Abstract
Palladium silicide coated silicon specimens have been formed by thermally evaporating palladium onto clean field evaporated n-type silicon (100) tips. The thin palladium overlayer is reacted to form palladium silicide by thermal annealing at 675 K. The tips were studied by field ion imaging, pulsed laser atom probe and field emission current-voltage characterisation. These analyses were carried out in a modified atom probe field ion microscope which allows all these techniques to be employed without breaking vacuum. The stoichiometry of the 2–3 nm thick silicide layer was close to that expected for Pd 2Si. All analyses showed a thin silicon rich layer on top of the palladium silicide. Fowler-Nordheim plots of the field emission characteristics of silicide coated tips were obtained as the layer was removed by field evaporation. Analysis of the slopes and intercepts of these plots indicates that the silicide coated tips have a rougher surface than the silicon tips. This was confirmed by field ion microscope and field emission microscope images which showed localised electron emission from the sharpest areas of the tip. PLAP analysis of a tip exposed to air for 4 days showed an oxidised silicon rich surface layer which was 2–4 monolayers thick.
Published Version
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