Quantum Transport Study Of Bi₂O₂Se Nanoplates And Nanowires

Searching for new-type low dimensional semiconductors with excellent electron transport properties is not only of great significance to the realization of future nanoscale devices in industrial applications,but also provides promising platforms for fundamental research concerning strong spin-orbit coupling.Recently,a new layered oxide semiconductor Bi₂O₂Se attracted ever growing attention due to their superior electronic performance and stability in the ambient environment along with an ultrahigh mobility and a moderate bandgap.In this dissertation,by studying the quantum transport properties in Bi₂O₂Se nanoplates and nanowires at ultra-low temperatures,our work demonstrates low dimensional Bi₂O₂Se as a promising platform for constructing multifunctional hybrid superconducting devices as well as for the design of future quantum electronics.The main contents of this dissertation include:In chapter 1,we will briefly introduce the excellent properties of Bi₂O₂Se,and the background knowledge of related theories and experiments.And then,we introduce the motivation of this dissertation.In chapter 2,we will briefly introduce the synthesis of high-quality Bi₂O₂Se thin films and nanowires in a horizontal tube furnace.The method and process of sample preparation are also introduced.In chapter 3,we constructed proximity-type Josephson junctions based on Bi₂O₂Se nanoplates,a new emerging semiconductor with strong spin-orbit coupling?SOC?.Through electrical gating,we show that the supercurrent can be fully turned ON and OFF,and its real-space pathways can be configured either through the bulk or along the edges.Considering the remarkable properties and the strong SOC,our work demonstrates Bi₂O₂Se as an ideal platform for studying numerous novel phenomena.In Chapter 4,we reported on low-temperature electron transport investigations of a new form of material—Bi₂O₂Se semiconducting nanowires.Gate-tunable h/e periodic resistance oscillations in longitudinal magnetic field were observed unexpectedly,demonstrating the existence of novel quasi-ballistic,phase-coherent surface states in Bi₂O₂Se nanowires.By reaching a very good agreement between the calculated density of states and the experimental data,we clarified the mechanism based on the formation of one-dimensional subbands along the circumference of the nanowire rather than the usually considered Aharonov-Bohm interference.A qualitative physical picture based on downward band bending associated with the complex band structure is proposed to illustrate the formation of the surface states.Chapter 5 is the summary and prospect.