Abstraction of α-deuterium on Si(1 1 0) surfaces with H atoms

Abstraction of α-deuterium on Si(1 1 0) surfaces with H atoms was studied with thermal desorption spectroscopy and direct product detection. The α-state 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 monodeuteride. D2 desorption from isolated α-D occurs around 960 K. Abstraction of α-D with H towards HD at 640 K initially proceeds with a cross-section of 1.8 Å2, but the simultaneous formation of the monohydride reduces this value to 0.2 Å2. Post-reaction desorption spectra revealed that monohydride H and α-D do not react with each other. Abstraction of α-D at 875 K, whereby formation of monohydride is suppressed, proceeds with a cross-section of 0.7 Å2 and leads to a complete removal of α-D and negligible population of α-sites by H. Stepwise abstraction of α-D at 640 K with repeated removal of the monohydride phase by flashing the sample to 875 K proceeds in each step with a cross-section of 1.8 Å2. The abstraction phenomenology is in accordance with an α-state which is related with sites underneath the surface layer.