DISSOCIATIVE ADSORPTION OF SIH2CL2 ON SI(111)7X7

Adsorption and reaction of SiH2Cl2 (DCS) with Si(111)7 x 7 at 300 K we re investigated by spectroscopic (XPS, AES) and atomically resolved to pographic (STM) measurements. It is shown that DCS adsorption proceeds under scission of a Si-Cl bond to produce SiH2Cl and Cl, where the fo rmer adsorb at a rest atom or corner hole dangling bond, while the Cl atom reacts with an adjacent adatom dangling bond. This is explained i n a four center reaction mechanism, involving two neighboring dangling bonds of the substrate and two centers of the polar DCS molecule. Eva luation of the Cl site occupation, including pair correlation and site blocking effects, shows a preferential Cl termination of center adato ms. This mechanism also explains the observed second order kinetics fo r DCS adsorption.