Surface And Interface Structures Of Epitaxial Sb2se3 On Mica

Sb2Se3 thin film is an emerging photon absorber used in solar cells. We report the study of surface and interface structures of Sb2Se3(120) film grown on mica substrate by a high-rate vapor transport method. The interface epitaxial relationship between Sb2Se3 and mica examined by the cross- sectional TEM images and diffraction patterns along the [001] and [10](2) over bar directions of Sb2Se3 reveal a rectangular structure with lengths of 4.03 +/- 0.1 angstrom and 5.29 +/- 0.1 angstrom, consistent with the [120] out-of-plane direction of Sb2Se3 bulk lattice parameters. In contrast, the two-dimensional reciprocal space map (2D map) constructed from azimuthal reflection high-energy electron diffraction (ARHEED) patterns from the surface exhibits a decorated hexagonal structure. This surface structure emerges from six epitaxial orientation domains/rods and each domain has a rectangular unit mesh of 3.94 +/- 0.09 angstrom and 26.95 +/- 1.16 angstrom along the [001] and [10](2) over bar directions. The 26.95 angstrom is consistent with the unit mesh of the outermost layer of the Sb2Se3 (120) domains/rods. Our 2D map reveals surface information that are not easily observed by other diffraction techniques.