The Exploration On Chemical Vapor Synthesis And Photodetection Performance Of Two-dimensional Te Flake

Two-dimensional(2D)elementary materials have been extensively studied in the field of optoelectronics,topological superconductivity and nanosensing owing to their peculiar electronic properties,such as Mott-like insulator states,quantum Hall effect and massless Dirac fermions.However,most reported 2D elementary materials are concentrated on group IIIA to VA,while the research on group VIA is still in the initial stage.Typically,2D tellurium(Te)is expected to be applied in the field of novel optoelectronic devices thanks to the intriguing properties such as ultra-high carrier mobility,significant optical absorption and anisotropic lattice thermal conductivity.Therefore,this thesis mainly carried out research work on the synthesis of high-quality 2D Te nanoflakes by chemical vapor deposition and the exploration of their photoelectric performance.The main research contents are as follows:(1)The hydrogen-assisted chemical vapor deposition method was developed to achieve the controlled preparation of high quality trigonal 2D Te nanoflakes on mica substrates which thickness can be thinned down to?5 nm.The growth mechanism was confirmed by density functional theory(DFT)calculation.It was found that the introduction of H₂ generated two unstable intermediate transition states during the reaction process,which resulted in the orbital hybridization and the rearrangement reaction,promoted the formation of Te chain frame structure,and finally realized the controllable preparation of Te nanoflakes.The hydrogen-assisted strategy may provide a new approach for synthesizing other high quality2D elementary materials.(2)The photoelectric device based on Te flake was constructed to study the regulation mechanism of temperature and gate voltage on performance.Because the thermal activation defects are suppressed at 80 K,the device shows excellent performance:high on/off ratio(?10⁴),ultralow off-state current(?8×10^-13 A)and negligible hysteresis.The regulation mechanism of gate voltage on the photoelectric performance of the device is explored and it is found that the photocurrent plays a leading role in the whole regulation process.Furthermore,with gate voltage varying from-70?70 V,giant gate-dependent photoresponse was observed:I_on/I_off is increased by?40-fold,and responsivity is reduced by?45-fold.