MoO₃ Limited Growth Of Tin Disulfide Nanosheets And Rapid Thermal Annealing Effect In Field Effect Transistors

According to the Moore’s law,the integration of integrated circuits in semiconductor industry will be twice then before every one and a half years to two years.However,the silicon materials used in traditional processes are restricted by the preparation process and are almost to the limit.Searching for suitable materials to replace silicon has become a necessary trend for discovery.Graphene has become a research hotspot in various fields since it was successfully prepared in the laboratory.Because of its mobility up to 15000 cm2V-1s-1,it has become one of the candidate materials for the next generation semiconductor industry.However,because of its bandgap is zero,the turn-off current of the device is high and the switch ratio is very low after the semiconductor device is manufactured.Therefore,how to open the band gap of graphene has become the focus of research.In the existing reports,it has been successful to open the band gap of graphene,but at the same time the high mobility of graphene will decrease,so its industrialization needs further study.However,based on the discovery of graphene,Two-dimensional materials have become a research hotspot because of their natural advantages.Among of which,Two-dimensional layered metal chalcogenides are one of the most important,Their band gap is leV-3eV,which makes the fabricated field-effect transistors have high switch ratio and become one of the excellent candidates for the next generation of semiconductor industry materials.Consideringthe cost,non-toxicity,mobility and other factors,we choose non-toxic and tow-cost tin disulfide as the researchmaterial,ultra-thin nanosheets were prepared.and studied the performance of FET,the main work is as followings:1.Two-dimensional tin disulfide material was grown on Si/SiO2 substrate by chemical vapor deposition.SnI2 was selected as tin source and high-purity sulfur as sulfur source,The thickness of the Nanosheets was over 10 nm.However,Tin disulfide nanosheets with a thickness of4.12 nm and a size larger than 100μm were prepared by mixing molybdenum trioxide powder with tin source.Atomic Force Microscopy(AFM)characterization shows that SnS2 nanosheets grown by using stannous iodide as tin source have helical dislocations,while the existence of molybdenum trioxide powder makes SnS2 grow model is layer by layer,and the obtained SnS2 nanosheets have no dislocation and have smooth surface.The thickness of tin disulfide grown under with mixing molybdenum trioxide powder is decreases,which proves that the oxide film plays a restrictive role in thinning the thickness of nanosheets.The prepared nanosheets were characterized by Raman spectroscopy,which confirmed that without the presence of molybdenum disulfide..The analysis of XPS and Raman spectra show that there is no Mo doping in tin disulfide.2.Using the Ti/Au electrode as the source electrode and drain electrode,the Si/SiO2 substrate as the gate electrode,the SnS2 prepared is used to make the field response transistor with back gate structure,and test the performance of the transistor.It is found the device mobility is 2.851cm2V-1s-1 and the switch ratio is 105.In the process of device fabrication,it is found that there is a problem in the contact between metal electrode and material in some devices,which affects work of the devices.The rapid annealing of these devices can improves the contact between the material and the metal electrode,and improves the test results of the device.It is found that the annealing temperature is 400 ℃ and the holding time is 60s,we can get best performance of devices.Before annealing,the mobility of the device is 0.596cm2V-1s-1,the switching ratio is 105.After annealing,the mobility of the device is 3.213cm2V-1s-1 and the switch ratio is 105.It can be found that after rapid annealing of the devices,the performance of the devices as good as the devices in good contact,and there is no damage to the devices in good contact After annealing,the mobility of the device is increased from 2.851 cm2V-1s-1 to 3.021cm2V-1s-1.The switch ratio is still 105.It is shown that rapid annealing can effectively improve the success rate of device fabrication,which is very important for mass production.3.In order to explore the general applicability of rapid annealing method.Tin disulfide were obtained by mechanical stripping using commercially purchased single crystal tin disulfide,and field response transistors were fabricated.It is found that the performance difference of the devices before and after annealing as the same as that of SnS2 nano sheets prepared by chemical vapor deposition(CVD)under the same annealing conditions for the devices with poor contact.Before annealing,the mobility of the device is 0.713cm2V-1s-1,and the switching ratio is 105.After annealing,the mobility of the device is 3.752cm2V-s-1 and the switch ratio is 105.It is proved that the rapid annealing method is universal to the tin disulfide prepared by different methods.