Li, TianfengChen, YonghaiLei, WenZhou, XiaolongLuo, ShuaiHu, YongzhengWang, LijunYang, TaoWang, Zhanguo2015-12-101556-276Xhttp://hdl.handle.net/1885/58801Catalyst-free, vertical array of InAs nanowires (NWs) are grown on Si (111) substrate using MOCVD technique. The as-grown InAs NWs show a zinc-blende crystal structure along a < 111 > direction. It is found that both the density and length of InAs NWs decrease with increasing growth temperatures, while the diameter increases with increasing growth temperature, suggesting that the catalyst-free growth of InAs NWs is governed by the nucleation kinetics. The longitudinal optical and transverse optical (TO) mode of InAs NWs present a phonon frequency slightly lower than those of InAs bulk materials, which are speculated to be caused by the defects in the NWs. A surface optical mode is also observed for the InAs NWs, which shifts to lower wave-numbers when the diameter of NWs is decreased, in agreement with the theory prediction. The carrier concentration is extracted to be 2.25 × 1017 cm-3 from the Raman line shape analysis. A splitting of TO modes is also observed.Keywords: As-grown; Bulk materials; Catalyst-free; Catalyst-free growth; InAs; Longitudinal optical; Nucleation kinetics; Phonon frequencies; Phonon properties; Raman line shapes; Si substrates; Si(111) substrate; Surface optical; Theory predictions; Transverse opt201110.1186/1556-276x-6-4632016-02-24