Time-dependent measurements of the melt and solidification behavior of amorphous Si, formed by ion implantation of In, have been obtained following irradiation with ∼3 ns ruby laser pulses. The recently observed buried In sheets formed under such conditions are shown to result from internal nucleation of melt, contrary to previous interpretations. Under no conditions was surface nucleation of either amorphous or crystalline Si observed from a surface melt. These results resolve previous inconsistencies in the understanding of phase formation during rapid melting and solidification of Si.

Periodic structures are generated by solid state reaction between platinum (Pt) and silicon carbide (SiC). At temperatures above 900°C, periodic structures consisting of alternating layers of platinum silicides and carbon are produced in the diffusion zone. The composition profile across the diffusion zone and the chemistry of the periodic structures are investigated by scanning electron microscopy (SEM), scanning Auger microscopy (SAM), x-ray diffraction (XRD), and laser Raman microprobe. The formation of the platinum silicides causes an interfacial melting between Pt and SiC. X-ray diffraction indicates that Pt3Si is formed at 900°C, while Pt2Si is formed at 1000 °C. Laser Raman spectroscopy indicates that carbon is in either an amorphous state or a highly ordered graphitic state, depending upon its location from the reaction interface. The mechanism of formation of the periodic structure is discussed in terms of the solubility of carbon in platinum silicide during the solidification process.

We have studied the structure of Bi films grown on BaF2 substrates as a function of the distance from the interface with the substrate. Close to the interface the films show a polycrystalline structure and probably contain some amorphous regions. The crystallite size increases as the distance from the interface increases. At distances ≥90 nm the film becomes single crystalline and has the (111) trigonal direction normal to the film surface. Our structural data relate very well to mobility measurements performed on samples grown under the same conditions. Our results suggest that the carrier mobility is higher at distances ≥90 nm from the interface, where the film is single crystalline, than close to the interface, where it is polycrystalline.

The electrical resistivity of potassium-graphite intercalation compounds (K–GICs) was measured in the course of reactions with ammonia, oxygen, water, etc, The hydrogen absorption behavior at 77 K was also investigated on K–GICs before and after the reactions. The electrical resistivity of KC8 increased by reactions with ammonia, furan, and water vapor, whereas almost no change was observed in the case of the reaction with oxygen. Molecules of ammonia, furan, and water are considered to penetrate into the KC8 interlayers, while oxygen draws potassium from interlayer spaces toward the surface with resultant potassium-diluted mixed stage compounds. The hydrogen absorption isotherms of K(NH3)xC31 (0 ≤ x ≤ 2.65) at 77 K showed that the saturated amount of absorbed hydrogen, (H2/K)sat, decreased linearly with increasing ammonia content, x, When x went up to 2, (H2/K)sat became zero. Similar behavior in the degradation of the hydrogen absorption capacity of K(H2O)xC25 (0 ≤ x ≤ 1.3) was observed. Contrary to such behavior, partially oxidized KC24 could not absorb hydrogen gas. These facts are also explained by taking into account the fact that ammonia and water molecules penetrate K–GICs, while oxygen draws potassium atoms toward the surface, as predicted from the electrical resistivity measurements. Successive oxidation and heat-treatment processes made KC8 more able to absorb hydrogen, while similar processes of ammoniation and hydration followed by heat-treatment did not.

A variety of materials of the general type A2BB′O6 that have an ordered perovskite structure have been prepared and examined as possible substrate candidates for high Tc superconducting films. Materials containing either Ca or Sr as the A cation and either Ga or Al in combination with Nb or Ta as the B and B′ cations have been shown to be congruent melting compounds. These compounds have melting points easily accessible using conventional rf heating techniques and are therefore materials that could possibly be grown in bulk form using the Czochralski growth technique.

