Sputtering yield as a function of incident ion energy and angle in wurtzite-type GaN crystal

A molecular dynamics simulation has been performed for the physical sputtering of a wurtzite-type GaN(0001) surface by an energetic Ar ion. Potential parameters and unit cell parameters are determined on the basis of the periodic restricted Hartree-Fock ab initio method. A sputtering of crystal atoms takes place within about 100 fs after the impact of an incident ion due to a linear collision-cascade mechanism. After approximately 200 fs, the kinetic energy is distributed among many atoms in the crystal creating a hot spot in the impact region of the ion. Nitrogen atoms are mostly sputtered. Ga atoms are always sputtered with N atoms in pairs. The threshold energy is 100eV for N sputtering for perpendicular incidence. The sputtering yield increases as the ion incidence becomes more inclined for the angle range of 60 to 90°.