We have developed two new etchant systems by adding H2O2 and HBr into the conventional HCI–H3PO4 etchant for the fabrication of InP-based channeled substrate heterostructure (CSBH) lasers. These etchants do not erode photoresists and they provide high quality etched side walls. The etch factors for the new etchant systems based on HBr and H2O7 are 17% and 12% higher than that of the: conventional 5HCI–H3PO4 etchant, respectively. These high etch factors give a narrow V-groove in InP and they lead to a lower magnitude and a better control of the threshold current of CSBH lasers.

Diffusion of several impurity atoms (Cu, Al, Au, and Sb) has been studied in Zr61Ni39 and Fe82B18 amorphous alloys. A definite correlation between the diffusion coefficient (D) and the atomic size of the diffusant is seen for the metal-metal (M–M) alloy, while it is not clear for the metal-metalloid (M–Me) alloy. Based on the present data, as well as other published data in binary amorphous alloys, empirical correlations have been found between (i) the activation energy (Q) and the energy required to form a hole of the size of the diffusing atom in the host alloy, and (ii) the pre-exponential factor (D0) and Q. While the former correlation is seen only for binary M–M type of amorphous alloys, the latter correlation is more general and holds for all types of amorphous alloys. Based on the correlation between D0 and Q, it is proposed that there are two distinct mechanisms of diffusion in amorphous alloys.

The difference in density between liquid and solid is shown to be altered at the interface of a rough surface. Since it has been argued previously by the author that density difference plays a major role in interface velocity, I conclude that the rough (100) surface of silicon can have both a larger slope and less asymmetry in the freezing-melting velocity versus temperature relation than does the smooth (111) surface. This may provide partial explanation for some recent experimental results and apparent controversy.

The mechanical behavior of GaAsP alloy semiconductor was investigated by means of compressive deformation and compared with those of GaAs and GaP. The nature of collective motion of dislocations during deformation was determined by strain-rate cycling tests. The dynamic characteristics of dislocations in GaAsP were found to be similar to those in elemental and compound semiconductors such as Si, Ge, GaAs, and GaP. An alloy semiconductor has a component of the flow stress that is temperature-insensitive and is absent in compound semiconductors.

We have studied the dependence of the electrical and structural properties of ultrathin cobalt silicide films on the annealing temperature and deposited Co thickness. If less than 10 Å of Co is deposited, epitaxial type B CoSi2 forms immediately. As the deposited thickness approaches 10 Å, small amounts of Co2Si are observed. If greater than 10 Å of Co is deposited, epitaxial Co2Si forms at room temperature, which proceeds either via the reaction Co2Si ⇉ CoSi ⇉ CoSi2 or via Co2Si ⇉ CoSi2 during annealing. In these thicker films our results suggest that the formation of type A CoSi2 is correlated with the presence of Co2Si; the presence of CoSi as an intermediate phase is correlated with the occurrence of type B CoSi2. Both film thickness and reaction temperature strongly influence the electrical transport in these films such that very high resistivities are encountered when films either become very thin or are reacted at low temperatures. In the former case the size effect is responsible whereas in the latter the transport properties are dominated by extensive atomic-scale disorder.

The microstructure of icosahedral Al(Mn) in melt-quenched surface alloys has been characterized with TEM. Single-phase alloys with 20 at. % Mn show angular misorientations (up to ∼7°) across internal boundaries radiating from the nucleation centers of grains. Lowering the Mn content results in fcc Al at grain boundaries and between branches of the icosahedral grains; the presence of Al-rich liquid around growing grains apparently eliminates the misorientations seen with 20 at. % Mn. The grains have a dense distribution of dislocation-like defects, but have sufficient orientational order to exhibit well-defined diffraction contours. Weak reflections in diffraction patterns from small areas (0.7 μm) of grains exhibit deviations from exact icosahedral symmetry positions which were analyzed to evaluate a phason strain tensor and characterize misordering defects in the quasicrystalline structure. A negative matrix element (m ≍–0.05) for a tensor axis along a twofold icosahedral axis accounts for most of the distortions in these patterns and those from other melt-quenched icosahedral Al(Mn) and Al(Mn, Si) alloys; this dominant element lowers the symmetry to D2. This axis is nearly perpendicular to the growth direction, which suggests that the misordering is due to rapid growth during the quench; however, the D2 distortion may also result from an elastic instability predicted for icosahedral phases. Distortions in Al(Cr, Ru) can be fit with a similar tensor but with m>0. Thus the phason character identified here may apply to other aluminum-transition metal icosahedral phases as well.