Ion beam mixing using 120 keV Fe+ ions at doses varying from 3.0 to 20 ⊠ 1015 cm2 was carried out on Pt–Fe bilayer samples over a temperature range from 298 to 523 K to produce alloys of various compositions. The mixing was characterized using Rutherford backscattering with 2 MeV 4He+ ions and transmission electron microscopy. Ion beam mixing and thermal anneals led to grain growth of the polycrystalline films and to formation of Pt3Fe as an alloy phase. At T ≤ 373 K, mixing was athermal and took place by ballistic collisional processes. At T ≥ 473 K, iron migrated rapidly into platinum; the observed activation energy of 0.3 eV suggested that diffusion was of the short-circuit type controlled by lattice vacancy and grain boundary transport. The surface Pt concentration in the mixed films remained high at ∼90 at. %. This resulted in a reduction of ∼25% in the cathodic overpotential compared to pure Fe electrodes for H2 evolution in 30 wt. % KOH solution. An ion beam mixed Pt–Fe surface layer was more stable than Fe coated with evaporated Pt; this is attributed to improved Pt–Fe adhesion as a result of the ion beam mixing process.

A change in microstructure, including dislocation Burgers vector, length, and behavior, has been observed to occur when the epilayer mismatch is varied in GexSi1−x layers grown on (100) Si. At low mismatches (<1.5%), there is an orthogonal array of very long 60° misfit dislocations. At higher mismatches (>2.3%) there is an orthogonal array of short edge dislocations. At intermediate mismatches (1.5 to 2.3%) there is a mixture of 60° and edge dislocations. The nature of the microstructure has a pronounced effect on the density of threading dislocations in the epilayer, which increase by a factor of ∼60× through a relatively small range of mismatch (1.7 to 2.1%, corresponding to x ranging from 0.4 to 0.5). These morphologies are discussed in the light of recent work on the sources of misfit dislocations. While mechanisms for the introduction and propagation of dislocations at low mismatch have recently been observed and explained, the high misfit case is clearly very different; i.e., surface nucleation seems to be likely in the latter case as opposed to operation of an internal source in the former. A mechanism for edge dislocation formation is proposed.

LiyV2O5 films were produced by reactive de magnetron sputtering followed by electrochemical posttreatment in LiClO4. X-ray diffraction showed an orthorhombic structure. Spectrophotometric transmittance and reflectance measurements demonstrated that the luminous and solar absorptance increased moderately when y increased from zero to unity. It is argued that LiyV2O5 is useful as an ion storage material operating in conjunction with electrochromic films.

We have applied Coherent Anti-Stokes Raman Spectroscopy (CARS), using a narrowband, scanned colinear configuration, to measure temperatures, relative concentrations, and detect species in low pressure CVD of polycrystalline diamond. CARS measurements were obtained for methane, hydrogen, and acetylene in either or both a rf plasma reactor and a hot filament reactor. In the rf PACVD experiments a mixture of 1% CH4 in H2 was used at a total pressure of 5 torr. The rf power input to the plasma was 300 watts and the H2 and CH4 flow rates were 99 and 1 seem, respectively. As acetylene (C2H2) has been proposed as an intermediate in diamond growth, it was selected for the initial series of measurements. In the absence of rf power, a sensitivity of 5 mtorr was observed; in the plasma downstream of the rf coils, no observable signal attributable to C2H2 was evident. This places an upper limit to conversion of methane to acetylene at 20%, a figure representing the observed sensitivity to C2H2. In the hot filament reactor, the gas flow was 200 sccm of 1% CH4 in H2 at a total pressure of 150 torr. Under these conditions, C2H2 was detectable. Absolute concentrations were not calculated, but the observed spectra are within an order of magnitude of our sensitivity limit. This allows estimation of the C2H2 partial pressure near the substrate as 5–50 mtorr or from 0.66 to 6.6% conversion from methane. In view of this low conversion percentage, the absence of a signal in the rf experiments must be taken as inconclusive. CARS spectra of methane were also obtained in both reactors. In the rf reactor, under similar conditions to those described previously, the methane relative concentration decreased to 25% as the rf power was increased from zero to 400 watts. In the hot filament reactor, CH4 CARS signal profiles were obtained as a function of axial distance from the hot filament, and parametrically as a function of filament temperature. Comparison of these profiles, in which the observed signal decayed monotonically as the filament was approached and increased monotonically downstream of the filament, was made with theoretical calculations. This comparison showed that the fluctuations were attributable to temperature/pressure effects and not to chemistry. To determine if the observed depletion in the rf plasma was similarly attributable, the CARS signal of hydrogen was observed as a function of axial distance downstream of the rf coil centerline and parametrically as a function of rf power. In contrast to expected behavior in the thermal hot filament reactor, little rotational excitation was observed in the plasma. Rotational temperatures were assigned to hydrogen based upon comparison with theoretically derived spectra. At 450 watts of rf power, rotational temperatures of 340 K were observed 4 to 6 cm downstream of the coil, the region where the 25% decrease in CH4 was observed. Little or no density fluctuations accrue due to these temperatures, indicating that the observed depletion in methane signal is attributable to decomposition or chemical reaction in the plasma. In summary, CARS is applicable to reactant species (CH4) axial profiling in both reactors, but can be limited by sensitivity in the detection of intermediate or product species (C2H2). In addition, CARS thermometry can be utilized to profile the rotational temperatures of selected species.

