黑磷各向异性拉曼光谱表征及电学特性

采用机械剥离法制备出层状黑磷,通过微纳加工制备0°—360°四对对称电极并以黑磷作为沟道材料的背栅型场效应晶体管,对层状黑磷的拉曼光谱及其场效晶体管的电学输运特性进行了研究.偏振拉曼图谱结果表明,黑磷的3个特征峰强度随偏振角改变呈现180°周期变化;不同角度电极源漏电流表明,黑磷在0°(180°)扶手椅方向附近呈现最大源漏电流,均表现出黑磷各向异性特性.另外,不同电极角度栅压-源漏电流转移特性曲线表明其在45°(225°)和90°(270°)方向呈现微弱双极性,在0°(180°)和135°(315°)方向呈现空穴型输运特性.

Anisotropic Raman characterization and electrical properties of black phosphorus

As a new family member of two-dimensional materials,black phosphorus has attracted much attention due to its infrared band gap and strongly anisotropic properties,bringing new concepts and applications in different fields.In characterizing black phosphorus,optical method and electrical method are typically used to obtain structural information and fundamental properties in terms of behaviors of electrons.So far,more studies are still needed to understand in depth the physical principle and facilitate applications.In this paper,multilayered black phosphorus flakes are synthesized via mechanical exfoliation from the bulk crystal,and field-effect transistors based on few-layer black phosphorus are fabricated by micro-nano fabrication technology,which owns 0°-360°four pairs of symmetrical electrodes.We experimentally obtain the characteristics of Raman modes Ag1,B2g,and Ag2 in parallel(XX)and vertical(XY)polarization configuration.Furthermore,the angledependent source-drain current angle is measured through a BP field-effect transistor.The Raman spectrum results demonstrate that three characteristic peaks are located at 361,439 and 467 cm^-1 in a range of 200-500 cm^-1,corresponding to the vibration modes of Ag^1,B2g,and Ag^2,respectively.The fitting experimental data of polarization-dependent Raman spectra also show that the intensity for each of the three characteristic peaks has a 1800 periodic variation in a parallel polarization configuration and also in a vertical polarization configuration.The maximum Raman intensity of Ag is along the AC direction,while that of B2g is along the ZZ direction.On the other hand,the electric transport curves illustrate that the largest source leakage current can be obtained near 0°(180°)armchair direction.Such results indicate the anisotropy of black phosphorus.Furthermore,transfer curves with different electrode angles show that the weak bipolarity of black phosphorus at 45°(225°),90°(270°),and p-type performance at 0°(180°),135°(315°)can be offered,respectively.This work is conducive to studying the properties and practical applications of devices based on black phosphorus.