ELECTRICAL, OPTICAL AND MATERIALS PROPERTIES OF ION-BEAM SYNTHESIZED (IBS) FESI2

The electrical and optical properties of FeSi2 structures produced by ion beam synthesis (IBS) are investigated. Above 150 K both alpha and beta FeSi2/n-Si structures display good Schottky diode characteristics . beta FeSi2/n-Si exhibits a low reverse leakage current up to - 20 V after which abrupt avalanche breakdown occurs. As expected, the revers e leakage current of alpha FeSi2/n-Si for the same diode area, is an o rder to magnitude higher than that for the beta FeSi2/n-Si diodes and the breakdown is less abrupt. The characteristics of both types of dio de suggest that thermionic emission is the main conduction mechanism a cross the barrier. For samples implanted with higher doses of Fe, wher e a continuous layer of beta FeSi2, is produced, the photoluminescence (PL) signal is indistinguishable from the background noise at 80 K. H owever, for lower dose samples (in the dose range 5x10(15)-1x10(17) Fe cm(-2)) although the peak position remains the same the signal intens ity is significantly increased and is visible at 80 K. Cross-sectional transmission electron microscopy (XTEM) results from these samples sh ow precipitates with diameters of 400-600 Angstrom at the surface and smaller precipitates < 50 Angstrom in diameter around the projected ra nge of the implant. For even lower dose samples (1 x 10(14) Fe cm(-2)) no PL signal is observed which correlates to the lack of beta FeSi2 p recipitates in the XTEM micrographs.