Morphology, structure and optical properties of MOCVD grown pseudo-binary alloy nanowires of Zn_1-xCd_xSe on Si and GaAs substrates

Abstract

Long and fine Zn_1-xCd_xSe pseudo-binary alloy nanowires of various compositions x covering the entire range were grown by metalorganic chemical vapor deposition, using diethlyzinc, dimethylcadmium and diisopropylselenide as precursors, on Si (100) and GaAs (100) substrates; sputtered gold was used as a catalyst to promote nanowire formation. By controlling the ratio of the flows of the precursors, the temperature and the pressure during growth, we obtained nanowires of desired compositions. The morphology, structure and optical properties of the nanowires were studied by various techniques, including secondary electron microscopy, atomic force microscopy, transmission electron microscopy, X-ray diffraction, photoluminescence, and Raman scattering. Depending on the substrate, composition and conditions of growth, either the zincblende or wurtzite nanowires were obtained. At compositions where the stable form would have been normally wurtzite, the zincblende form could be obtained under certain growth conditions. From the orientations of the ordered nanowires on the substrate surface, their directions of growth were deduced and confirmed by high resolution lattice imaging. The relationship between the band gap and the composition of the nanowires were measured and found to deviate from that of bulk alloys and epilayers. The interplay between the growth conditions and compositions and morphology of the nanowires are discussed.