The adsorptıon and dıssocıatıon of AsH₃ and B₂H₆ molecules on stepped ge(100) surface

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2011
Türkmenoğlu, Mustafa
In this work, the doping processes of the SA type stepped Ge (100) surface by arsine (AsH3) and diborane (B2H6) gas flow have been simulated seperately by the possible adsorption and dissociation models. The most stable adsorption and dissociation models of AsH3 and B2H6 on stepped Ge(100) surface have been determined by the local minimum total energy and/or binding energy calculations based on Hartree-Fock Theory. The present calculations have shown that, the step region (both up and down terraces) of the stepped Ge (100) surface has the most attractive sites for the initial adsorption stages of the gas molecules. It has been found that the thermodynamically preferred structures in the dissociation paths of arsine and diborane are the same; AsH3 , BH3 (fragment of diborane), AsH2 and BH2 products prefer to be bounded to a single surface Ge atom, but AsH and BH prefer to be bridged between two adjacent surface Ge atoms. It has been also found that, at the first step of the adsorptions, AsH3 can only dissociate to AsH2, but BH3 can dissociate to both BH2 and BH. This remarkable result has showed that dissociation of BH3 on Ge(100) surface can be easier than AsH3’s. According to the optimization calculations, the dissociation path has started with the adsorption of AsH3 (or BH3) on the electron deficient side (buckled down) of the Ge dimer bond and ended with the occupation of the empty Ge sites in the surface layers by As (or B) atom substitutionally. In the present work, the beginning of the n – (or p-) type doping of the stepped Ge(100) surface has been illustrated by the As (or B) electronic states obtained in the optical energy gap of Ge very close to HOMO (or LUMO) energy edge.

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Citation Formats
M. Türkmenoğlu, “The adsorptıon and dıssocıatıon of AsH₃ and B₂H₆ molecules on stepped ge(100) surface,” M.S. - Master of Science, Middle East Technical University, 2011.