Simulation method of Kelvin probe force microscopy at nanometer range and its application
Simulation method of Kelvin probe force microscopy at nanometer range and its application
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DOI：
10.1103/physrevb.82.195433
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发表时间：
2010-11
影响因子：
3.7
通讯作者：
A. Masago;M. Tsukada;M. Shimizu
中科院分区：
文献类型：
--
作者：
A. Masago;M. Tsukada;M. Shimizu
提出了基于分块实空间密度泛函的紧束缚（PR-DFTB）方法，用于Kelvin探针力显微镜（KPFM）中量子电子态的模拟计算.这种方法可以使用时，一个尖端设置在一个非轨道杂交距离和施加偏压的样品表面。PR-DFTB方法可以对由两个子系统（尖端和样品）组成的系统进行自洽计算。每个子系统由Fock矩阵的块元素表示，因此由块元素中的费米能级表征。因此，可以单独计算两个子系统上的电荷分布。此外，还可以计算在外加偏置电压下，子系统接近所引起的电荷重分布。使用所提出的PR-DFTB方法，我们可以通过观察局部接触电位差（LCPD）来阐明机制。与开尔文力的传统描述不同，作用在偏置尖端和样品之间的力不仅取决于尖端和样品之间转移的净电荷，而且取决于尖端和样品内的微观电荷分布所产生的多极力。这是负责观察“明显”LCPD的机制。从力-偏置曲线中的最小偏置电压生成的KPFM图像（即，LCPD图像）的理论模拟使用尖端模型的硅或氢化硅团簇的简单模型的表面，一氢化物Si（001）表面有/没有缺陷，和二聚体吸附原子堆垛层错（DAS）表面。
The partitioned-real-space density-functional-based tight-binding (PR-DFTB) method is proposed as a simulation method for calculating the quantum electronic states in Kelvin probe force microscopy (KPFM). This method can be used when a tip is set on a sample surface with a nonorbital-hybridization distance and an applied bias voltage. The PR-DFTB method can perform self-consistent calculations of a system that consists of two subsystems (the tip and the sample). Each subsystem is expressed by a block element of the Fock matrix and thus is characterized by the Fermi level in the block element. Consequently, charge distributions on the two subsystems can be calculated individually. Furthermore, charge redistributions in the subsystems induced by approach of them under an applied bias voltage can also be calculated. Using the proposed PR-DFTB method, we can clarify the mechanism by observing the local contact potential difference (LCPD). Unlike the conventional description of the Kelvin force, the force acting between a biased tip and a sample depends not only on the net charge transferred between the tip and the sample but also on the multipole forces generated by the microscopic charge distribution within the tip and the sample. This is the mechanism responsible for observing the “apparent” LCPD. KPFM images generated from the minimum bias voltage in the force-bias curve (i.e., LCPD images) are theoretically simulated using tip models for a Si or hydrogenated Si cluster for simple models of asurface, a monohydride Si(001) surface with/without a defect, and adimer-adatom-stacking fault (DAS) surface.