Low energy Ar+ bombardment of GaN surfaces: A statistical study of ion reflection and sputtering

Abstract

Statistical molecular dynamics simulations are performed to analyze the sputtering of w-GaN (wurtzite) and z-GaN (zinc blende) surfaces under 100 eV Ar+ ion bombardment. Ion reflection and physical sputtering mechanisms are investigated as a function of the ion impact angle and the crystalline nature of samples. The probability of ion reflection is lower for the w-GaN phase and increases with the angle of incidence θi. As θi becomes more glancing, the reflected ions become more energetic and their angular distribution tends to narrow. The sputtering yields of w-GaN and z-GaN surfaces are maximum for θi=45°. For near-normal incidence, the probability of sputtering is smaller for the w-GaN phase, suggesting that the atomic arrangement in the pristine state modifies the characteristics of the momentum transfer occurring between the ion and the surface atoms during the collision cascade. Atomic nitrogen sputters preferentially and represents 87% to 100% of sputtered species due to its lower mass. These statistical results differ from the predictions of continuous ion bombardment simulations since the surfaces are not allowed to evolve self-consistently during the gathering of impact statistics.