Transport Properties And Gas Sensor Research Of Single SnO₂Nanowire Device

With a Quartet of rutile structure of SnO2nanowire is a kind of direct wide bring gap N-typesemiconductor material, the band gap is3.6eV at room temperature. Due to the morphology of thenanowires structure with large specific surface area, high surface activity and quantum size effect of thecharacteristics such as excellent optical and electrical properties, making them such as gas sensor, UVdetectors, solar cell and lithium-ion batteries have a wide range areas of application value. In this thesis, wesuccessfully built Schottky contact form SnO2-based nanowire devices by AC electric field method ofassembling, via annealing and ultraviolet light radiation method of regulating to study current transportproperties of SnO2nanowires. Based on the transport properties of nanowires, we tested under differentconditions of single gas sensing properties of SnO2nanowire devices. Specific research contents thefollowing points:In2thchapter, we utilize methods of chemical vapor deposition to synthesize the SnO2nanowires,through characterization of the morphology and structure of nanowires, we concluded that the growth ofnanowire composite VLS mechanism. And successfully loads the diameter about20nm gold nanoparticlesat the nanowire by hot pressing method. Finally a single SnO2nanowire devices assembled in AC electricfield method to construct.In the third chapter, we successfully build a single nanowire device and annealed at differenttemperatures found: with increasing annealing temperature, part devices consists of Schottky contactsturned into Ohmic contact, while another parts remain Schottky contacts. Subsequently we do a electricaltest under UV on different contact types of nanowire devices and get results: based on Schottky contact ofdevices compared to Ohmic contact of devices on purple outside light has is high of sensitivity and fast ofresponse speed, on purple outside light of sensitivity up to4orders of magnitude. We analysis the reasonmay be two kinds of contact in different types of device response mechanism to UV light.Chapter4, we are in contact with different types of devices under different conditions, respectively, to10ppm H2S and100ppm CO do the air-sensitive lab test: Under the same conditions of temperature,Schottky type device for the sensitivity of H2S is almost two orders of magnitude higher than Ohmic type device, response and recovery speed also have greatly improved, mainly because of the Schottky barrierreverse current varies with the adsorption and desorption of oxygen caused an exponential change. UnderUV-radiation, gas sensors for H2S increase to80%in sensitivity, increased to317%sensitivity for CO,response, and recovery speed improves, description of UV radiation is an effective way of improvinggas-sensing properties of the devices. At the same time we synthesized size in about20nm goldnanoparticles, and successful modification to the surface of SnO2nanowires, and the single root ofmodified with gold nanoparticles SnO2nanowires devices gas sensitive test, results found that: comparedwith the nanowire device does not load, the sensitivity increased by1465%at the largest, response speedincreased by825%, recovery rate raised150times. We obtained modifying gold nanoparticles on thesurface of the nanowire is a more effective way to improve nanowires gas-sensing performance.