In situ radiotracer method for study of adsorption on semiconductor single crystal surfaces

The in situ radiotracer method has been applied to the studies of adsorption on single crystal semiconductor surfaces. On the basis of studies of formic acid and thiourea adsorption on n-Si (100) surface it was shown that the radiotracer method yields a qualitative and quantitative characterization of surface processes taking place on the surface of the semiconductor materials. Surface densities of adsorbed species as low as 5 × 1012 and as high as 2 × 1015 molecules per cm2 were detected. It has been found that during adsorption of formic acid a two-layer adsorbate is formed. The first layer is formed of COOH radicals while the second layer is formed of HCOOH molecules. Both layers are linked by hydrogen bonds. The adsorption layer formed during adsorption of thiourea consists of two products: thiourea molecules and either sulphur atoms or SH− anions.