Preparation And Photoelectric Properties Of Two-Dimensional MoS₂ And It's Device Performance

MoS₂ is a new two-dimensional material,owing to its unique structure and excellent performance has aroused widespread concern of researchers.MoS₂ also having a great potential in optoelectronic applications due to their adjustable bandgap.The large-scale application of two-dimensional materials is inseparable from the controllable growth of high-quality materials.In this paper,first time we have described on controlled growth mechanism in large-scale mono and multi-layer MoS₂ and also been studied systematically on the effects of growth conditions on the size,thickness and quality of MoS₂ layers.The Photoluminescence?PL?and Raman spectroscopy studies have been carried out at low and room temperatures.Finally,a single layer of MoS₂ based field effect transistor has been fabricated,and the carrier transport properties of MoS₂ were carried out at low temperatures.The datiled results are described as follows:1.The Chemical Vapour Deposition?CVD?method was used to control the growth of large scale mono and multilayers of MoS₂.The obtained monolayer of MoS₂ sizes in the range of 50-xx um whereas in case of multilayer MoS₂,uniformly covered with size of 1 cm x 2 cm or more achived.2.The photoluminescence and Raman spectra of monolayer and multilayer MoS₂ were investigated at both low and room temperatures.At 300 K,the photoluminescence properties of MoS₂ with different layers show that the emission of MoS₂ is enhanced with the decrease of the number of layers,and the reason for the enhancement of monolayer MoS₂ emission was analyzed.The low temperature photoluminescence of monolithic MoS₂ was studied.It was found that there were three excitons of A exciton,B exciton and A-exciton at low temperature of monolithic MoS₂;The low temperature Raman spectra of monolithic MoS₂ were studied.It was found that the monolayer of MoS₂ film was affected by temperature,and the lattice structure was stable at low temperature.It is also found that the electron concentration of monocrystalline sulfide increases with the increase of temperature,and during the temperature rise,the 12)mode suddenly becomes weak or the 22)1 mode suddenly becomes stronger.This anomalous change in vibration will affect the carrier transport properties of a single layer of MoS₂ field effect transistor.3.The properties of MoS₂ field effect transistor devices and the transport properties of MoS₂ carriers were investigated.It was found that the threshold voltage of the device decreases with increasing temperature,indicating that the electron concentration in the monolayer of MoS₂ increases with increasing temperature.At a temperature of 300 K,a single layer of MoS₂ field effect mobilities have been estimated for sevaral devices and their values were found to be in the ranges of of XX-53 cm2.V-1.s-1 and is so far reported that there is no high dielectric constant dielectric layer coated single-layer MoS₂ FET highest Mobility;Through the relationship between MoS₂ mobility and temperature change,when the temperature drops below 220 K,the charged impurity Coulomb scattering is not only caused by the defects at the interface,but also on the scattering of the carriers between the S atoms.When the temperature rises above 220 K,the scattering mechanism that affects the mobility is dominated by phonon scattering,and dominates the optical phonon scattering of the Mo atom and the S atom in the plane.