Kelvin Probe Force Microscopy with Atomic Resolution
Kelvin Probe Force Microscopy with Atomic Resolution
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DOI：
10.1007/978-3-319-75687-5_14
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发表时间：
2018
期刊：
影响因子：
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通讯作者：
Y. Li;H. Wen;Zongmin Ma;Li Kou;Y. Naitoh;Y. Sugawara
中科院分区：
文献类型：
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作者：
Y. Li;H. Wen;Zongmin Ma;Li Kou;Y. Naitoh;Y. Sugawara
利用Kelvin探针力显微镜（KPFM）测量的表面电位分布受针尖和表面之间的接触电势差（CPD）、悬臂梁的杂散电容以及表面和针尖上的固定电荷的影响。原子尺度KPFM对比研究的解释一直存在争议。在这里，我们研究原子分辨率的KPFM中的对比度机制。首先，在FM、AM和外差AM-KPFM模式下探讨了杂散电容对电位测量的影响。AM-KPFM中的调制静电力的距离依赖性比FM和外差AM-KPFM中的弱得多，并且在FM和外差AM-KPFM中几乎完全消除了悬臂梁的杂散电容，该杂散电容强烈影响AM-KPFM中的电势测量。AM-KPFM中极小的局部接触电位差（LCPD）是由于地形反馈引起的伪影。其次，我们研究了TiO 2（110）-1 × 1表面上的LCPD，并进行了原子依赖的偏距光谱映射。TiO 2（110）的LCPD不仅受针尖原子与表面之间的永久表面偶极子的影响，而且受针尖与样品之间化学作用诱导的偶极子的影响。最后，我们提出了一种新的多图像的方法来获得频移，隧穿电流，和LCPD图像。首次在78 K下获得了TiO 2（110）表面原子级分辨率的三幅图像。LCPD在缺陷位置上比在附近的O行上具有更高的值，因为由表面缺陷引起的过量电子在附近的Ti行上离域。多重图像法可用于研究纳米粒子与表面位之间的电荷转移现象，并阐明催化反应的机理。
The surface potential distribution measured using Kelvin probe force microscopy (KPFM) is influenced by the contact potential difference (CPD) between the tip and surface, the stray capacitance of the cantilever, and fixed monopole charges on the surface and tip. The interpretation of atomic-scale KPFM contrast studies has been controversial. Here, we investigate the contrast mechanism in KPFM with atomic resolution. First, the effect of stray capacitance on potential measurements is explored in the FM-, AM-, and heterodyne AM-KPFM modes. The distance dependence of the modulated electrostatic force in AM-KPFM is much weaker than that in FM- and heterodyne AM-KPFM, and the stray capacitance of the cantilever, which strongly affects potential measurements in AM-KPFM, is almost completely eliminated in FM- and heterodyne AM-KPFM. The very small local contact potential difference (LCPD) corrugation in AM-KPFM is attributed to an artefact induced by the topographic feedback. Next, an investigation of the LCPD on a TiO2(110)-1 × 1 surface and atom-dependent bias-distance spectroscopic mapping are performed. The LCPD of TiO2(110) is dominated not only by the permanent surface dipole between the tip apex atom and the surface, but also by the dipoles induced by the chemical interaction between the tip and sample. Finally, we propose a new multiple-image method for obtaining the frequency shift, tunneling current, and LCPD images. For the first time, we obtain three images on a TiO2(110) surface with atomic resolution at 78 K. The LCPD has a higher value on a defect site than on the nearby O rows because excess electrons caused by surface defects are delocalized on the nearby Ti rows. The multiple-image method can be used to investigate the charge transfer phenomena between nanoparticles and surface sites and to elucidate the mechanisms of catalytic reactions.