We study the nature and spectrum of fundamental vibrational excitations in the assembly of misfit accomodating dislocations. The physical system considered is a Lomer array of equispaced dislocations in a lattice-mismatched interface between a substrate and a thin film with similar elastic properties. Within the framework of the isotropie elasticity theory we calculate the effective force constants of harmonic springs that establish the dynamical correlations between the oscillating dislocations. Our interest is concentrated on the case where the thickness of the overlay er is much less than the separation between the nearest-neighbor dislocations. We show how in this situation the free surface of the film exerts a profound screening influence on the dislocation-dislocation correlations; it is demonstrated that the force constants exhibit sensitive dependence not only on the lattice mismatch, but also on the film thickness. We then deduce the dispersion of collective dislocation excitations and find that the latter propagate along the interface much more slowly than the ordinary sound waves. Our results reveal the manner in which the thickness of the film controls the magnitude of the vibrational quantum that characterizes the natural oscillations of arrayed dislocations. It is shown that this anomalous energy quantum manifests itself in the low-temperature heat capacity of the misfit array.

A magnetic rhombohedral PrCo2Cx (x=0.05∼0.25) phase (space group R3m), which is heavily twinned along the {110} and {211} planes, was identified. The twinning mechanism was explored by analyzing the reduction of crystal symmetry due to the cubic-rhombohedral phase transformation. The origin of the twinning and the formation of four twin variants were attributed to the insertion of carbon interstitials into Co4 tetrahedrons along the 3 axis in the rhombohedral lattice, which corresponds to one of the four equivalent <111> axes of its parent PrCo2 cubic-lattice.

Differences in the adhesion and fracture toughness of aluminum films on sapphire due to the presence of controlled contaminants are being investigated. Adhesion is evaluated by use of nanoindentation and continuous scratch tests. A comparison was made of the properties of textured thin films of aluminum (178 to 1890 nm) that were vapor deposited onto (0001) oriented sapphire substrates. A very thin (1 nm) layer of carbon was deposited at the interface of selected samples prior to the vapor deposition of the aluminum. Spalling was observed during continuous scratch testing in specimens with carbon at the interface but not in specimens without carbon at the interface.

Initial phase formation in thin film and bulk Fe/Si couples has been investigated using transmission and scanning electron microscopy (TEM and SEM). For the thin film couples, ≈165 nm of Fe was deposited by electron beam evaporation onto <111> oriented Si substrates. SiO2 capping layers (≈100nm thick) were used to protect the Fe from oxidation during subsequent annealing. Bulk diffusion couples were fabricated by clamping together polycrystalline Fe pieces and <111> oriented single crystal Si pieces and sealed in evacuated (≈10-4 torr) quartz capsules. Annealing of thin film couples was done at temperatures ranging from 300°C to 500°C for up to several hours. Bulk couples were annealed at 700°C for up to ≈1000hrs.

Interfacial reactions were detected in as deposited thin film couples. A layer =5nm thick was identified, through electron diffraction, as poorly crystalline off-stoichiometric Fe3Si. Iron was the major diffuser during the formation of Fe3Si. During annnealing off-stoichiometric Fe3Si transformed to stoichiometric Fe3Si. FeSi was the next phase to form - initially detected after annealing at 300°C for 3 hrs. Similar results were obtained for bulk couples. The first phase to form was ordered stoichiometric Fe3Si (initially detected after 7 hrs), followed by FeSi (≈23 hrs) and then FeSi2 (>200 hrs). The formation behavior of these phase is discussed.

On the basis of an assessment of both the phase-formation energies and the energies of interfaces and grain boundaries the driving force for solid state amorphization (SSA) in crystalline Ni- crystalline Ti and amorphous Ni- crystalline Ti multilayers was calculated. It followed that the structure of the interfaces and grain boundaries, and thus their energies is of crucial importance for the occurrence (or not) of SSA. The SSA behaviour of the two types of Ni-Ti multilayers upon annealing was investigated using X-ray diffraction and (high resolution) transmission electron microscopy. The crystalline Ni- crystalline Ti multilayers showed SSA at both the Ni-Ti interfaces and the Ti grain boundaries. The amorphous Ni- crystalline Ti multilayers exhibited SSA at the Ti grain boundaries only. These observations agree with the predictions from the thermodynamic model.

