We simulated the surface relaxation of the cubic perovskite paraelectric SrTiO3 crystal. The atomic positions in ten near-surface layers placed into the electrostatic field of the remainder of the crystal were calculated. Two-dimensional, periodic slab model was combined with the pair potentials treated in terms of the shell-model. Our calculations show that Ti+4, Sr+2 and O−2 ions shift differently from their crystal sites. This leads to a creation of a dipole moment near the surface which might give the paraelectric crystal the ferroelectric properties.

We examine height distribution functions (height histograms) of kinetically roughened metal films, making use of STM data for vapor-deposited Ag on quartz. The height distribution of the raw data is Gaussian to quite high accuracy. However, if one averages each height over a region of length scale L, the resulting distributions deviate increasingly from Gaussian behavior, becoming skewed as L increases. We quantified this behavior by means of moments of the distribution; with increasing L a non-negligible third moment appears. The responsible morphology is minima that tend to form steep valleys or deep pits while the corresponding (at the same height above the average) maxima tend to form rounded hilltops. Skewed height distributions have been predicted on the basis of model calculations, but not previously observed to our knowledge.

We have studied smoothing kinetics of Rh (111) surfaces during low temperature annealing using in-situ real-time reflection high energy electron diffraction and scanning tunneling microscopy. The initial surface features were produced by low temperature homoepitaxial growth of Rh (111). Two types of surfaces were studied, surfaces with two-dimensional (2D) islands at submonolayer coverages, and those with 3D multilayered features. 2D islands coarsen rapidly at the onset of the anneal. 3D features are more stable initially. Their annealing process exhibits a distinct transition from an initial slow coarsening, characterized by a nearly linear growth of lateral size, to a rapid flattening. The activation energy for the transition is ˜ 0.6 eV. The observed behavior indicates that the smoothing kinetics in the low temperature regime is limited by adatom detachment from the step-edges, and that the fast process for the 3D features is made possible by the formation of a network of “chain-like” structures which provide new pathways for diffusion thus overcoming the slow detachment kinetics. These effects determine the low temperature stability of the non-equilibrium epitaxial morphologies.

Heteroepitaxial Si1−x Gex thin films deposited on silicon substrates exhibit surface roughening via surface diffusion under the effect of a compressive stress which is caused by a lattice mismatch. In these films, surface roughening takes place in the form of ridges aligned along either <100> or <110> directions depending on the film thickness and composition. In this paper, we compare the relaxation behaviour of capped and uncapped heteroepitaxial Si1−xGex thin films containing 22% Ge, with surface roughening being inhibited in films with a capping layer. Films with 50 nm thickness were deposited on bare silicon substrates in a LPCVD reactor. Annealing experiments were conducted in a Hydrogen atmosphere in the reactor chamber. Transmission electron microscopy and atomic force microscopy have been used to study the surface morphology and microstructure of these films. XRD measurements were conducted to determine the amount of relaxation in these films. In-situ transmission electron microscopy/annealing experiments have been performed on uncapped Si1−x Gex/Si structures to study the dynamics of surface roughening and defect formation in a vacuum ambient. Finally, we compare surface morphologies and defects in samples subjected to annealing in vacuum and H2 ambients.

Niobium films of thickness 50 nm to 1000 nm were deposited by ion beam assisted deposition (IBAD) using ion energies of 0, 500 and 1000 eV, and R ratios (ion-to-atom arrival rate ratio) of 0, 0.1, and 0.4 on (100) silicon and (0001) sapphire substrates. The films have columnar structures and the column width increases with normalized energy (En = E × R). The surface morphology depends on both the normalized energy of the ion beam, En, and the film thickness. All films have dome-like surface features that are oriented along the ion beam incident direction. The dimension of these features increases with normalized energy and film thickness. Surface roughness also increases with normalized energy and film thickness, with the root mean square (rms) roughness increasing from 1.6 nm for the PVD sample (100 nm thick) to 36.7 nm for the IBAD film (1000 eV, R = 0.4, 800 nm thick). The surface morphology of IBAD films is the result of a combination of channeling and shadowing effects.

The morphological stability of strained-layer thin films is analyzed using classical nucleation theory. For the case where strain relaxation occurs by formation of coherent islands, the model predicts that the critical thickness for transition from two-dimensional (2D) to three dimensional (3D) growth depends inversely on the square of the misfit. The predicted dependence of critical thickness on misfit is in agreement with recent experimental studies on the heteropitaxy of III-V compounds.

Specular and diffuse reflectance and spectroscopic ellipsometry were used to characterize a series of Cosi2 films obtained by heat treatment on a Co/Ti bilayer. The surface quality is strongly affected by etching procedures. The intrinsic optical properties of the CoSi2 film exhibit a small dependence on the growth technique.

