Synthesis and characterization of single-crystal Cu(In,Ga)Se-2 nanowires: high Ga contents and growth behaviour

Abstract

Precise control over the defect density, a high Ga content, and uniform stoichiometry are critical for controlling the physical and optical properties of Cu(In,Ga)Se-2 (CIGS) nanowires (NWs). In this study, we investigated the synthesis of epitaxially grown, single-crystal CIGS NWs by a vapour-phase transport method using multiple sources of Ga2Se3, In2Se3, and Cu2Se as the precursors. No catalysts were employed, and r-cut Al2O3 substrates were used for the fabrication of the NWs. The synthesized CIGS NWs had a uniform composition along their length, and the NWs with the highest Ga/(In + Ga) content ratio (0.8) had a chalcopyrite structure. The bandgap energy of the CIGS NWs was higher than that of typical CIGS thin films grown by co-evaporation methods because of the high Ga content ratio. These single-crystal CIGS NWs offer an attractive platform for exploring various concepts related to hierarchical nanostructures and devices based on fully epitaxial semiconductor structures.