Optical and electrical measurements on nitrogen ion-implanted diamond-like carbon films are presented. Raman scattering measurements, which probe the crystallinity of the film surface, indicate that nitrogen implantation reduces the finite crystallographic order in the pristine carbon films. The absence of molecular vibrations in the infrared absorption spectra of the films argues against a polymeric structure of the ion-implanted films. Spectroscopic ellipsometry experiments determine the change in the optical constants of the carbon film due to nitrogen implantation. Electrical de conductivity measurements are interpreted within the framework of a schematic density of states picture of graphitic τ-electrons in an amorphous carbon system. Taken collectively, the optical and electrical measurements suggest that nitrogen implantation increases the density of localized states within the 1.5 eV bandgap of the quasi-amorphous carbon film, thereby reducing the bandgap and increasing the conductivity of the nitrogen-implanted films.

A new ternary material Co3(SbTe3)2 was prepared by using a rapid precipitation metathesis reaction between the Zintl material K3SbTe3 and CoCl2 in aqueous solution. The dc specific resistivity of this material is in the region for metallic conductors (p = 2.75 × 10-3 Ω-cm). The dc magnetic susceptibility of Co3(SbTe3)2 is reported over a 2.2 K-300 K temperature region, and the material is characterized as a spin glass with a freezing temperature of about 5 K. Magnetization data are also reported as both thermal remanent magnetization and isothermal remanent magnetization as a function of magnetizing field and temperature. When cooled well below the glass freezing temperature, the frozen spin glass has been observed to exhibit photomagnetic effects consistent with a disruption of the spin-glass state caused by uv-radiation.

The hardness, H, and rate sensitivity of the hardness, m = ∂ ln H/∂ ln ∊eff|xp, where ∊eff is an effective strain rate and xp the plastic depth, are measured in molybdenum at room and low temperature (160 and 170 K) using as-received and annealed specimens. Based on these measurements it is found that H separates into two components: one depending on indentation rate and temperature, and the other depending on the starting state of the material. An activation volume is defined, v∗ = 9kT/mH, which falls within the range of values derived from other experimental techniques. The values of m obtained from indentation creep, indentation load relaxation, and indentation rate-change experiments agree closely with each other provided a consistent analysis is used. The results of these experiments suggest that the rate- and temperature-dependence of the hardness can be used to discriminate between strengthening mechanisms at low temperature.

The effects of loading and unloading rate on fracture features formed during sharp indentation of polycrystalline Al2O3 have been studied. It was found that there is a transition between intergranular and transgranular fracture if the loading rate is increased by a factor of 104 during the whole indentation cycle. By varying the loading or unloading rate during indentation, and correlating the corresponding dependence of fracture features, the part of the indentation cycle can be identified in which specific segments of cracks are generated. Hence, the fracture sequence during indentation is established. The fracture sequence for polycrystalline Al2O3 is compared with those reported from direct observation in optically transparent materials such as soda-lime glass and various single crystal ceramics.

Silicon 〈111〉 single crystals were implanted with 70 keV Ar ions to the dose of 1017 ions/cm2. Next, the friction coefficient between a Si crystal and a hard steel ball was measured using a pin-on-disk setup in air and in vacuum. The wear tracks were measured using a surface profilometer. For measurements performed in vacuum, a strong influence of implantation on friction force and wear tracks was found. The microstructure of the samples was subsequently investigated using RBS, ERD, and x-ray diffraction (XRD) techniques. Micro-RBS measurements showed that Ar had been removed from the wear tracks, despite their continued exhibition of low friction.

An oxy-acetylene flame, impinging vertically upward on an Si(001) substrate, is systematically examined for morphological variations in the resulting diamond deposits. The flame is operated under near neutral (O2/C2H2 ratio near 1.0) conditions in the unconfined, open atmosphere. Singly twinned crystal morphologies in addition to the usual (001) faceted structures are observed and reported for the first time. Similar morphological variations are observed along the radial as well as the axial (vertical) coordinate directions in the flame. Large changes in morphology are observed for changes in vertical position as small as 50 μm.

