Research On Preparation Of Large Area Thin Layer MoS₂ And Its Gas Sensing Application

Two-dimensional materials have great application prospects in photoelectric devices,sensors and short channel devices due to their excellent photoelectric performance and their atomic thickness.Among them,MoS₂ has attracted the most attention due to its stable chemical properties and suitable band gap width.A variety of preparation methods have been reported,including mechanical stripping,chemical vapor deposition?CVD?,and liquid phase stripping,but it has been a challenge to easily obtain high-quality MoS₂ films over large areas.In this paper,the preparation of large-area high quality MoS₂ films and the application of MoS₂ in gas detection are studied.The main work and innovation points of this paper mainly include the following three aspects:1.Preparation of high quality MoS₂ films.By taking advantage of the relatively strong interaction between gold and sulfur bonds,we can effectively strip off a large area of thin layer of MoS₂ with the size up to several hundred microns by evaporation and plating a layer of gold on the massive MoS₂ surface.Through the systematic optimization of the preparation process,the stable molybdenum sulfide film was obtained.The mobility of the FET can be up to 10⁶,which is similar to that of the chip by the traditional stripping method.This provides convenience for the subsequent regulation of the electrical properties of MoS₂ and its application in gas detection.2.Preparation of MoS₂ FET and study on the performance of organic and inorganic heterojunction.Due to the large size of the prepared MoS₂,the source leakage electrode was prepared by means of a metal mask,so that we could not rely on the complicated micro-nano process in the process of device preparation.MoS₂ material intrinsic will exist a large amount of sulphur vacancy,and the existence of sulphur vacancy exists a large number of free electrons in MoS₂,resulting in MoS₂ transistor under negative grid voltage open,we through a series of organic material deposition on the surface of MoS₂ formation heterojunction,found to be effective adjustment of the MoS₂ transistor voltage.This regulation mechanism is also analyzed.The small organic molecules can capture the electrons in MoS₂,and the gate voltage can be considered as the charge carrier for MoS₂.Finally,we compare the regulation of FET by three kinds of organic molecules with different affinity.3.Improvement of gas detection performance by organic/MoS₂ heterostructure.Large area MoS₂ has great advantages in gas detection applications.However,the detection performance of MoS₂ to the donor gas molecules is severely limited by the large number of electrons in MoS₂.We greatly improved its response to ammonia?210 times?and detection range?up to3000 ppm?by regulating the carrier concentration of MoS₂ through the heterostructure composed of small organic molecules and MoS₂.By changing the coverage of organic molecules,the mechanism of the hybrid system's response to gas sensation was explored.