THE THERMAL-DISSOCIATION OF DECABORANE ON SI(111)-(7X7) AND DOPING EFFECTS IN THE NEAR-SURFACE REGION

The thermal decomposition of decaborane (B10H14) and its doping effects on Si (111)-(7 x 7) has been investigated by surface spectroscopies. Upon adsorption between 100 and 300 K, molecular decaborane was identified on the surface by high-resolution electron-energy-loss spectroscopy (HREELS) by the absence of Si-H surface species production. The thermal decomposition of adsorbed decaborane molecules at higher temperatures involves a preferential removal of hydrogen from the weaker B-H-B linkage. H-2 thermal desorption was observed to cover a wide temperature range between 300 and 900 K. Clean boron deposition on the surface was achieved at approximately 900 K. Upon heating to approximately 1275 K, extensive boron diffusion into bulk silicon produced a highly B-doped region below the surface (approximately 10(3) angstrom) with a carrier hole concentration on the order of approximately 10(19) cm-3 depending upon the initial surface boron coverage and annealing conditions. The surface adopted a (square-root 3 X square-root 3)R30-degrees reconstruction with a nominal 1/3 ML boron occupying subsurface substitutional sites. Both the localized B-Si vibration and carrier surface plasmon excitation were observed by HREELS at 100 K.