Silicon dioxide for use as a diffusion barrier between soda lime glass and fluorine-doped tin oxide is deposited uniformly by atmospheric chemical vapor deposition from silane. oxygen, and nitrogen using a simple single-slot injector head. With a sufficiently thick silicon dioxide layer, the conductivity of the tin oxide is greatly improved by reducing the diffusion of sodium into the tin oxide as it is deposited between about 500 to 600 °C. Based upon the conductivity of thin lightly doped tin oxide films, it appears that at least 250 nm of silicon dioxide deposited on soda lime glass are required to essentially eliminate the diffusion of sodium into the tin oxide. However, only about 10 nm of silicon dioxide are required to obtain almost the full benefit of 250 nm thick films for moderately doped tin oxide films approximately 500 nm thick, The silicon dioxide deposition process is examined between 350 and 580 °C. The activation energy for the deposition is about 27 kJ/mole. Peak and average film deposition rates greater than 50 nm/sec and 10 nm/sec, respectively, may be obtained. The dependence of the film growth rate on the silane, oxygen, and propylene (an inhibitor) concentration is examined. The deposition rate is found to be limited by the rate of gas-phase reactions. Deposition conditions which yield high silane utilization and good film uniformity are discussed. The origin of undesirable by-product powder is studied. At low silane concentration, powder is mainly formed as the gases cool due to condensation from intermediate species.

Since 1976 NiAl–Ni2AlTi alloys have been known to possess elevated temperature mechanical properties approaching those of Ni-base superalloys; however, due to their apparent brittleness, little additional work has been undertaken to exploit this strength. In an attempt to instill ductility in these materials, small grain size single (Ni–45Al–5Ti) and two (Ni–40Al–10Ti) phase intermetallics were fabricated by XDTM technology and tested (XDTM is a trademark of Martin Marietta Corporation). As these compositions have the potential for being the matrix material in high temperature composites, Ni–40Al–10Ti and Ni–45Al–5Ti with 20 vol.% TiB2 in the form of ∼1 μm diameter particles were also investigated. The as-fabricated materials were fully dense and polycrystalline. The grain sizes measured ∼8 μm for Ti-poor and about 15 μm for the Ti-rich unreinforced materials but could not be determined for either TiB2 containing composite. Elevated temperature compression testing was conducted to about 8% deformation between 1200 and 1400 K with strain rates varying from ∼10−4 to ∼10−7 s−1. The majority of the tests exhibited diffuse yielding over approximately 1% strain followed by negative strain hardening. However, a few experiments resulted in steady state behavior where deformation continued under a constant stress. The flow strengths on yielding of both forms of Ni–40Al–10Ti were higher than those for the Ni–45Al–5Ti versions. For each matrix composition the addition of 20 vol.% TiB2 decreased the strength at the higher strain rates in comparison to the TiB2-free forms. During slow deformation conditions, however, the particles do provide reinforcement. Light optical microscopy of tested specimens revealed that these materials are generally quite brittle as numerous longitudinal and transverse cracks were found irrespective of the type of stress-strain behavior.

The nature of the disordered state of hydrogenated amorphous silicon is examined for the first time by measurement of anelastic relaxation behavior. It is demonstrated that local structural units and their modifications control the relaxations in these films under different conditions of deposition, aging, and light exposure. Specifically, the light-induced state in this material is shown to be characterized by four distinct relaxations.

The deposition of hydrogenated and fluorinated silicon-germanium alloys (Si1−xGex:H.F) by glow discharge decomposition of silicon tetrafluoride (SiF4) and germane (GeH4) mixtures has been studied. Optical emission spectroscopy (OES), for the analysis of the emitting species in plasma phase, and mass spectroscopy (MS) for the analysis of the stable species, are used for the plasma diagnostics. In addition, in situ measurements of the deposition rate by laser interferometry are performed. A series of alloys with germanium content ranging from 0 to 55% has been prepared by varying the gas compositional ratio. Data on the optical gap (Ec), sub-gap absorption, and photo-to-dark conductivity ratio (δσ/σ) are used to evaluate the quality of the materials. An alloy a–Si0.75Ge0.25: H, F having Ec δ 1.5 eV and δσ/σ = 104 has been prepared by adding 1% of GeH4 to SiF4 in the feed.

