By varying the incident laser wavelength, the intrinsic Raman spectrum of porous silicon formed on nondegenerate p-type silicon is identified and used to determine the dependence of the average pore size and porosity on the depth of the porous silicon layer. It is found that with increasing layer depth, the average pore size and porosity decreases, which is contrary to that of porous silicon formed on degenerate n-type silicon. This may indicate a different formation mechanism for these two types of porous silicon.

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Application of porous silicon formation selectivity to impurity profiling in ptype silicon substratesThe photoluminescence spectra from a series of porous silicon samples formed in HF concentrations at constant current density and fixed forming times, are presented. A novel steplike behavior of photoluminescence peak energy was observed. A formation mechanism based on the quantum confinement of porous Si walls has been proposed to explain the experimental results.642

Multilayer Pt/CoCrTa thin-film structures have been prepared which display little intergranular exchange coupling and nearly 100% remanence in the perpendicular direction. Magnetic recordings of continuous square wave patterns have been made and characterized using an inductive contact recording transducer and by magnetic force microscopy. Written transitions appear to retain good fidelity at more than 300 000 transitions per inch. With exchange isolation of the grains, media noise becomes negligible relative to thermal noise from the recording system electronics. Analysis of magnetic force microscopy images yields a signal to integrated noise ratio of 17 dB at 309 000 transitions per inch written in a 4 μm wide track, which is comparable to a measured signal to total noise ratio of 8 dB at 350 000 reversals per inch measured using an inductive transducer at 100 in./s. These results are contrasted with observations on exchange coupled Pt/Co multilayers.

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