The dominant pathway for thin film interdiffusion and interface reactions is often via grain boundaries. We have made EXAFS measurements of grain boundary constituents for two systems: interdiffusion in Ag-Au bilay-ers and solid state reaction of Nb with a copper-tin bronze to form Nb3Sn. The Ag-Au results indicate that Au in saturated Ag grain boundaries has an environment similar to a dilute Au in Ag solution with reduced coordination. For the Nb-bronze reaction, the results for the Cu environment indicate distinct changes in the grain boundary environment when small amounts of Ti, Hf, Zr, and Ta are added to the starting Nb. Both results demonstrate the ability of EXAFS to probe grain boundary environments, and to provide important structural information in understanding solid state diffusion and interdiffusion in thin film systems.

Fe/Cu multilayered films prepared by means of Facing Targets Sputtering have distinct multilayered structure at layer thicknesses above 7Å. The saturation magnetization of Fe in the multilayered film takes almost the bulk thicknesses Fe value above this thickness. However, multilayerd structures did not clearly form at layer thicknesses below 7Å and the saturation magnetization decreased to about half of the bulk value. Considerable variation of confirmed layer thickness, saturation magnetization and coercivity in the multilayerd films were obtained when the total thickness was below 1000Å.

Silicon core and valence levels were studied in hydrogenated amorphous silicon (a-Si:H) as a function of hydrogen concentration. The techniques used to establish the core levels were X-ray Photoelectron Spectroscopy and core-level Electron Energy Loss Spectroscopy. Changes in the local densities of states of the silicon 3s and 3p levels were examined with Auger Electron Spectroscopy. The a-Si:H samples were grown by RF sputtering. Their hydrogen concentrations varied from zero to nearly fifteen percent.

Multilayer films consisting of alternating Fe and Cu thin films have been made by a twin-gun sputtering device with a rotating substrate platform. Both proportional modulated films and films with a fixed Cu layer have been fabricated, where the Fe layer has been varied between 10 and 150 Å. These films have been studied by x-ray diffraction, Mö;ssbauer spectroscopy and SQUID magnetometry. Thin Fe layers with thicknesses less than 25 Å, exist only as fee α-Fe. Thicker Fe layers contain both bec and fee Fe. The interface between Fe and Cu appears very sharp with no evidence of Fe-Cu alloys. The α-Fe state orders magnetically below 100 K with a small magnetic moment.

Group IV-IV heterostructures with Sn as one constituent have potentially important applications. We report on an investigation of the initial stages of interface formation for deposition of Sn on Si(100)2×1 and Si(111)7×7. We find that simple growth occurs up to a critical coverage θc. (α1.25×1015 cm-2), independent of temperature. Beyond θc. growth continues to be laminar for deposition at 150 K only, while island formation is observed at temperatures at and above room temperature. The Si(111)7×7 reconstruction seems unperturbed by Sn deposition at room temperature while the Si(100)2×1 begins to order. However, the reordering, a necessary condition for perfect growth, is incomplete.

The use of hexachlorodisilane (Si2Cl6) as an alternative to silane for growth of polycrystalline silicon films has been investigated. Films were grown at atmospheric pressure in both hydrogen and nitrogen carrier gases over a temperature range of 450–900°C. Deposition rate data indicate the existence of two growth regimes at high and low temperatures and in the presence or absence of hydrogen. The change from amorphous to polycrystalline growth takes place at 600–650°C. At 600°C deposited films are amorphous but crystallize during the growth process. The chlorine content of high-temperature films was found to be less than 0.01 at.%.

Silicon oxynitride thin films made by RF reactive sputtering can be made with varying composition along the silicon dioxide - silicon nitride tie line by control of the sputtering gases. Compositional determination was made by the Rutherford backscattering technique. A simple model relating film composition to the composition of the reactive gases is proposed which fits the experimental results.

The first experimental investigation of the vibrational properties of 1–19 raonolayers of behenic acid deposited on various substrates using a new IR technique : Spectroscopie Phase Modulated Ellipsometry (SPME) is presented. The influence of the cleaning procedure of the substrate is discussed. The preferential tilting direction of the aliphatic chain along the withdrawal direction is confirmed. High sensitivity makes SPME a useful tool to study the structure of more complex organic molecules.

