During the long-time diffusion of transmutation doped silicon a variety of large CuSi precipitates is introduced into the material. The precipitates have been found to be metastable and transform during subsequent heat treatments. One of the most surprising results of such a transformation is the generation of large, extended monolayer precipitates, which are shown to represent the stable configuration of the precipitate system.

The structure of a low angle tilt boundary with a [110] misorientation axis and a (111) initial boundary plane in a bicrystal prepared by a hot-pressing technique has been studied. The boundary consists of a periodic array of dislocations as expected but contains a new feature, namely microtwins which lie parallel to the boundary plane. High resolution transmission electronmicroscopy has been used to characterize the boundary structure and to determine the Burgers vector of the dislocations present. The relationship between the structure of the twin-free regions and the twinned regions is discussed.

The structure and dissociation of grain boundaries in Ge bicrystals, grown by the Czochralski method, have been analyzed by visible light and transmission electron microscopy. The seed crystals were oriented to yield either a symmetric or an asymmetric grain boundary plane with a 15° rotation about a common <110> direction. The asymmetric boundary, with a {111} boundary plane, dissociated along most of its length into a first order twin boundary (Σ 3) and a symmetric 55° grain boundary (Σ 41c). The symmetric 15° boundary is composed of an array of Lomer dislocations. Contrary to theoretical predictions, this boundary is stable.

Rapid grain growth has been induced in semiconductor films at relatively low temperatures by allowing contact with metals or metal/semiconductor eutectic melts. Mechanisms by which such enhanced grain growth can occur are discussed, and Diffusion Induced Boundary Migration has been shown to be a plausible explanation for the experimental observations from the Sn/Ge, Al/Ge and Au/Ge systems. Interface migration driven by the decrease in free energy during phase transformations however provides a better explanation of the large Si grains produced on heating the Au/Si samples.

A systematic TEM study of the morphology of the polysilicon - SiO2 interface has been performed. LPCVD films were deposited on thermally oxidized silicon substrates, doped via diffusion or ion implantation, and oxidized in pyrogenic steam. Several aspects of the interface have been investigated as a function of dopant species, dopant concentration, oxidation time and oxidation temperature.

We report on the first non-destructive measurement of the chemical and physical characteristics of the interface between bulk SiO2 and thick aluminum films. Both X-Ray Photoelectron Spictroscopy (XPS) and electrical measurements of unannealed, resistively evaporated Al films on thermal SiO2 indicate an atomically abrupt interface. Post metallization annealing (PMA) at 450°C induces reduction of the SiO2 by the aluminum, resulting in the layer ordering SiO2/Al2O3/Si/Al. The XPS measurement is performed from the SiO2 side after the removal of the Si substrate after etching with XeF2 gas and thinning of the SiO2 layer with HF:ETOH. This represents a powerful new approach to the study of metal-insulator and other interfaces.

The chemical reaction at the Ni/InP (110) and Ni/GaAs (110) interfaces produced by sequential deposition of thin Ni overlayers onto cleaved semiconductor surfaces has been investigated with valence band (VB) and core level photoemission and Auger spectroscopies using synchrotron radiation as the excitation source. By monitoring changes in the VB, P 2p, In 4d, Ga 3d, As 3d, and Ni 3p photoemission spectra and the lineshape of the P LVV Auger transition during the initial stage of Schottky barrier formation, we found that for both interfaces the first few Å of Ni react strongly with the surface resulting in the formation of a nickel phosphide or nickel arsenide. At the same time, segregation of metallic In or Ga is observed.

Room-temperature interfacial reactions at the Ag/InP (110) interface have been studied using soft x-ray photoemission spectroscopy of the In 4d and P 2p core levels. For low Ag coverages (less than 1 monolayer (ML)) no measurable change in core level shapes is observed, and the shift in core level position is due solely to band bending. At high Ag coverages (up to 72 ML) we observe dissociated In metal, P atoms near the surface, and Ag clustering. Fermi level movement is deduced from these spectra using a deconvolution technique, and pinning positions of 0.40 ± 0.05 eV below the conduction-band minimum for n-type and 0.5 ± 0.l eV above the valence-band maximum for p-type are found. These positions are in close agreement with calculations of native defect levels.

The cu-GaAS(ll0) interface formation nas been Studied with soft x-ray Photoemssion spectroscopy (SXPS) for Cu overlayers deposited at room temperature. Tne evolution of the tia 3a and As 3a spectra snow that strong interactions occur between Cu and the substrate during the formation of the Cu-GaAs interface. A cnemically smifted Ga 3d peak at 0.8 eV lower binging energy and strong moaification of the As 3d lineshape has been found. Detailed analysis nas shown that the dissociated As is preterentially segregated on the metal layer, but Ga remains mainly in the interfacial reion for trick Cu coverages (30 - 60 Å). Using a deconvolution tecnniqie we nave found that the final stabilized position of the interface Fermi level lies at about 0.9 eV below the conduction band minimum.

High-resolution, soft x-ray photoemission investigations of fluorine chemisorption on silicon (111) surfaces are reported. The distribution of fluorosilyl moieties was found to be strongly dependent upon the surface structure. The 2×1 reconstruction exhibited only monofluoro species, while the 7×7 showed a distribution of mono-, di-, and trifluorosilyl groups.

A novel technique is described for directly measuring the Seebeck coefficient across the solid-liquid interface of gallium as a function of temperature and crystallographic orientation. The results are compared with those calculated from the absolute thermoelectric power of solid and liquid gallium. The temperature ranges for the measurements were 248 to 302K for solid gallium, and 278 to 353K for the liquid; the liquid was supercooled up to 25K. The effect of crystal orientation on the thermoelectric power of gallium single crystals grown along the a, b, and c axes was investigated. The anisotropy of the thermoelectric power is discussed based on the electronic properties of gallium.

