Magnetic Properties of Intrinsic Vacancies on the GaN(10 (1)over-bar0) Surface: a Density-functional-theory Study

Abstract

We report density functional theory calculations on the vacancy-induced magnetic properties of the wurzite GaN(10 (1) over bar0) surface. Among various intrinsic vacancies on the surface, we focus on the monatomic Ga and N vacancies. We have found two stable geometries of a surface Ga vacancy and one stable geometry of a surface N vacancy. Two stable surface Ga vacancy structures are shown to have magnetic moments of 3 mu(B), which is the same as for the bulk Ga vacancy. Differently from the bulk N vacancy carrying null magnetic moment, the monatomic surface N vacancy has a finite magnetic moment of 1 mu(B). These results support the experimental claim that the room-temperature ferromagnetism observed in inorganic nanoparticles is due to surface vacancies and their complexes. We also present simulated scanning tunneling microscope images for comparison with those obtained in future experimental studies.