The Growth, Characterization, And Applications Of Doped Sno₂ Nanowires

The thesis reports on the growth of single-crystalline SnO₂ nanowires via vapor transport. Sb-doped SnO₂ nanowires have been synthesized from in-situ doping during Vapor-Liquid-Solid growth process. Furthermore, undoped SnO₂ nanowires have been grown expitaxially on Sb-doped SnO₂ nanowires backbones via the two-step Au catalyzed growth technique and three dimensional branched SnO₂ nanostructures have been obtained. Scanning Electron Microscopy was used to characterize the morphologies of SnO₂:Sb nanowires and the branched nanostructures from different synthetic procedures. High Resolution Transimission Electron Microscopy (HRTEM), Selected Area Electron Diffraction (SAED) and Raman Spectroscopy were applied to characterize the microstructure of individual SnO₂ nanowires, SnO₂:Sb nanowires and SnO₂/SnO₂:Sb branched nanostructures. The single-crystalline nature was confirmed of these three types of nanostructures.Sb-doped SnO₂ and SnO₂ nanowires were integrated into nanowire metal-oxide-semiconductor field effect transistors (MOSFET) by the conventional microelectronics procedures. The Square-Law Model that describes the threshold voltage of conventional one-dimensional MOSFET, in conjunction with modification of the gate dielectric constant, was used to extract material physical parameters of SnO₂:Sb and SnO₂ nanowires, respectively. The free carrier concentration of the SnO₂:Sb nanowire is calculated to be ².8×1020cm^-3; while for the latter, the field effect mobility is calculated to be 2.67V.cm²/s. The SnO₂:Sb nanowires were found to be degenerately doped and are promising for the electrical interconnections in future"bottom-up"nanoelectronic circuits.The mixture of SnO₂:Sb and SnO₂ nanowires (material I) and the SnO₂/SnO₂:Sb branched nanostructures (material II) were fabricated into nanofilm type chemical sensors. Both sensors were measured of their sensing properties towards ethanol vapor under 30% relative humidity and 300°C operation temperature. The sensor based on material I exhibited detection limit as low as 10ppm, linear range from 30ppm to 500ppm, and very short response and recovery time---the shortest 2 seconds while the longest 47 seconds in this linear range. The sensor based on materialⅡexhibited detection limit as low as 10ppm too, linear range from 10ppm to 100ppm, and very short response and recovery time---the shortest 3 seconds while the longest 14 seconds in this linear range.