Investigation Of Sensors Based On Semiconductor Nano-wires

Hydrogen, as a green energy, has some important and potential applications in the field of new energy. Since H2 is colorless and odorless, with a wide explosion limit, it is urgent to develop the detection technology which can detect H2 in a wide concentration range effectively. Humidity sensors have some important implications for daily life and industry. Nowadays the novel physical and chemical properties of nanomaterials offered can greatly improve the sensor performance, which opens up a new door for the sensor development. Due to great specific surface-to-volume ratio and high surface activity, silicon nanowire arrays and ZnO nanowire arrays become the potential sensing element in many fields. In this paper, the preparation and application of Pd/SiNWs/p-Si Schottky barrier diode (SBD) hydrogen sensors and ZnO nanowires humidity sensor are stuided. The main content of this paper is as follows:Firstly, the Pd/SiNWs SBD structure is fabricated and characterized by SEM, XRD and EDS tools. SiNWs are prepared by wet chemical etching. The nanowire diameter of SiNWs is 40-80 μm. The XRD results show that the crystalline structure and orientation of SiNWs is same as the silicon substrate. The SEM results show that a porous film composing of Pd particles with size of 1-3 μm are formed on the top of SiNWs, which is an excellent gas sensitive materialSecondly, the Pd/SiNWs/p-Si SBD hydrogen sensor is constructed. The performance of hydrogen sensor is characterized by I-V and I-t test. The impact of Pd layer thickness and SiNWs’ length on the response is studied. And the optimal preparation conditions for Pd/SiNWs/p-Si SBD hydrogen sensor, with etching time of 50min and electroless plating time of 20 min, is obtained. Experimental results indicate the prepared hydrogen sensor has a good performance which can work at room temperature. The chemisoprtion model is employed to analyse the response characteristics and the sensitive mechanism of the Pd/SiNWs/p-Si SBD sensor.Thirdly, the contact characteristics of Pd/SiNW /p-Si SBD are investigated and the electrical mechanism of hydrogen sensor is revealed. Based on Chueng’s model, the data fitting method is developed to extract the characteristic parameters of SBD. The temperature dependent relationships of ideality factor, barrier height and series resistance are analyzed. The influence of hydrogen addition on the aforementioned parameters of SBD is evaluated.Fourthly, ZnO nano-wire arrays humidity sensor was prepared. ZnO seed layer is first deposited on interdigital electrodes prepared by MEMS technology. Then, ZnO nano-wire arrays are fabricated chemical bath deposition method. Experimental results show that the humidity sensor can work under both resistive mode and capacitive mode. For two type sensors, the response time is about 1～2 s. For capacitive sensor, the largest hysteresis is about 3.9%. Under low humidity level, the sensitivity is 78.24 pF/%RH while the sensitivity is 420 pF/%RH under high humidity level. For resistive sensor, the largest hysteresis is about 9.1%. And the sensitivity is up to 3.11 kΩ/%RH under low humidity level and 0.29 kΩ%RH under high humidity level.