A First-principle Study On Transport Properties Of Two-dimensional Borophene Gas Sensor

Gas sensors are widely used in industrial production and daily life.In recent years,with the emergence of new materials and devices,a variety of new sensors have also received extensive attention and intensive research.Among them,two-dimensional（2D）materials have unique advantages,such as large surface area to volume ratio and abundant surface properties,so more and more people begin to pay attention to 2D materials,and try to make 2D materials gas sensors theoretically and experimentally.Among many 2D materials,borophene（B）has excellent optical and electrical properties,and many theoretical calculation articles have reported the related work of using borophene to prepare gas sensors.However,these theoretical works are generally only concerned with the transport properties of borophene or borophene-based vertical heterostructure when adsorbing different gas molecules,without considering the influence of metal electrodes on the transport properties of the whole system.In this work,from the complete structure of borophene-based gas sensor device,a complete transport model including metal electrodes,borophene or its vertical heterostructure and related adsorption molecules is constructed.And the effects of gas molecules,molybdenum disulfide（MoS₂）substrate and gold（Au）electrodes on the transport properties of borophene-based gas sensor are studied by using the first-principle.The results show that:（1）When B and MoS₂ form a heterostructure,due to the charge transfer from molybdenum atom to boron atom,molybdenum atom produces a new band contribution at Fermi level near G point.Compared with pure borophene gas sensor,the current-voltage（I-V）characteristic curve of B-MoS₂ heterostructure sensor loses its linear relationship in low voltage region.（2）By comparing the changes of charge transfer and potential energy before and after adding gold electrode,it is found that the existence of gold electrode will reduce the current of the system.This is because when the gold electrode and borophene form a heterostructure,a potential barrier will be formed in the central scattering region,thus hindering the tunneling of electrons.It can be seen that it is of great significance for device design to consider the device system including electrode.（3）By calculating and analyzing the sensitivity（S）of the gas sensor,it can be obtained that the gas sensor based on borophene can be used to detect carbon monoxide（CO）,ammonia（NH₃）,nitrogen dioxide（NO₂）and nitric oxide（NO）.The sensitivity of the sensor to NO₂ gas is the highest under small bias voltage.With the increase of bias voltage,the sensitivity of the sensor will gradually decrease.The research results of this paper not only have important guiding significance for the theoretical design of the borophene-based gas sensor,but also fundamentally discuss the influence of Au electrodes on the transport properties of borophene,which has important enlightening value for understanding the transport properties of metal-2D heterostructure.