The stability of ordered semiconductor alloys has been studied, using total energy pseudopotential calculations. The ordered alloys are found to be stabilized with respect to disordered alloys via reduction of the internal strain and by chemical interactions. The Si–C and Si–Ge systems are used as illustrations, finding that ordered Six Ge1−x should be a metastable alloy, in agreement with experimental observations.

A model for the kinetic growth of oxygen-related thermal donors in Czochralski silicon at about 450°C is presented. The model, which is based on the work of Suezawa and Sumino, derives forward reaction rates for the electrically active species by comparing analytic expressions for the early-time annealing kinetics with the infrared electronic absorption data. The analytic expressions, which are independent of the chemical structure of each species, result from three assumptions: (1) the donor defects beyond the first donor species (TD-1) are chemically stable at the donor formation temperature, (2) the reactions for the TD-1 and those electrically inactive clusters smaller than TD-1 are in equilibrium, and (3) the oxygen interstitial concentration remains constant for short annealing times. The parametrized values of the rate constants indicate that the forward rates of reaction vary widely between species, with a sharp peak at the reaction which takes the first electrically active species to the second. If the rate constants are taken to be of the form K = 4πRD, where R is the capture radius for the given forward reaction and D represents the effective diffusion coefficient, then the variation between reaction constants may be associated with differences in capture radii between species, with the diffusion coefficient assumed to be the value determined by Stavola et al. [Appl. Phys. Lett. 42, 73 (1983)] for “as-provided” material, which has an activation energy of 1.95 eV. The model is successfully applied to the two available sets of infrared absorption data (the Oeder-Wagner and Suezawa-Sumino data) when differences in the annealing temperatures and initial oxygen concentrations are taken into account. The best-fit parameters found by fitting the analytic expressions are then applied to a set of chemical reaction equations which characterize the formation rates of specific oxygen aggregates. The use of such a set of coupled, nonlinear differential equations, which must be solved numerically, introduces free parameters for the oxygen clusters smaller than the first thermal donor. It is shown that the assignments of a thermal donor core containing two, three, four, or five oxygen atoms are all capable of fitting the experimental data. This result indicates that a best fit to the kinetic data cannot be used to argue for a specific thermal donor core. Finally, the authors discuss possible mechanisms for the enhanced values of the capture radii.

Thin AuGa2 films were grown by codeposition from separate Au and Ga evaporation sources on clean GaAs(001) substrates in ultrahigh vacuum, and were studied by Auger electron spectroscopy, electron energy-loss spectroscopy, low-energy electron diffraction, scanning electron microscopy, and x-ray diffractometry. The morphology and crystallinity of the AuGa2 were highly dependent upon the film deposition and annealing history. Films grown on room-temperature substrates were continuous, specular, and polycrystalline, but the dominant orientation was with the (001) planes of the crystallites parallel to the substrate surface. Annealing to temperatures between 300°and 480°C caused the film to break up and coalesce into rectangular crystallites, which were all oriented with (001) parallel to the surface. An anneal to 500°C, which is above the AuGa2 melting point, resulted in the formation of irregular polycrystalline islands of AuGa2 on the GaAs(001) substrate. No interface roughening or chemical reactions between the film and substrate or interface were observed for even the highest-temperature anneals.

ZnSe layers have been grown on (100)-oriented Ge substrates by molecular beam epitaxy for the first time. The optimum in-situ Ge substrate preparation technique was found to consist of argon-ion sputtering at room temperature followed by annealing at ∼400°C. This cleaning technique provided Ge surfaces which exhibited (2X2) surface reconstruction as observed by reflection high-energy electron diffraction and which had O and C contamination levels below the detection limit of the Auger electron spectroscopy system. ZnSe layers grown on argon-ion sputtered and annealed (100)Ge substrates using a variety of substrate temperatures and Zn to Se beam pressure ratios were characterized by 4.2 K photoluminescence (PL) measurements. The highest quality layers as judged by PL analysis were grown in the substrate temperature range, 310–350°C, with a Zn to Se beam pressure ratio around unity. ZnSe layers grown under these conditions exhibited a dominant donor-bound exciton peak at 2.7976 eV having a minimum linewidth of ∼1.1 meV.

High electron mobility thin InSb films were prepared on mica substrates by conventional vacuum evaporation of InSb to obtain highly sensitive magnetoresistance (MR) elements. The 0.15–0.5 μm thick InSb films were prepared in the present work. An optimum evaporation programming pattern was obtained. The crystal properties of these InSb films of 0.2–0.3 μm were investigated using a transmission electron microscope. It was shown that films thinner than 0.2 μm were semitransparent and consisted of [111] oriented single-crystal films. The 0.15–0.3 μm thick InSb films are therefore most useful for low-cost MR elements because of their high element resistance, small temperature coefficient of electron mobility, and high sensitivity.

