Abstract
The scope of this thesis covers the fabrication of a single titanium oxide nanodot (ND) by atomic force microscopy (AFM) nanolithography, growth of Cu2O nanoparticle (NP) modified ZnO nanowires (NWs) and applications for ultraviolet (UV) light and NO gas sensing. In the first part of thesis, we report on the fabrication of a single titanium oxide ND UV sensor by AFM nanolithography. A single titanium NW is first fabricated by AFM nanomachining and gold contact electrodes are then created by photolithography. By subsequent AFM nano-oxidation, a single titanium oxide ND sensor is produced. Two types of ND sensors, namely ohmic contact and Schottky contact, have been obtained and the sensitivities are around 0.25 and 320, respectively, under ultraviolet illumination. The rise and the reset times of the Schottky contact sensor are also significantly faster. In the second part of thesis, gas sensing using the titanium oxide ND sensor is realized by the photo-activation and the photo-recovery approaches. It is found that a senor with a smaller ND has better performance than a larger one. A response of 31%, a response time of 91 s, and a recovery time of 184 s have been achieved at a concentration of 10 ppm for a ND with a size of around 80 nm. The present work demonstrates the potential application of single metal oxide NDs for gas sensing with performance that can be compared with metal oxide nanowire gas sensors. In the third part of thesis, we report on the NO gas sensing performance of Cu2O nanoparticle (NP) modified ZnO nanowires (NWs) under ambient environment. ZnO NWs are grown on Si substrates using a solution method and then modified with Cu2O NPs by photoreduction. The response of the NP modified NWs sensor to 1 ppm NO gas is 353%, which is 14.7 times as high as that of unmodified NW sensor. A response of 8.5% has been achieved at 60 ppb, showing the good potential for low concentration NO sensing.