Tungsten films were deposited on Si substrates by the H2 or Si reduction of WF6 under various experimental conditions. The composition and structure of as-deposited samples as well as the interfacial reactions and interdiffusion of elements in annealed samples were characterized by nuclear reaction analyses, sheet resistance measurements, x-ray diffraction technique, and Rutherford backscattering spectroscopy. The amount of oxygen at W–Si interfaces was found to be dependent on the cleaning treatment of the Si surface used before WF6–Si interaction. The interfacial oxygen concentration was less than 1 ⊠ 1014 at./cm2 (detection limit of the nuclear reaction analysis) and (2–7) ⊠ 1016 at./cm2 using an HF cleaning and the RCA treatment, respectively. For W/Si samples, the formation temperature of WSi2 was dependent on the dopant level in the Si substrates and the oxygen concentration at W–Si interfaces. The silicidation reaction occurred at 625 °C in “oxygen free” W/Si structures while for structures containing interfacial oxygen atoms, this reaction occurred above 800 °C. In Al/W/Si structures, the intermetallic compound, WAl12, was formed by annealing at 450 °C for 90 min. Furthermore, the formation of WSi2 was observed in structures annealed at a temperature in the range of 550 °C–600 °C regardless of the oxygen concentration at the W–Si interface. A model to explain the effect of interfacial oxygen atoms on the silicidation reaction and the influence of the Al overlayer on the thermal stability of Al/W/Si structures is proposed and discussed in this paper.

Isothermal annealing studies of hillocks formed on Al–15 wt.% Cu films, vapor deposited at 25 °C on oxidized silicon wafers, were carried out in situ in a scanning electron microscope. The original hillocks formed as a result of substrate-induced thermal expansion strains which caused material to diffuse out of the film to form the hillocks when the films were heated to the isothermal annealing temperatures. During isothermal annealing the hillock density decreased and the average size of the hillocks increased. Measurements of these quantities as a function of time were made at a series of temperatures ranging from 200 to 300 °C. The activation energies for these two cases were found to be 0.29 and 0.28 eV, respectively. X-ray energy spectroscopy analysis of the films showed that the hillocks were richer in copper than the matrix. Transmission electron microscopy showed that the average hillock and grain sizes in the variously annealed films were linearly related and of the same order of magnitude. The results were also analyzed using Chakraverty's models for surface and interfacial diffusion. It was concluded that the evidence clearly shows that the observed processes could be well characterized by a typical Ostwald ripening model.

Ni3Ge-containing nickel-germanium alloys with 12.10 to 16.8 at. % Ge were investigated. Nickel-saturated Ni3Ge had a lattice parameter of 3.57015 × 10−10 m and contained 22.5 at. % Ge over the temperature range 650 to 1100 °C. However, the precipitates in the initial stages contained 24.44 at. % Ge and were almost cubic in shape. The strengthening effects of Ni3Ge were appreciable. In alloys containing higher percentages of germanium, precipitates were observed in as-quenched specimens. The hardness after quenching was high and did not change appreciably with time. Hardness was reduced in the presence of aluminum.

A radio-frequency glow discharge is used for the synthesis of submicron, amorphous, silicon nitride precursor powders from silanc and ammonia. Powders are produced with a range of Si/N ratios, including stoichiometric, Si-rich, and N-rich, and contain substantial amounts of hydrogen. The powders appear to be similar to silicon diimide and are easily converted to oxide by water vapor. The powders lose weight and crystallize to a mixture of α and β–Si3N4 after prolonged heating at 1600 °C. Studies of spectrally and spatially resolved optical emission from the plasma are reported.

The solid state oxidation kinetics of Pb–Sn single-phase (2.5 at. % Sn) and eutectic alloys were studied with Auger Electron Spectroscopy combined with sputter depth profiling. The single-phase samples were oxidized in air in the temperature range 22 °C to 250 °C, while the eutectic samples were oxidized from 22 °C to 175 °C. Both alloys oxidize logarithmically between 22 °C and 90 °C and parabolically at temperatures greater than 120 °C. The activation energies for the parabolic oxidation of the single-phase and eutectic alloys are 69.5 and 67.1 ± 8 kJ/mole, respectively.

