Epitaxial growth and characterization of high-quality aluminum films on sapphire substrates by molecular beam epitaxy

High-quality Al epitaxial films with homogeneous thickness have been epitaxially grown on 2 inch sapphire substrates by molecular beam epitaxy with an in-plane alignment of Al[1 (1) over bar0]/Al2O3[1 (1) over bar 00]. The as-grown about 200 nm-thick Al (111) films grown at 750 degrees C show excellent uniform thickness distribution over the whole 2 inch substrate and a very flat Al surface with the surface root-mean-square roughness of 0.6 nm, as well as high crystalline qualities with the Al (111) full width at half maximum as small as 0.05 degrees. There is no interfacial layer existing between as-grown Al epitaxial films and sapphire substrates. Instead, sharp and abrupt Al/Al2O3 hetero-interfaces are achieved. The effects of the growth temperature on the surface morphologies and the crystalline qualities of the as-grown Al epitaxial films have been studied in detail. This achievement of Al epitaxial films is of great importance in the application of Al-based microelectronic devices.