Amorphous Ni69Cr14P17 specimens thinned for transmission electron microscopy have been studied in situ during thermal treatment. In the thinnest regions of the specimens (thickness d < 50 nm), a metastable hexagonal (Ni,Cr)3P phase nucleates at the perforation edge with the c-axis perpendicular to the specimen surface. The crystal width of this phase grows linearly with time. Above 530°C the hexagonal phase transforms into a stable b.c.t. (Ni,Cr)3P phase. It is concluded that the surface and grain boundary energies dominate nucleation and growth.

The interfaces in Si0.65Ge0.35/Si superlattices grown at different temperatures (250–750 °C) and number of repetitions (5, 10, 20) are studied by x-ray and Raman scattering techniques. At 250 °C the interfaces are chemically abrupt, but exhibit a pronounced vertically correlated physical roughness that increases in magnitude with thickness. In the range of 400–550 °C interfaces are smooth but intermixed over at least two monolayers, and asymmetrically broadened with the alloy/Si interfaces width about twice (0.25 vs 0.5 nm) that of the Si/alloy interfaces. At higher temperatures (620–750 °C) undulations of 1 nm amplitude and 100 nm length scale develop at the alloy/Si interfaces. This morphological change appears to be strain-driven and causes some relaxation of the built-in strain. Moderate annealing (20 s at 750 °C) induces partial relaxation of the superlattices and out-diffusion (∼0.5 nm) of Ge into the contiguous Si layers, but has relatively little effect on the interfacial widths.

Scanning tunneling microscopy has shown that large, two-dimensional Ag clusters undergo observable diffusion on Ag(100). The variation of the diffusion coefficient with cluster size in the range studied, 100 to 540 atoms per cluster, indicates that two-dimensional evaporation-condensation is the main mechanism of cluster diffusion. The experimental data consistently show evidence for a backward-correlation in the cluster motion. The meaning and origin of this correlation is discussed.

The correlation of surface morphology with strain relaxation in the In0.15Ga0.85As epilayer on GaAs(100) grown by chemical beam epitaxy using unprecracked monoethylarsine has been investigated. The surface morphology of InGaAs was analyzed by atomic force microscopy as the epilayer thickness was increased from 0.025 to 1.668 μm. The changes in the surface morphology indicated that surface roughening is related to the process of strain relaxation in the film. The strain-induced shifts in the GaAs-like longitudinal optical phonon in the Raman spectrum also indicated that the strains in the InGaAs epilayer relax via step-wise process with increasing the film thickness beyond the critical thickness, which agrees well with the changes of surface mophology.

In this study we report on manipulation of nucleation by means of periodic modulation of the growth rate, R, during molecular beam epitaxial growth of Si on Si(l11). We have found that the bilayer (BL)-by-BL growth can be improved by applying the R-modulation synchronized with the nucleation and that the phase of reflection high-energy electron diffraction (RHEED) intensity oscillations can be shifted independently of the bilayer (BL) deposition. A beating phenomenon of the RHEED oscillations was observed, which can be attributed to the superimposed effects of the R-modulation and the regular BL-by-BL growth. We have used the phenomenological correspondence between the surface step density and the RHEED oscillations as a basis to discuss the growth. By employing a kinetic solid-on-solid Monte Carlo model without vacancies and overhangs all significant experimental features could be simulated.

The structural and morphological evolution of growing β-SiC films was investigated in dependence on the ramp rate and the propane concentration. It is shown that the film structure depends critically on the formation of an initial SiC layer during heating-up. A growth model was proposed to explain the obtained different resulting film structure.

