Surface evolution of NaCl-type cubic AlN films on MgO (100) substrates deposited by laser molecular beam epitaxy

Abstract

Highly oriented NaCl-type cubic AlN (c-AlN) films were successfully deposited on MgO (100) substrates by laser molecular beam epitaxy (LMBE) technique, and the time-dependent evolution of film surface was characterized. Based on the topography images and roughness analysis, c-AlN surfaces display the Stranski–Krastanov growth mode. In the initial stage, AlN adatoms prefer to settle along the substrate steps and the surface appears to be slightly rough. The following deposition causes an undulate surface, and the nucleation and early growth of 3D islands are observed. During the islands growth, a rapid increase of roughness occurs, and large and deep gaps on the top of islands are striking. A smooth surface with a roughness of 1.06nm is obtained at the growth time of 2h owing to the spread and coalescence of islands.