Shape memory alloy TiNi thin films on GaAs have been investigated. A series of TiNi compositions were electron beam deposited on GaAs initially as thin multilayers of Ti and Ni. The intermetallic phase of TiNi was formed by annealing and complete intermixing of the multilayers at 370oC. The intermetallic phases were investigated with X-ray diffraction techniques. The annealing kinetics and resistivity investigations were carried out in order to minimize the sheet resistance of the intermetallic phase. TiNi Schottky barriers on GaAs have been fabricated and their performance will be reported. Additional investigations on surface morphology using the energy dispersive spectroscopy as well as TEM investigations show the correlation between microstructure, intermetallic phase formation and sheet resistance.

We have studied the formation of InAs quantum dots (QDs) grown by molecular beam epitaxy on top of GaAs and 2 ML-thick AlAs layers in the temperature range from 350 to 500°C. In-situ reflection high energy electron diffraction (RHEED) patterns were recorded in real time during the growth and analyzed to characterize the 2D-to-3D transition on the surface, including QD formation, and ripening process. The kinetics of QD formation was studied using the InAs growth rates ranging from 0.01 to 1 ML/s and different ratios of As2/In fluxes. RHEED patterns and ex-situ atomic force microscopy images were analyzed to reveal the development of sizes and shapes of the single-layer and stacked QD ensembles. The critical InAs coverage for QD formation was shown to be consistently higher for dots grown on the AlAs overlayer than for those grown on GaAs surface. Self-assembly of multilayer QD stacks revealed the reduction of the critical thickness for dots formed in the upper layers.

For dry high speed cutting the oxidation resistance of the protective hard coating of the cutting tool surface is very important. Therefore the effects of heat treatment on a TiAlN based hard coating deposited by the combined cathodic arc unbalanced magnetron sputtering technique have been studied using cross sectional transmission electron microscopy (XTEM) and energy dispersive X-ray analysis (EDX). The combination of these analytical techniques revealed the diffusion paths and preferences in diffusion of various coating and substrate elements in a physical vapour deposited (PVD) type coating after heat treatment. The structure comprises a ~2 µm thick TiAlCrYN coating on top of a 0.25 µm thick TiAlCrN base layer deposited on a stainless steel substrate. In the as-deposited sample Y was distributed in a fine layered structure (1.7 nm) throughout the coating. The coating was heat treated at temperatures between 600 °C and 900 °C in air for 10 hrs duration. With increasing temperature the microstructure changed gradually from interrupted columnar growth to a fully columnar structure at 900 °C as observed with XTEM. EDX analysis after heat treatment at 700 °C showed the presence of substrate elements Fe and Cr mainly at column boundaries in the base layer. In contrast no evidence of substrate elements could be observed in the TiAlCrYN coating, thus showing a sharp change in elemental composition concerning Cr and Fe between base layer and coating. This indicates that Y segregation in the TiAlCrYN coating along column boundaries inhibited column boundary diffusion of the substrate elements Cr and Fe. Energy dispersive X-ray distribution maps recorded after 800 °C annealing showed distinct segregation of Y along the column boundaries. The substrate elements, Fe and Cr, were observed through the coating along column boundaries up to 0.95 µm from the base layer/coating interface. After heat treatment at 900 °C the substrate elements had diffused from the substrate/coating interface to the coating surface. Y out-diffused, too and was concentrated adjacent to TiO2 crystals in the oxide layer.

Copper is becoming the metal of choice for interconnect applications in integrated circuits due to its lower electrical resistivity and higher electromigration (EM) resistance. The effects of grain size, preferred orientation, and interfacial layers, on electromigration in Cu lines are, however, not yet well understood. In this paper, we compare the EM characteristics of epitaxial Cu(111) lines with that of polycrystalline lines with a (111) texture. We also investigate the effects of Ta, TaN and TiN interfacial underlayers and Cu crystal quality on the EM response of epitaxial Cu(001) lines. EM tests were carried out on 2-μm-wide Cu lines at a constant current density between 0.02 and 3.5 MA/cm2 in an Ar ambient at 300 °C. Our results indicate that EM resistance of both (111) and (001) epitaxial lines have a higher mean time to failure (MTTF) than polycrystalline Cu lines. The presence of a TiN or TaN interfacial layer increases the MTTF in Cu(001) films, while a Ta underlayer degrades EM resistance. X-ray diffractograms indicating a smaller full-width-at-half-maximum of Cu(001) films on nitride underlayers suggest that lower defect densities in these Cu films is the likely reason for improved EM resistance. Both (111) and (100) orientations fail by formation of faceted voids.

