Low-temperature structural relaxation in amorphized Ge has been characterized by extended x-ray-absorption fine-structure spectroscopy and Raman spectroscopy. A relaxation-temperature-dependent decrease in the mean value and asymmetry of the interatomic distance distribution has been shown to accompany the well-documented reduction in bond angle distribution. While the initial, as-implanted state of amorphous Ge was ion-dose dependent, relaxation at 200 degreesC yielded a common ion-dose-independent interatomic distance distribution. The heat release upon structural relaxation due to reductions in both bond length and bond angle distortion was calculated separately and the former exhibited an ion-dose dependence. The results provide compelling support for the defect annihilation model of structural relaxation and imply that the heat release upon structural relaxation should be implant-condition dependent.

The structure of implantation-induced damage in Ge has been investigated using high resolution extended X-ray absorption fine structure spectroscopy (EXAFS). EXAFS data analysis was performed with the Cumulant Method. For the crystalline-to-amorphous transformation, a progressive increase in bond-length was observed without the presence of an asymmetry in interatomic distance distribution (RDF). Beyond the amorphization threshold the RDF was dose dependent and asymmetric, where the bond-length and asymmetry increased as functions of ion dose. Such an effect was attributed to the formation of three- and five-fold coordinated atoms within the amorphous phase. Low-temperature thermal annealing resulted in structural relaxation of the amorphous phase as evidenced by a reduction in the centroid, asymmetry and width of the RDF, as consistent with a reduction in the fraction of non four-fold coordinated atoms. The results have been compared to other EXAFS studies of amorphous Ge, and it is suggested that the range of bond-lengths reported therein is related to the sample preparation method and state of relaxation.

Extended X-ray absorption fine structure and Raman spectroscopy have been utilised to measure implantation-induced micro-structural modifications in amorphous Ge including increases in bond length, broadening of the bond-angle distribution, and non-Gaussian static disorder as functions of ion dose. The resulting evolution of the inter-atomic distance distribution, over an ion dose range extending two orders of magnitude beyond that required for amorphisation, demonstrates the influence of implant conditions on amorphous phase structure. Results are attributed to increased fractions of three- and fivefold coordinated atoms as a means of accommodating implantation-induced point defects in the amorphous phase. In contrast, a common, ion-dose-independent structure is apparent following low-temperature, thermally-induced relaxation as consistent with the annealing of point defects in the amorphous phase. Structural relaxation is manifested by reductions in both bond-length and bond-angle distortion and the relaxation enthalpy for each component has been calculated separately.

After sputter-deposited amorphous TiNi films were subjected to heat treatment higher than 600 K, the shape memory alloys (SMAs) showed strong dependence of the transformation temperatures on heat treatment conditions and composition. Unlike Ni-rich films, the transformation temperatures of Ti-rich films are above the ambient temperature and largely depend on annealing temperatures from 600 to 1200 K. But they remain relatively constant on the various annealing temperature domains, 600–740 K, 740–1000 K, 1000 K +, delimited by exothermic peaks originating from the formation of precipitates. The measurements by differential scanning calorimetry, performed on TiNi thin films annealed below 740 K, showed transformation temperatures appropriate for medical applications and very small transformation temperature hysteresis of 3 K, resulting in a beneficial effect of SMA cyclic microactuators. Furthermore, using these lower annealing temperatures reduces both thermal and mechanical stresses and makes possible the development of SMA micro-actuators on substrates, that are unstable at elevated temperatures, and on electronic devices.

Implantation-induced, microstructural modifications including increased bond length and non-Gaussian static disorder have been measured in amorphous Ge using extended x-ray absorption fine-structure spectroscopy. The evolution of the amorphous phase interatomic distance distribution as functions of ion dose and implant temperature demonstrates the influence of implantation conditions on amorphous phase structure. Results are attributed to increased fractions of three- and fivefold coordinated atoms as a means of accommodating implantation-induced point defects.

