Synthesis And Optoelectric Properties Of Layered Transition Metal Dichalcogenide

Transition metal dichalcogenide,a two-dimensional?2D?material,is of great importance for the applications including optoelectric and electronic devices because of its moderate bandgap,high carrier mobility and thin thickness.At present,the carrier mobility of FET based on TMDc material can reach more than 10 cm²·V^-1·s^-1,and the switching ratio can reach more than 10⁶ and can efficiently detect from visible to near infrared light source.However,there are still two problems in the application of TMDc materials in the field of optoelectronic devices.For one,in order to realize the wide application of TMDc materials and electronic devices,the performance of time response and photogain of devices still needs to be further improved.For another,we should study high efficiency and large area preparation of TMDc materials.Therefore,in order to solve the above two bottleneck problems,this paper mainly carried out the following work.Firstly,Carrier mobility is a very important performance index for FET devices and the First-principle simulations show that HfSe₂ has a very high carrier mobility in many TMDc materials.Therefore,we fabricated the MoS₂ and HfSe₂ field effect transistors and measured the performance of these two type devices.The result shows that MoS₂ is very suitable for optoelectronic and electronic devices,because it with a high on-off ratio?>10⁵?which far greater than HfSe₂?<10?.For HfSe₂,we analyzed the reason of low on-off ratio and prospected some improvement schemes.Secondly,for bare MoS₂ photodetector,the photocurrent generation was mostly arose from the photogating effect which shows higher photogain and slow response speed.For solving this problem,we proposed a MoS₂-CdSe QDs hybrid structure and applied photodetectors which photocurrent derived from thethe generated electrons in CdSe QDs conduction band transfer to the MoS₂.This MoS₂-CdSe QDs photodetector can solve the contradiction between photogain and response speed.It also enable both high photogain,fast photoresponse and increase carrier mobilityThirdly,in order to solve the problems of mechanical exfoliation in the preparation of two-dimensional materials,such as small size,uncontrollable morphology and other bottlenecks.We used the chemical vapor deposition?CVD?for grown MoS₂ and investigated the effects of growth time and temperature on the growth of MoS_2.It provides a basis for the preparation of large area MoS₂ by chemical vapor deposition and has important research value for the application of MoS₂ and other two-dimensional materials in flexible electronic chips,integrated circuits.