The simultaneous gettering of iron and nickel in a float-zone silicon wafer in the (100) orientation and implanted with 2.5 ⊠ 1015 argon ions/cm2 at 280 keV has been investigated. Iron was deposited on one half of the back surface of the wafer and nickel was deposited on the other half. Chemical analyses by secondary ion mass spectroscopy, energy dispersive x-ray spectroscopy, and high-resolution imaging by high-resolution electron microscopy revealed the gettering rate of iron was orders of magnitude lower than that of nickel. The results also suggested that gettering is a metal-diffusion-controlled process. The simultaneous gettering of iron and nickel results in a complex distribution of the two metals in the silicon wafer.

The intercalation reaction of NiCl2 from the mixture of CuCl2 and NiCl2 has been studied by using natural graphite and a stage 1 graphite intercalation compound with CuCl2 at different temperatures from 400 °C to 550 °C for a wide range of residence times up to 8 days. In the mixture of CuCl2 and NiCl2, CuCl2 was found to be intercalated preferentially in the beginning of the reaction. At low reaction temperatures, NiCl2 was intercalated with the increase in heating time, but its content was saturated at a rather low value, NiCl2/C = 25 wt.% after 3 days at 450 °C, for example. At temperatures as high as 550 °C, however, the content of CuCl2, which had been intercalated in the beginning of the reaction, was found to decrease and NiCl2 started to be intercalated by prolonged heating, suggesting the exchange of the former with the latter. From the reactions of a stage 1 CuCl2–GIC with the mixture of CuCl2 and NiCl2, it was clearly revealed that the intercalated CuCl2 was replaced successively by NiCl2 in keeping the stage 1 structure. The saturated content of NiCl2 in respect to graphite depended strongly on the reaction temperature, attaining NiCl2/C = 150 wt.% at 550 °C. As seen by energy dispersive x-ray spectroscopy, NiCl2 intercalation proceeds from the periphery of the host particles. To form a uniform distribution of both intercalates, CuCl2 and NiCl2, it took a long time of residence, more than 3 days at 550 °C.

Dopant induced grain growth in LPCVD polysilicon films has been investigated using BBr3 as the diffusion source at 900 and 950 °C. TEM and sheet resistance measurements indicate rapid growth under such doping conditions. Results are compared with the grain growth observed during (a) PBr3 doping of similar films, and (b) during anneals in ambients containing 1% oxygen in nitrogen, similar to that used during BBr3 or PBr3 doping. The results clearly demonstrate the rapid grain growth induced by both types of dopants, although phosphorus is more effective in inducing this grain growth.

The microstructural development of compacted nanocrystalline TiO2 powder was studied as a function of sintering temperature up to 1000°C. Grain growth was monitored using x-ray diffraction and scanning electron microscopy. The specific surface area and total porosity were determined quantitatively using the nitrogen adsorption BET. The density was measured by gravimetry using Archimedes principle. The green body density of compacted n-TiO2 with average grain size of 14 nm is as high as 75% of theoretical bulk density. Low temperature surface diffusion leads to the disappearance of small pores, while noticeable densification commences at 600°C and reaches near theoretical values at 900°C. Grain growth also begins at 600°C, accelerating rapidly by 1000°C. Hot isostatic pressing is observed to enhance densification while suppressing grain growth.

We have developed a new growth process for GaAs that combines advantages found in several methods currently in commercial use, while at the same time minimizing many of the problems inherent in these presently used processes. The new technique, a form of vertical Bridgman (VB) growth, is capable of producing either doped (semiconducting) or undoped semi-insulating GaAs with very low dislocation density.

