The microstructural evolution of ruthenium-silicon dioxide bilayer structures upon annealing is studied using transmission electron microscopy. SiO2/Ru/SiO2 structures, with thicknesses of 2/1/2 nm, 4/2/4 nm, 8/4/8 nm, and 20/10/20 nm, are formed by magnetron sputtering and annealed at 300 or 600°C. As-deposited films have grain sizes on the order of the Ru film thickness. After annealing at 600°C, significant grain growth is observed for all thicknesses, such that the final grain sizes are approximately 3 to 20x greater than the original film thickness. The largest increase in the average Ru grain size is observed for the 2 nm thick ruthenium film possibly due to the coalescence of Ru grains. The coalescence of the Ru particles in the 1 and 2 nm thick films results in the formation of lamellar Ru grains, which disrupts the contiguity of the Ru film. In all other cases, the increase in grain size is attributed to normal grain growth, but the formation of anomalous spherical grains is also observed.

Ionized cluster beam deposition (ICBD) technique has been used to deposit Ag films on both Si(111) and Si(100) substrates. Sizes of clusters in ionized cluster beam are found to distribute in a range of 100–600 atoms/cluster. X-ray diffraction (XRD), and α-step profile methods are used to analyze the properties of Ag films. As a comparison, Ag films deposited by conventional evaporation are also investigated. Highly textured Ag films with strong (111) orientation on Si (111) have been obtained at high accelerating voltage Va=4kV. The crystallinity and surface flatness of Ag films can be improved by ICBD at high accelerating voltages.

The structure and phase composition of thin films formed by 40 KeV cobalt ion implantation into organic substrate (polyester) were studied by transmission electron microscopy in conjunction with electron diffraction. Varying current density and dose implantation over the range 0.3×1016 – 2.4×1017 cm-2 we obtained island-like cobalt films of different type as well as labyrinth-like structure at the highest dose value. The granulometric and morphologic parameters were derived from the micrographs of the investigated films. Both amorphous state and α-Co crystalline lattice of cobalt granules were established from electron diffraction patterns of synthesized films. Along with discontinuous films, we formed monocrystalline plates of α-phase cobalt under the determined implantation regimes and conditions. Cross-section images of synthesized films showed that films are of about 300 Å thick and buried at the depth of 150 Å from the principal surface of the polyester.

A quantitative description of the nucleation and growth kinetics determining the interface reactions between two phases is given. Particular focus is given to the understanding of the mechanisms causing the distinct phase selection occurring during the early stages of interface reaction. Thereby the microstructure of the parent phases and the new phases formed are also taken into account and discussed with respect to their influence on the phase selection. The conclusions are applied to the results of two model systems, Al-Ni and Zr-Ni.

The paper is built around a nonexhaustive review of the literature on the role of grain boundaries in reactive phase formation. Examples are chosen to illustrate these effects in silicide and oxide growths, and later on in metal-metal interactions. A short section deals with the effect of grain boundaries and grain boundary adsorption of impurities on the kinetics of growth and on the morphology of the growing layer. Some attempts at understanding the mechanisms of phase growth from the tracking of isotopes are briefly analyzed.

An alternative model is proposed to extend the conventional view of diffusion under a concentration gradient in a grain boundary phase of width δ. The conventional model is well developed and readily applied to the thickening kinetics of polycrystalline product phases in binary diffusion couples, however it is not readily extended to other phenomena of interest in thin films, i.e., the nucleation and growth of the product phase crystallites prior to formation of a product phase layer. In the alternative model presented here, non-equilibrium thermodynamics is used to define the chemical potentials, μi, for each atomic specie in the grain and interphase boundaries of a polycrystalline diffusion couple. The chemical potential difference for each specie between the bulk phases of the diffusion couple is partitioned between the driving force for grain boundary diffusion and that for interfacial reaction. This partition leads to a characteristic decay length that describes the spatial variation of μi. Numerical calculations of μi are used to show that boundary diffusion favors heterogeneous nucleation. Product nucleation in thin film reactions is seen to be similar to precipitation from a bulk solid solution.

The phase selection which is generally observed in the early stages of solid-state reactions was studied using Ti-Al multilayer films as a model system.

Although all Ti-Al intermetallic phases have similar driving forces of about 30 kJ/g-atom, TiAl3 is the only phase which is formed as long as the reactants are not consumed. The critical thickness beyond which a second phase is formed is larger than 100 μm. We found that the formation of TiAl3 takes place by nucleation and growth, demonstrating that the driving force available for first-phase formation is considerably reduced by a preceding formation of solid solutions. Furthermore, we observed that nucleation continues at later stages, indicating that non-equilibrium conditions are maintained which are possibly influenced by grain-boundary diffusion. However, the phase selection is determined by the different growth velocities, being much higher for TiAl3 than for all other phases.