The in-depth distribution of phases in c-BN films deposited by Ion Beam Assisted Deposition (IBAD) at two different ion energy values (300 and 600 eV) was investigated using the quantitative IR transmission measurements and the HREM technique. Whatever the value of the studied ion energies, the characteristic layered morphology of c-BN film is observed including the interfacial sp2 zone between the substrate and the c-BN volume. In the case of 600 eV ion energy, this interfacial zone is less well-defined in comparison with 300 eV ion energy and the corresponding thickness is more important. Furthermore, the h-BN phase is more diluted within the c-BN film volume showing that the purest phase concentration of c-BN is found for the lowest ion energy, i.e. 300 eV.

An investigation of the formation behavior and mechanism of onion like fullerene / metal polycrystalline film under electron beam irradiation is presented. Metallic nanoparticles of Al, Au and Pt having diameters of 1∼35 nm, were supported on an amorphous carbon film with thickness of about 20 nm. The amorphous carbon film transformed into onion-like fullerene film under electron beam irradiation, with intensity about 1020e/cm2·sec using high resolution transmission electron microscopy. The transformation mechanism and growth morphology have been investigated. It is found that the nucleation and growth process of onion-like fullerenes from amorphous carbon were divided into several steps: Firstly, a few elliptic shells of carbon were induced under Al, Au or Pt nanoparticles; secondly, a gradual reorganization took place into the structures composed of quasi-concentric spheroid or sphered graphite, i.e., onion like fullerenes, and finally, fullerenes were bonded to each other into a film.

The crystal textures of polycrystalline films of gold-palladium couples on an oxidized silicon (100) substrates were investigated via x-ray diffraction (XRD) pole figures. Studies were performed on both as-deposited and thermally annealed films. Scanning electron microscopy (SEM) was used to examine the microstructures of the seed layer thin films as deposited. The {111} texture formation of gold-palladium thin film couples displayed a strong dependence on the nature of the underlying seed layer. Gold films deposited on a palladium seed layer revealed much less degree of {111} texture, than gold films deposited directly on a silicon dioxide surface. In contrast, palladium films deposited on polycrystalline gold films showed a higher degree of {111} texture, compared to palladium films deposited directly on silicon dioxide. The {111} texture of annealed gold-palladium alloy thin films was greater for palladium on gold than for gold on palladium. These results are interpreted in terms of the gold-palladium diffusion mechanism and the interaction of the condensing metals with the oxygens of the SiO2 substrate surface.

A simple computer model is proposed to simulate the microstructural evolution of Al-4wt%Cu lines. The model includes the coarsening and pinning of Al2Cu precipitates which occur during normal grain growth. This model is used to explore how Cu-rich precipitates evolve during normal grain growth, and how they affect the evolution of grain structure from polycrystalline to bamboo.

Transmission electron microscopy (TEM) in both cross sectional and plan view is used to study the effect of annealing Ag-Ti bilayers deposited on SiO2/Si substrates in an NH3 ambient. The resulting structure, texture and grain size are investigated. Comparisons are made between films annealed at 400, 500 and 600 °C. Silver films show increasingly strong <111> texture with annealing temperature while exhibiting a bamboo-like grain structure at 600 °C. Considerable grain growth with lateral grain sizes of up to 5 times the thickness of the Ag film is observed at 600 °C. The grains typically extend through the Ag film thickness. The Ti/SiO2 interface uniformity and the absence of voids at the substrate surface are positive indicators of the role of titanium as a good adhesion promoter. At 600 °C, a uniform TiN encapsulation layer is observed on the Ag surface.

