Field Effect Transistors Based On Two-Dimensional Black Phosphorus And Molybdenum Sulfide Semiconductor Nanomaterials

The cornerstone of modern information society is very large scale integrated circuit,and the basic building block of integrated circuit is metal oxide semiconductor field effect transistor（MOSFET）.In the 1960s,Gordon Moore,one of the founders of Intel,proposed the famous Moore’s law:the number of transistors on a chip doubles every 18-24 months,while its performance doubles and its price is halved.With the continuous progress of processing technology and technological innovation,the size of silicon-based field effect transistors（FETs）has approached the physical limit,and the continuation of Moore’s law is facing major challenges.It is necessary to find new electronic device technology to continually promote the development of integrated circuit technology in the future.Two-dimensional semiconductor materials,including black phosphorus and molybdenum sulfide,have excellent electrostatic control characteristics and high carrier mobility,which may be a new material to continue Moore’s law.In this thesis,high performance FETs were prepared based on black phosphorus and molybdenum sulfide by micro/nano fabrication technology.Their transport characteristics were studied,and a simple integrated circuit was constructed.The main contents are as follows:（1）Black phosphorus based FETs and the corresponding passivation technology.FETs were constructed based on layered black phosphorus,which was obtained by mechanical exfoliation.Tin films were deposited on the channel area by electron beam evaporation to form a flat and compact tin oxide film via natural oxidation,which can effectively block water vapor and oxygen in the air to protect the black phosphorus in the channel and thus the transistor.The stability of the devices in the air was studied,and it was found that the device with tin deposition,the mobility of the holes,the current on-off ratio,the maximum current and the sub-threshold swing of the device with a tin film deposition could be maintained in the air for more than 15 days,which indicated the realization of a good protection of black phosphorus-based FETs via passivation.（2）N-type FET based on black phosphorus.Top-gated FETs were prepared by using black phosphorus as channel material,tin oxide thin film as a buffer layer on the channel,and hafnium oxide film grown by atomic layer deposition（ALD）as gate dielectrics.On one hand,tin oxide thin film protects the black phosphorus channel during ALD growth.On the other hand,together with hafnium oxide,it introduces electron doping in black phosphorus,which results in the high performance n-type FET based on black phosphorus.（3）CVD-grown monolayer molybdenum sulfide-based transistor and integrated circuit.Large area and high quality monolayer molybdenum sulfide was grown on silicon wafer with300 nm thick silicon oxide by CVD method.Monolayer molybdenum sulfide-based FETs with top gate were prepared by micro/nano fabrication with hafnium oxide grown at low temperature as dielectrics.The mobility of the devices reached 36.4 cm²V^-1s^-1.Contact resistance between titanium and monolayer molybdenum sulfide were extracted by transfer length method（TLM）.The relationship between contact resistance and channel length is studied,and a simple integrated circuit is demonstrated.