Abstraction of alpha-deuterium on Si(110) surfaces with H atoms

Abstr. of alpha -deuterium on Si(1 1 0) surfaces with H atoms was studied w ith thermal desorption spectroscopy and direct product detection. The a-sta te was populated by admission of D from a thermal source to annealed Si(1 1 0) surfaces at 640 K and subsequently isolated by flashing off the monodeu teride. D, desorption from isolated alpha -D occurs around 960 K. Abstracti on of alpha -D with H towards HD at 640 K initially proceeds with a cross-s ection of 1.8 Angstrom (2), but the simultaneous formation of the monohydri de reduces this value to 0.2 Angstrom (2). Post-reaction desorption spectra revealed that monohydride H and alpha -D do not react with each other. Abs traction of alpha -D at 875 K, whereby formation of monohydride is suppress ed, proceeds with a cross-section of 0.7 Angstrom (2) and leads to a comple te removal of alpha -D and negligible population of a-sites by H. Stepwise abstraction of alpha -D at 640 K with repeated removal of the monohydride p hase by flashing the sample to 875 K proceeds in each step with a cross-sec tion of 1.8 Angstrom (2), The abstraction phenomenology is in accordance wi th an a-state which is related with sites underneath the surface layer. (C) 2001 Elsevier Science B.V. All rights reserved.