The structure of ion implantation-induced damage in Ge substrates has been investigated with a combination of ion- and photon-based techniques including Rutherford backscattering spectrometry (RBS), perturbed angular correlation (PAC) and extended X-ray absorption fine structure (EXAFS) spectroscopy. For MeV Ge ion implantation at −196°C, the dose dependence of the decrease in local atomic order, determined from EXAFS and PAC, was compared to the number of displaced atoms determined from RBS measurements. An EXAFS determined damage fraction was shown to be a better estimate of amorphous fraction than the number of displaced atoms. PAC was used to elucidate the evolution of defective configurations, and was compared to the RBS and EXAFS results. A fit to the Overlap model with the overlap of two ion cascades for complete amorphization best described the experimental results.

The influence of intense x-ray irradiation on the local bonding structure of Ga dopants in both hydrogen-free (a-Si) and hydrogenated (a-Si:H) amorphous Si thin films has been studied. Prior to x-ray exposure, extended x-ray absorption fine structure measurements revealed that H reduced the static disorder around the Ga atoms in amorphous Si. Thereafter, x-ray irradiation modified the local structure in the a-Si and a-Si:H samples. The Ga coordination number increased from <3.5 to ∼3.80 atoms for both types of amorphous material as consistent with a greater fraction of electrically active, tetrahedrally coordinated dopant atoms. Also, greater structural disorder was observed around Ga atoms after x-ray irradiation suggesting that tetrahedrally coordinated Ga atoms were less well ordered than in threefold-coordinated sites.

Extended x-ray-absorption fine-structure has been utilized to measure the composition dependence of the Ge-Ge and Ge-Si bond lengths in both crystalline and amorphous GexSi1-x alloys. Utilizing a new sample preparation technique, transmission measurements were performed over greater ranges of photoelectron momentum and composition and with lesser uncertainty than previously reported. As a consequence, the proposed increase in bond length as a function of Ge composition has been unambiguously verified for the crystalline GexSi1-x alloys. For amorphous material, experimental results were also consistent with a bond length composition dependence and a phase-independent topological rigidity parameter. Though of greater uncertainty, the experimental values of Ge-Si bond length exhibited a lesser composition dependence than the Ge-Ge results. [S0163-1829(99)08339-3].

The sputtering of TiNi polycrystalline alloys without and with a titanium mesh has been investigated for the development of shape memory alloy (SMA) micro-actuators. The thickness and composition distributions of TiNi thin films have been determined by Rutherford backscattering spectroscopy (RBS). The composition of sputtered films was demonstrated to depend on the density of the titanium mesh and the distance from the target center, thus enabling easy fabrication of high and low temperature SMA actuators. The transition temperatures and resistivity have been measured with respect to the composition.

A novel methodology has been developed for the preparation of amorphous semiconductor samples for use in transmission extended x-ray absorption fine structure (EXAFS) measurements. Epitaxial heterostructures were fabricated by metal organic chemical vapour deposition (group III-Vs) or molecular beam epitaxy (group IVs). An epitaxial layer of ~2 μm thickness was separated from the underlying substrate by selective chemical etching of an intermediate sacrificial layer. Ion implantation was utilised to amorphise the epitaxial layer either before or after selective chemical etching. The resulting samples were both stoichiometric and homogeneous in contrast to those produced by conventional techniques. The fabrication of amorphous GaAs, InP, In 0.53 Ga 0.47 As and Si x Ge 1-x samples is described. Furthermore, EXAFS measurements comparing both fluorescence and transmission detection, and crystalline and amorphised GaAs, are shown.

Helium and xenon gases implanted into muscovite micas increase the reversible thermal expansion perpendicular to the silicate layers by one or two orders of magnitude. The gas‐mica composite behaves like a gas within an elastic membrane, and this can be developed into a thermal actuator or heat sensor. Helium gas is implanted into muscovite mica to simulate the anomalous thermal expansion behavior of water in phlogopite. The implanted Xe gas has been studied by Rutherford backscattering and by counting and measuring gas bubble radii. Helium gas appears to diffuse out of the structure, since the anomalous thermal expansion decreases slowly over a period of several months. All of the implanted Xe is found to remain within the mica structure.