Monocrystals of LiF, ion implanted with Ar+, were exposed to thermal shock in a plasma of different intensities. Ion implantation substantially alters the fracture pattern and characteristics of the material, particularly in reducing the thermal shock resistance parameter, S′, and in increasing the damage resistance parameter, S″. The former parameter indicates that ion implantation allows fracture to be initiated at lower thermal shock temperature differences and the latter parameter is associated with higher crack densities and lower crack penetration depths. The increase in the parameter S″ indicates that ion implantation can result in a higher mechanical stability and greater durability of the crystals damaged by thermal shock. Surface melting at very high heat fluxes eliminates any effect of ion implantation.

Measurements of the emission of charged particles, photons, and radio frequency signals accompanying the deformation and fracture of polycrystalline Ti metal and deuterated Ti are described. Preliminary evidence for charge separation created by crack propagation is presented which supports a proposed fracture mechanism to explain neutron bursts observed during treatment of deuterated metals.

Recently there has been an emphasis on the importance of using cooling scans in DSC experiments in studying the glass transformation kinetics of glasses. The physical interpretation of the apparent activation energy from DSC heating scans has been questioned as not being meaningful. The present paper reports glass transition temperature (Tg) measurements derived from Differential Scanning Calorimetry (DSC) experiments on bulk and film amorphous selenium samples subjected to heating, at constant rate r, and cooling, at constant rate q, scans. Film samples were prepared by thermal evaporation techniques in vacuum. It is shown that for both bulk and film forms of a–Se, within experimental errors, log(r/T2gm) vs 1/Tgm plot where Tgm is the peak glass transformation temperature, and log(r) vs 1/Tgh plot, where Tgh is the glass transition onset temperature from DSC heating scans, are parallel to the log(q) vs 1/Tgc plot where Tgc is the glass transition temperature from cooling scans. Within the Hutchinson and Kovacs formulation of the glass transformation phenomenon, the results imply that the structural contribution to the mean retardation time, τ, is negligible in comparison with the temperature dependent part. The mean structural relaxation time for both bulk and film forms was found to exhibit a typical Vogel-Tammann-Fulcher type of temperature dependence. Furthermore, the structural relaxation rate was observed to be inversely proportional to the viscosity, η(T), implying that the mean structural retardation time is proportional to the viscosity, τ ∼ η. The results also confirm that the earlier studies of glass transformation kinetics in a–Se utilizing only DSC heating scans remain meaningful.

The misorientation phase space for symmetrical grain boundaries is explored by means of atomistic computer simulations, and the relationship between the tilt and twist boundaries in this three-parameter phase space is clucidated. The so-called random-boundary model (in which the interactions of atoms across the interface are assumed to be entirely random) is further developed to include relaxation of the interplanar spacings away from the grain boundary. This model is shown to include fully relaxed free surfaces naturally, thus permitting a direct comparison of the physical properties of grain boundaries and free surfaces, and hence the determination of ideal cleavage-fracture energies of grain boundaries. An extensive comparison with computer-simulation results for symmetrical tilt and twist boundaries shows that the random-boundary model also provides a good description of the overall structure-energy correlation for both low- and high-angle tilt and twist boundaries. Finally, the role of the interplanar spacing parallel to the grain boundary in both the grain-boundary and cleavage-fracture energies is elucidated.

Diamond-like films containing no hydrogen can be deposited from laser plasmas that are highly ionized. Growth rates of 0.5 μm/h over 100 cm2 areas have been realized on untreated substrates of a variety of materials including Si, Ge, ZnS, glass, and plastics. Measurements of optical properties and mass densities support the identification of this laser plasma diamond as a conglomerate of very fine grains of diamond polytypes in a matrix of other carbon forms.

High temperature forming of a fine-grain ceramic is demonstrated by a series of extrusion experiments with fine-grain ZrO2, 3 mole% Y2O3. Piston velocities, ranging up to 5 mm/min (for a die with an initial diameter of 30 mm and a final diameter of 10 mm), can be achieved at 1500 °C with piston stresses of 70 MPa and graphite paper lubrication. These piston velocities are consistent with a calculation based on the creep behavior of this ceramic. The calculation is based on a model of material flow through the die, consistent with experiments involving internal markers of graphite foil.