Chemical sputtering of GaN crystal with a chlorine-adsorbed layer

A molecular dynamics simulation has been carried out to investigate the chemical sputtering of wurtzite-type GaN(0001) surfaces with and without a Cl-adsorbed layer. Sputtering of crystalline atoms is examined with Ar impacts at energies less than 250 eV. Ga sputtering does not take place at all on the clean surface without Cl-adsorption. On the other hand, Ga sputtering yield has a large finite value for Ar impact on the Cl-adsorbed surface. Generally, Ga is sputtered in the form of Ga-Cl₂, and sometimes in the form of Ga-Cl, Ga-N-Cl, Ga-N, and Ga-N-Ga-Cl₂. Ga atoms are not singly sputtered. Atoms escape from the surface in the time range of 200-3000 fs after the impact of the incident Ar atom. The shorter and longer escape times correspond to physical and chemical sputtering, respectively.