Research On Electronic Structure And Surface Adsorption Properties Of InAs Nanowires

InAs nanowires(NWs)show broad application prospects in a new generation of infrared optoelectronic devices and high-speed electronic devices due to their narrow band gap and high electron mobility.Due to the large surface-to-volume ratio,a large number of surface states exist on the surface of NWs.Since surface states can lead to the deterioration of nanowire device performance,reliable passivation of nanowires has become one of the keys to improve device performance.Molecular passivation technology has become a research hotspot in recent years.On the other hand,the surface states significantly enhance the gas-sensing properties of NWs,which have important application potential in novel optoelectronic devices such as high-sensitivity sensors.Therefore,it is of great academic significance and potential application value to carry out the research on the surface adsorption properties of InAs NWs.In this paper,the electronic structure of InAs NWs and the effect of S atom and O atom adsorption on its physical properties were studied based on first-principles.The main research results and innovations are as follows:(1)The electronic structure and optical properties of S-passivated(110)surface of InAs NWs were investigated.The results show that when adsorbing 0.5 monolayer,the S atom occupies the interchain bridge site and has a lower adsorption energy;when adsorbing 1 monolayer,the structure in which S atom occupies both the interchain bridge site and the bridge site is the most stable structure.After S adsorption,the energy band of the InAs NWs moves to the low-energy region as a whole,the density of states near the Fermi level increases,the surface photoconductivity increases,and the absorption characteristics in the infrared band are improved.(2)The initial oxidation process on(110)surface of InAs NWs was investigated.The study found that O atoms will preferentially bond with surface atoms that have previously adsorbed O,that is,oxides tend to grow in clusters from an energy point of view;the initial bonding mode is In-OAs bridge bonds,and with the increase of O coverage,O triple bonds with two In and one As atoms appear,and the adsorption energy of the triple bonds is about 1 eV higher than that of the bridge bonds.(3)The effect of oxidation on the electronic structure and optical properties of InAs NWs was investigated.The results show that the electrons on the NW surface are transferred to O atoms,and the density of states near the Fermi level increases;with the increase of O coverage,the band gap changes from direct to indirect,and the band gap value increases first and then decreases.The trend of absorption coefficient,refractive index and reflectivity decreases slightly,which has a certain influence on the light absorption characteristics.