Model of noncontact scanning force microscopy on ionic surfaces
Model of noncontact scanning force microscopy on ionic surfaces
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DOI：
10.1103/physrevb.59.2436
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发表时间：
1999-01-15
影响因子：
3.7
通讯作者：
Foster, AS
中科院分区：
文献类型：
--
作者：
Livshits, AI;Shluger, AL;Foster, AS
我们分析了离子表面非接触SFM成像中对比度形成的机制，并计算了NaCl，MgO和LiF完美表面的恒定频移扫描线。非接触式扫描力显微镜（SFM）的操作是由一个扰动振荡器使用原子静态和分子动力学技术的力场计算建模。采用周期密度泛函理论（DFT）方法计算了不同原子污染的硅针尖和MgO针尖的静电势。他们的分析表明，极性基团或化学吸附物质（如氧原子）的存在使得作用于Si尖端表面离子的静电力成为对图像对比度最重要的贡献之一。发现纳米尖端的（MgO）（32）立方体模型代表了广泛的一类极性尖端，并用于图像计算。这些计算的结果表明，在非接触SFM离子表面成像的对比度是基于静电和货车范德华力的相互作用。对比度形成的主要贡献来自于针尖与交变表面电位的相互作用以及针尖电场诱导的表面极化。结果强调了针尖诱导的表面离子弛豫在针尖-表面相互作用和图像对比度中的重要性。用同样的方法计算了LiF表面Mg ~（2+）-阳离子空位缺陷的非接触SFM图像。[S0163-1829（99）08803-7]。
We analyze the mechanisms of contrast formation in noncontact SFM imaging of ionic surfaces and calculate constant frequency shift scanlines of the perfect surfaces of NaCl, MgO, and LiF. The noncontact scanning force microscopy (SFM) operation is modeled by a perturbed oscillator using atomistic static and molecular-dynamics techniques for the force-field calculations. The electrostatic potentials of silicon tips contaminated by various atoms and that of a MgO tip are calculated using a periodic density-functional theory (DFT) method. Their analysis demonstrates that the presence of polar groups or chemisorbed species, such as oxygen atoms, makes the electrostatic forces acting on the surface ions from the Si tip one of the most important contributions to the image contrast. The (MgO)(32) cube model of the nanotip was found to be representative of a wide class of polar tips and used in the image calculations. The results of these calculations demonstrate that the contrast in noncontact SFM imaging of ionic surfaces is based on an interplay of the electrostatic and van der Waals forces. The main contributions to the contrast formation result from the interaction of the tip with the alternating surface potential and with the surface polarization induced by the electric field of the tip. The results emphasize the importance of the tip-induced relaxation of the surface ions in the tip-surface interaction and in image contrast. The noncontact SFM image of the Mg2+-cation vacancy defect on the LiF surface is calculated using the same method. [S0163-1829(99)08803-7].