Earlyllate transition metal systems such as Ni-Zr and Co-Zr exhibit solid state amorphization (SSA) in which the amorphous phase is formed by reaction between the crystalline elements. The rate of the amorphization is governed by the diffusion of the faster species, Ni or Co. Here results are presented on the homogenization of compositionally modulated thin films which show that the Zr diffusion is up to 106 times slower. The difference in diffusivities is correlated with atomic size. The consequences of the marked diffusional asymmetry are considered, particularly for the interpretation of results on the indiffusion of Co into amorphous Co-Zr. It is proposed that for amorphous alloys such as Ni-Zr and Co-Zr, changes in composition by rapid diffusion of Ni or Co can yield structures which are not in internal equilibrium. This would affect, for example, the validity of the common tangent construction as applied to predict the limiting compositions of the amorphous phase in contact with the elemental layers during SSA.

A quaternary phase diagram for Ti–W–N–Al has been calculated from existing thermodynamic data, and is used to predict the Al/TiW-nitride reaction. The predicted reaction products-TiAl3, WAl5, WAl12, and AlN—were observed by XRD and TEM in annealed Al/TiW(-nitride) thin films. The sheet resistance of Al/TiW films increased by an order of magnitude at 550°C, whereas the increase in the case of the Al/TiW-nitride films was not even two-fold. The formation of an interfacial AlN layer was observed in the Al/TiW-nitride metallization. This AlN layer limits the interaction between Al and TiW-nitride, thus providing good thermal stability.

We show that the decagonal Al3Pd phase can be formed by solid state reaction in lateral and conventional thin film couples of Al and Pd. The metastable decagonal phase forms after the initial growth of the Al3Pd2 compound.

Tracer impurity diffusion coefficients for Co and Hf were measured in a series of amorphous NixZr(1−x) alloys in the range 0.30 < × < 0.70 and at temperatures between 250°C and 350° C. The diffusion coefficients for the Co atoms are between 2 and 4 orders of magnitude greater than those for Hf depending on alloy composition and temperature. Diffusion coefficients for Hf are independent of alloy composition, whereas those for Co decrease strongly with increasing Ni content. The activation enthalpies of diffusion and the pre-exponential factors were both found to be significantly smaller for the Hf than the Co tracer impurity atoms. These results are discussed in terms of possible diffusion mechanisms in amorphous metallic alloys.

The phase- and grain microstructure and surface morphology of Al-Ge films formed by electron beam co-deposition have been studied as a function of the deposition temperature. X-ray diffraction, scanning- and transmission electron microscopy with x-ray fluorescence analysis were used to characterize the films. At room temperature and above, crystalline, phase separated films are obtained. The phase dimensions and surface roughness were observed to increase with the deposition temperature and the dependence yields activation energies for atomic migration consistent with a surface diffusion mechanism. The surface roughness is observed to reflect the microstructure under the surface.

A notable aspect of the copper-chromium phase diagram is the strong chemical aversion between the two elements. At room temperature, the solubility of chromium in copper is limited to .02%, while that of copper in chromium is believed to be even less [1]. The elements are even immiscible in the liquid state, exhibiting a miscibility gap which persists to an undetermined temperature. Cu-Cr alloys are of technological interest in applications ranging from electrical switches [2] to catalysis [3]. Fabrication of Cu-Cr alloys is hindered, however, by the large positive heat of mixing exhibited by the system. Cu-Cr multilayers are also of technological interest for application as soft x-ray mirrors [4]. Here the limited mutual solubility of the constituents is advantageous since interfacial mixing is reduced. In this study, we show that vapor deposition can be used to achieve complete solubility in the Cu-Cr system. On the other hand we present evidence suggesting that Cu-Cr multilayers possess sharp composition modulations with little interface mixing.

Pb1−xEuxTe alloys with 0.41 ≤ x ≤ 0.51 have been observed to be unstable when grown at a temperature of 573K on BaF2 substrates. The alloys are stabilized when a buffer layer of PbTe is grown prior to the growth of the Pb1−xEuxTe alloy. In this work, we have observed tha the solid solution of Pb1−xEuxTe with x ≈ 0.5 can also be stabilized by increazing the growth temperature to 623K. Our results suggest that the critical temperature for decomposition is in the range 573–623K. We present a qualitative phase diagram for Pb1−xEuxTe alloy films.

The tunability of synchrotron radiation was used to perform anomalous small angle x-ray scattering (ASAXS) experiments on amorphous metal-germanium (a-Mx Ge1−x) alloys with the aim of detecting and characterizing compohitioK modulation and phase separation. Small angle x-ray scattering is sensitive to electron density fluctuations on a scale of tens to thousands of Angstroms. The combination of SAXS with the anomalous dispersion effect allows one to distinguish composition modulation from density fluctuations arising from voids and defects. Data gathered from a-FexGe1−x and a-WxGe1−x samples in the low metal concentration regime show nanometer scale composition modulation. In these samples the density of Ge atoms is uniform throughout the sample. The small angle x-ray scattering arises from fluctuations in the density of metal atoms.

