer. Another conclusion is that the total bandwidth for the relaxed monolayer is about 1.5 eV larger than the value for the bulk truncated monolayer. The cohesive energy is increased by about 0.3 eV per atom upon relaxation. These findings are important in the study of thin-film deposition on substrates and in the molecular beam epitaxy. Another area for which our work has implications has to do with the electronic structure of a Cu(001) monolayer.
LPE growth conditions for Cd1−xMnxTe and Hg1−xMnxTe epitaxial layers
Authors: Becla P. , Wolff P. A. , Aggarwal R. L. , Yuen S. Y.
Published: July 2002

An LPE tipping technique for the growth of ternary semimagnetic semiconducting CdMnTe and HgMnTe epitaxial layers from Te-rich solution is described. Liquid isotherms, growth conditions, and electronic characteristics of the layers have been investigated. High quality HgMnTe layers have been obtained on lattice-matched CdMnTe substrates.
Indium ion implantation in Hg0.78Cd0.22Te/CdTe
Authors: Destefanis G. L.
Published: July 2002

Indium ion implantation in p-type Hg0.78Cd0.22Te/CdTe epilayers has been investigated by secondary ion mass spectroscopy (SIMS) and 77 K Hall effect measurements. In this paper we show that indium diffusion strongly depends on the way annealing is done after ion implantation. On the low mercury pressure side (annealing under vacuum, samples ZnS shielded) indium diffuses in a rather classical way for temperatures above 250 °C. In the temperature range 250–400 °C, annealing of the n+ electrical activity related to radiation damage is observed and electrical activity of at least a part of the implanted indium impurities is demonstrated. Removal of defects and electrical activity related to indium is also found to occur for annealing done on the high mercury pressure side. Nevertheless, in this case, mercury diffusion induces a quenching of indium diffusion and unusually sharp profiles are observed. During annealing, most of the implanted indium remains in the samples, except above 350 °C annealing, where important losses occur. The doping efficiency has been roughly evaluated and found to increase when the implanted dose is decreased. As a conclusion, the fact that diffusion of implanted indium can be controlled within a few micrometers and that annealing of defects and electrical activity of indium are obtained in a reasonable range of temperature, make indium an interesting candidate for the formation of n-p junctions by ion implantation in CMT epilayers.
Photochemical oxidation of (Hg, Cd)Te: Passivation processes and characteristics
Authors: Janousek B. K. , Carscallen R. C.
Published: July 2002

We have demonstrated the controlled growth of photochemical native oxide on (Hg, Cd)Te by the UV photodissociation of N2O. The initial growth rate is ∼7Å/min, is insensitive to temperature over the range from 40 to 100 °C, and is dependent on the surface Hg concentration. Encapsulation of the native oxide with photochemical SiO2 results in a degradation of the (Hg, Cd)Te–native oxide interface electrical properties. The presence of photochemical HgO between the native oxide and SiO2 results in superior (Hg, Cd)Te surface electronic properties. However, MOS structures comprising SiO2 on a double layer of HgO on photochemical native oxide undergo an electrical degradation at room temperature, likely owing to reactions between HgO and the native oxide or (Hg, Cd)Te substrate.
Surface characterization of Hg0.7Cd0.3Te native oxides
Authors: Wager J. F. , Rhiger D. R.
Published: July 2002

