First-Principles Study of Intrinsic Point Defects of Monolayer GeS

The properties of six kinds of intrinsic point defects in monolayer GeS are systematically investigated using the“transfer to real state”model,based on density functional theory.We find that Ge vacancy is the dominant intrinsic acceptor defect,due to its shallow acceptor transition energy level and lowest formation energy,which is primarily responsible for the intrinsic p-type conductivity of monolayer GeS,and effectively explains the native p-type conductivity of GeS observed in experiment.The shallow acceptor transition level derives from the local structural distortion induced by Coulomb repulsion between the charged vacancy center and its surrounding anions.Furthermore,with respect to growth conditions,Ge vacancies will be compensated by fewer n-type intrinsic defects under Ge-poor growth conditions.Our results have established the physical origin of the intrinsic p-type conductivity in monolayer GeS,as well as expanding the understanding of defect properties in lowdimensional semiconductor materials.     

基于光子计数能谱CT的含能材料等效原子序数测量方法

双能CT或能谱CT可以测量材料的等效原子序数,对含能材料的成分检测和生产工艺改进具有重要意义,但现有方法存在复杂度高、设备要求高等缺点.为提高等效原子序数的测量精度,并降低设备要求和算法复杂度,提出了一种基于新型CeT e光子计数探测器的等效原子序数测量方法.该方法利用材料的衰减特性,重新推导了两个能量区间线性衰减系数...