Formation of intermetallic phases upon heating of films composed of alternating layers of metal and amorphous silicon has been studied using power-compensated differential scanning calorimetry, crosssectional transmission electron microscopy, and thin film x-ray diffractrometry. Results for Ni/amorphous-Si (Ni/a-Si), Ti/a-Si, V/a- Si, and Co/a-Si are reviewed. In the first three cases, an amorphous silicide is the first phase to form. Further heating leads to thickening of the amorphous silicide and eventually to formation and growth of layers of crystalline silicides. In the case of Co/a-Si multilayer films, a crystalline silicide (CoSi) appears to be the first phase to form. In these systems calorimetric measurements suggest that there are barriers to nucleation of the crystalline phases, even though the energy reduction that would accompany their formation from pure components is large. It is suggested that interdiffusion may precede the formation of new phases at the original metal/a-Si interfaces, resulting in a significant decrease in the driving force for nucleation of the crystalline phases.

The thermodynamic and structural aspects of amorphous titanium silicide formation by solid-state reaction have been addressed. The radial distribution function of an amorphous Ti60Si40 reaction product has been determined by electron diffraction. It is an amorphous metallic alloy, with a coordination number of about 11.4, and a local arrangement of atoms which is similar to that in a crystalline silicide, Ti5Si4. The free energy of the amorphous alloy as a function of composition has been determined from the heats of crystallization of co-deposited amorphous Ti-Si alloys, and the heat of formation of the amorphization product as measured by differential scanning calorimetry (DSC). The latter was measured to be 35 ± 5 kJ/mole. Using these data, free energy of the amorphous Ti-Si phase has been calculated by applying the CALPHAD method. These results are discussed in light of the mechanism and energetics of the amorphization reaction.

Formation and growth of amorphous interlayers (a-interlayers) in nine refractroy metal and silicon systems by solid-state diffusion have been investigated by conventional and high resolution transmission electron microscopy. The amorphous interlayers were found to form in samples annealed at 350–650 °C. The growth was found to follow a linear growth law initially then slow down until a critical thicknees was reached. The interface structures were examined. The correlations among difference in atomic size between metal and Si atoms, growth rate and activation energy of the linear growth, critical and maximum a-interlayer thickness, the largest heat of formation energy for crystalline silicides, the calculated free energy difference in forming amorphous phase as well as atomic mobility in refractroy metal/silicon systems are discussed.

The growth of an amorphous Ti-Si phase and subsequent formation of crystalline silicides during solid-state reactions in Ti/a-Si multilayer films have been studied using power-compensated differential scanning calorimetry, cross-sectional transmission electron microscopy, and thin-film x-ray diffraction. By analyzing calorimetric data we have determined the activation energies for the formation of the various silicides (amorphous Ti-silicide, TiSi, C49-TiSi2, Ti5Si3) as well as their heats of formation. An amorphous silicide is the first phase to form during heating and we have measured the composition profile of this amorphous layer using scanning transimission electron microscopy. Metastable phase equilibria in the Ti-Si system are discussed in light of the thermodynamic and compositional information obtained in our experiments.

Solid-state amorphizaiton reactions (SSAR's) between Co thin-films and GaAs and InP have been investigated by transmission electron microscopy and Auger electron spectroscopy. Upon annealing at 260–300 °C, an amorphous phase was observed in the Co/GaAs system. Annealing at higher temperatures or for longer times led to the crystallization of this phase into a supersaturated CoAs structure. In the Co/InP system, annealing at 200°C for 1 hour led to the simultaneous formation of Co2P and an amorphous Co-In phase. At higher temperatures the amorphous phase crystallized into CoIn2 structure. For both systems, the amorphization reactions are attributed to the rapid diffusion of Co into the III-V substrates. The factors governing SSAR in ternary systems were discussed, with emphasis on the role of kinetics as opposed. to thermodynamic considerations.

Multilayer structures of W/C, WC/C, and Ru/C, of various periods were prepared and studied by high-resolution transmission electron microscopy. Comparison of the phases in the layered structures is made for as-prepared and annealed samples. Both as-prepared and annealed WC/C multilayers are predominantly amorphous, while the phases in the W/C depend on the periods. The 2 nm period W/C multilayer remains amorphous after annealing, and the longer periods recrystallize to form W2C. The layered microstructures of W/C and WC/C are stable on annealing at all periods, while the amorphous Ru-rich layers in the 2 nm period Ru/C multilayer agglomerate upon annealing to form elemental hexagonal Ru crystallites. Larger period Ru/C multilayers show stable layered structures, and indicate hexagonal Ru in the Ru-rich layers. X-ray measurements show that the multilayer periods expand on annealing for all metal-carbon multilayers studied.