The texture in polycrystalline Ag thin films prepared by e-beam evaporation has been characterized by an x-ray diffraction technique as a function of underlayers and encapsulation temperatures. The Ag films deposited on Ti layers showed a strong <111> fiber texture with a fiber axis parallel to the film normal, whereas an almost random orientation was observed in the Ag films on Cr layers. This underlayer dependence of texture is associated with the lattice match between Ag and underlayer metal. In addition to <111> texture, the Ag films on Ti also exhibited a <511> texture component, which is the result of twinning of <111> -oriented grains. After the encapsulation process, the <111> texture in the Ag films on Ti was significantly improved, as evidenced by an increased (111) diffraction intensity and a slightly narrower space distribution of the texture along the fiber axis. The highly textured Ag films are expected to exhibit an improved electromigration resistance.

Photovoltage images of Cu(In,Ga)Se2 solar cells taken using near-field scanning optical microscopy (NSOM) show reduction of photoresponse along grain boundaries. Two factors might be responsible for this contrast. The first is that the topographic changes associated with the grains could cause the NSOM tip to move further from the sample, resulting in a reduction in photoresponse. The second possibility is that the contrast is due to real physical properties of the sample, e.g. higher recombination velocities near grain boundaries. We show convincing evidence that the major contribution to the contrast in the photovoltage images is due to the latter.

We present an investigation of structural changes occurring in bilayer stacks with crystalline columnar growth when one of the layers is substituted by layers known to grow amorphous. In Co/Cu multilayers the Co layers were substituted by CoZr layers of varying Zr content and layer thickness. Structural characterisation was performed by transmission electron microscopy (TEM). We show that the amorphisation of the CoZr layers leading to a destruction of the columnar growth depends both on the Zr content and on the thickness of the CoZr layers. Additionally a change to textured growth with a <111> normal to the substrate occurs with increasing Zr content. We explain our observations by a simple picture based on the hard sphere model.

TiN films were obtained by Chemical Vapour Depositon (CVD) under different deposition conditions. Their grain structure, morphology and preferred crystal orientation were investigated. It was observed that well-defined columnar grams developed under conditions of atmospheric thermal CVD, giving rise to strong preferred orientations. In this study, grain structures of CVD-TiN films were classified with respect to the substrate temperature. Films of zone I structure were obtained at 1173K (0.35Tm), and those of zone II were obtained at 1223K (0.38Tm). Crystal shape of the zone II columnar grains was influenced by the partial pressure of TiCl4 (PTiCl4), and the crystal orientation of films was related to the crystal shapes. Columnar grains increased their thickness during deposition process under conditions of low PTiC14 and high temperature (>1250K). The increase rate of grain size had a similar time dependence to that of normal grain growth. The “quadrangular-shaped” and “star-shaped” columnar crystals were formed. They consisted of several crystals and contained twins. Their microstructures were observed in relation to their crystallographic features.

Polycrystalline silicon-germanium alloys (poly-SiGe) are deposited by chemical vapour deposition at atmospheric and reduced pressure. The stress, as well as its profile along the growth direction, are measured. Depending on the deposition pressure the stress can be compressive or tensile, the profile of the stress is in both cases rather uniform. The behaviour of the stress as a function of annealing temperature is also investigated. Films which are compressive as grown can be made tensile by annealing, films which are tensile as grown remains tensile even after high temperature annealing.

Magnetron sputter deposition was used to fabricate body centered cubic (bec) and A-15 crystal structure W thin films. Previous work demonstrated that the as-deposited crystal structure of the films was dependent on the deposition parameters and that the formation of a metastable A-15 structure was favored over the thermodynamically stable bec phase when the films contained a few atomic percent oxygen. However, the A-15 phase was shown to irreversibly transform into the bec phase between 500°C and 650°C and that a significant decrease in the resistivity of the metallic films was measured after the transformation. The current investigation of 150 nm thick, sputter deposited A-15 and bec tungsten thin films on silicon wafers consisted of a series of experiments in which the stress, resistivity and crystal structure of the films was measured as a function of temperature cycles in a Flexus 2900 thin film stress measurement system. The as-deposited film stress was found to be a function of the sputtering pressure and presputter time; under conditions in which the as-deposited stress of the film was ∼ 1.5 GPa compressive delamination of the W film from the substrate was observed. Data from the thermal studies indicated that bec film stress was not affected by annealing but transformation of the A-15 structure resulted in a large tensile increase in the stress of the film, regardless of the as-deposited stress of the film. In several instances, complete transformation of the A-15 structure into the bec phase resulted in ≥ 1 GPa tensile increase in film stress.

