In this contribution the cosegregation-induced epitaxial growth of two- and three-dimensional chromium nitrides on ferritic Fe-15%Cr-N(100) (CN = 30 wt-ppm) single crystal surfaces will be discussed. The two-dimensional CrN surface compound is stable between 600 and 720°C. From the (1 × 1) LEED pattern it is inferred that the surface compound is epitaxial to the bcc(100) alloy surface. XPD and LEED-IV investigations have revealed that this surface compound consists of a single CrN compound layer plus an additional subsurface chromium layer with a huge interlayer expansion between both layers. The CrN surface precipitate formed at temperatures T < 600°C is also epitaxially arranged on the bcc(100) substrate surface. Its structure corresponds to the rocksalt structure, i.e. the structure of the well-known bulk CrN. Starting from a sputter cleaned alloy surface the growth of the epitaxial CrN surface precipitate proceeds via the two-dimensional CrN surface nitride. After completion of this two-dimensional CrN layer the nucleation and growth of the three-dimensional CrN surface precipitate takes place.

The occurrence of metastable long range order (LRO) along the growth direction with a periodicity twice that of a disordered alloy is now a well established result in epitaxial hcp [0002] Co-Ru and Co-Pt alloy thin films. We first present a review of previous results obtained in Co-rich Co1−xRux alloy thin films (x = 0.25) prepared at various growth temperatures (TG) and the diffusive model developed to account for the observed behavior. This model which takes into account the competition between surface and bulk interactions and surface and bulk diffusion during the growth time reproduces the TG dependence of the LRO parameter (η) and of the lattice constants. Then we present new results on the occurrence of this LRO in Co1−xRux films for higher Ru concentrations (0.22 ≤ x ≤ 0.78) prepared at the optimal temperature for the occurrence of this LRO (570-595 K). Chemical ordering is observed over the whole explored concentration range and it is found to be in agreement with results obtained in a previous series prepared at 610 K with lower Ru content. The LRO parameter deduced from the difference in composition between two successive planes normalized with respect to the concentration of the minonty element displays a nearly symmetric dependence with concentration characterized by a maximum around x = 0.2 and a minimum around the equiatomic composition. These results are qualitatively discussed in terms of a balance between the different energetic contributions to the surface segregation that arise from the release of the elastic energy and the difference in the wetting energy of each element. The important role played by the quality of the substrate in determining the value of η is outlined.

The same specimen of Pb/Cu grown under Ultra High Vacuum (UHV) conditions has been investigated by Scanning Tunneling Microscopy (STM), Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM). We show that the information obtained by these techniques is consistent when comparable, and complementary. In particular, three different morphologies of Pb islands with specific orientation relationship are observed; AFM reveals the faceted shape of the islands; STM permits an accurate determination of the atomic structure of the facets; TEM moir6 patterns reveal that Pb islands are well relaxed.

The theory of the nucleation and growth of islands is maturing rapidly. This advance is driven by the increased availability of experimental data, as well as the need for better control over growth processes. Recently, a number of authors have studied the effects of introducing a second species onto the surface in order to influence the ultimate growth morphology. In some situations, the addition of a second species results in a signficant change (approximately a factor of 1000) in the nucleated island density. The origin of this increase in density has been linked to the anomalous diffusion induced by the presence of the additional species of atoms. In the current paper, this dependence is explored further. In particular, earlier work focused on nucleation and growth in the regime in which the second species is essentially immobile. This constraint is relaxed here, and the subsequent model studied through application of a self-consistent mean-field theory. Predictions for the total island density are presented.

Interactions dictating the shape and stability of surface islands have been examined for a simple model system, palladium clusters on the W(110) plane. Observations in a field ion microscope of the distribution of two Pd adatoms over the surface yield quantitative values for pair interactions. These are found to be complex, extending over distances longer than 10 A and to vary strongly with the orientation of the pair axis on the (110) surface. Using the measured pair energies it has been possible to infer the magnitude of many-atom effects necessary to account for the equilibrium shape of the clusters. Many-atom interactions turn out to make by far the largest contribution to cluster cohesion; modeling of growth phenomena in terms of nearest-neighbor bonds only is clearly problematic.

Growth phenomena and magnetism of metallic films are not easy to describe at the same level of precision. A small variation of distances can drastically modify the magnetic properties of thin metallic films. In this contribution different aspects encountered in the growth of thin magnetic metallic films are addressed. Within an itinerant magnetism scheme, the main difficulty arises from the number of possible magnetic arrangements induced by the competition between nearest-neighbors Ferromagnetic and Antiferromagnetic couplings. However we show that the description of the electronic and magnetic structure at T = 0 K by well-established band structure frameworks provides useful and precise information on the growth of a transition metal on another. Due to the large amount of experimental data available, the Fe/Cr system is taken as an example. The influence of steps at the interface is discussed and the possibility of magnetic domains is shown. A simple model of growth taking into account variable interdiffusion rate and layer-by-layer quality is given. These simulations are used to explain experimental results where interdiffusion at the interface is very common.

