Photo-sensitive And Pressure-sensitive Sensors Based On ZnO And ZnS Nanobelts

With the development of device micromation, integration, and intellengence, nanostructures have attracted considerable attention due to their novel physics and chemistry characteristics for the potential applications in micro- and nano-devices. Many complex nanostructrues, such as nanofibers, nanobelts, nanowires and nanorods have been reported and the size effect, surface effect and dielectric confinement effect have been also explored. ZnO and ZnS nano materials are direct band gap semiconductor,and both of them are hexagonal wurtzite structure with the forbidden gap energy of 3.37 and 3.68 eV at room temperature. Due to the size effect and surface effect, ZnO and ZnS nanomaterials with some novel properties, such as excellent photosensitive and pressure-sensitive properties, become the hot topic in recent years. In this dissertation, the photo-sensitive and pressure-sensitive sensors based on ZnO single nanobelt, ZnO and ZnS nanobelts film were fabricated. For the former sensor the current-voltage (I-V) characteristics and response were measured under different illumination conditions, and for the latter sensors they were tested in air and under different vacuum pressure. The experimental results were explained by oxygen chemisorption and desorption mechanism combining with the schematic diagram of energy band. The main contents of the paper are given as follows.(1)Pt interdigital electrodes were fabricated on SiO2/Si substrate by using radio frequency magnetron sputtering and photolithography method. By controlling the concentration of mixed solution and using the probe technique, ZnO single nanobelt was set up on the interdigital electrodes, and the photo-sensitive sensor was fabricated. I-V characteristics of the photo-sensitive sensor were measured by semiconductor parameters tester and oscillograph. The results show that the photo-sensitive sensor has well shut off performance in darkness. Within the wavelength range of 280-340 nm, the shorter the wavelength is, the higher photocurrent and the larger photosensitivity are. As the UV-light turns"on"and"off", the circuit state can be reversibly controlled by photosensitive sensor conversion between"0"and"1".(2)The acetone solution containing ZnO and ZnS nanobelts were spined on the planar interdigital electrodes to assemble the vacuum pressure-sensitive sensor. I-V characteristics of the prepared pressure-sensitive sensor based on ZnO and ZnS nanobelts film were measured by Agilent 4156C semiconductor parameters tester. The results show that both pressure-sensitive sensors are of high impedance in darkness. With the decrease of the atmospheric pressure, sensor current increases. Resistance-pressure curves got from I-V characteristics curves vary linearly with the vacuum pressure change, the pressure of surrounding environment can be judged according to the changed resistance. The sensitivity range of pressure-sensitive sensor is comparative broad, and the vacuum to atmospheric pressure response is realized.(3)The I-V characteristics and time response of photo-sensitive sensor based on ZnO single nanobelt is reasonably explained by using the photoconductive effect and surface to volume ratio combine with oxygen absorption and desorption theory. I-V characters of the pressure-sensitive sensor based on ZnO and ZnS nanobelts film are explained by using the surface to volume ratio and long transmission path in conjunction with oxygen absorption and desorption theory.