We have examined the novel heteroepitaxy of magnetic oxide thin films on ultra-smooth sapphire substrates by laser MBE for fabrication of low-dimensional structures. Employing the atomically controlled substrate surfaces with atomic steps and terraces, we demonstrate the deposition of magnetic oxide nanowires (~0.5 nm high and ~20 nm wide) and nanodots of (Mn, Zn) ferrite, Fe3O4 and NiO.

Magnetoresistance measurements were performed in magnetic fields up to 5 T, to examine the effects of boron doping on the electron transport properties of Ni3Al thin (500 Å, nominal, thickness) films. Both a doped (~200 ppm B) and undoped film were investigated. Four-probe magnetoresistance (magnetic field = 50 G and 5 T) measurements indicate that both samples undergo a phase transition in the 200 K – 300 K temperature range.

The chemical and microstructural properties of a surface have a strong influence on the growth mode and the morphology of a film evaporated onto this interface. Changes in the growth stress of thin titanium films, measured in situ by a cantilever beam technique, evaporated under UHV-conditions are used to monitor the chemical and microstructural properties of a substrate surface. The starting substrate film used in this study was a quasi single-crystalline TiO2-film (d=50 nm) prepared by reactive evaporation of titanium in an oxygen atmosphere and subsequent annealing (20 min, 400°C). The Ti-growth stress on this substrate is compressive up to monolayer coverage and tensile at higher film thickness, which is interpreted to indicate a strong interaction between TiO2 and the arriving Ti atoms at the interface during monolayer formation and strained (tensile) layer epitaxy at higher film thickness. In a second series of experiments the TiO2-film was covered with Al-overlayers of varying thickness. Due to oxygen interdiffusion from the TiO2-film an amorphous Al-oxide layer is formed at the interface eliminating the high degree of order of the substrate TiO2-film. On this amorphous substrate the stress vs. thickness curve of the Ti-film, in terms of our stress model, is interpreted to indicate island formation and growth of a polycrystalline Ti-film. At Al-layer thicknesses above about 3 nm the Al-interface becomes metallic. The structure of this Al-surface depends on the film thickness and substrate temperature during its deposition. During deposition of the first Ti-monolayer on metallic Al a large incremental tensile stress (up to 45 GPa) is measured. The magnitude of this tensile stress is closely related to the surface microstructure of the Al substrate. The surface roughness deduced from the tensile interface stress is compared with the surface roughness measured by AFM.

For comparison, analogous experiments were made with Al2O3/Al substrate bilayers. The results of these experiments qualitatively agree with those on the TiO2/Al-substrate. The general shape of the stress vs. thickness curve is comparable, however quantitative differences are interpreted to be due to differences in the structure and/or chemical composition of the substrate Al-film.

Silicon-germanium virtual substrates have been synthesized by low-pressure chemical vapor deposition. We obtained threading dislocation densities ranging from 105 to 106 cm−2, surface roughness ranging from 1.5 to 4 nm, and also cross-hatch pattern densities, depending on the grading rate and top layer germanium composition. For the typical sample, which has a linear-graded structure with a grading rate of 20%/[µm, and germanium composition of 30 % at the top layer, we obtained dislocation densities of about 106 cm−2 and root mean squared surface roughness of about 3 nm. The obtained dislocation densities are equivalent with the virtual substrates synthesized by ultra-high vacuum system. On the other hand the surface roughness is superior to the typical reported values. In this study three kinds of structures, i.e. linear-graded, stepwise, and graded-step structures, were considered. We found the defects are effectively reduced by introduction of an optimum number of steps in the graded layer.

The effects of laser energy fluence on the growth of pulsed laser deposited ZnO thin films on c-plane sapphire substrates were systematically investigated by using x-ray diffraction, Rutherford backscattering spectrometry with ion channeling, and scanning electron microscopy techniques. Optical and electrical properties of the ZnO epilayers were characterized by using ultraviolet-visible transmission spectroscopy and Van der Pauw measurements, respectively. It was found that the laser fluence has strong effects on the crystalline, optical and electrical qualities of the ZnO films. At low laser fluence, ZnO film grows via 3D-island mode with low deposition rate, loss of Zn near the surface and particulates on top of the film. High laser fluence may also cause simultaneous multi-layer growth and the degradation of crystalline, electrical, and optical quality of the ZnO films. The optimal laser fluence window was found between 1.2J/cm2 and 2.5 J/cm2 for obtaining high quality ZnO films for optoelectronic applications. The dependence of laser fluence on the ZnO growth mode, surface morphology and electrical and optical properties is discussed.