The mechanism for plastic deformation of 0.5 μm thick, 0.5 μm grain-size evaporated Al films on oxidized Si wafers has been studied using wafer curvature measurements over a temperature range from room temperature to 500 °C. Extensive evidence for both morphology changes and plastic deformation was obtained. Transmission electron microscopy confirmed the occurrence of grain growth, and stress changes attributed to recrystallization were observed. Deformation under tension could be explained by dislocation glide according to the kinetics observed in bulk Al at the same temperatures, stresses, and grain sizes. The kinetics of deformation under compression were investigated at 400 °C and were completely different from those under tension. This is either due to a difference in the deformation mechanism or to the occurrence of work softening.

The purpose of this investigation was to study the effect of changes in composition and thermal history on some properties of potential leucite-glass composites made by a coprecipitation process. Four compositions from the K2O–Al2O3−SiO2 system were investigated for differences in phases, density, thermal expansion, and strength. Strength, density, and thermal expansion increased with increasing leucite content. Strengths of up to 140 MPa were obtained with air-fired specimens. Composites with different thermal expansion coefficients could be obtained by altering SiO2 content in a predictable way. Leucite-glass composites offer potential for improved dental porcelains.

The absolute concentration of methyl radicals (CH3) and the mole fraction of acetylene (C2H2) are measured in a hot filament chemical vapor deposition (CVD) system both during and after an initial pretreatment that has been used successfully in microwave plasma and oxyacetylene torch CVD systems to produce more uniform and higher density crystal nucleation. The pretreatment technique, which consists of deposition for a relatively short time with a high input concentration of hydrocarbon in the feed gas, was studied for both methane (CH4) and C2H2 as the input hydrocarbon diluted in H2. Scanning electron micrographs of diamond films deposited under the conditions studied indicate that the pretreatment using CH4 is not effective in increasing the crystal nucleation density, but is moderately effective in increasing the crystal size. The C2H2 pretreatment has no apparent effect upon either the crystal size or nucleation density. The spectroscopie measurements suggest that the surface condition of the filament is the prominent factor affecting the gas phase chemistry both during and after the pretreatment stage.

In previous studies, sublimed C60-rich fullerene films on silicon, when slid against a 52100 steel ball under dry conditions, have exhibited low coefficient of friction (∼0.12). Films with different purities can be produced by sublimation at different substrate temperatures. In this paper, effects of purity of fullerene films and ion implantation of the films with Ar ions on the friction and wear properties of sublimed fullerene films are reported. C60-rich films (called here films with high purity) exhibit low macroscale friction. An increased amount of C70 and impurities in the fullerene film determined using Raman and Fourier transform infrared (FTIR), increases its coefficient of friction. Microscale friction measurements using friction force microscopy also exhibited similar trends. Low coefficient of friction of sublimed C60-rich films on silicon is probably due to the formation of a tenacious transfer film of C60 molecules on the mating 52100 steel ball surface. Based on scanning tunneling microscopy (STM), transmission electron microscopy (TEM), and high resolution TEM (HRTEM), we found that fullerene films primarily consisted of C60 molecules in a fcc lattice structure. Nanoindenter was used to measure hardness and elastic modulus of the as-deposited films. Ion-implantation with 1 × 1016 Ar+ cm−2 reduced macroscale friction down to about 0.10 from 0.12 with an increase in wear life by a factor of 4; however, doses of 5 × 1016 ions cm−2 gave three times higher friction and poorer wear life; higher doses disintegrated the C60 molecules. Based on STM, TEM, Raman, FTIR, and laser desorption Fourier-transform ion cyclotron resonance mass spectrometer (LD/FT/ICR) studies, we found that the ion implantation with a dose of 1 × 1016 Ar+ cm−2 resulted in smoothening of the fullerene film surface probably by compacting clusters, but without disintegrating the C60 molecules. However, a high dose of 5 × 1016 Ar+ cm−2 damaged the C60 molecules, converting it to an amorphous carbon. Nanoindentation studies show that ion implantation with a dose of 1 × 1016 Ar+ cm−2 resulted in an increase in the hardness from about 1.2 to 4.0 GPa and in elastic modulus from about 70 to 75 GPa and modified the elastic-plastic deformation behavior.

