Characterization of grain boundary properties in BaSi2 epitaxial films on Si(111) and Si(001) by Kelvin probe force microscopy

Grain boundaries (GBs) in a-axis-oriented semiconducting n-BaSi₂ epitaxial films on Si(111) and Si(001) grown by molecular beam epitaxy were evaluated using Kelvin probe force microscopy. The GBs of n-BaSi₂ on Si(111) has a higher electrostatic potential by approximately 30 meV than the grain interior. Thus, a concave band structure of the valence band minimum (VBM) is assumed and the GBs do not work as recombination centers for minority carriers (holes) in the n-BaSi₂. In contrast, the GBs of BaSi₂ on Si(001) has a lower electrostatic potential by approximately 50 meV than the grain interior. This means that the GBs have a convex band structure of the VBM, and thus are likely to work as trap centers for holes in n-BaSi₂. These results present the difference in the GB character of a-axis-oriented n-BaSi₂ epitaxial films, depending on the Si surface used.