Micron-scale palladium lines have been produced by a photothermal laser direct-write process in thin palladium acetate films. The range of observed structures relates to the complex thermal profiles generated by coupling of the incident laser radiation with the exothermic heat of reaction. Surprisingly, the chemical composition of these features does not vary significantly as a function of laser power and scan speed. Rather, deviation of the electrical resistivities of these features from that of pure palladium results from porosity in the lines.

The reaction CoSi+Si→CoSi2 has been investigated in the temperature range of 500–600 °C, using Rutherford backscattering, x-ray diffraction, transmission electron microscopy, and four-point sheet-resistance measurements. The reaction is very slow at 500 °C and extremely fast at 600 °C, and appears to occur in four stages: (a) nucleation of the CoSi2 phase at the grain-boundary triple points, (b) lateral growth from nucleation sites to form a continuous layer on the silicon surface, (c) growth in thickness by diffusion through this disilicide layer, and (d) the lateral epitaxial growth by eliminating the grain boundaries. The diffusion through the disilicide layer seems to be a rate-limiting process with high activation energy.

No abstract

No abstract

The growth of GaAs thin films by a laser photodecomposition process is reported. Ga(CH3)3 and As(CH3)3 mixtures are photolyzed above (100) Si and GaAs substrates by a 193-nm argon fluoride excimer laser beam directed normal to the substrate surface. Gas-phase products diffuse to, and stick on the surface where further laser irradiation leads to the formation of polycrystalline GaAs, with grain sizes between ∼20 and 2000 Å. Deposited films contain ∼1–3 at. % carbon, as determined by Auger electron spectroscopy. Surface irradiation by the transmitted beam improves the optical constants of the film to values approaching bulk GaAs, but annealing is not sufficient to promote epitaxial growth at fluences as high as 70 mJ/cm2, for average substrate temperatures up to 400 °C. Laser irradiation of the GaAs substrates exposed to BCl3 or As(CH3)3 immediately prior to deposition removes the native oxide and carbon contamination.