INTERACTION OF HCN DCN WITH SI(100)-2X1

We have investigated the spectroscopy and reaction of HCN (DCN) adsorb ed on Si(100)-2x1 at T(s) greater-than-or-equal-to 100 K using HREELS, XPS, and UPS. HCN (DCN) formed dimers and/or polymers on the surface at 100 K and higher dosages (D > 4 langmuirs). The HREEL spectrum obta ined after warming a 4.5-langmuir HCN dosed surface to 220 K resembles that obtained with a lower HCN dosage (D < 0.6 langmuir). Two major s pecies, HCNH and CN, could be identified from this spectrum. The forme r species showed peaks at 160, 368, and approximately 400 meV for HC=N H, CH, and NH stretching vibrations, respectively, while the latter sh owed a peak at 263 meV due to the C=N stretching vibration. In the cor responding DCN experiment, the DC=ND stretching mode was observed at 1 24 meV. Annealing the sample at 560 K appeared to cause the reorientat ion of the CN radical from an end-on to a side-on adsorption geometry as evidenced by HREELS, UPS, and XPS analyses. At 600-800 K, the break ing of NH and CN bonds occurred on the surface. Above 1000 K, a mixtur e of silicon carbide and silicon nitride was formed after the complete dissociation of CH, NH, and CN bonds and the desorption of H species.