EuTe on PbTe is an example of a strained layer heteroepitaxial system with a moderate lattice-Mismatch of 2%. Using reflection high-energy electron diffraction (RHEED), the phase diagram of heteroepitaxial growth of EuTe on PbTe (111) by molecular beam epitaxy was established, indicating that only in a narrow regime of growth conditions does two dimensional layer-by-layer growth occur. Using in situ RHEED, combined with ex situ atomic force Microscopy, the evolution of the surface morphology during heteroepitaxial growth was investigated. It is found that at the critical layer thickness an abrupt surface roughening occurs. Studying the dependence of this surface roughening transition on substrate temperature and on the Eu-to-Te2 beam flux ratio used for growth, the critical layer thickness is found to decrease strongly as the surface kinetics are enhanced, even if the substrate temperature is kept constant. These results indicate that the surface roughening is driven only by the surface kinetics, which strongly supports the model of strain relaxation by coherent three dimensional islanding.

The interaction of group III Metal clusters with the underlying III-V compound semiconductor substrate is examined. Specifically, both In and Ga on InP and GaAs (001) are discussed. Two Methods of obtaining an excess concentration of the group III Metal are treated: thermal decomposition in UHV where preferential group V dissociation and vaporization leaves a supersaturation of metal and Knudsen cell deposition in an MBE system. It is shown that the resulting morphologies for all cases are attributable to significant cluster/substrate interactions.

Scanning tunneling Microscopy (STM) is used to investigate the initial stage of metal overlayer formation on semiconductor surfaces. STM scans are presented of preformed nanometer diameter Au clusters deposited at room temperature on molybdenum disulfide and hydrogen terminated silicon substrates. These scans show that the Au clusters are substantially deformed by interfacial forces between the cluster and substrate. The extent of deformation depends on the substrate.

Cluster-assembled thin metal films exhibit properties which are different from those of films obtained by conventional atomic-deposition. We present TEM data on the evolution of 2-D Microstructure and SFM data on the evolution of 3-D Microstructure in thin films grown by vacuum deposition of preformed silver clusters and of preformed acetylene-silver clusters on flat SiO2, and Mica. Electrical resistivity measurements of cluster-based Ag and Ag/C2H2 films deposited on glass substrates with nominal film thicknesses of 5 nm - 50 nm are also presented and discussed.

We investigate the influence of mass forces (in particular, of gravitation and van der Waals forces) on the critical film thickness of thin films attached to solid substrates and establish corresponding corrections of the earlier published formula Hcril = ΣΜ/τ2 (where Σ is the surface energy, Μ - the shear Modulus, and τ - the mismatch stress). It is assumed that the films’ particles are able to rearrange their relative positions in the lattices, and the equilibrium rearrangement is determined by minimizing the total static energy. Recently, it was demonstrated that morphological stability of interfaces in crystalline solids with the rearrangement is extremely sensitive to the presence of shear stresses. Equilibrium theory of elasticity of pre-stressed solids with the rearrangement of their material particles has already allowed the prediction of the appearance of corrugations in He4 films and to explain the dislocation-free Stranski-Krastanov pattern of epitaxial growth of thin solid films. The explicit asymptotic formulae announced here are especially useful in the case of small mass force, the effects of which can be detectable and even significant for some of the above mentioned phenomena.

The results of a detailed study of the scaling and percolation behavior of the sub-Monolayer in a model of molecular beam epitaxy are presented. In our model adatoms are randomly deposited on a square lattice and then allowed to diffuse. Whenever an adatom encounters another adatom or an island, it is attached to them and becomes immobile. We have found and studied four distinct scaling regimes, corresponding to a low-coverage (nucleation) regime, intermediate-coverage regime, an aggregation regime, and coalescence and percolation regime. At low coverage the islands have a dendritic structure such as seen in Au/Ru (0001) while at higher coverages they become compact. The scaling of the cluster fractal dimension, island density, Monomer density, island size distribution, and structure factor and pair-correlation function are studied as a function of the coverage θ and the ratio R = D /F of the diffusion rate to the deposition rate.

MBE growth of 2% lattice-Mismatched EuTe on PbTe (111) is studied combining in-situ reflection high-energy electron diffraction (RHEED) with UHV scanning tunneling Microscopy (STM) to investigate the evolution of the EuTe surface Morphology. Using RHEED we have found that 2D nucleation and layer-by-layer growth occurs only in a very narrow range of growth conditions as a result of a strain induced coherent islanding of the surface[l], which leads to a roughening transition at the critical layer thickness hc of 45 Monolayers (ML). Starting with a very smooth initial (111) PbTe surface with terrace widths of 50 to 200 nm, islands of monolayer height are formed due to 2D nucleation of EuTe. For EuTe layer thicknesses below hc, the root mean square roughness (RMS) is essentially constant and equal to about one ML. Beyond hc, the surface roughness increases strongly and islands of about 20 ML height are observed for an EuTe layer thickness of 66 ML.