Thermal interdiffusion mechanisms and kinetics have been studied for Ta-Permalloy (Ni80Fe20), Ta-Ni and Ta-Fe thin film couples, in the temperature range 300°C - 600°C. Interaction modes identified for the Ta-NiFe system include: fast diffusion of Ta into grain boundaries of NiFe, and nucleation and growth of Ni3Ta, with consequent depletion of Ni in the remaining NiFe, and eventual segregation of Fe.

X-ray photoelectron spectroscopy (XPS) has been used to investigate grain boundary diffusion of Ag through 250 Å thick Ni80Fe20 (permalloy) films in the temperature range of 375 to 475°C. Grain boundary diffusivities were determined by modeling the accumulation of Ag on Ni80Fe20 surfaces as a function of time at fixed annealing temperature. The grain boundary diffusivity of Ag through Ni80Fe20 is characterized by a diffusion coefficient prefactor, D0,gb, of 0.9 cm2/sec and an activation energy, Ea,gb, of 2.2 eV. The Ni80Fe20 film microstructure has been investigated before and after annealing by atomic force microscopy and x-ray diffraction. The microstructure of Ni80Fe20 deposited on Ag underlayers remained relatively unchanged upon annealing.

The atom probe/field ion microscope is introduced as a new powerful investigation device to study the early stages of the solid state amorphization reaction (SSAR). A bilayer of Zr and Co was condensed under UHV conditions on W wire tips and analyzed in a field ion microscope (FIM) combined with an atom probe (AP). The reaction of Co with Zr has been studied at room temperature. FIM pictures and AP analysis have shown that even at low temperatures an amorphous phase is formed at the Zr/Co interface and in the Zr grain boundaries. In these areas concentration profiles have been taken on a nanometer scale. Most likely, the extended solid solution of Co found in α- Zr grain boundaries causes the formation of the amorphous phase. Further, Rutherford backscattering spectrometry (RBS) suggests that even point defects and dislocations at the surface of an α- Zr single crystal are sufficient to initiate the SSAR between a polycrystalline Co layer vapour- deposited onto that single crystal.

Based on atom probe field ion microscopy (AP/FIM) studies, electromotive force (EMF) measurements and CALPHAD calculations we discuss the earliest stage of the solid state amorphization reaction (SSAR) in Zr/Co-layers. The AP measurements show that two amorphous phases are formed at the Zr/Co interface from the early stages of the reaction. The metastable two phase field between these amorphous phases is shown by direct measurement of the chemical potential of Zr in amorphous co-sputtered ZrCo alloys by the EMF method. The comparison between the atom probe data and the CALPHAD calculation shows that the interfaces between the different layers are far away from metastable equilibrium in the beginning of the reaction. The amorphous phase formation at the Zr/Co interface and in the hcp-Zr grain boundary is preceded by a supersaturation of the hep ZrCo solid solution that transforms polymorphically into the amorphous state.

The influence of the interfacial structure on the solid state reaction products in Fe-Ti multilayers has been studied using various preparation conditions and characterization techniques. Sharp and diffused interfaces were produced by using either sequential or co-evaporation in the interfacial region. The reaction product, in the case of the sharp interface, is the bcc supersaturated solid solution of Ti(Fe) while, in the case of the diffused interface, an amorphous phase is formed. Therefore, nucleating the amorphous phase at the interface by local co-evaporation alters the reaction path observed in Fe-Ti multilayers. The solid state reactions were studied using low and high angle X-ray diffraction and Mossbauer measurements. The results are discussed in light of recent thermodynamic calculations on the Fe-Ti system.

The diffusion in Au-Cu and Pt-Cu thin films has been studied by Rutherford backscattering spectrometry (RBS) under the kinetic regime “B” (within the temperature interval of 175–290°C) and “C” (room temperature). The 1,5-2,0 MeV He+ RBS spectra were taken using 14–18 keV resolution. The RBS spectra were changed to depth-concentration profiles for both bulk and grain boundary (GB) diffusion. Under the kinetic regime “C” the absolute values of GB diffusion coefficients were obtained. Under the kinetic regime “B” the triple products δKDb, (δ is the GB width, Db is the GB diffusion coefficient, K is the enrichment ratio) were obtained using Whipple’s and Gilmer-Farrell’s models. The activation energies for both GB diffusion and bulk diffusion were determined for Au-Cu system as well as for Pt-Cu system. The comparison between the data on the GB diffusion for kinetics “B” extrapolated to room temperature and the data on the GB diffusion for the kinetics “C” enables one to derive the product δK and to separate the contribution of segregation into the parameters of GB diffusion for systems under study.

Liquid metal grain boundary corrosion is discussed in terms of grain boundary etching profiles with equilibrium dihedral angles at the vertex of the grooves close to zero. It is shown that if the liquid solution is in equilibrium with the solid, then only grain boundary grooving occurs, producing small grooves growing in time as t½. However, if the equilibrium cannot be reached, a long liquid filled canal develops along the grain boundary, rapidly propagating with constant velocity. To stop such rapid grain boundary corrosion certain measures should be taken to reach the equilibrium state. This explains, for example, why removal of oxygen from the Nb(s)-Li(l) system prevents rapid grain boundary corrosion of Nb.

