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

E. GONZÁLEZ; P. JASEN; A. JUAN; S. COLLINS; M. BALTANÁS; A. BONIVARDI

SURFACE SCIENCE

Elsevier

Lugar: Amsterdam; 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 â-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 b Ga2 O3 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 1980cm-1 infrared bands to the stretching frequencies of Ga(I)–H and Ga(II)–H bonds, respectively.