SURFACE-CHEMISTRY OF S-TRIAZINE ON SI(100)-2X1

The thermal decompositon of s-triazine (ST) on Si(100)-2X1 was studied with HREELS, UPS, XPS, and TDS. Two desorption peaks at 180 and 235 K were noted in the TD spectra due to the overlayer and the mono- or su bmonolayer adsorbates, respectively. Above 200 K, the ST is likely to lie flat on the surface as indicated by the virtual absence of the asy mmetric ring breathing mode at 145 meV in HREELS and by the relatively lower ST coverage (<0.3 L) at T-s > 200 K. Annealing a 1.2-L ST-dosed sample at 550 K caused the dissociation of ST into HC=N, accompanied by the formation of NH and SiH bonds. Further annealing the surface at 780 K dissociated the CN-containing species and the NH bond. Above 80 0 K, a mixture of silicon nitride and silicon carbide was formed on th e surface following the cracking of the CH bond and the desorption of the H species. The photodissociation of ST on Si(100)-2x1 was also exa mined; CN radicals and the HCN species could be identified on the surf ace after it was exposed to 308-nm excimer laser radiaton at 100 K. Th e appearance of CN radicals reflects the difference between the therma l decomposition reaction and the photodissociation process.