A new double-layered stacked LSI fabrication process has been developed for the purpose of realizing short fabrication turn-around time, high fabrication yield, and high integration density. This process, which is named “Elemental Level Vertical Integrated Circuit (ELVIC)” technology, puts two conventionally made LSI chips face to face and bonds them by thermal compression. The process includes, in addition to the conventional LSI fabrication process, vertical interconnection (VI) formation in the upper and lower LSI layers, planarization of both upper and lower layer surfaces, and inter-level connections using pressure and heat. In the experimental version, about 52 000 10X10μm2 Au-on-Ti VIs were connected on a 5×5 mm2 chip. Each pair of mated VIs was measured and had a tensile strength of 4 mg · force. A two-layer, 31-stage inter-CMOS/bulk ring oscillator consisting of p-channel MOSFETs on the upper layer and n-channel MOSFETs on the lower layer has been built. Propagation delay time per stage is 1.86 ns at the supply voltage of 5 V. ELVIC technology can produce a variety of benefits such as high production yield, doubling integration density, latchup-free CMOS LSIs, radiation-damage-free LSIs, multifunction, and complete mixing of bipolar, CMOS, and GaAs technologies.

Electron-beam-induced changes in the structure of partially amorphous CdS surfaces have been observed directly by atomic-resolution electron microscopy. A sequence of atomic rearrangements leading to nucleation and growth of cubic CdS and hexagonal Cd has been documented. Inelastic electron collisions lead to crystallization of overlying amorphous CdS material whereas electron-stimulated desorption of S from the underlying CdS crystal results in precipitation of Cd crystallites at the crystalline/amorphous interface. From 100 to 500 keV the events are almost energy-independent.

Radiation effects in a natural, metamict zirconolite from Sri Lanka that has received an alpha-decay dose greater than 1026 alpha decays/m3 have been studied using x-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), electron paramagnetic resonance spectroscopy (EPR), extended x-ray absorption fine structure spectroscopy (EXAFS), and x-ray absorption near edge structure spectroscopy (XANES). The same techniques were applied to the sample annealed between 1000°and 1100°C. The heat of recrystallization was measured by differential thermal analysis (DTA) with values of 40 to 50J/g. In contrast to previous work [A. E. Ringwood, Am. Scientist 70, 201 (1982); Mineralog. Mag. 49, 159 (1985)], these results demonstrate that there are fundamental differences at the atomic level between the annealed, crystalline, and the natural, fully damaged zirconolite. We suggest that the most likely structure for the fully damaged state is that of a random, three-dimensional network with no atomic periodicity extending beyond the first coordination sphere. Even within the first coordination sphere, there is a reduction in coordination number and an associated decrease in bond length for principal cations (Ca and Ti). Despite this structural modification and the great age of the specimen (∼550 million years), the natural zirconolite shows only minor signs of geochemical alteration. The metamict structure is readily annealed, initially to a disordered, flourite-type structure, and finally, at higher temperatures, to a highly twinned, monoclinic zirconolite structure.

Implanted, polymeric films have been produced by accelerator-ion-beam irradiation of metallic substrates immersed in hydrocarbon gases. Typical substrates include silver, aluminum, and steel; hydrocarbon gases include 1,3 butadiene and ethylene at 6.6 Pa pressure; ion beams employed include singly ionized H, He, and Ar at 30 keV. Experimental procedures and corrosion-resistance properties of the films are reviewed (each discussed elsewhere). A theory of the film-formation process is presented. It is concluded that the films form as the result of a two-stage process: glow-discharge adhesion and polymerization followed by radiation-induced implantation resulting from collisional recoil and substrate sputtering.

The pH of the solution that zirconia is precipitated from defines the crystal phase formed after calcination of the material at 400°to 600°C. A metastable tetragonal form is obtained for either low (less than about 5) or high (greater than about 13) pH. The tetragonal phase formed at high pH is much more stable at the calcination temperature than the material obtained at a low pH is. For a material obtained by precipitation at a low pH, monoclinic crystallites, determined by x-ray line broadening, were obtained that were smaller than the tetragonal crystals that produced them. A crystallite size effect, based on x-ray line broadening, is not responsible for the formation or stabilization of the tetragonal phase.

The effect of lateral cracks on strength controlling contact flaws in brittle materials is examined. Inert strength studies using controlled indentation flaws on a range of ceramic, glass, and single crystal materials reveal significant increases in strength at large contact loads, above the predicted load dependence extrapolated from strength measurements at low indentation loads. The increases are explained by the growth of lateral cracks decohesing the plastic deformation zone associated with the contact from the elastically restraining matrix, thereby reducing the residual stress field driving the strength controlling radial cracks. A strength formulation is developed from indentation fracture mechanics which permits inert strengths to be described over the full range of contact loads. The formulation takes account of the decreased constraint of the plastic deformation zone by lateral crack growth as well as post-contact nonequilibrium growth of the radial cracks. Simple extensions permit the strengths of specimens controlled by impact flaws to be described, as well as those failing under nonequilibrium (fatigue) conditions. The implications for materials evaluation using indentation techniques are discussed and the dangers of unqualified use of strength measurements at large indentation loads pointed out. The work reinforces the conclusion that a full understanding of the residual stress field at dominant contact flaws is necessary to describe the strength of brittle materials.

Depth-sensing indentation instruments provide a means for studying the elastic and plastic properties of thin films. A method for obtaining hardness and Young's modulus from the data obtained from these types of instruments is described. Elastic displacements are determined from the data obtained during unloading of the indentation. Young's modulus can be calculated from these measurements. In addition, the elastic contribution to the total displacement can be removed in order to calculate hardness. Determination of the exact shape of the indenter at the tip is critical to the measurement of both hardness and elastic modulus for indentation depths less than a micron. Hardness is shown to depend on strain rate, especially when the hardness values are calculated from the data along the loading curves.