A non-contact and non-destructive laser-based acoustic technique called impulsive stimulated thermal scattering (ISTS) is used to measure thicknesses of films in single-layer and multilayer assemblies such as W/Si, Ti/Si, and Ti/SiO2/Si structures. Thicknesses are determined to within a few percent accuracy with a laboratory version of the measurement apparatus, using conventional large-frame lasers and optics, and in a commercial prototype using compact diode-pumped and diode lasers and optics which all fit onto a 1-ft × 2-ft breadboard. ISTS and conventional measurements (profilometry, SEM, and 4-point resistance) are made on the same samples and the results are found to compare favorably.

Angular distribution measurements of the helium atom scattering intensity from monolayer films of KCN/KBr(001) for several azimuths over a temperature range of approximately 40–200 K reveal that above ˜95 K the KCN monolayer forms a (1×1) overlayer structure with respect to the KBr substrate. (The lattice spacing of bulk KCN in the rocksalt-structure phase differs from that of KBr by only ˜ 1%.) Below this temperature the overlayer appears to be (2×1), and “missing” diffraction spots in the <110> high symmetry direction suggest the existence of a glide plane. The inferred structure for this low temperature phase consists of K+ ions fixed in their rocksaltstructure positions relative to the substrate and the CN− ions oriented so that their dipoles are aligned antiferroelectrically within the new unit cell.

The growth by sputtering of a series of thin films of Fe/Au on MgO(001) substrates was analyzed using Bragg and diffuse X-ray scattering. The Fe (bcc) layer grows rotated by 45° with respect to the MgO – Au(fcc) (001) epitaxial orientation, resulting in an almost perfect match between the two metallic structures. By collecting the X-ray diffuse scattering under grazing incidence using a 2-dimensional image plate detector, we mapped the reciprocal space of these films. We characterized the correlated interface roughness starting with a buffer of Fe in which only three interfaces are present. The propagation of the roughness was subsequently characterized for Fe/Au multilayers with 40 and 100 bilayers. We observe an enlargement of the surface features as a function of time, evidenced by the longer lateral cutoff length measured for thicker films.

Fe/Au and Fe/Ag films grown on MgO(001) oriented substrates exhibit the same in-plane epitaxy since Au and Ag have the same fcc bulk structure and nearly equivalent lattice parameters. Using synchrotron X-ray reflectivity and high-angle Bragg scattering we show that Fe(15Å)/Au(21Å) multilayers grown by sputtering exhibit different profiles for Fe/Au and Au/Fe interfaces. We analyze this in view of the action of Au as a surfactant during the growth of Fe. Similar Fe/Ag multilayers have considerably worse interfacial quality since Fe and Ag do not interdiffuse, and this leads to the result that the interfaces cannot be described by error function profiles. Using non-specular x-ray reflectivity we show that whereas Fe/Au interfaces are self-affine, Fe/Ag interfaces exhibit two regimes of scaling behavior as a function of spatial wavelength. This suggests that two different mechanisms are important in describing the growth of Fe/Ag films.

We report on the differences in the epitaxial growth mechanisms between Ge1−xCx (O<x<0.1) and Ge1−x−ySixCy (x=0.2, 0<y<0.05) alloys grown on Si(100) using low temperature( 200°C) molecular beam epitaxy. Thin films (50˜65nm) were characterized in situ by RHEED and ex situ by transmission electron microscopy and x-ray diffraction. With increasing C concentration, the microstructure of both Ge and GeSi alloys changes from 2D layer growth to 3D islanding. The d400 spacing of the relaxed alloys decreases marginally, with a maximum of 1at.% C being substitutionally incorporated. Ge-C films with higher C content have a high density of planar defects, typically twins and stacking faults. The addition of 20% Si does not appear to increase the amount of substitutional C in the films. Rather, the additions of 20% Si to Ge-C alloys somehow seems to enhance the tendency for the formation of planar defects.

Molecular beam epitaxial growth of Ge on Si(110) surfaces reveals interesting aspects of the heterogeneous nucleation of coherent Ge islands. Cleaning of the Si substrate by desorption of a passivating oxide layer at high temperature creates surface pits. Two sets of experiments, including deposition of Ge on as-cleaned substrates, and surfaces with a thin Si buffer layer are compared to illustrate the nucleation behavior of Ge. Typical Ge deposition temperatures range from 600°C to 725°C.

For Ge deposition on as-cleaned surfaces, the faceted edges of pits serve as preferential sites for the heterogeneous nucleation of coherent Ge islands. Experiments were also performed on surfaces with thin (˜20nm) Si buffer layers grown on the as-cleaned surface. Though the faceted pits have not been completely covered by the Si buffer layer, they have decreased in lateral size. In addition, the Si(110) surface shows ledges that are formed along specific crystallographic directions. Ge deposited on the Si buffer nucleates first at the corners of the pits, in an interesting dipole orientation, as well as along the ledges on the surface.