Grazing incidence x-ray scattering (GIXS) with a synchrotron source was used to measure elastic strain gradients as a function of temperature in aluminum and aluminum alloy thin films of different thicknesses on silicon. The stresses in the films are induced as a result of the difference in thermal expansion coefficient between film and substrate. Disregarding minor deviations at the surface, it is shown that there are no gross strain gradients in these films in the range of temperatures (between room temperature and 400 °C) considered. Significant x-ray line broadening effects were observed, suggesting an accumulation of dislocations on cooling the films and their annealing out as the films were being reheated. The variation of the dislocation density during thermal cycling compares well in nature with that of the concurrent variation in film stress, indicating that large strain hardening effects contribute toward the film flow stress.

MgAl2O4 thin films, to be studied as active elements for humidity sensors, were deposited on Si/SiO2 substrates by radio-frequency sputtering. This paper discusses the x-ray photoelectron spectroscopy (XPS) investigation of these films. XPS demonstrated that the thin films had a stoichiometry close to that of MgAl2O4. The evaluation of the modified Auger parameter α' for Al gave structural information about the order of the crystalline structure of the thin films. The combination of Ar+ ion etching and XPS analysis showed the simultaneous presence of Mg, Al, and Si at the film-substrate interface. The thicknesses of the interfaces were calculated between 7 and 10 nm. The analysis of the binding energy (b.e.) values of the XPS peaks at different etching depths showed that O 1s and Si 2p b.e. values were characteristic of a silicate at the interface, whereas in the substrate they were typical of silica. This suggests a chemical interaction took place between film and substrate with the formation of a silicate layer at the interface, which may be the cause of the good adhesion of MgAl2O4 films to silica, as observed by peel tests with Scotch tape.

The solid-state epitaxial-regrowth kinetics of ion-beam-amorphized SrTiO3 surfaces annealed in water-vapor-rich atmospheres have been studied using time-resolved reflectivity (TRR). For this material, the conversion of the reflectivity-versus-time data obtained from the TRR measurements to recrystallized depth-versus-time data is more complicated than in systems such as silicon, where the reflectivity can be fit by assuming that the refractive index N (N = n + ik) in the amorphous layer is constant. In SrTiO3, agreement between measurements made directly with Rutherford backscattering spectroscopy (RBS) and those made using TRR can be obtained only when N is permitted to vary within the amorphous layer, with nonzero values for both the real and imaginary components. In some cases, the roughness of the amorphous/crystalline interface must also be considered. Additionally, a model for H2O-enhanced epitaxial regrowth is presented, which is in good agreement with the shape of the depth-versus-time profiles that are obtained from the TRR data.

NaZr2P3O12 (NZP) is emerging as an important family of a large number of isostractural compounds in which several members have demonstrated very low thermal expansion characteristics. Ba1+xZr4P6−2xSi2xO24 and Sr1+xZr4P6−2xSi2xO24 crystalline solutions are two such systems belonging to the NZP family. Here, we report the bulk thermal expansion and axial thermal expansion behavior of various compositions in these systems. The low expansion behavior of these materials is attributed to their unique crystal structure, which is framework open structure, and can accommodate numerous ionic substitutions at various lattice sites.

Studies of the reactive melt infiltration of silicon-niobium alloys in microporous carbon preforms prepared by the pyrolysis of a polymer precursor have been carried out using modeling, DTA, and melt infiltration. Mercury porosimetry results indicate a very narrow pore size distribution with virtually all the porosity within the carbon preforms open to infiltrants. The morphology and amount of the residual phases (niobium disilicide and silicon) in the infiltrated material can be tailored according to requirements by careful control of the properties (pore size and pore volume) of the porous carbon preforms and alloy composition. The average room temperature four-point fiexural strength of a reaction-formed silicon carbide material (made by the infiltration of medium pore size carbon preform with Si–5 at. % Nb alloy) is 290 ± 40 MPa (42 ± 6 ksi) and the fracture toughness is 3.7 ± 0.3 . The fiexural strength decreases at high temperatures due to relaxation of residual thermal stresses and the presence of free silicon in the material.