We study the properties of CuInSe2 thin films grown on glass and on Mo substrates. The investigation is carried out with X-ray diffraction, RBS, XTEM and SEM.

CuInSe2/Mo contact stability is investigated after annealing at 600°C. RBS reveals that this treatment induces an interdiffusion between the metal and the chalcopyrite. To clarify this reaction, we have investigated the individual thin-film couples upon annealing. RBS and X-ray diffraction reveal insignificant interaction between Mo/Cu and Mo/In, but Se reacts with Mo.

We demonstrate remarkably rapid oxidation of (100) silicon at room temperature catalyzed by the presence of Cu3Si. Thermal oxidation of Si is normally carried out at temperatures above 700°C. Oxidation of many metal silicides occurs more rapidly than that of Si, but under controlled conditions results in a surface layer of SiO2. In contrast, the oxidation process described here produces a thick layer of SiO2 underneath the copper-rich surface layer. The SiO2 layer grows spontaneously to over one micrometer in thickness in several weeks in air at room temperature. Analysis by Rutherford backscattering, Auger electron spectroscopy, cross-sectional transmission electron microscopy and scanning electron microscopy reveals the presence of Cu3Si at the buried SiO2/Si interface, epitaxially related to the underlying Si substrate. Catalytic action by this silicide phase appears responsible for the unusual oxidation process.

The nucleation and transformation kinetics of the amorphous-to-crystal transition in Si films under 1.5 MeV Xe+ irradiation have been investigated by means of in situ transmission electron microscopy in the temperature range T = 480–580°C. After an incubation period during which negligible nucleation occurs, a constant nucleation rate was observed in steady state, suggesting homogeneous nucleation. A significant enhancement in nucleation rate during high energy ion irradiation (6 orders of magnitude) was observed as compared with thermal crystallization, with an apparent activation energy of Qn = 3.9 ± 0.75 eV. Independent analyses of the temperature dependence of the incubation time, the crystal growth rate, and nucleation rate suggest that interface rearrangement kinetics and not the thermodynamic barrier to crystallization, are affected by ion irradiation.

Heteroepitaxial InxGa1−xAs/GaAs structures have been formed by pulsed laser induced mixing of molecular beam deposited In films (˜200Å) on Si doped n+-GaAs (100) substrates. The Si dopant and deposited In are redistributed in a rapid melt-solidification process driven by a XeCl pulsed excimer laser. It is found, from high resolution cross-sectional transmission electron microscopy, that the epitaxial layers are crystalline and lattice matched to the substrate except for the misfit dislocations lying along the InxGa1−xAs/GaAs interface. These interfacial dislocations are used to identify the laser melted and unmelted regions. The dip and pile-up regions in the Si SIMS profiles are attributed to a segregation effect. Numerical simulation based on the liquid-solid interface velocity dependent segregation coefficient is used to investigate this effect and has approximated the trends in the measured characteristic In and Si profiles.

Thin alloy films were prepared by evaporating a standard magnetic Nd2Fe14B ingot in a high vacuum e-gun system at roam temperature. The as-deposited films of 50 nm thick were characterized by transmission electron microscopy (TEM) and in situ energy dispersive spectroscopy (EDS). Bright field examination showed that a novel morphology with holes of varied sizes emerged in the films. The hole-like white areas enriched with Nd, and the dark network with Fe. The electron micrograph was digitized by an VAX image processor. An infinite cluster was proved to be a two-dimensional percolating structure at the percolation threshold. The fractal dimension and the percolation threshold were calculated to be 1.90±0.04 and 0.60±0.04, respectively, which are in good consonance with the theoretical predictions. The as-deposited samples were aged at roam temperature for about two months. Enhanced diffusion and solid state reaction induced another percolating networks camposed essentially by Fe7Nd and Nd-riched solid solution.

The lattice diffusion of boron in bulk cobalt disilicide has been studied at temperatures between 450 and 950°C. Two different diffusion sources, a deposited surface layer of boron and an implanted boron distribution, were used. The lattice diffusion coefficient has been deduced from the boron profiles measured by secondary ion mass spectrometry (SIMS); in the studied temperature range the coefficient varies between 6.2×10−17 and 3.0× 10−11 cm2/s with an activation energy of 2.0 eV. These values reveal a very rapid lattice diffusion and agree with results reported previously in the literature concerning redistribution of boron implanted in thin films of CoSi2, and it also emphasizes the important role played by interfaces during the boron redistribution.