Measurement Condition for Atomic Resolution imaging on Reactive Surfaces Using Atomic Force Microscopy

在这个项目中，我们研究了Si尖端和Si(111)<平方根>3x<平方根>3-Ag表面之间的力相互作用，以及Si尖端和Ag（111）表面之间的力相互作用，使用非接触原子力显微镜（AFM）在超高真空（UHV）下工作。在Si(111)<平方根>3x<平方根>3-Ag表面上的AEM图像显示出三种类型的对比，这取决于尖端与样品表面之间的距离。在样品尖端距离约0.1 ~ 0.3nm处，AFM图像呈现蜂窝状排列。在约0-0.05nm的尖端采样距离处，图像显示出由三个亮点组成的三角形的周期性结构，对比度相对较强。另一方面，在0.05 ~ 0.1nm的距离上，图像对比度似乎是上述两种对比度的综合。当尖端距离样品表面较远时，尖端-样品相互作用力主要由尖端尖端的Si原子与样品表面上的Ag计时器之间的库仑力和/或范德华力（vdW）等物理键合作用主导。另一方面，在接触前，由于尖端顶端的Si原子悬空键与表面的Si- ag共价键轨道之间的杂化，导致尖端-样品相互作用力主要由化学键相互作用主导。此外，还实现了Ag（111）纯金属表面的原子分辨率成像，表明非接触原子力显微镜在纯金属表面的研究具有潜力。

In this project, we investigated the force interactions between a Si tip and Si(111)<square root>3x<square root>3-Ag surface as well as between a Si tip and Ag (111) surface, using noncontact atomic force microscopy (AFM) operating in ultrahigh vacuum (UHV). AEM images on Si(111)<square root>3x<square root>3-Ag surface showed three types of contrasts which depended on the distance between a tip and a sample surface. At the tip-sample distance of about 0.1-0.3nm, AFM image showed the honeycomb arrangement. At the tip-sample distance of about 0-0.05nm, the images showed the periodic structure of the triangle consisting of three bright spots with relatively strong contrast. On the other hand, at the distance of 0.05-0.1nm, the image contrast seemed to be the synthesis of the above two types of contrasts. When the tip is far from the sample surface, the tip-sample interaction force is dominated by physical bonding interaction such as the Coulomb force and/or the van der Waals (vdW) force between the tip apex Si atom and Ag timer on the sample surface. On the other hand, just before the contact, the tip-sample interaction force is dominated by the chemical bonding interaction due to hybridization between the dangling bond out of the tip apex Si atom and the orbit of Si-Ag covalent bond on the surface. Furthermore, atomic resolution imaging of pure metallic surface of Ag (111) was achieved, suggesting that noncontact AFM has potential for investigation of pure metallic surface.