Selected interface phenomena associated with metal semiconductor contacts are discussed in relation to recent experimental and theoretical work on the electronic properties, interface formation and structure, and device characteristics of nickel-silicon interfaces. Evidence is presented which suggests that a well-defined interfacial phase is present at all nickel silicide-silicon boundaries formed by deposition of nickel atoms onto silicon surfaces. The existence of this phase is shown to account for several important interface properties of the nickel silicide system including selective growth, the rotational twin structure of epitaxial films and the observed invariance of the nickel silicide-silicon Schottky barrier height as the silicide contact stoichiometry is varied.

The early stages of silicide formation on metal and silicon surfaces have been studied in the atom-probe FIM. Precursors to silicide formation are low temperature diffusion of single Si atoms, their interactions, and adsorption layer superstructure formation. These phenomena have been studied quantitatively. At high temperatures, silicide films can be formed. Four distinctive stages of silicide formation on tungsten surfaces have been observed from the atomically resolved FIM images. Formation of silicide layers on platinum, nickel, and silicon surfaces have also been studied. From both the atom-probe compositional depth profiling and the FIM observation one can conclude that the interface formed at low temperature is sharp. At high temperature, Si atoms can diffuse deep into a Pt matrix and Ni atoms into a Si matrix. Conclusions drawn from these atom-probe studies are summarized, and future directions suggested.

Structural effects of sub-monolayer epitaxial films are described by the pair correlation function of surface atoms. We have developed a new scheme to evaluate this atomic pair correlation function analytically and exactly for the combined overlayer and substrate system during the first stages of epitaxy. We employ this correlation function to calculate electron diffraction profiles from model surfaces and compare these calculations to recent LEED measurements of Si/Si(111) and W/W(110) epitaxy.

This review considers the growth and characterization of epitaxial alkaline earth fluoride compounds on semiconductors. The field has developed quite rapidly in recent years, from the original demonstration of epitaxial growth in these systems to the investigation of the structure and properties of the layers. Two recent developments are reviewed in detail: the epitaxial relations which have been discovered between fluoride films and semiconductor substrates and the variety of interface structures which these systems display. These findings are beginning to lead to an understanding of the epitaxial growth process in these systems and how it relates to that in other more thoroughly studied systems.

Growth conditions and structural properties of vacuumevaporated fluoride films on Si(lll) and (100) substrates are reviewed. It has been found that single crystal CaF2 films are grown on both (111) and (100) substrates at temperatures of 600–800°C and 500–600°C, respectively. It has also been found that SrF2 and BaF2 films of good crystalline quality are grown on Si(lll) at temperatures around 600°C, but that the films grown on Si(100) contain (111) oriented crystallites. In epitaxial growth of a Si/CaF2/Si structure, a novel growth method is presented, in which a thin Si layer is deposited at room temperature prior to deposition of a thick Si film at elevated temperature. Investigations on growth of mixed fluoride films, radiation damage in CaF2 films, and epitaxial relations in the fluoride/Si heterostructures are also presented.

Crystals with the cubic fluorite structure and small lattice mismatches can be grown epitaxially on cubic semiconductors. In this manner thin-film single-crystal metals (NiSi2 and CoSi2) and insulators (e.g. CaF2 , BaF2) have been grown on silicon, germanium and indium phosphide. With close attention to deposition and growth parameters, afforded either by atomically clean conditions or transient thermal processing, great control can be exerted over the crystallography and interfaces of these systems. This has resulted in films with unique physical properties and exceptionally high quality and reproducibility. We review the microstructure of these films in this paper and identify two important new growth regimes for these materials: very thin films (less than 30Å) and transient thermal processing with ultra-fast laser pulses. Examination of the structure of these films, using high-resolution electron microscopy, provides insight into these nucleation and growth processes. One intriguing observation is that all these fluorite structure thin films have an overwhelming tendency to grow with a 180° rotated orientation (B) on (111) semiconductors.

Epitaxial GaAs layers have been grown on Ge-coated Si substrates. Deposition of epitaxial Ge was performed by electron beam evaporation onto a <100> Si substrate. GaAs was then deposited by organometallic vapor-phase epitaxy. Films grown over large areas (∼1 cm2) and by selective epitaxy in stripe patterns (∼50 μm wide) have been evaluated by a number of techniques to determine structural and electrical properties. In addition, we report what we believe to be the first LEDs fabricated in GaAs/Ge/Si heterostructures.

A new crystallographic theory of interfacial structure is applied to the case of interfaces between NiSi2, CoSi2 and Pd2Si grown epitaxially on Si. In the case of NiSi2 layers grown in parallel orientation it is shown that dislocations with Burgers vectors ¼<111> separate energetically degenerate interfacial domains on {hko} interfaces. Observations, of such defects on (001) interfaces, using transmission electron microscopy, are presented and show detailed agreement with the theory.

The crystalline perfection of epitaxial PtSi thin films and the microstructure of the PtSi/Si interface have been examined using transmission electron microscopy (TEM), including lattice image techniques. Epitaxial PtSi layers grow with domains which have three different positions on a (111) Si substrate. Inside a domain the crystalline perfection is high, and at the domain boundary no intermediate region has been observed. The undulation of the PtSi/Si interface is larger than that of other epitaxial silicide/Si interfaces. Despite the large undulation, a cross-sectional lattice image shows the epitaxial layer extends to the interface. The interface is abrupt in the epitaxial PtSi/Si system.