The laser-induced forward transfer technique in which material is ablatively transferred from a thin film to a target substrate by a pulsed excimer laser has been extended to 532 nm using a frequency-doubled YAG laser. Cu and Ag have been deposited on fused silica substrates using microscope objectives for focusing, resulting in reductions in feature size over that obtainable with the multimode excimer laser. The photothermal deposition process has been modeled using the one-dimensional thermal diffusion equation, including a moving solid-melt boundary, with good agreement between theoretical and experimental results.

After hafnium carbide has been oxidized at temperatures in the range of 1400" to 2060°C, three distinct layers are present in the film cross section: (a) a residual carbide layer with dissolved oxygen in the lattice, (b) a dense-appearing oxide interlayer containing carbon, and (c) a porous outer layer of hafnium oxide. Experimental measurements of layer thicknesses and oxygen concentrations are combined with an extended formulation of moving-boundary diffusion theory to obtain the diffusion constants of oxygen in each of the three layers. The results indicate that the oxide interlayer is a better diffusion barrier for oxygen than either of the other layers. Based on X-ray microanalysis, X-ray diffraction, and resistance measurements, the interlayer is an oxygendeficient oxide of hafnium with a carbon impurity. The interlayer hardness equals that of the residual carbide layer.

No abstract

Aluminum hyperfine interactions of the Al + -0 -trapped-hole center in a number of oxides containing Al ions either as a constituent (A1203.Mg, Na P-alumina) or as an impurity (Ge02, SiO2) are analyzed with use of a semiempirical model of the exchange polarization mechanism of transferred hyperfine interactions. The theory quantitatively predicts the observed strong dependence of the negative isotropic hyperfine constant on the 0 -Al + distance and, from estimates of the electrostatic-crystal-field energy at 0, indicates a reasonable outward expansion (-10%)of the Al + ions next to the 0 hole center. The theory also accounts well for the observation that the anisotropic hyperfine constants in these centers vary only slightly despite the large variation in the corresponding isotropic splittings.

Absorption and emission spectra of Na atoms trapped in raregas matrices