HYDROGEN ADSORPTION ON β-Ga2O3(100) SURFACE CONTAINING OXIGEN VACANCIES

ESTELA A. GONZALEZ; PAULA V. JASEN; ALFREDO JUAN; SEBASTIAN E. COLLINS; MIGUEL A. BALTANAS; ADRIAN L. BONIVARDI

SURFACE SCIENCE

ELSEVIER SCIENCE BV

Año: 2005 vol. 575 p. 171 - 180

0039-6028

The understanding of hydrogen (H) adsorption on gallia is an important step in the design of molecular sensors and alkane dehydrogenation–aromatization catalysts. We have simulated the (100) surface of β-Ga2O3, which is the more frequent cleavage plane. Our study has considered oxygen vacancies in that plane. We have used the Atom Superposition and Electron Delocalization Molecular Orbital (ASED-MO), a semi-empirical theoretical method, to understand both the electronic and bonding characteristic of H on β-Ga2O3 surface. As a surface model, we have considered both a cluster and a five-layer slab. We have found that H adsorption occurs on Ga sites close to oxygen vacancies.   Two types of Ga have also been considered; namely, Ga(I) and Ga(II), with different coordination: Ga(I) is four-coordinated and Ga(II) six-coordinated. The Ga(I)-H bond is ~24% stronger than Ga(II)-H while Ga(I)-O(I) bond is ~44% stronger than Ga(II)-O(I). Also, Ga(I)-O(III) is ~56% stronger that Ga(II)-O(III). The Ga-H and Ga-O interactions are always bonding. The Ga-Ga overlap population is null.    We have assigned the 2003 and 1980 cm-1 infrared bands to the stretching frequencies of Ga(I)-H and Ga(II)-H bonds, respectively.