Research On Preparation And Photoelectric Propreties Of Narrow Band Gap PdSe₂ Nanosheet

The chips are integrated by transistors.Advances in science and technology need to continuously improve the integration of chips,which requires continuous reduction in the size of transistors.When the size of the transistor is reduced to a certain extent,it is easy to produce a short channel effect,which will cause the device invalidated.The two-dimensional material has an atomic-level thickness and has strong immunity to short channels becoming the leader of electronic device materials in the post-Moore era.Through mechanical exfoliation,vapor deposition and other methods,ultra-thin two-dimensional materials with atomic level flat interfaces can be directly obtained,The mechanical exfoliation can obtain single-layer or few-layer nanosheets,but the method has poor controllability of yield,size,and thickness.The chemical vapor deposition(CVD)method can prepare high-quality,uniform two-dimensional material nanosheets and films,and has become the mainstream method for synthesizing large-size two-dimensional materials.In addition,the instability of most two-dimensional materials in the air easily leads to the degradation of device performance,which greatly affects its promotion in practical applications.In view of this,the efficient synthesis of new two-dimensional materials with good crystallinity and air stability through the CVD method and the full exploration of its excellent electrical and optoelectronic properties are of great significance for future two-dimensional material devices.This thesis first introduces the development of two-dimensional layered materials,and summarizes the structural properties of three typical two-dimensional layered materials.Secondly,we briefly summarizes the current preparation methods of two-dimensional layered materials.Next,the application of two-dimensional layered materials in the fields of electricity and optoelectronics is described.Based on this background,we synthesized palladium diselenide(PdSe₂)by CVD method as a new two-dimensional material,and constructed a field effect transistor(FET)with high mobility and a phototransistor with high responsivity at the same time.The specific work is as follows:(1)We systematically observed the growth law of PdSe₂nanosheets.We made statistics on the thickness,nucleation density,and average lateral size of the nanosheets at different substrate temperatures,and analyzed the effects of different substrate temperatures on the growth mode in detail.(2)The crystal structure of the synthesized PdSe₂nanosheets was characterized by X-ray diffraction(XRD),Raman spectrometer,and transmission electron microscope(TEM).(3)Based on PdSe₂nanosheets,FETs were designed,and their electrical and optical properties were measured.The results show that PdSe₂shows an n-type output operation,an on-off ratio of 10³,and a high mobility of 105 cm²·V^-1·s^-1under different bias voltages.In addition,after the device was placed in the air for 6 months,the mobility only dropped from 100cm²·V^-1·s^-1to 99cm²·V^-1·s^-1,demonstrating the ultra-high air-stability of the device.(4)The photoelectric properties of PdSe₂were measured under the illumination of 914nm laser.PdSe₂phototransistor exhibited good switching performance,and a responsivity of 660 A·W^-1,which is much higher than other phototransistor prepared by chemical vapor deposition grown two-dimension most of nanosheets.The results show that PdSe₂nanosheets with high crystallinity have broad application prospects in future electronic devices and new near-infrared photodetectors.