Pulsed laser induced modifications of metal silicide layers

Abstract

Irradiating a solid by a nanosecond, high power, laser pulse produces rapid surface melting followed by non-equilibrium solidification for which very often metastable structures are produced. In the present, experimental evidence of the production of metastable and in some cases novel phases of metal silicides are reported. Iron, nickel, cobalt and titanium silicide layers on single-crystal silicon substrates were irradiated by neodymium or ruby laser pulses; surface melting was monitored by time-resolved reflectivity measurements and the final sample structures were investigated by Rutherford backscattering spectrometry, transmission electron microscopy and X-ray diffraction. Amorphous, polycrystalline or epitaxial layers were found on solidification and in many cases the resulting phase was metastable. In some cases it was found that the structure or the phase of the solidified layer was strongly affected by the solidification velocity. The solidification velocity was lowered by pre-heating the sample using a pulsed electrical discharge synchronized with the laser pulse.