PAES (Positron Annihilation induced Auger Electron Spectroscopy) intensities from ultrathin Au films deposited at 198 K on Cu(100) were measured as a function of temperature (from 198 K to 348 K) for three different Au coverages. Intermixing of Au and Cu atoms with the increase of temperature was directly monitored. The measurements indicated that the intermixing was not reversible as a function of temperature. EAES (Electron induced Auger Electron Spectroscopy) results were compared with PAES results for each experiment, and the comparison showed the feasibility of PAES over EAES for the study of surface alloy formation as a function of temperature.

Fine β-spodumene-type amorphous powders were obtained through sol-gel techniques using Si(OC2H5)4, Al (OC2H5)3, LiOCH3, and Ti(OC2H5)4 as the starting metal alkoxides. Differential thermal analysis (DTA), x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron diffraction (ED) analysis were utilized to study the phase transformation behavior of the LAST gels. The viscosity of the LAST solution increased abruptly at longer time when the TiO2 content was increased. As the TiO2 content was increased, the peak position of β-spodumene phase formation in DTA curves was shifted to a lower temperature. For calcination of LAST gels at 800°-1200 °C, the crystallized phases are composed of the major phase of β-spodumene and a minor phase of rutile (TiO2). Unlike earlier studies, heating the dried LAST gels from 800 °C to 1200 °C did not show β-eucryptite, nor found γ-spodumene.

Porous α-alumina ceramics were prepared using the spray-pyrolyzed powder from aluminum nitrate solution and aluminum sulfate solution. Porosity and pore size distribution of the samples were examined with respect to the forming pressure and firing temperature. The porosity obtained changed from around 80% in the green compacts to 60–70% in the fired bodies fired at 1500 °C. The porosity of 30–40% remained even by firing at 1700 °C. Although there was no significant difference in the porosity of the fired bodies prepared from the sulfate and nitrate solutions, the fired bodies prepared from the nitrate solution showed apparently larger pore size than those from the sulfate solution. Fired bodies with an average pore radius from 0.2 to 0.8 μm can be prepared by this method. The four-point bending strength of the fired bodies, which had a porosity of 57% and an average pore radius of 0.23 μm, was 35 MPa.

The nucleation, growth, and orientation of lead zirconate titanate thin films prepared from organometallic precursor solutions by spin coating on (111) oriented platinum substrates and crystallized by rapid thermal annealing was investigated. The effects of pyrolysis temperature, post-pyrolysis thermal treatments, and excess lead addition are reported. The use of post-pyrolysis oxygen anneals at temperatures in the regime of 350–450 °C was found to strongly affect the kinetics of subsequent amorphous-pyrochlore-perovskite crystallization by rapid thermal annealing. The use of such post-pyrolysis anneals allowed films of reproducible microstructure and textures [both (100) and (111)] to be prepared by rapid thermal annealing. It is proposed that such anneals and pyrolysis temperature affect the oxygen concentration/average Pb valence in the amorphous films prior to annealing. Such changes in the Pb valence state then affect the stability of the transient pyrochlore phase and thus the kinetics of perovskite crystallization.

Copper and diamond both have cubic crystal structures and similar lattice constants, making Cu an excellent candidate substrate for the heteroepitaxial growth of electronic device quality diamond. In this study a Cu substrate preparation method was developed to obtain large-area, free-standing polycrystalline diamond films. Concurrently, a statistically designed experiment was used to maximize the diamond film quality and resulted in (111) and (100) faceted films of quality comparable to or better than those grown on Si. The diamond films were analyzed by Raman spectroscopy, x-ray diffraction, and scanning electron microscopy.