Up to date, different groups have reported ordering phenomena in nitride alloys like InGaN or AlGaN. These evidences of ordering during and after growth lead us to study the atomic arrangement of Al and Ga on site III in the AlGaN alloy using a thermodynamical approch. We have defined the enthalpy and the entropy of our system using the Keating model and the cluster variation method limited to the first coordination shell. This study gives us a good way to understand ordering, and moreover to see why at three special compositions (25%, 50% and 75%), the alloys have good chances to present a better crystalline quality than in other cases.

We have grown AlGaN samples increasing the Al composition by 10% steps, in the full range of composition from GaN to AlN. All the growth parameters were kept constant except for the alloy composition. X-Ray diffraction measurements performed on these samples indicate that FWHM increases linearly with Al composition, except for three compositions, where according to our thermodynamical study, we observe an improved crystalline quality.

Novel Si-Al nanocomposite thin films were made by radio frequency co-sputtering of Si and Al with Al content from 0 at.% to 69 at.%. Microstructure and optical properties of the films were characterised by conventional and high resolution transmission electron microscopyand spectrometry in the wavelength range from 200 to 3000 nm. The film microstructure consisted of Al nanoparticles (2-9 nm) embedded in an amorphous Si-Al matrix. Optical absorption spectra of the films up to 50 at.% Al exhibited a sharp absorption peak below500 nm and relatively low absorption above 500 nm. In addition, the absorption peak shifted towards longer wavelengths and the general absorption above 500 nm increased remarkably as Al content increased. For the Si-69at.%Al films, however, an absorption plateau appeared between 300 nm to 700 nm and a second weak and broad absorption peak appeared at around 900 nm. The results are analysed and compared with the optical absorption predicted by various effective medium theories.

We report on an unusual phenomenon of pattern formation in the mixture of Ni and C60 codeposited on the single crystal of MgO(100). Under certain deposition kinetics an array of periodic stripes was formed. The stripes consist of sub-half-micrometer Ni droplets (embedded in the complex Ni-C base) and encompassed with a polymerized C60 rind. The stripes are bound to the thin double-layer platform consisting of the epitaxial Ni and amorphous C (a-C) layers. During co-deposition the C60 molecules partly disintegrate and transform towards the a-C structures. Accumulation of a-C (immiscible with Ni) may induce thermodynamic instability in the system and trigger the process of spontaneous partitioning. As a principal mechanism of the stripe formation a sequential drift and co-ordinate release of the incited instability was proposed.

Effects of phosphorus dopant on thin Pd and Pt silicide films on (100) Si substrates have been studied. As for the samples formed by implanting BF2 dopant into thin Pd films deposited on Si substrates and then annealing, the thermal stability of thin Pd2Si films can be improved relative to the control samples without dopant incorporation. The degree of improvement is affected by the fluorine concentration around the silicide/Si interface and thus the BF2 implant energy. On the other hand, as for the samples formed by implanting phosphorus dopant into thin Pd films and then annealing, both the thermal stability and the silicide conductivity of thin Pd2Si films can be significantly enhanced. The large improvements in the thermal stability and the silicide conductivity are nearly independent of the phosphorus implant energy, and which are primarily due to the formation of textured Pd2Si structures. In addition, the Pt silicides formed by implanting phosphorus dopant into thin Pt films and then annealing also show considerably improved thermal stability.

An analytical model taking into account the influence of capillarity on the process of changing the cross-sectional shape of a cylindrical liquid inclusion enclosed in an anisotropic crystal under non-stationary thermal conditions is suggested. It is shown that the capillary effect confines the possibilities for controlling the inclusion shape under non-stationary thermal conditions. The capillarity influence becomes stronger with decreasing cross-sectional area and increasing interfacial energy. The results of calculations of the limit inclusion shape under different thermal conditions are presented and discussed.

The growth of TixAly-alloy films was investigated by measuring the film stress during as well as after the film deposition under UHV-conditions with a cantilever beam technique. The alloy films were deposited on alumina substrates from two separate evaporation sources. The substrate temperature was varied from room temperature to 500°C and the alloy stoichiometry from Ti25Al75 to Ti75Al25.

