First-principles Study On The Vacancy Defects And Transport Properties In Armchair Black Phosphorene Nanoribbons

With the decrease of the electronic components size,the development of silicon-based nanoelectronic devices has encountered bottlenecks.Therefore,exploring a new type of field effect transistor that can improve carrier transport property and reduce leakage current is one of the important ways to achieve the innovation in nanoelectronic science and technology.Recently,the black phosphorene(BP),as an emerging two-dimensional material,not only has suitable direct bandgap,extremely high mobility and other excellent electronic characteristics,but also has strong mechanical properties,so it has attracted intensive attention by scientists in physics,chemistry and material science.However,BP is easily oxidized at room temperature because of its wrinkled structure.A variety of defects,such as vacancy and Stone-Wales defect,may be generated,which will change its electronic and magnetic properties.In addition,the transport properties of BP can be adjusted by the size and the edge effects.Therefore,in order to deeply understand the performance of BP nanoribbons as FET channel materials,it is necessary to investigate the effect of vacancy defects on the transport properties.For these issues,in our work,we studied the formation and migration of vacancy defects in armchair black phosphorene nanoribbon(APNR),electronic band structure,electron transmission spectrum and I/V characteristic curve of defective APNR,on the basis of the framework of density functional theory and non-equilibrium Green's function method.Our results are shown as follows:(1)We explore the structural stability and the band structure of APNRs containing atomic vacancies with different distributions and concentrations.It is found that vacancies prefer to distribute at the edge of APNR owing to low formation and high diffusion barrier.In addition,the newly generated defect acceptor level can take a deep-to-shallow transformation by increasing width of nanoribbons.The bandgap can be adjusted by changing defect concentration.Applying strain can improve the stability of APNR,and also modulate the band structure and magnetism of nanoribbon.(2)We investigate the regulation effect of various types of point defects on the transport properties of APNR double-ended devices.The results show that the transport current intensity will be enhanced with 1.2 to 1.5 times after introducing a low concentration of vacancy defects.For the case of APNR,the shorter the separation between defect level and valence band maximum,the more the number of defect level,the greater the current intensity.The rectification and negative differential resistance effects can be observed in the Schottky devices constructed by armchair and zigzag black phosphorus nanoribbons,which can be modulated by the defect engineering.