Ultraviolet photoelectron spectroscopy (UPS), x-ray photoelectron spectroscopy (XPS), and electron energy loss spectroscopy (ELS) were used to characterize the surfaces of Hg0.7Cd0.3Te native oxide films grown by air exposure, ozone treatment, oxygen plasma, and electrochemical anodization. The surfaces of the air-grown, plasma-grown, and anodically grown native oxides were found to all be relatively rich in Cd, while the ozone oxide was rich in Hg. Two ELS absorption edges were detected at ∼2.1 and ∼3.6 eV and are attributed to an oxide trap state and the fundamental band gap of the oxide, respectively. Changes in the ELS and XPS spectra following prolonged electron beam exposure resulted from a loss of Hg from the oxide and incomplete bonding of Te in the oxide. The electron beam induced changes were much more dramatic in the ozone oxide spectrum than for any of the other samples studied. XPS analysis of the interface of an air-grown native oxide which was subsequently covered with a thin layer of photochemical SiO2 demonstrated that the air-grown native oxide was partially, but not completely, reduced by chemical reaction with SiH4 during the deposition of SiO2. A generic energy band diagram of the native oxide Hg0.7Cd0.3Te interface is constructed and discussed in terms of its implications for the passivation of Hg1−xCdxTe surfaces.
MBE growth of CdTe, Hg1−xCdxTe, and multilayer structures: Achievements, problems, and prospects
Authors: Farrow R. F. C.
Published: July 2002

In this review the reasons for pursuing MBE (molecular beam epitaxial) growth of multilayer structures involving CdTe and Hg1−xCdxTe films are discussed. One major reason is that the poor structural quality of commercially available CdTe substrate wafers leads to limitations and degradation in structural quality of homoepitaxial CdTe films and Hg1−xCdxTe films grown on CdTe substrates. Double-crystal x-ray rocking curve (DCRC) analysis and x-ray topography have been used to identify intrinsic defects in CdTe which are responsible for this degradation. Progress toward MBE growth of a Hg1−xCdxTe /CdTe/InSb multilayer structure, which avoids the use of CdTe wafers and is based on high-perfection InSb substrates, is described. It is seen that the iterative use of powerful characterization techniques such as DCRC analysis and cross-section transmission electron microscopy (XTEM) is essential to the development of such structures. Major challenges to the approach of MBE to preparation of multilayer structures are considered.
Magnetic field effects in the plasma-enhanced chemical vapor deposition of boron nitride
Authors: Yuzuriha T. H. , Mlynko W. E. , Hess D. W.
Published: July 2002

The effect of a low intensity magnetic field on the deposition rate of boron nitride films in a parallel plate plasma reactor was investigated. Operating impedance bridge measurements and optical emission spectroscopy were used to characterize the rf glow discharge consisting of diborane, ammonia, and hydrogen. The deposition rate was greater with the applied magnetic field at pressures below 400 mTorr, while at pressures above this value, the deposition rate was higher without magnetic field enhancement. These effects appear to be due to the change in ion flux and energy upon the application of the magnetic field.
An x-ray standing wave interference spectrometric analysis of chemisorption of selenium on silicon(111) and (220) surfaces
Authors: Dev B. N. , Thundat T. , Gibson W. M.
Published: July 2002

Study of location and coverage of selenium atoms adsorbed from weakly acidic methanol solution on chemically cleaned silicon (111) and (220) surfaces has been made by x-ray standing wave interference spectrometry (XSWIS). In addition to measurement of the adatom location normal to the crystal surface plane, the atom positions relative to the planes inclined to the surface were measured. For the (111) and (220) crystals, inclined (220) and (111) planes were used, respectively. We conclude from these measurements that on (111) surfaces selenium atoms bridge two nearest surface silicon atoms. On (220) surfaces selenium atoms are in an interchain bridged position. The substrate surface atoms appear to be in bulklike positions for (111) surfaces. For (220) surfaces the substrate atoms may have a multilayer inward relaxation. Based on minimum energy calculations for relaxed and unrelaxed surface models, the selenium–silicon bond lengths are assumed to be similar (2.55±0.05) Å for both surfaces and is somewhat greater than the sum of the covalent radii of the respective atoms. Measurements on selenium–adsorbed cleaved silicon (111) surfaces show the same results as for the chemically cleaned counterpart within the experimental error.
Thin solid lubricant film formation by fast atom bombardment sputter deposition
Authors: Kuwano Hiroki , Nagai Kazutoshi
Published: July 2002