The depth distribution, chemical bonding, and electrical behavior of N quenched into Si by pulsed laser-induced melting have been investigated by secondary ion mass spectroscopy, infrared (ir) absorption, transmission electron microscopy (TEM), and electrical conductivity. The results demonstrate that laser-induced melting of N-implanted layers provides access to a useful range of otherwise inaccessible conditions for the study of N in Si. Nitrogen concentrations four orders of magnitude above equilibrium solid solubility are retained in implanted layers with limited diffusion during laser-induced melt and rapid solidification. The N is incorporated predominantly as N–N pairs bonded to Si, similar to the bonding configuration for equilibrium concentrations introduced during ingot growth. Formation of SixNy clusters is suggested to explain ir absorption bands, features in TEM, and shallow donor activity observed after furnace annealing near 750 °C. These cluster effects are removed by a melt/solidification sequence which restores the N to N–N pair centers together with a small fraction of off-center substitutional N.

He ion channeling and backscattering experiments have been performed on MBE-grown Si1−xGex/Si strained layers to investigate the tetragonal lattice distortion and the Ge diffusion after thermal annealing. The tetragonal strain of the epitaxial layers has been determined by measuring the angular deviations of inclined 〈110〉 orientations of the adjacent layers. The measured angular shifts indicate a nearly pseudomorphic layer growth of the virgin sample. The angular yield scans of the Ge signal show a pronounced asymmetry, caused by beam steering in the tetragonally distorted lattices of the different layers. Thermal annealing above 800 °C results in strain relaxation and in layer mixing due to the diffusion of germanium. The observed Ge diffusion is strongly enhanced by the elastic strain in the layered structure.

Silicon oxynitride films have been grown by a photochemical vapor deposition process utilizing VUV light of a deuterium lamp from a gas mixture of Si2H6, NH3, and NO2 at the substrate temperature of about 330 °C. The deposition rate of the film varied with NO2 flow rate and also with the excitation light spectrum which was varied by a low-pass filter of a synthetic or fused silica plate. The composition of the films was sensitive to the NO2 flow rate which was smaller than that of NH3 by a factor of 103.

A study has been made of fatigue and fracture in zinc bicrystals. It is shown that cleavage cracks are nucleated, both under tension and as a result of fatigue, in regions of multiple slip adjacent to grain boundaries at stresses below those for crack nucleation in single crystals. The nature of crack penetration through the boundary is observed as a function of orientation across the boundary. Low angle tilt boundaries are barriers to crack propagation, increasing effective surface energies for crack propagation by 1.6–2 times. Twist boundaries, due to the tearing that accompanies penetration, can result in a twelvefold increase in effective surface energy. Nonbasal cleavage is associated with a twinning mechanism, and an even higher surface energy is required to propagate a crack into a crystal oriented for this type of cleavage. The results carry the implication that, in the absence of surface defects, fatigue, failure in polycrystalline zinc is nucleated at the first internal grain boundary and not at the surface.

Thin carbon films grown from a low pressure methane-hydrogen gas mixture by microwave plasma enhanced CVD have been examined by Auger electron spectroscopy, secondary ion mass spectrometry, electron and x-ray diffraction, electron energy loss spectroscopy, and electron microscopy. They were determined to be similar to natural diamond in terms of composition, structure, and bonding. The surface morphology of the diamond films was a function of position on the sample surface and the methane concentration in the feedgas. Well-faceted diamond crystals were observed near the center of the sample whereas a less faceted, cauliflower texture was observed near the edge of the sample, presumably due to variations in temperature across the surface of the sample. Regarding methane concentration effects, threefold {111} faceted diamond crystals were predominant on a film grown at 0.3% CH4 in H2 while fourfold {100} facets were observed on films grown in 1.0% and 2.0% CH4 in H2. Transmission electron microscopy of the diamond films has shown that the majority of diamond crystals have a very high defect density comprised of {111} twins, {111} stacking faults, and dislocations. In addition, cross-sectional TEM has revealed a 50 Å epitaxial layer of β3–SiC at the diamond-silicon interface of a film grown with 0.3% CH4 in H2 while no such layer was observed on a diamond film grown in 2.0% CH4 in H2.