At a substrate temperature of 200°C the dependence of the growth stress of the alloy film on stoichiometry is pronounced and varies from tensile stress in the case of titanium rich alloy-films to compressive stress in aluminium rich films. The stress changes after deposition at 200°C are negligible for titanium rich alloys but in the case of aluminium rich alloys small tensile stress changes are measured.

At a substrate temperature of 500°C the film stress is compressive and the dependence on stoichiometry is rather small. The stress vs. thickness curves of Ti25Al75-films, however, show unexpected oscillations during growth while at lower aluminum content stable stress curves are measured. The stress changes after deposition are large in each case, interpreted to indicate film recrystallisation and/or continued alloy formation.

In a second series of experiments we have measured the internal stress changes in Ti25Al75-alloy films during annealing. It can be shown that the changes in the film stress can be correlated with changes in the film microstructure seen in the electron microscope (TEM).

A rich variety of two-dimensional patterns can be formed in the early stages of film growth. In this paper, we will show that, when a surfactant layer is used to mediate the growth, a counter-intuitive fractal-to-compact island shape transition can be induced by increasing deposition flux or decreasing growth temperature. Specifically, we introduce a reaction limited aggregation (RLA) theory, where the physical process controlling the island shape transition is the shielding effect of adatoms stuck to stable islands on incoming adatoms. Also discussed is the origin of a transition of compact islands from triangular to hexagonal then to inverted triangular in Pt (111) homoepitaxy with the presence of CO adsorbates. We will provide a coherent and unified picture for the interpretation of these intriguing observations based on kinetic Monte Carlo simulations, with energy barriers from first-principles calculations.

The formation of the silicide MnSi1.7 by reactive deposition of Mn onto Si(001) has been studied using Sb as a surfactant. The growth was performed under UHV conditions by simultaneous or consecutive exposure of the Si substrates, held at high temperatures (550°C, 600 °C), to a flux of Sb and Mn atoms. The presence of Sb during the growth strongly increases the island density and changes the crystalline orientation of the MnSi1.7 grains. The morphology and the orientation of the resulting silicide are the same both for the deposition of Mn on a Sb terminated Si(001) surface and for the co-deposition of Mn and Sb on Si(001). A residual Sb coverage close to one monolayer (ML) at the sample surface has been determined for both of the preparation modes at Tsub = 550 °C. The transition from the growth mode without Sb to the surfactant-controlled growth has been studied for Tsub = 600 °C. It has been found that the silicide morphology and orientation strongly depend on the thickness of Sb pre-coverage, which was increased from 0 to about 0.7 ML (1 ML = 6.78·1014 atoms cm-2).

Field-dependent transverse susceptibility measurements based on a novel tunnel-diode oscillator (TDO) method were used to probe the magnetic anisotropy and switching in epitaxially grown CrO2 films on TiO2 substrates. The static field was applied in three different orientations (0°, 45° and 90° ) with respect to the magnetic easy axis. Singular peaks in the transverse susceptibility were observed that are associated with the anisotropy and switching fields in CrO2. Theoretical calculations based on a coherent rotation model display remarkable agreement with the experimental data. A new peak emerges at low temperatures and is identified to be a consequence of temperature-dependent magnetoelastic contributions resulting from the in-plane tensile strain in the films due to varying coefficients of thermal expansion in the film and the substrate.

Ultrathin iron films grown on Cu(100) have been found to exhibit a rich variety of structural and magnetic phases. In the present work, Fe/Ni bilayers have been prepared by molecular beam epitaxy to explore novel magnetic phenomena introduced by the ferromagnetic (FM) Ni underlayer. Unusual properties have been observed by measuring the temperature dependent magnetic properties. For 5.3 ML Fe on 7 ML Ni, a temperature dependent exchange coupling in the Fe film has been observed between the FM surface layer and FM interface layer.

We investigated the differences in the interface structures and magnetotransport properties between surfactant-mediated multilayers and normal ones. From the observations of RHEED and High-Resolution X-ray diffraction patterns, we confirmed that the surfaces of Fe/Cr(100) multilayers with Pb are flatter and the interfaces are sharper than one without Pb, which means that Pb operates as an effective surfactant. The magnetoresistance(MR) ratio of the multilayers prepared with Pb was larger than that of the multilayers prepared without Pb. The change of resistance with magnetic field was larger for the multilayers with a surfactant.