A fast atom bombardment sputter deposition (FAB-SD) method is proposed for the formation of MoS2 solid lubricant films and to control their stoichiometry. In the FAB-SD process, the charging of targets is not a serious problem. The beams in a McIlraith-type ion source are demonstrated to be capable of almost full neutralization. An Mo–S complex target is used for the purpose of stoichiometric control in the sputtering. Durability and friction coefficients of films deposited using this target are superior to those of films deposited using a conventional MoS2 target. The friction coefficient of the annealed film deposited using the Mo–S complex target is less than 0.05.
Ultraviolet assisted growth of II–VI compounds
Authors: Mullin J. B. , Irvine S. J. C.
Published: July 2002

Photo-MOVPE of HgTe, CdTe, and CdxHg1−xTe using UV radiation in the system Et2Te:Me2Cd:Hg:H2:He is discussed. Two growth regimes can be identified one involving a heterogeneous surface controlled reaction which leads to high quality epitaxial growth and one which gives rise initially to a homogeneous gas phase reaction and compound formation as a ‘‘dust.’’ Potential reaction mechanisms responsible for these growth processes are discussed and analyzed. The respective roles of H2 and He as radical chain promotors and inhibitors in the decomposition of the alkyls is considered in the context of the potential generation of supersaturated atmospheres of Cd and Te.
Loss of Ga in sputtered deposits made from a Pu-4 at. % Ga alloy
Authors: Rizzo H. F. , McClanahan E. D. , Margolies D. S. , Echeverria A. W.
Published: July 2002

Deposits of 5 to 500 μm thick coating were produced at rates from 0.025 to 2.5 μm/min on Al, Cu, Fe, and Kapton substrates in a triode system. Sputter parameters were as follows: Kr gas pressure (0.27–0.44 Pa), substrate temperature (21–184 °C), target voltage (300–2000 V), substrate bias (−35 to −100 V), ion current density (60 to 120 A/m2). A minimum substrate temperature of 100 °C was necessary to fully stabilize the fcc structure in the deposits. Chemical analyses and energy dispersive spectroscopy indicated that deposits, under certain conditions, contained substantially less Ga than the target. The loss of Ga was controlled by increasing the substrate temperature above 180 °C. The angular distribution of Pu and Ga sputtered under normal Kr+ ion impingement on a flat polycrystalline target was also measured. The Pu distribution was found to be ‘‘under cosine’’ for 300 eV ions and ‘‘cosine’’ for 900 eV ions. The Ga atom distribution showed a wide variation at different angles (normal to the target) depending upon conditions. At 0° the ratio of Ga to Pu was higher than in the target.
Structural studies of Cd0.95Zn0.05Te and Cd0.90Mn0.10Te under pressure
Authors: Qadri S. B. , Skelton E. F. , Webb A. W. , Kennedy J.
Published: July 2002

X-ray diffraction data obtained under hydrostatic pressures are used to determine the volume compressibilities (χ) for the B3 phases of CdTe, Cd0.95Zn0.05Te, and Cd0.90Mn0.10Te; estimates of the B3-to-B1 transition pressure (Pt) are also given. Replacement of 5% of the Cd with Zn causes approximately a 15% decrease in χ and a 12.5% increase in Pt; on the other hand, replacement of 10% with Mn causes approximately a 21% increase in χ and a 12.5% decrease in Pt, confirming the expectation that substitution of Zn tends to strengthen the tetrahedral bond in CdTe, whereas substitution of Mn tends to weaken it.
Crystal orientation of CdTe film on GaAs by metal–organic chemical vapor deposition
Authors: Lu P.-Y. , Williams L. M. , Chu S. N. G.
Published: July 2002

Annealing of GaAs substrates can affect the crystal orientation of the CdTe growth on GaAs. On annealed (100)GaAs substrates, (111)CdTe films with excellent morphology can be reproducibly grown. Whereas on unannealed (100)GaAs substrates, (100)CdTe will be obtained. Cross-sectional TEM shows that the (100)CdTe/(100)GaAs interface has a high defect density because of the large lattice mismatch between (100)CdTe and (100)GaAs. On the other hand, high quality crystal perfection was observed at the (111)CdTe/(100)GaAs interface. TEM studies also show the formation of the twin plates within the (111)CdTe epilayer. The density of the twin plates decrease progressively towards the surface of the CdTe film.
A study of the defect structures in CdTe crystals using synchrotron x-ray topography
Authors: Lu Y.-C. , Feigelson R. S. , Route R. K. , Rek Z. U.
Published: July 2002

