A method has been developed to synthesize metal and metal oxide nanostructures in high yields on the
surface of SiO2/Si substrate. In this method, starting materials in a covered alumina crucible are thermally
evaporated under a high vacuum or a low pressure of ambient air. Spherical gold nanoparticles with a
size of 15nmand nanowires with a diameter of 70nmwere synthesized. SnO2 rough microwires, smooth
nanowires, and nanoknives were synthesized by using Sn granules, SnO powder, and SnO2 powder as
source materials, respectively. The microwires showed a quadrangular cross section and a length of
several microns, while the nanowires showed a circular cross section and approximately the same length.
The effects of source temperature and deposition time on nanostructure growth were studied. X-ray
diffraction patterns suggested that the as-synthesized products consisted of crystalline nanostructure.
Nanocomposite gas sensors on the base of noble metal and metal oxide were fabricated. These SnO2
nanowire gas sensors showed a reversible response to dilute NO2 gas at operating temperatures ranging
between room temperature and 300 ◦C even at high concentrations. The results demonstrated that gold
doping improved the sensor response.