Infrared absorption of epitaxial NiSi layers on Si(111).

Infrared absorption of epitaxial type A and type B NiSi sub 2 layers on Si(111) has been measured with photoacoustic spectroscopy. Type A silicides showed identical absorption as type B layers with corresponding thicknesses. The observed dependence of absorption on silicide thickness agrees with calculations based on no interface absorption, in sharp contrast to previous studies of nonepitaxial silicide interfaces. These results suggest that the densities of electronic states at epitaxial NiSi sub 2 interfaces are below the detection limit of this technique, ~10 sup (14) cm sup (-2).