OBSERVATION OF SLOW POSITRON-ANNIHILATION IN SILICIDE FILMS FORMED BYSOLID-STATE INTERACTION OF CO TI/SI AND CO/SI/

Slow positron beam was used to investigate the solid state reaction of Co/Si and Co/Ti/Si. Variable-energy (0-20 keV) positrons were implant ed into samples at different depths. The Doppler broadening of the ann ihilation gamma-ray energy spectra measured at a number of different i ncident positron energies were characterized by a line-shape parameter ''S.'' It was found that the measured S parameters were sensitive to thin-film reaction and crystalline characteristics. In particular, the S parameter of epitaxial CoSi2 formed by the ternary reaction was qui te different with that of the polycrystalline CoSi2 formed by direct r eaction of Co with Si.