We have studied the chemical stability of reactively sputtered aluminum nitride film with plasma-enhanced chemical vapor deposited SiO2 and SiNx films. It was found that the PECVD SiO2 film reacted with A1N to form aluminosilicate (3Al2O3·2SiO2) at the SiO2/A1N interface after annealing above 550°C. The presence of Al-0 bonds at the SiO2/AlN interface was verified with x-ray photoelectron spectroscopy and x-ray induced Auger electron spectroscopy. The formation of aluminosilicate resulted in significant decrease in the wet etch rate of A1N layer. For SiNx/AlN/Si layered structure, no interfacial reactions were detected at the SiNx/AlN interface after annealing up to 850°C. These results confirm the thermodynamic predictions on the mutual stability of SiNx/AlN and SiO2/AlN.

While (Ti,Al)N coatings are well known and established in wear applications like drilling and milling, the corresponding TiC based metastable system Ti-Al-C is not well examined. This paper investigates the phase stability and the phase transition behaviour of post-deposition heat-treated Ti-Al-C coatings. The samples were annealed in a temperature range from 600–1400 °C in a high vacuum furnace. The influence of deposition parameters like coating compositions via the Ti/Al ratio and the metal/metalloid ratio on the properties were investigated. Another very important parameter in this investigation is the carbon carrier gas. Examined gases were methane, ethane, ethylene and ethine. The changes in microhardness, lattice parameters and particle sizes were analysed with respect to their temperature dependence.

The phase formation depends on the target composition and on the reactive gas. A formation of a metastable (Ti,Al)C phase can be observed. A higher C:H ratio of the reactive gas leads to better incorporation of carbon into the coating. An Al-loss independent of the coating composition begins 1000 °C. The microhardness increases with higher annealing temperature and decreases with higher Al-content.

The kinetics of formation of reaction layers at the interface between a Ti-based alloy (β-21s) and graphite blocks coated first, by CVD techniques, with a 100 μm layer of SiC and then either TiC or C were determined. The rate controlling step for reaction at 900°C and 10 MPa for up to 6 hours was found to be carbon diffusion through the reaction layer. The behaviour was found to be consistent with that of composite systems for prolonged heat treatment and the same growth behaviour was exhibited by both systems. Incubation times of 0.42 and 0.9 hours were determined for reaction layer growth in the TiC- and C-coated systems respectively. The reaction layer/Ti-alloy bond strength was good but all couples failed readily, especially if any C layers remained. The growth conditions of TiC coatings by reactive magnetron sputtering were determined for two different types of gas mixtures: CH4/Ar and C2H2/Ar. The composition and structure of the films were extensively studied.

Investigation of the formation of new metastable phases in alloy thin films requires ways of quickly determining the crystalline structure of samples with different compositions. We report a novel technique for acquiring structural information from films intentionally grown with a composition gradient. For example, binary metal alloy films were deposited using a phase-spread sputtering method. In this way essentially the entire composition range could be grown in a single deposition. By using a narrow incident x-ray beam and a translating sample stage combined with a position sensitive x-ray detector technique, detailed information of the metastable phase diagram can be obtained rapidly. Compositional resolution of the order of ±0.2% can be achieved, and is limited by the brightness of the x-ray source. Initial results from studies of phase formation in Zr-Ta alloys will be presented. Extensions of the analysis technique to ternary systems will be discussed.

Ni/Ti multilayered thin films can be efficient neutron guides and are therefore of great interest in neutron optics. Ni/Ti and NiC/Ti multilayers with various layer thicknesses were fabricated by magnetron sputtering and characterized by high resolution transmission electron microscopy (TEM). The TEM studies, performed on cross-sectional specimens, revealed that both kinds of layers were textured and snowed coherence in the growth direction. The presence of a 2 nra thick amorphous zone at the Ni/Ti interface in the carbon free thin films was also confirmed. On the contrary, sharp interfaces were obtained in NiC/Ti multilayers. The fine structure of the different layers will also be reported.

Magnetic recording media used today are based on sputtered cobalt alloy films with thicknesses in the order of 50 nm. As recording density is increased, the microstructure of the film must be controlled with increasing level of sophistication to achieve the magnetic properties necessary for good recording performance. Recording density has been increasing at the compound annual rate of 30%, and in recent years at a higher rate. Already, 1 Gb/in2 has been achieved in the laboratory [1], and 10 Gb/in2 is being contemplated [2]. In order to achieve such densities, microstructural characteristics such as grain morphology, size distribution, crystallographic orientation, and grain separation must be controlled with great precision, and their relationship to magnetic properties must be understood. The paper will describe the effect of sputter process conditions and the selection of magnetic alloys on the film microstructure and describe what might be required to achieve high recording densities. Particular attention will be paid to grain size distribution and grain separation. Grain separation is important for low noise performance of the media. Alloy selection and sputtering conditions can be manipulated to achieve different levels of separation between the grains.