Single- and double-shelled coaxial nanocables of GaP with silicon oxide and carbon

Coaxial nanocables of gallium phosphide (GaP) core with three different-typed single and double shells (i.e., silicon oxide (SiO(x)), carbon (C), and SiO(x)/C) were exclusively synthesized by the chemical vapor deposition method. The GaP/SiO(x)) nanocables were directly grown on gold-deposited silicon substrates. Deposition of C on the GaP nanowires and GaP/SiO(x) nanocables produces the GaP/C and GaP/SiO(x)/C nanocables, respectively. The outer diameter of the nanocables is <50 nm. The thickness and crystallinity of the C outer layers were controllable by the growth conditions. X-ray photoelectron spectroscopy, X-ray diffraction, Raman spectroscopy, and photoluminescence reveal that the outer layer formation reduces the surface defects of GaP nanowires. A great enhancement of the conductivity due to the C outer layers has been measured by the four-probe method. The growth process of these nanocables has been discussed on the basis of the vapor-liquid-solid mechanism.