Mechanism of arsine adsorption on the gallium-rich GaAs(001)-(4 x 2) surface

The kinetics and mechanism of arsine adsorption on the (4 x 2) surface of g allium arsenide (001) has been studied by scanning tunneling microscopy, in frared spectroscopy, and ab initio quantum chemistry calculations. Arsine f orms a dative bond to a gallium dimer, Then, this species either desorbs fr om the surface or decomposes to an AsH2 or AsH fragment with hydrogen trans fer to an arsenic site. Finally, desorption of hydrogen leaves arsenic dime rs on the surface. The energy barriers for arsine desorption and dissociati on into AsH2 are estimated to be 9.3 and 16.5 kcal/mol, respectively. Galli um hydride is not produced upon dissociation of AsH3 because this process i s not energetically favorable.