The growth of Au on TiO2 (110) has been examined by high resolution fielc emission scanning electron microscopy (HRSEM) in combination with electror backscattered diffraction (EBSD). The Au was evaporated under UHV conditions onto stoichiometric TiO2 (110) surfaces in the temperature range from 300 to 475 K. At 300 K and for low coverages (<1.5 nm), Au grows as discrete particles. For thicker coverages (>1.5 nm), the particles coalesce to form a network, but percolation is absent even aftel deposition of 5 nm Au. Upon annealing or deposition (≥ 5 nm) at 475 K, the particles, appear clearly faceted and are oriented along specific crystallographic directions. EBSE patterns taken from individual particles reveal two equivalent domain orientations rotated by 180° with epitaxial orientation relationships corresponding to (111)Au//(110)TiO and [110] // [001]TiO2 (Orientation I) and [110] // [001]TiO2.(Orientation II)

We demonstrate that the formation of TiSi2 for Ti films deposited on undoped Si(100) substrates leads to rougher surfaces than for Ti films deposited on undoped poly-Si substrates. The successive formations of TiSi2, C49 (high resistivity) and C54 (low resistivity) phases from titanium films deposited on either Si(100) or poly-Si substrates were monitored in situ during rapid thermal annealing using elastic light scattering, x-ray diffraction and resistance measurements. For both types of substrates, the roughening occurs only during the formation of the first TiSi2, phase (C49) by light scattered from lateral length scales of ˜0.5 μm. Atomic force microscopy (AFM) images. quantified using Fourier filtering, are consistent with the light scattering results.

The new kinetic model for homoepitaxial growth on a singular surface is presented. The model combines a familiar rate equations approach and a concept of a feeding zone that allows to connect the growth processes in neighbouring monolayers. The model involves the irreversible 2D nucleation, growth and coalescence of the islands in each growing monolayer and consists of an infinite set of coupled rate equations for the adatom and island densities and coverage in successive monolayers. With using this model the temporal evolution of the surface morphology (rms roughness and RHEED intensity) is studied. It is shown that the growth mode is fully determined by a single dimensionless parameter μ = D/J where D and J are the normalized surface diffusion coefficient and deposition flux, respectively. There exist five regions of m corresponding different growth regimes varying from smooth 2D layer-by-layer growth at sufficiently high values of μ (>108) to very rough Poisson-like random deposition growth at μ<10−4. The extension of the model to the case of heteroepitaxy is also discussed.

Recently we developed a method that allows to derive a height-height autocorrelation function (ACF) for a randomly rough surface of a thin – film growing by the 3D island mechanism. In this paper, the ACF and roughness spectrum for several versions of the island growth model deduced by this method are presented and discussed. In the model dimension d=1+1 the ACFs are deduced in exact analytical form, and for d=2+1 the ACF' s are calculated numerically. In both model dimensions for the rms roughness the universal analytical expression connecting its with physical deposition parameters is derived. The impact of the growth hillock shape and the hillock space distribution are studied. It is shown that the ACF form is determined by the hillock space distribution and in the cases of an ideally random Poisson distribution and slightly ordered distribution the ACF is nearly gaussian although the surface profile height distribution is non-gaussian. The rms roughness is strongly dependent on the hillock shape while the autocorrelation length is determined by the hillock number density. The theoretical predictions are compared with published TEM and STM-data and the scaling behaviour of the rms roughness is analysed.

SrBi2Ta2O9 (SBT) films have been prepared by MOCVD processes. The phase formation, surface structure, morphology and surface roughness of SBT films on Pt/Ti/SiO2/Si wafers were measured by XRD, SEM, AFM and ellipsometry. It was found that amorphous SBT formed below 500°C, amorphous and polycrystalline growth occurred successively between 500°C and 650°C. The surface roughness of the SBT thin films also increased with increasing deposition temperature. The AFM results showed the nucleation of SBT started by island formation, then continued across the surface of substrates at lower deposition temperatures. When the SBT film was deposited at higher temperatures, the nucleation and grain growth occurred at the same time, resulting in an inhomogencous structure and much higher surface roughness. Therefore, a two step process is used to improve surface roughness and interface mismatch between film and substrate. In addition, the relationships between surface structure, morphology and the electric properties of SBT thin films were also investigated.

Three-dimensional Kinetic Monte Carlo simulations were used to model the deposition of a hyperthermal molecular beam at varying angles of incidence. The simulations incorporate incident atom-substrate interactions, many layer growth, and attempt to mimic deposition and growth of Si on a Si(100) substrate. At high angles of incidence, the formation of “flake”-like structures are seen. The growth of the flakes follow the same general trends as previous two-dimensional simulations where non-local shadowing produces a porous thin film and the columns grow into the incident beam. Increased substrate temperature increased the widths of the flakes perpendicular to the path of the beam and allowed the grown film to remain defect-free for a time before columnar structure begins.