Electronic and optoelectronic devices using chemical vapour deposited 2D materials

Two dimensional (2D) materials bear a lot of expectations on playing important role in next generation electronics and optoelectronics. Driven by the thrust of this, this project studies the electronic and optoelectronic properties of 2D materials through device fabrication with 2D materials. Graphene and WS2 are the representative 2D materials studied in this thesis. In the study of graphene, a simple method to grow uniform continuous layer of graphene via chemical vapour deposition (CVD) is developed. Factors cause micro-defects like cracks and holes in the graphene sheet are revealed. Our study helps to develop the growth and transfer method of producing chip-sized continuous single layer graphene. This growth and transfer method is currently used as the routine for high quality graphene production in our lab. The study on graphene device fabrication soon extends to device fabrication with other 2D materials like WS2. WS2 photo conductor is fabricated with the CVD WS2. Large gain factor up to several hundred is achieved in WS2 photo conductor. A close link between the large gain and trapped states between WS2 and metal contact is revealed. A photo induced Schottky barrier lowering is measured in this study. Subsequent studies aim to deepen the understanding on the relation between WS2 microstructure and its electronic properties results the fabrication of in-situ electronic devices. A novel in-situ electronic measurement TEM chip is designed and fabricated. Our measurement reveals the detailed atomic structure of WS2 after electronic break-down. Furthermore we developed a one-step method to synthesis WS2 nanoparticles decorated graphene film by electric shock. Our in-situ electronic measurement concludes with a discovery of negative electronic responsivity in the conductance of suspended WS2 single crystal domain. This result cast light on the fabrication of novel 2D direct electron detector.