The properties of metal fluoride films (MgF2 CeF3, LaF3 CaF2 and SrF2) deposited using cw laser and electron-beam evaporation were compared. The differences in film properties were subtle, but important. Films obtained by laser evaporation have lower losses in the UV (185–250 nm) and slightly better crystallinity than the films deposited by e-beam evaporation. Other optical and mechanical properties were independent of preparation method. Differences in the film properties were tentatively attributed to the higher proportion of dissociated species in the évaporant plume of the laser-evaporated materials.

Comparative thin film adhesion studies were performed on GaAs substrates using Au or Au-Ni-Ge, metallization materials. The influence of parameters such as crystal orientation, substrate surface preparation, deposition vacuum conditions, thickness and composition of films, and post-evaporative treatment such as ion-beam mixing and thermal annealing, on film adhesion was considered. The quality of the adhesion bond was measured using Scotch tape tests and a Sebastian adhesion tester. Film interfaces were characterized using AES, XPS, and RBS techniques. The results indicate that the most important factors dominating the quality of adhesion were surface preparation and the deposition vacuum conditions. Films deposited under optimum conditions were found to adhere so well that the GaAs crystal would fracture before the film would pull free of the substrate. The influence of ion beam mixing on the quality of adhesion was tested and only in the cases of depositions under the less optimum conditions, where the adhesion was poor, could an improvement be made in the adhesive properties.

The formation of TiSi2 thin films on Si has been investigated by in situ x-ray diffraction and by electrical transport. The x-ray results show unequivocally that the staging proceeds through two orthorhombic polytypes of TiSi2 according to the sequence: sputter-deposited metallic Ti films on Si (001) → TiSi2 (C49 structure) → TiSi2 (C54 structure), with no evidence of lower suicides. Electrical transport shows metallic behavior for all phases and distinctive features in the annealing curves which correlate with the structural transformations. Most importantly, the resistivity, characteristically very high for the C49 phase, undergoes a precipitous drop at the C49 → C54 transition. Total energies for both phases are calculated and, consistent with the occurrence of a structural phase transformation, are found not to differ appreciably.

The intermixing of AlAs/GaAs superlattices has been investigated as a function of Si concentration following anneals in the range of 500 to 900 C. The superlattice samples were grown by molecular beam epitaxy(MBE) and the near surface layers were doped with silicon at concentrations of 2×10 to 5×1018 cm-3. Si and Al depth profiles were measured with secondary ion mass spectrometry (SIMS).The diffusion length and activation energy of Al as a function of silicon dopant concentration are derived from the SIMS data. In the temperature range studied an activation energy for the Al interdiffusion of -4eV is observed with the diffusion coefficients increasing rapidly with Si concentration.

The interfacial structures resulting from the metallurgical reactions between a Ni/Au/Ge/Au film and (100) GaAs substrate were studied by cross-section TEM. Annealing at 300 – 350°C causes a complicated solid-solid phase reaction, resulting in the multilayer structure of Ni2Ge/Au7Ga2/NiAs/Au7Ga,/GaAs. The contact shows non-ohmic character, since most of the doping element Ge is trapped in the surface Ni2Ge layer When the contact is annealed at above 400°C. the layered structure is destroyed because one of the phases (Au-Ga) becomes liquid but other phases (Ni-Ge, Ni-As) remain solid Ge, which is captured in the surface layer, diffuses out of the Ni2Ge phase into the contact/GaAs interface through the Au-rich melt. Above this temperature, a Ge-doped n+ region is probably formed at the NiAs/GaAs interface and the contact becomes ohmic. With increasing annealing temperature, continuous grain growth of NiAs is found to occur and the NiAs/GaAs interface area increases. Thus the ohmic behavior of Au-Ge-Ni on n-GaAs can be explained by the low barrier height of the NiAs/GaAs interface and the formation of Ge-doped n+ region under the NiAs phase.

Variable Angle of incidence Spectroscopie Ellipsometry (VASE), Rutherford Backscattering (RBS) and Cross-sectional Transmission Electron Microscopy (XTEM), are used to measure heterojunction layer thicknesses in an AlGaAs/GaAs sample. All three techniques yield the same thickness values within error limits.

It has been shown recently that variable angle of incidence spectroscopie ellipsometry (VASE) is a sensitive technique for determining semiconductor multilayer model parameters, e.g. layer thicknesses and ternary compositions. In this paper we show that VASE is, in addition, sensitive to the Franz-Keldysh effect induced by band bending in the barrier layer of a GaAs-AlGaAs-GaAs (MODFET) structure. VASE measurements differ from electro-reflectance and photoreflectance, in that the internal heterojunction region electric field is directly probed, without the application of a modulating field. The Franz-Keldysh effect appears in the VASE spectra near the AlGaAs bandgap energy. Data for two samples, with different doping profiles, are quantitatively modeled to determine the internal electric field amplitudes.

