Humidity Effect On The Electrical Properties Of Graphene Silicon Schottky Junction

Graphene was first found by scientists from the UK with mechanical exfoliation of graphite. Since then, it has been touted as "the wonder material" for its superior electric conductivity, high thermal conductivity, large mechanical strength and almost transparency. The large specific surface area and atomic-layer 2-dimensional properties have made graphene get unprecedented attention in the sensors applications, from that of traditional tactile sensors, positional sensors to superconductivity detectors and particle detectors, from the chemical sensors to variant biosensors. In the foreseeable future, the graphene based sensors will get further development.In this thesis, the microelectronic process to fabricate the graphene/silicon Schottky junction based devices has been developed in the clean room on the Platform for Micro and Nano Fabrication of Zhejiang University. The influence of humidity on the electrical properties of graphene/silicon Schottky junction under different humidity conditions has been studied. A multi-mode low power humidity sensor was fabricated. And for the first time, we proposed a novel graphene oxide/graphene/silicon heterostructure by spin-coating GO solution to that of graphene/silicon Schottky junction for practical applications. Thus we have demonstrated the potential applications of graphene oxide in the humidity sensing field. A detailed study is show below:1. A mature and stable process has been achieved to fabricate graphene/silicon Schotttky junction. Based on the Platform for Micro and Nano Fabrication of Zhejiang University, we have successfully developed the process for graphene/silicon Schottky junction based devices.2. The i-v, c-v characteristics under DC and AC condition of the graphene/silicon Schotttky junction have been studied under different humidity conditions and the appropriate theory has been proposed. A multi-mode, i.e. Schottky junction mode, resistance mode, capacitance mode, and low power graphene heterostructure humidity sensor has been fabricated. We found that the humidity effect on the electrical properties of graphene/silicon Schottky junction is a comprehensive result of Langmuir adsorption, p-doping and the penetration of water molecules by experiment. The macro result of these effects is the changes of resistance and capacitance of the Gr/Si Schottky devices.3. A demonstration has been made to show the potential applications of graphene oxide in the humidity sensing field. By spinning-coating a hydrophilic layer of graphene oxide to the surface of graphene/silicon Schottky junction, we made the heterostructure device. The charge transfer process between graphene oxide and water molecules enhances the current of the sensor. By measuring the junction current, we have got the primary performance of the sensor.The process that we have developed to fabricate graphene silicon Schottky junction device is simple and compatible with the traditional silicon semiconductor processes. It is expected to be applied in solar cells, photodetectors and a variety of biochemical sensors. The newly proposed X/Gr/Si structure may help enlarge the range of applications of graphene and graphene like 2-dimensional materials, and broaden our view of 2-dimensional materials.