Theory of Adsorption and Desorption ofH2Molecules on the Si(111)-(7×7)surface

Abstract
The physics of adsorption and desorption of H2 molecules on the Si(111)- (7×7) surface is investigated through first-principles density functional theory calculations. The calculated adsorption and desorption energy barriers are 0.8 and 2.4 eV, respectively. The process of adatom backbond breaking is identified as the fundamental microscopic mechanism determining the adsorption energy barrier and the kinetic energy of the desorbed H2 molecule. These results shed light on controversial experimental findings for this classic surface–molecule system.