Growth and characterization of zinc-oxide films grown by using plasma-assisted molecular beam epitaxy on (111) silicon substrates with Ti and titanium compound buffer layers

Abstract

The possibility of sputter-deposited Ti and processed Ti compounds as buffers for the growth of epitaxial ZnO films on (111) Si substrates by using plasma-assisted molecular beam epitaxy (PAMBE) were studied. We used four types of substrates: 1) a bare (111) Si substrate, 2) an as-deposited Ti/Si (111) substrate, 3) Ti/Si (111) substrates nitrided or oxidized by using an electric furnace under a N(2) or an Ar+O(2) ambient and 4) Ti/Si (111) substrates treated with a N or an O plasma in the PAMBE chamber. The ZnO films were not single crystalline, but grew with a highly preferred orientation along the < 0001 > direction. The buffers investigated in this study were effective in improving the crystal quality of the ZnO films on (111) Si substrates although single-crystalline ZnO films were not grown. Among the investigated samples, the ZnO film on the oxidized Ti/Si substrate had the narrowest X-ray rocking curve (XRC) with a Full width at half maximum (FWHM) of 3.05 degrees while the ZnO film on the bare Si substrate showed a very broad XRC with a FWHM of 11.793 degrees. We expect that epitaxial or high-quality Ti oxide may be a promising buffer for the growth of high-quality, epitaxial ZnO films on (111) Si substrates.