Hydrogen adsorption on β-Ga2O3(100) surface containing oxygen vacancies

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 beta-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 semiempirical theoretical method, to understand both the electronic and bonding characteristic of H on (beta-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 similar to24% stronger than Ga(II)-H while Ga(I)-O(I) bond is similar to44% stronger than Ga(II)-O(I). Also, Ga(I)-O(III) is similar to56% 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 1980cm(-1) infrared bands to the stretching frequencies of Ga(I)-H and Ga(II)-H bonds, respectively. (C) 2004 Elsevier B.V. All rights reserved.