Laser physical vapor deposition (LPVD) has been used to study the growth morphology of copper thin films on siliconi 100) substrates with epitaxially grown titanium nitride buffer layers. The epitaxial TiN film was grown on hydrogen-terminated Si substrate at 600°C. The Cu films were grown on TiN/Si at different substrate temperatures ranging from room temperature to 600°C in vacuum (∼10-7 torr) with a pulsed KrF excimer laser (τ = 248 nm, ι = 25 ns). The pulse repetition rates were 15 and 30 Hz. The X-ray diffraction (XRD) results indicate that below 200°C, the Cu film has a mosaic spread of (001) textures of about 2.3° and that a small fraction (0.05 ) is of (111) textures. But above 200°C there is only (001) textures Cu of about 0.42° to 0.40° depending on the substrate temperature (200° - 600°C). The Rutherford backscattering (RBS) spectra show that the TiN has a yield (xmin) of 13.5 % whereas that for Cu is 70 %. A detail high resolution transmission electron microscopy (HRTEM) was performed to reveal the growth morphology of Cu films with substrate temperature. It was observed that at 15 Hz, Cu grows three-dimensionally on TiN with the island sizes ranging from 0.3 – 1.5 μm depending upon the substrate temperature. All of these islands grow epitaxially on TiN giving rise to <100>Cu ║ <100>TiN ║ <100>Si. At 30 Hz, there is a uniform growth of epitaxial cube-on-cube Cu film on TiN/Si. The Cu/TiN and TiN/Si interfaces are quite abrupt with absolutely no indication of interfacial reactions between them. Moiré fringe spacings suggest that both TiN and Cu unit cells are completely relaxed. Although there exist a large lattice misfit between Cu and TiN (15.8%) and as well as between TiN and Si (24.6%), it has been possible to grow epitaxial Cu/TiN/Si(100) heterostructures by means of domain epitaxial growth. In this case, there are 4-to-3 match in unit cells for TiN/Si structure and 7-to-6 match for Cu/TiN structure giving rise to remaining lattice misfits of only 4.0% and 0.6% respectively.

The growth morphologies of vicinal hillocks on KH2PO4 {101} surfaces have been investigated using atomic force microscopy. Both 2D and spiral dislocation growth hillocks are observed on the same crystal surface at supersaturations of ∼5 %. Growth occurs on monomolecular 5 Å steps both by step-flow and through layer-by-layer growth. The distribution of islands on the terraces demonstrate that surface diffusion is an important factor during growth. Terraces that are less than the diffusion length do not contain any islands. This, together with the length scale of the inter island spacing and the denuded zones provide an estimate of the diffusion length. In situ experiments at very low supersaturation (∼0.1 %) show that growth is a discontinuous process due to step pinning. In addition, in situ images allow for the direct determination of the fundamental growth parameters a, the step edge energy, and β, the kinetic coefficient.

Copper overlayers deposited on nearly stoichiometric SrTiO3(001) have been investigated with scanning tunneling microscopy (STM). Vapor deposition of Cu on a SrTiO3(001) surface at ambient temperature leads to the formation of three dimensional islands (clusters). The distribution of Cu islands appears to be inhomogeneous with two characteristic morphologies. In regions with a low density of Cu islands the Cu was always associated with step edges or defect sites. In regions with a high density of Cu islands the islands exhibit a random but nearly close packed morphology. The variation of Cu island density is indicative of diffusion of Cu clusters on the SrTiO3(001) surface. Diffusion was further confirmed by annealing the Cu/SrTiO3 at elevated temperatures yielding agglomeration of Cu clusters.

The initial stages of epitaxial growth of Ag on InP(100) has been studied using in-situ and ex-situ electron microscopy techniques. Vicinal InP substrates were cleaned by heating to about 450°C in ultra-high vacuum. Silver was subsequently deposited at substrate temperatures between 350–500°C. The microstructural evolution was monitored for coverages between 0.5 – 8ML using high spatial resolution secondary electron microscopy and transmission electron microscopy.