Low Energy Ion Scattering (LEIS) techniques have been used to examine epitaxial NiS2 films grown on the (001) surface of Si. The experimental results support a model of a NiSi2(001) surface that is a bulk-like but relaxed (001) Si plane with a 25%-30% concentration of vacancies. The 1/3-, 1/4-, and 1/5-order LEED spots observed for these surfaces may be the result of ordering of the vacancies, such that there are domains in which every 3rd, 4th, or 5th [110]-type atomic rows are missing in the Si terminated (001) plane.

In exploring new techniques to produce controllable lateral variations in the physical properties of semiconductor superiattices, substrates containing etched patterns were used for epitaxial crystal growth. High resolution TEM was used for the first time to study this kind of structures. It was found that the resultant superlattices exhibit wavy or zigzag layers which register the history of the topographic evolution of the crystal surfaces during growth and reveal useful information on the fundamental mechanism of the epitaxial process.

Alternate layers of Al0.3Ga0.7As and GaAs were grown by MBE and OMCVD on (100) GaAs substrates patterned with grooves and mesas along the [011] and [011] directions. The morphology of the superlattices grown on the grooves and mesas was analyzed with TEM cross-sectional imaging. It was found that the evolution of non-planar crystal surfaces depends not only on the source flux and surface affinity, but also on the lateral diffusion of the adsorbed atoms or molecules on the crystal surfaces. Several growth features at the intersections of adjacent facets are illustrated in this work. Implications on the epitaxial process are discussed.

We have measured the radius of curvature of InGaAsP/InP heterostruc-ture wafers grown by liquid phase epitaxy, after growth and after broad area p-and n-metallizations used in the fabrication of 1.3vm lasers, by the x-ray automatic Bragg angle control technique. The heterostructure consisted of an n-InP buffer layer (0.2μm), an InGaAsP active layer (0.3 – 0.4μm), a p-InP layer (0.7μm) and either a p-InGaAsP or a p-InGaAs cap layer (0.6 – 0.7μm) grown on a 250 μm thick n-Inp substrate. The radius of curvature measured after growth was found to be in good agreement with the value calculated using the lattice mismatch strains. The changes in the radius of curvature after deposition and alloying of a 1000 Å thick AuZnAu p-metallization and after thinning the substrate to 86μu followed by 2900 Å thick alloyed GeAu n-metallization are such that the metal films are under a tensile strain. The value of the strain is calculated to be 8 × 10-3 and 1.6 × 10-3 respectively for the p- and n-metals. The radius of curvature was measured after the final metallization and annealing of 2500 A thick TiPt layer on the p-side. The annealed TiPt layer was found to have a compressive strain of 6 × 10-3. The stress in the active layer remained tensile at all times for both wafers and it was in the range 9 × 10 – 1.4 × 10 dyne cm-2. These values are less than the estimated fracture stress of InGaAsP by an order of magnitude.

Arsenic or phosphorus doped polycrystalline-Si (poly-Si) acts as a diffusion source when deposited on GaAs. Non-Fickian Si diffusion into GaAs has been observed following heat treatments above 700°C. In this paper, the diffusion of In and P from poly-Si at temperatures between 800 and 1020°C is presented. These impurities, introduced into the poly-Si by in-situ plasma deposition, implantation or vapor annealing, diffuse rapidly into the GaAs. Results from particle induced x-ray analysis, transmission electron microscopy, Rutherford backseat tering and secondary ion mass spectroscopy indicate 80% substitutional In and P at interface concentrations of approximately 10 and 25 at%, respectively.

Electrical and optical properties of single-domain GaAs heteroepitaxial films grown on Si(100) by using metalorganic chemical vapor deposition have been investigated. Cathodolumi-nescence and electron-beam induced current experiments have revealed that signal nonuniformities on the film surface agree in number with GaAs microdefect densities observed through chemical etching, rather than conventional aligned etch-pit densities. The cathodoluminescence experiments also indicate that GaAs properties are improved with increases in film thickness. This nonuniformity and the film-thickness dependence are related to GaAs solar cell characteristics fabricated on the Si substrate. A GaAs/Si interface study proves that p-type Si substrates cause type conversions near the interface due to GaAs growth. Evidence of positive interface charges in the GaAs/Si system is determined by using Hall effect measurements, secondary-ion mass spectroscopy and electron-beam induced current experiments.