We show that stress in sputter-deposited silicon nitride films can be controlled, making either compressive or tensile stress films achievable. These films were deposited via reactive rf magnetron sputtering using an elemental Si target and N2 as a reactive gas in an Ar ambient. Variation of stress as a function of deposition pressure and N2/Ar gas mixture ratio was examined over a wider range of these two parameters than in previous work. More importantly, this parameter space includes conditions which produce near-stoichiometric Si3N4 films over a wide range of deposition pressures. We demonstrated that both low compressive stress and even tensile stress can be achieved at the proper deposition conditions. The film stresses as a function of deposition pressure or N2/Ar gas flow ratio are explained in the context of previously developed peening models.

Doped and undoped zinc oxide fims are widely used as transparent window and contact layers in thin film solar cells. Up to now the role of film stress on the layer and solar cell properties was not investigated in detail. In this paper the influence of the energy input from the magnetron sputtering plasma on the structural and electrical layer properties was investigated. The energy input during the deposition could be varied by using a simultaneous RF- and DC-excitation at a fixed sputtering pressure. The energy and the density of the ions bombarding the substrate at floating potential have been measured by a plasma monitor and by a Langmuir probe. Plasma monitor measurements displayed the different plasma potentials and ion energies at a floating substrate. While the DC-discharge is characterized by low plasma potentials and low ion energies, the RF-mode shows up to 2.5 times higher ion energies of EAr++ ≈ 50 eV.

The structural and electrical properties of doped and undoped ZnO-films, deposited with different RF/DC-power ratios can be explained by taking into account the different ion energies and densities during the deposition. Higher ion energies (RF-excitation) improve the structural quality and reduce the film stress, which decreases the specific resistance, both by a higher charge carrier mobility as well as higher carrier concentrations. The lowest resistivities and film stresses were ≈ 6–10-4 Ωcm and 0.5 GPa, respectively. Layers with different film stresses have been used to prepare CuInS2/CdS/ZnO-solar cells. Lower stress in the ZnO-films leads to higher cell efficiencies. For the first time, these results can explain why RF-sputtering is almost exclusively used for the window preparation of thin film solar cells.

BaxSr1-xTiO3 (BST), PbZrxTi1-xO3 (PZT) and two layer PZT-BST films were prepared on Pt, Si(100) and Si(111) substrates by a sol-gel method. XRD analysis shows that the PZT films on the Si(111) substrates tended to be preferentially oriented in the (110) direction. The nondestructive readout of the state of ferroelectric polarization was investigated by three methods: the pyroelectric effect, the non-linearity of the capacitance and the field effect in MOS structures. It is shown that all three methods provide nondestructive readout, and the choice between them depends on the intended use.

We apply the technique of High Resolution X-ray Reciprocal Space Mapping (HRRSM) to the study of wavy layers in InGaAs multilayer thin films on InP substrates. By accurately measuring the positions of the layer Bragg peaks in reciprocal space we obtain measurements of the compositions and residual coherency strains in the layers. We discuss the contributions to the diffuse scatter around the Bragg peaks from factors such as lattice tilts and interface roughness. By modelling the shapes of the diffraction profiles we obtain measurements of mosaic block size both perpendicular and parallel to the multilayer/substrate interface. We conclude that the wavy interface morphology arises predominantly from layer thickness variations rather than lattice tilts.