Study On Physical Property Modulation Of Two-dimensional Nanomaterials And Devices

Monoatom-level two-dimensional(2D)nanomaterials with excellent physical properties have been widely used in the field of electronics and optoelectronics,and have attracted much attention since their discovery.However,the intrinsic 2D nanomaterials obtained by mechanical peeling often have problems such as uncontrollable thickness,uncontrollable carrier concentration/type,and easy degradation in the air.These problems have led to the instability of the performance of nanodevices fabricated in 2D nanomaterials,making them difficult to apply in practice.Therefore,effective modulation of the physical properties of 2D nanomaterials and devices(such as material thickness,stability,anisotropy,carrier type,carrier mobility,switching ratio,contact resistance,etc.)is the key to the practical application of 2D nanomaterials.On the one hand,the methods of modulating the stability,thickness and electrical properties of black phosphorus(BP)were systematically studied.On the other hand,two methods of doping molybdenum selenide(Mo Se₂)were innovatively proposed,and the Mo Se₂ homojunction was constructed,which provided a new idea for its application in the field of photoelectric detection.The main research contents are as follows:1.The methods of enhancing the stability of BP were studied.In this paper,the BP material is treated with water/acetone solution containing TEMPO and[Ph₃C]BF₄to achieve the surface modification of BP by TEMPO molecule,thus inhibiting the interaction between BP and O₂ and H₂O molecules in the air.This method can keep the excellent stability of BP in air for more than four months,and can significantly improve the working life of BP thin film devices and photodetectors.2.The method of modulating the thickness of BP was studied.Two schemes for BP thinning are proposed in this paper:wet-chemical thinning of BP and two-step annealing thinning of BP.The former uses dichloromethane solution containing 2,2,6,6-tetramethylpiperidine nitrogen oxide(TEMPO)and triphenyltetrafluoroborate carbon([Ph₃C]BF₄)to treat and thinning BP materials.The method has good selectivity,and the thinning rate is equivalent to that of physical thinning(?4 nm/min),so it can be used for large-scale thinning of BP.The latter is annealed in air to oxidize the surface of BP,then annealed in nitrogen and hydrogen mixture to sublimate the oxide and realize the thinning of black phosphorus.This method can produce single layer of BP.The Bp obtained by these two methods has fewer lattice defects and lower surface roughness.The hysteresis of the field effect transistor(FET)fabricated by these two methods is significantly reduced and the switch ratio is increased by two orders of magnitude.3.The method of adjusting the carrier concentration of BP was studied.In this paper,TEMPO molecule is used to modify the surface of BP.By controlling the modification time and solution concentration,the carrier concentration and mobility of BP P-type carriers can be effectively adjusted,thus the current on/off ratio,contact resistance and electrical and optical anisotropy of BP FET can be adjusted.4.The homojunction of Mo Se₂ and its application in photoelectric detection are studied.Firstly,the method of converting Mo Se₂ from n-type to p-type by rapid annealing is proposed.Secondly,the n-type doping of Mo Se₂ is realized by triphenylphosphine(PPh₃).Finally,the homo junction of Mo Se₂ is prepared by these two methods and applied in the field of photoelectric detection,with a response of 1.3A·W^-1.