At sub-monolayer coverages, square islands of Ag are formed with edges aligned along InP <110> directions. Subsequent deposition leads to secondary nucleation or growth of pre-existing islands, depending on the substrate temperature. Surfaces with a uniform distribution of steps have a higher island density than those without steps but the steps are not preferred sites for island nucleation. Coalescence of islands begins at a smaller coverage for lower temperatures and for stepped surfaces. At the early stages of coalescence, island shapes with low symmetry are formed, with diminished island heights. These subsequently transform into shapes of higher symmetry. Except at the highest temperatures studied (500°C), island shape transformations (e.g. from square to elongated) are not very significant. Plan view transmission electron microscopy shows that the islands are epitaxially aligned and that even the smallest islands are generally incoherent. Island size distributions are used to analyze the growth mechanisms.

Homopolymerizations of multifunctional monomers produce densely crosslinked polymer networks with structures that are often complex and difficult to characterize. The complexity in the structure arises primarily from the heterogeneous nature of the polymerization such as the formation of microgels. This work presents progress towards developing a better understanding of the highly crosslinked polymer structure through combined experimental and modeling techniques. Electron spin resonance (ESR) spectroscopy was used to examine the concentration and local environment of the radicals, i.e., the fraction of radicals that were trapped and terminate on a long time scale as compared to those which are more mobile and terminate on a shorter time scale. A kinetic gelation simulation was developed to verify the ESR results and provide further information regarding the structural evolution of the network and its heterogeneities.

We report the results of a combined experimental and theoretical study of thin film growth. The theoretical approach is able to capture nonlocal shadowing effects, allows for an arbitrary topology of the growing interface, provides information on the density in the film interior, incorporates surface tension in a natural manner and enables a unified study of diverse growth phenomena ranging from diffusion-limited aggregation to ballistic aggregation. The theoretical results are found to have many of the features observed in our experiments on physically vapor deposited films.

The nucleation and growth of in situ doped, LPCVD silicon films was analyzed using atomic force microscopy, variable-angle spectroscopie ellipsometry, and transmission electron microscopy. The RMS surface roughness initially increases from 0.5 to 5.7 nm with increasing deposition times and then rapidly decreases to 0.5 nm for longer times. Ellipsometry data was modeled using two layers where the top layer consists of a mixture of amorphous Si plus voids and the bottom layer is a continuous amorphous Si layer. Cross-section TEM reveals the nuclei size and structure for these silicon films and confirms the results of the other techniques.

The structure, morphology and epitaxy of nanometer scale solid clusters of gold atoms supported on the atomically flat basal (0001) plane of MoS2 are studied by TEM and STM. These metal film nuclei are deposited onto the substrate, which is held at 400°C, by two dif-ferent methods: (1) vacuum evaporation (PVD) and (2) soft landing of preformed Au clusters (CBD). In both cases the nuclei are single fcc crystals. In the case of atomic deposition the nuclei assume the shape of truncated tetrahedra with all their facets Au (111) planes. In the case of soft landed clusters the nuclei retain their free space morphology, that of truncated octahedra with hexagonal Au (111) and square Au (100) faces. Both PVD and CBD nuclei are heteroepitaxially aligned with (111)Au ║ (0001)MoS2; [220]Au ║ [1120]MoS2.

In-situ doped polysilicon films were deposited by single wafer low pressure chemical vapor deposition (LPCVD) over a temperature range of 590–640°C using SiH4 and dopant gases of B2H6, AsH3, and PH3. Deposition rate, sheet resistance, step coverage and surface roughness measurements of the films were made. The surface chemistry of these three in-situ doping processes is reviewed. Analysis shows how the physical properties of the deposited polysilicon films derive from the surface chemistry.

