Changes in morphology and growth rate of quasi-one-dimensional ZnSe nanowires on GaAs (1 0 0) substrates by metalorganic chemical vapor deposition

Abstract

Different forms of zincblende ZnSe nanowires were obtained by metalorganic chemical vapor deposition on GaAs (1 0 0) substrates. The growth of the nanowires was greatly enhanced by depositing a thin ZnSe epilayer on the GaAs substrate and use of a 5 nm gold film sputtered on the epilayer. The dependence of growth rates and morphology of the nanowires on the growth pressure and temperature was studied systematically. For growth at a constant temperature of 550 °C, the optimum pressure was found to be around 50 Torr. For growth at a constant pressure of 100 Torr, the optimum temperature was around 520 °C. Several forms of nanowires were found to coexist. The fraction of each form in a sample was sensitive to temperature but not to pressure. As temperatures changed, one or two forms could dominate the sample. Short rod-like form growing along 〈1 1 1〉 occurred at low temperatures, longer wire-like form growing along 〈1 1 0〉 and blade-like form growing along 〈1 1 2〉 occurred at intermediate temperatures and nodular nanowires, resulting from overgrowth on wires and blades, appeared at high temperatures. Both the epitaxial nature and the direction of growth of the nanowires determined their preferred direction of alignment on the substrate. As the growth direction changed with temperature so did the alignment.