Synchrotron x-ray topography has been used to study structural defects in CdTe crystals. Substrates from six commercial sources as well as crystals grown in our own laboratory by the vertical Bridgman method were studied. X-ray topography is known to be very sensitive to lattice strain and it reveals a broad range of defects. Extensive subgrain structure was detected in virtually all substrate material studied, in basic agreement with chemical etching, cathodoluminescence, and double crystal rocking curve (DCRC) analysis. Dislocations, dislocation tangling, and microprecipitates were revealed as well. In addition, we found extensive slip systems and large, long-range misorientations (average 200–500 arc s). These findings suggest there may be serious problems with mechanical and/or thermal stresses during the growth of CdTe. We also include results from preliminary studies on ZnCdTe substrates.
Estimation of C2 and C3 hydrocarbon production yields of graphite due to hydrogen ion bombardment
Authors: Yamada R.
Published: July 2002

A numerical method is proposed for estimating the production yields of C2 and C3 hydrocarbons, which are generated by bombarding graphite with hydrogen ions, from signal intensities of a quadrupole mass spectrometer (QMS). It is shown that the C2H2, C2H4, C2H6, C3H4, C3H6, and C3H8 production yields can be easily estimated by fitting the calculated intensities of QMS signals, by means of summing up the crackings of species, to the measured ones, whose masses range between 24 and 44. The derived formulas can uniquely determine the yields, using the measured data of the cracking coefficients and sensitivities of purified standard gases for the QMS as well as of the intensities of QMS signals.
Effects of Au film on the kinetics of platinum silicide formation
Authors: Song Jerng-Sik , Chang Chin-An
Published: July 2002

It has been known that silicon atoms can diffuse out through a gold film and accumulate on the top surface at low temperatures. To investigate the effect of this phenomenon on the silicide formation kinetics, a gold layer was deposited between a platinum layer and a silicon layer. After annealing, the progress of silicide formation was probed with Rutherford backscattering spectrometry. It was found that the PtSi formation rate is greatly enhanced by a gold film while the Pt2Si formation rate shows little changes. These are explained in terms of different dominant diffusing species during the formation of silicides.
Examination of thin films in the ZrO2–SiO2 system by transmission electron microscopy and x-ray diffraction techniques
Authors: Farabaugh E. N. , Feldman A. , Sun J. , Sun Y. N.
Published: July 2002

The microstructure of thin films of ZrO2 and ZrO2–SiO2 formed by electron-beam coevaporation have been examined by x-ray diffraction and transmission electron microscopy. Results of these examinations suggest that films composed of 100% ZrO2 grow by the formation of tapered polycrystalline columns. Near the substrate the columns are of small diameter and contain a single crystalline phase, but at increasing distances from the substrate the column diameters increase and material with two crystalline phases occurs. Small additions of SiO2 to the film composition result in a smaller column diameter at a given distance from the substrate. Films with greater than 30% SiO2 by volume, which earlier had been shown to display an amorphous x-ray diffraction pattern, have been shown to display an amorphous electron diffraction pattern as well. The surfaces of the amorphous films are nearly featureless and are significantly smoother than the surfaces of 100% ZrO2 films.
Oxidation-resistant reflective surfaces for solar dynamic power generation in near earth orbit
Authors: Gulino Daniel A. , Egger Robert A. , Banholzer William F.
Published: July 2002