Fluorine-doped tin oxide films were produced by atmospheric pressure chemical vapor deposition (APCVD) from the reaction of tin tetrachloride, water, and difluoroethanc. Tin oxide films deposited on glass substrates containing high sodium concentrations tended to be of lower quality with higher resistivities than films deposited on low sodium glass. Scanning electron Microscopy (SEM) was used to study the differences in film nucleation on the high and low sodium containing glass substrates. Eiarly in the nuclcation process, individual grains of tin oxide crystals arc observed to be distributed discontinuously over the substrates. As the deposition time was increased the number of nucleation sites increased and the individual grains became larger. The number of nucleation sites was consistently higher on the high sodium glass. However, numerous inclusions of sodium chloride crystals were observed by EDX in the tin oxide films deposited on the high sodium glass. SEM cross sections revealed how the film growth converted from the grains, which initially nucleated on the glass surface, to columns in the direction perpendicular to the substrate surface. Results for tin oxide grown on sodium-containing glass over coated with silica are also be presented.

Domain-free epitaxial layer of CuInSe2 has been successfully grown on (lOO) GaAs at the substrate temperature above 470°C. Both TEM and X-ray analyses were performed to verify this result. The CuInSe2/GaAs interface was examined by high resolution TEM. For films high in indium, InSe was identifed by X-ray diffraction. TEM observations showed that the InSe precipitates were rectangular in shape and the habit plane was determined to be (110). Photo-assisted MBE technique had also been used for the growth of CuInSe2 films with high crystalline quality. The epitaxial temperature was significantly reduced to 300°C.

We have carried out the Raman spectroscopy of titanium nitride films grown on Si(001) substrate by laser physical vapor deposition. The first order Raman defect induced acoustic and optical phonon peaks have been recorded for films grown at different substrate temperatures ranging from room temperature 25°C to 600°C.The ratio of the acoustic and the optical peak intensities and the width of the peaks are correlated with the nitrogen deficiency, crystalline size and stresses in the films. The results of Auger analysis, resistivity measurements and microstructural observations substantiate the finding that the stoichiometry of the films in terms of nitrogen concentration is improved at higher substrate temperatures.

We have shown that epitaxial films can be grown on highly lattice mismatch systems by domain epitaxial growth. For titanium nitride films on (100) silicon substrates, it is shown that epitaxial growth can occur by Matching M TiN = n asi, where M and n are simple integers with values of 4 and 3 respectively, giving rise to less than 4.0% Misfit. We have investigated the formation of epitaxial titanium nitride films grown on (100) Si by pulsed laser (KrF: λ = 248 nm, τ = 25 ns) physical vapor deposition technique at different substrate temperatures, ranging from 200°C to 600°C. After optimizing the deposition conditions for epitaxial TiN film on Si, we have grown epitaxial silicon film on TiN. The epitaxial relationship was found to be <100> Si ∥ <100> TiN π <100> Si. This semiconductor-Metal-semiconductor device configuration has potential applications in three-dimensional integrated circuits and radiation hardened devices. The success of this technology is predicted on our understanding of: (a) defects at interfaces of Si/TiN/Si, and (b) stresses/strains at interfaces. This paper focuses on the nature of epitaxial growth and analyzes the atomic structures of defects at Si/TiN/Si interfaces using high resolution transmission electron Microscopy (HRTEM). These results are correlated with the results from theoretical modeling of Si/TiN/Si heterostructures.

Epitaxial (110) titanium nitride films have been grown on (100) GaAs by pulsed laser deposition technique. The film quality has been found to be a strong function of the processing parameters. The films have been characterized using four point probe resistivity technique, Raman spectroscopy, X-ray diffraction analysis, and transmission electron Microscopy. Single crystal films were obtained at the deposition temperature 450° C and the room temperature resistivity was found to be 49.7 ΜΩ-cm. The epitaxial orientation relationship of the TiN films with the substrate is given by [001]TiN//[110] GaAs and [īlO]TiN// [līO]GaAs. Modeling studies have been performed to characterize the domain epitaxial growth in these large mismatch systems.

There are a number of published reports on the epitaxial growth of Al(111) on Si(111) surfaces usually following a high temperature treatment of the Si surface in UHV. In contrast to these results, we have for the first time observed dominant epitaxial growth of Al(100) films on Si(111) surfaces that have been carefully cleaned and hydrogen terminated and not heated prior to effusion cell deposition of Al at room temperature in UHV. X-ray diffraction shows sharp and intense Al (200) diffraction, enhanced by post deposition annealing. Crystal quality and the dominance of Al(100) structure depend strongly on the substrate treatment and the off-cut angle, both of which control the steps on the Si(111) surface. The steps were found responsible for the epitaxial alignment of the film and the substrate lattices. Details of this alignment were observed in TEM cross-sectional images of the interface.

