Solvothermal preparation and spectroscopic characterization of copper indium diselenide nanorods

Single-crystalline chalcopyrite CuInSe(2) nanorods (CuInSe(2)NRs) of 50-100 nm in diameter and up to a few micrometers in length have been synthesized solvothermally. High-resolution transmission electron microscopic images of the CuInSe(2)NRs reveal the d-spacing of 0.335 nm for the (112) crystalline planes and a growth direction along [331]. The near-infrared absorption spectrum of the chalcopyrite CuInSe(2)NRs shows a peak maximum at 1162 nm and an onset at 1262 nm, indicating no apparent blue-shift compared with those of Cu-rich CuInSe(2) thin films. An intense peak at 175.1 cm(-1) in the room-temperature Raman scattering spectrum of CuInSe(2)NRs corresponds to the A(1) phonon mode of tetragonal CuInSe(2) chalcopyrite. The narrower full width at half-maximum (fwhm) of 9.5 cm(-1) for CuInSe(2)NRs, in comparison with fwhm approximately 12 cm(-1) for CuInSe(2) films, indicates a uniform size distribution and single crystallization in the nanorods. Analysis of the photoluminescence from the single-crystalline CuInSe(2)NRs measured at 10 K has categorized the emission into seven groups of transitions as characterized by free excitons, bound excitons, conduction band to acceptor levels, and bound excitons at different defects.