Reflective surfaces for Space Station power generation systems are required to withstand the atomic oxygen-dominated environment of near earth orbit. Thin films of platinum and rhodium, which are corrosion-resistant reflective metals, have been deposited by ion beam sputter deposition onto various substrate materials. Solar reflectances were then measured as a function of time of exposure to a rf-generated air plasma. Similarly, various protective coating materials, including MgF2, SiO2, Al2O3, and Si3N4, were deposited onto silver-coated substrates and then exposed to the plasma. Analysis of the films both before and after exposure by both electron spectroscopy for chemical analyses (ESCA) and Auger spectroscopy was also performed. The results indicate that Pt and Rh do not suffer any loss in reflectance over the duration of the tests. Also, each of the coating materials survived the plasma environment. The ESCA and Auger analyses are discussed as well.
Auger electron spectroscopy studies of silicon nitride, oxide, and oxynitride thin films: Minimization of surface damage by argon and electron beams
Authors: Chao S. S. , Tyler J. E. , Tsu D. V. , Lucovsky G. , Mantini M. J.
Published: July 2002

The surfaces of silicon oxide, nitride, and oxynitride thin films are susceptible to damage by energetic ion and electron beams so that caution must be exercised in studies of the chemical bonding via Auger electron spectroscopy (AES), x-ray photoelectron spectroscopy, and electron energy-loss spectroscopy; in this paper we focus on the AES spectra. Induced damage is readily evident in the generation of a satellite structure in the AES Si LVV spectrum that results from the creation of Si–Si bonds within the surface region of the dielectric film. We have empirically determined the conditions for minimizing, in some cases effectively eliminating any detectable beam induced damage using Ar ions for sputter cleaning, and electrons for AES excitation. The threshold for electron beam damage is similar in all of the Si dielectrics, whereas the conditions for Ar ion beam are different in the oxides and nitrides.
Local stoichiometry and atomic interdiffusion during reactive metal/mercury–cadmium–telluride junction formation
Authors: Wall A. , Raisanen A. , Chang S. , Philip P. , Troullier N. , Franciosi A. , Peterman D. J.
Published: July 2002

We summarize synchrotron radiation photoemission studies of Ag, Ge, and Sm overlayers on Hg1−xCdxTe(110) surfaces. These metals exhibit widely different interface reactivity with Hg1−xCdxTe and yield a range of different interface morphologies. To assess the relative importance of the microscopic driving forces that determine the local composition at the interface and in the semiconductor near-surface region we present a systematic comparison of our data with calculated thermodynamic parameters such as the cation–metal heat of solution, the heat of alloying from Miedema’s semiempirical model, and the metal–telluride formation enthalpy.
Preparation of a magneto-optical disk using a rare earth–transition metal alloy target
Authors: Asari S. , Asaka T. , Ota Y. , Nakamura K. , Itoh A.
Published: July 2002

We have evaluated the basic performances of TbFeCo and TbCo alloy targets for the sputter deposition of magneto-optical recording media. The composition of the sputtered film shifts from the original one of the target, and the Tb concentration in the sputtered film is always reduced by about 6 at. % in both alloy targets. Sputtered films were all perpendicular magnetic film with a squareness ratio (ratio of residual magnetization to saturation magnetization) of 1, and the residual Kerr rotation angle was about 20′ min. The measurements indicate no change in the sputtering characteristics of the targets after more than 100 h of use.
Sputtering target for production of CoNiCr/Cr sputtered hard disk
Authors: Yamada T. , Higuchi Y. , Tani N. , Ishikawa M. , Ota Y. , Nakamura K. , Itoh A.
Published: July 2002

We have developed a new target composed of Co–20(at. %)Ni–10(at. %)Cr for preparing the CoNiCr hard disk by the sputtering process. The target shows a higher utilization efficiency of more than 20%, which is about twice that of a conventional Co–30(at. %)Ni–7.5(at. %)Cr target. The new target also shows stable discharge characteristics during a long sputtering process. These results are due to low magnetic permeability of target materials. We named this new target an ‘‘MT target.’’ Hard disks prepared with the Co–20Ni–10Cr MT target show the equivalent magnetic properties, recording/reproducing characteristics, and weatherproof properties as hard disks prepared with the Co–30Ni–7.5Cr target.