O atoms segregate to the surface during Cu homoepitaxial growth on Cu(001)-(2√2×√2)-O to retain the (2√2×√2) surface. The presence of an O adlayer on the Cu surface raises the barrier height for the surface diffusion of the Cu adatom and increases the transition temperature of the growth mode from step flow to layer by layer. The growth proceeds by site exchange between Cu adatoms and O atoms. The site-exchange rate competes with the Cu deposition rate. There exists a critical Cu deposition rate above which the O atoms can not exchange the sites with Cu adatoms. The critical Cu deposition rate obeys an Arrhenius relation and the active energy for the site-exchange is estimated at 0.66 eV.

Giant magnetoresistance (GMR) spin valves of the form Ag/Py/Ag/Py/FeMn and Cu/FeMn/Py/Cu/Py have been studied using conventional and high-resolution electron microscopy complemented with fast Fourier transform (FFT) diffractogram analysis. Cross-sectional TEM thin foil samples were prepared in order to characterize the layer structures and interfaces. In the Ag/Py system, we have examined a simple spin valve, part of which was grown on the Nb contact and part directly on the Si substrate. The spin valve displays a polycrystalline structure when grown on the Nb contact. In contrast, when grown directly on the Si substrate, the first Ag layer of the spin valve grew as a continuous epitaxial single crystal while the rest of the layers were polycrystalline. Two Cu/Py spin valves, grown on Nb, with 30 nm and 3 nm thick Py layers have been investigated. TEM images reveal good contrast between the Nb contacts and the spin valves, but weak contrast between the individual spin valve layers. Both spin valves displayed columnar, polycrystalline grain structures. HRTEM analysis indicates some non-equilibrium structures exist in the spin valve layers.

Low-energy electron diffraction, x-ray diffraction, and x-ray absorption techniques are used to investigate the atomic structure of ternary silicides (MSi2, M = Co, Fe). 100 Å thick Co1−xFexSi2 films (with 0 ≤ × ≤ 1) were grown by codeposition onto a Si(111) substrate held at room temperature. The as-deposited films are metallic and adopt an ordered cubic structure of CsCl-type with essentially random vacancies, very similar to that of room-temperature grown FeSi2 and CoSi2 silicides. Upon annealing at 650°C, Fe-rich (x ≥ 0.85) films invariably convert into a semiconducting phase with a structure similar to the orthorhombic β-FeSi2 one. Yet, most interestingly, an almost cubic structure is preserved for x ≤ 0.85. Nevertheless, x-ray diffraction reveals a demixion into a Co rich CaF2-type silicide and a Fe-rich phase with a nearly cubic α-FeSi2 type structure. Extended x-ray absorption fine structure measurements indicate a local environment of Fe atoms similar to that in CsCl-type or α-FeSi2-type structure over the whole 0 < x < 0.85 composition range, showing that Fe does not merely substitute for Co atoms in a perfect CaF2-type CoSi2 structure, even for very low Fe content. In contrast, the local environment of Co atoms is similar to that in CoSi2 for Co-rich ternary compounds. Substantial modifications around Co sites are although observed in Fe richer silicides, suggesting that for x < 0.5, an appreciable amount of Co is incorporated in the α-FeSi2-type silicide phase.

Theoretical effort so far in understanding epitaxial growth has focused mainly on the one-component growth, i.e. growth that can be fully characterized by a surface (or height) profile. The predictions are also quite limited to the height-height correlation functions as a function of substrate size and the amount of deposition. In this paper, we consider the case of a two-component growth which is quite common in metallic thin films. Instead of using large-scale simulation, we first write down the appropriate two-component growth equations in continuum form. These equations are carefully designed such that in the limit of one-component growth the corresponding equation is recovered. Analytical and numerical analysis of the proposed equations allow us to study the long-range physics associated with these growth processes. Comparison with computer growth experiments is also mentioned.

The results of recent theoretical and simulational studies of submonolayer and multilayer homoepitaxial growth are discussed. In the submonolayer regime, the results of kinetic Monte Carlo simulations are presented and shown to provide a quantitative explanation for the variation of the submonolayer island density, critical island size, island-size distribution and morphology as a function of temperature and deposition rate found in recent experiments. In multilayer growth, a realistic model for homoepitaxial growth on fcc and bcc lattices which takes into account the correct crystal structure is reviewed. The effects of instabilities which lead to mound formation and coarsening are discussed and a unified picture of the effects of attractive and repulsive interactions at ascending and descending steps on surface morphology and island nucleation is presented. An accurate prediction of the observed mound angle for Fe/Fe(100) deposition is obtained analytically and by kinetic Monte Carlo simulations. The general dependence of the mound angle, and mound coarsening behavior on temperature, deposition rate, and strength of the step barrier in bcc(100) and fcc(100) growth is also presented and compared with recent experiments.