The evolution of the microstructure of submicron Al (.5wt%Cu) lines has been examined as a function of annealing and electromigration stressing time. We have studied lines of two different thicknesses (4000 and 2000 Å) and a range of widths from 0.2 to 1.0 Μm. Pre- and post- stressing studies of the microstructure have been performed, as well as real-time studies during stressing inside the transmission electron Microscope (TEM). We report the results of temperature cyclings over the range 400–525 C for both passivateci and unpassivated lines. IMprovements in the microstructure were observed in all cases. The Most dramatic improvement occurred for the unpassivated lines when annealed to 450 C and for the passivated lines upon annealing to 525 C. In both cases a true bamboo structure was very nearly achieved for lines of width ≤0.5 Μm. Grain growth was by far the greatest in the pads. In the 2000 Å thick passivated lines, voiding upon temperature cycling is more pronounced than for the thicker lines. Also, the bamboo microstructure is more difficult to obtain compared to the 4000 Å lines. Finally, we report our preliminary results on the microstructural changes which occur as a result of electromigration. Voiding and hillock formation are examined. Microstructure is correlated with electromigration reliability.

A variety of alloying elements are currently being investigated for their effects on the mechanical properties and reliability of thin aluminum films. In the present study, scanning electron microscopy and transmission electron microscopy are used to study the nucleation and growth of Al-1.5wt%Cu and Al-1.5wt% Cu-0.2wt% W films. Differences in Microstructure, nucleation and growth behavior are observed and are explained in terms of changes in surface energies and atomic Mobilities.

The template growth technique was applied to the growth of CrSi2 thin films on Si(111) by UHV E-gun evaporation. A 4He+ channeling yield of -50% was obtained for an epitaxial -2100 Å-thick film of continuous morphology grown at 450° C The heteroepitaxial relationship is CrSi2 (001) / Si (lll) with CrSi2[210] ∥ Si<110>.

In the case of film formation simply via reactive deposition epitaxy (RDE, chromium evaporation onto hot substrates) a severe crystallinity-Morphology tradeoff is always observed. Continuous films are formed at low temperature but no long-range epitaxy is found. On the other hand, high temperature annealing of these films induces the formation of islands that show good epitaxial alignment with the substrate. This tradeoff was addressed with the template growth technique.

The thermal stability of titanium disilicide (TiSi2) film under dielectric capping layers was studied. Dielectric capping layers prevent changes in sheet resistance and the film stress of the TiSi2 film during annealing at 900°C. The enhancement of thermal stability of the TiSi2 film was dependent on the nature of dielectric; thermal stability of the TiSi2 film was enhanced more effectively by the plasma-enhanced silicon nitride (PE-SiN) capping layer rather than the undoped silicate glass (USG; S1O2) capping layer. The dependence of thermal stability of the TiSi2 film with the nature of dielectrics was due to the difference in stress of dielectrics at anneal temperature. At 900°C, stress of the USG film was nearly twice of that of the PE-SiN film. Agglomeration of the TiSi2 film under the dielectric capping layer at high temperature annealing can be explained by a diffusional flow of atoms called Nabarro-Herring Microcreep. As the size of Ti-polycide lines becomes smaller, the nature of the dielectric film on the TiSi2 film will be more important for achieving thermal stability.

Nitridation of Cu-Cr alloy films under an NH3 ambient was studied using in situ transmission electron Microscopy. Cu-Cr thin films (40–100 nm) were deposited on a single crystal NaCl substrate by electron beam coevaporation, and were heat treated up to 750°C at 2.5–3.0 Torr NH3. The films were also vacuum (10-6 Torr) annealed under the same conditions for comparison. Initial observation of Cu and Cr crystallization occurred at 470°C for both environmental conditions. The nitridation process of Cr to form CrN was observed initially at 580°C and was followed by evolution of faceted Cu grain growth in the CrN Matrix.

Co-deposited Cu/Ti thin films were heated at various temperatures in an ammonia ambient in an environmental cell fitted in to the column of transmission electron Microscope (TEM). The reaction dynamics was observed in situ and recorded on video using a TV camera with 1/30 sec. time resolution. The nitridation of titanium accompanied by nucleation and growth of copper particles started at 370°C. Ti2N formed at lower temperatures while TiN was formed above 400°C. The nucleation of crystals occurred simultaneously (within a Minute) throughout the film indicating no effect of electron beam on reaction process. The growth rate of copper particles was observed to vary slightly from one particle to another indicating varying growth rate for different facets.

Selective Epitaxial Growth of silicon through windows in SiO2 using low-temperature SiH2Cl2/H2 chemistry in a hot wall LPCVD system was used to form Epitaxial Lateral Overgrowth (ELO) regions of Silicon-on-insulator. In cases where pattern ‘width was less than two times epi film thickness, the ELO regions merged to form a continuous epitaxial film. In this study, 2.5 μm thick single crystal silicon layers were grown perfectly over oxide regions with very low dislocation density (< 104/cm2). The epitaxial Si/oxide interfaces were smooth and defect-free. However, a “seam”-like defect was occasionally observed in the epitaxial film on top of the oxide, at the locations where two growth fronts merged together. This crystallographic defect in some case extends through the whole Silicon-on-Oxide film and would be expected to be detrimental to electronic devices built on or close to it. The sturctures of these seam line defects were investigated in detail by transmission electron Microscopy (TEM). The formation mechanisms of these seam line defects and possible origins are discussed.