We have monitored the microstructural evolution of Ag films grown on in situ cleaved GaAs(110) surfaces using nm spatial resolution secondary electron microscopy. Ag coverages between 1/2 ML and 256 ML were investigated for films deposited from an Ag Knudsen cell onto both room temperature (RT) and 250° C substrates. The initial stages of growth are markedly different for these two deposition temperatures. The room temperature grown films consist of approximately hemispherical islands while the 250° C films result in needle-like islands elongated along the <110> direction. This elongation may be due to a number of factors including anisotropie surface diffusion or bonding along the <100> and <110> directions, corrugations in the GaAs(110) surface or better lattice matching of Ag(100) to the GaAs(110) direction. At higher coverages, the films appear similar when lengths are scaled to account for increased diffusion at higher temperatures. The islands in the RT film impinge at lower coverages than the 250° C film and the RT film becomes quasi-continuous near 256 ML. The 250° C film forms larger, more widely spaced islands which impinge but do not form a quasi-continuous film for even the highest coverage. Island size distributions will be used to discuss the growth mechanisms for these films.

The growth morphology of Ag on GaAs (110) surface, at low coverage, is investigated with Monte Carlo simulations using a solid-on-solid model. Experimentally Ag deposited at room temperature forms isotropie islands and forms islands elongated along the <110> direction when deposited at 250°C. The preliminary results from our Monte Carlo simulations indicate that anisotropy in the surface migration and near-neighbor interactions are the main factors for the elongated islands observed for depositions performed at 250°C.

We present a computer simulation of the problem of competitive crystal growth of one-dimensional and two-dimensional single crystals restricted to a two-dimensional space. Two similar competition indexes ξ and χ accounting for the degree of preferred orientation developped during the growth process are defined and we show that they varies linearly with the film thickness. The existence of a clear formal similarity between ξ and χ indexes defined in the direct space with a textural index τ defined in the reciprocal space permits the identification of a competitive growth process by X-ray diffraction.

Step fluctuations on Ag(110) surfaces have been investigated with STMT atomic events that underlie these thermal fluctuations are quantified using a Langevin analysis. From the t1- scaling of the step-position correlation function, we deduce random attachment and detachment processes along the step edge, with a characteristic interval of 350 ms between successive detachments.

Upon oxygen adsorption on vicinal Ag(110), a dramatic change in step configuration occurs. Steps which are originally equi-spaced due to repulsive step-step interactions are compressed into bunches. This process is driven by the formation of large (110) facets, on which oxygen atoms arrange into chains along [001]. The faceting dynamics are sensitive to the orientation of the step edge: proceeding by nucleation for close-packed steps and by spinodal decomposition for steps at an acute angle to the oxygen chains.

A closer inspection of these oxygen chains reveals that each incorporates an additional row of silver atoms. When oxygen dosing pressures are kept below 10-6 Torr, silver atoms detaching from the step edge provide a sufficient supply necessary for the formation of the added row. With higher oxygen pressures, the silver atoms required for the oxygen chains are extracted directly from the terraces, resulting in the formation of large, long-lived etch pits.

The group IV metastable SnχGe1-χ alloy system is an interesting semiconductor material with potential applications in the fabrication of Si-based heterojunctions and long wavelength infrared optoelectronic devices. Band structure calculations have suggested that the SnχGe1-χ alloys may have direct energy gaps continuously tunable from 0.55 eV to 0 eV for compositions χ from 0.2 to 0.6 with very small electron effective masses and hence high electron mobilities. However, synthesis of SnχGeχ-1 alloy films in the direct gap composition range by conventional epitaxial or poly crystalline thin film growth techniques have not been successful due to the severe surface segregation of Sn during the film growth.

In this work, we report the synthesis of epitaxial SnχGeχ-1/Ge/Si(001) with compositions up to χ = 0.34 by ion-assisted molecular beam epitaxy with 30–100 eV Ar+ ions produced by an electron cyclotron resonance ionization source with ion to atom flux ratios of the order of unity in the substrate temperature range of 120 °C to 200 °C. High flux low energy ion beam irradiation greatly inhibits Sn segregation without interrupting epitaxy. In situ reflection high energy electron diffraction as well as x-ray rocking curve indicated epitaxial SnχGeχ-1 alloy films, and Rutherford backscattering spectra confirmed the SnχGeχ-1 alloy compositions and indicated an absence of Sn segregation.