Results of recent experimental model studies on ripening of submonolayer films via Ostwald ripening and dynamic coalescence are described. The experiments have been performed on ensembles of Ag-adatom or vacancy islands on a Ag(111) surface using Scanning Tunneling Microscopy. For Ostwald ripening of adatom islands, deviations from the classical mean-field ripening behaviour are observed which show up as pronounced local correlations in island decay and growth rates. For ripening via dynamic coalescence which is studied for ensembles of vacancy islands, it is found that the increase of the average island size with time in the late-stage regime is correctly described by the classical binary collision model.

A self-consistent rate equation (RE) approach to submonolayer growth for a restricted pair-bond model that is relevant to low and intermediate temperature metal (100) and (111) homoepitaxy is introduced. In contrast to previous standard rate equation results, the transition temperature from i = 1 to a higher critical island size is well predicted along with the average island and monomer densities. It is shown that the method's implicit introduction of short-range correlations between attachment/detachment rates, together with a careful estimate of the escape rates for small clusters, are important factors for a good agreement with the kinetic Monte Carlo simulation results.

Using simulations, we have studied the coarsening of an ensemble of atom-high two-dimensional islands on a square lattice. The parameters are chosen to represent metal-on-metal homogeneous epitaxy. We study first the elementary processes controlling coarsening: the evaporation of atoms from islands of various sizes and the migration of these islands due to material transport along their edges. The information obtained from these preliminary studies is used to produce a very efficient simulation of coarsening. This allows us to study how coarsening modifies the number of islands, the distribution of their sizes, and the positions of the islands on the surface.

The growth of strained thin films of gadolinium has been investigated with low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM) and compared to the film growth of unstrained gadolinium. Strained thin films of gadolinium are distinct from the unstrained films by a substrate induced preferential domain growth direction, which is also reflected in the electronic structure.

A theoretical analysis based on continuum elasticity theory and atomistic simulations is presented of the interfacial stability with respect to misfit dislocation formation and of the film surface morphology during layer-by-layer growth semiconductor heteroepitaxy. The strain in the coherently strained films, the energetics of a transition from a coherent to a semicoherent interface consisting of misfit dislocation arrays or networks, and the morphological details of the film surface profile are calculated for InAs/GaAs(110) and InAs/GaAs(111)A. The analysis is presented for the general case of heteroepitaxy on a finite-thickness compliant substrate. The results are discussed in the context of recent experimental data.

Results from in-situ measurements of stress during growth of (111)-textured Ni/Cu multilayers with small and large bilayer periods are presented. In multilayers with small bilayer periods, Ni is in uniform tension and Cu in uniform compression. This behavior is modeled as the growth of a coherent multilayer with alloying in the layers. In multilayers with large bilayer periods, stress relaxation is observed but the measured stresses are much lower than expected based on a Mathews-Blakeslee relaxation process. An alternative stress relaxation mechanism based on high defect densities is presented and discussed.

Epitaxial Co/Mn superlattices (0.6 to 4.8 nm thick Co) have been grown on (0002) hcp Ru buffer layer on mica substrates. The face centered cubic (fcc) phase of cobalt is stabilized by the very thin manganese layer. The structural properties of these layers have been studied through x ray diffraction and nuclear magnetic resonance.

Thin films created by the deposition or under influence of atoms with hyperthermal energies (E = 100 -104eV) exhibit properties which differ in many respects from those of films created by deposition of atoms with thermal energy. The morphologies of thin Pt-films deposited on Pt(111) under otherwise identical deposition conditions by molecular beam epitaxy (MBE), ion beam assisted deposition (IBAD) and sputter deposition (SD) differ in film structure size, island shapes and film roughness. The different film structure sizes are unambiguously traced back to two different island formation mechanisms inherent to these deposition methods. While in MBE the islands result from nucleation in a supersaturated adatom gas, in IBAD and SD they result by direct or indirect creation of adatom clusters as a consequence of single impacts of energetic atoms present in the depositing particle flux. The differences in film roughness are not only due to the different island formation mechanisms, but seem to be closely related to the different step edge structures at the growth front.

X-ray scattering is used to investigate the surface dynamics on Au(111) during Ar+ ion irradiation. During 500 eV Ar+ ion irradiation, we observe the three regimes of step retraction, quasi-layer-by-layer removal and three dimensional rough erosion, analagous to molecular beam epitaxy. The quasi-layer-by-layer sputtering regime has been studied to identify similarities and differences in surface evolution during ion irradiation and molecular beam epitaxy. X-ray measurements suggest that 500 eV Ar+ ion irradiation does not lead to stable adatom island formation. Also, in contrast to molecular beam epitaxy, adatom detachment and diffusion seems important in describing the surface kinetics during ion irradiation.