ATOMIC HYDROGEN-DRIVEN HALOGEN EXTRACTION FROM SI(100) - ELEY-RIDEAL SURFACE KINETICS

The interaction of atomic hydrogen with halogen-terminated Si(100) surfaces was studied by Auger electron spectroscopy (AES) and temperature-programmed desorption (TPD) mass spectroscopy. Efficient removal of surface halogen has been observed when the halogen-terminated Si(100) surface was exposed to atomic hydrogen at a substrate temperature, T less-than-or-equal-to 630 K. The reaction rate constants for halogen extraction on the Si(100) surface follow the trend k(I) > k(Br) > k(Cl). In addition, the halogen extraction kinetics are found to be first order in both the surface coverage of halogen and in the atomic hydrogen flux. Studies of the temperature dependence of the halogen extraction rate show the activation energies for the extraction of Cl and Br are 2.1 +/- 0.2 and 1.6 +/- 0.2 kcal mol-1, respectively. The extremely low activation energy for the reaction demonstrates that the H-extraction process follows an Eley-Rideal reaction mechanism where the surface reaction is mainly driven by the high internal energy of incident atomic hydrogen instead of thermal excitation from the Si(100) solid surface.