Analysis of surface electronic states based on the characteristics of surface interaction forces by atomic force microscopy

基于表面相互作用力特征的原子力显微镜表面电子态分析

• 批准号: 12650027
• 负责人: ARAI Toyoko
• 金额: $ 2.18万
• 依托单位: Japan Advanced Institute of Science and Technology (JAIST)
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2000
• 资助国家: 日本
• 起止时间: 2000 至 2001
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12650027/
• 关键词: noncontact atomic force microscopy; surface electronic states; interaction force; tunneling current; damping energy; Silicon; germanium; ultrahigh vacuum; 表面相互作用力; 化学結合力; トンネン電流; 散逸エネルギー

The aim of this study is to establish a new method utilizing noncontact atomic force microscopy (nc-AFM) in ultrahigh vacuum for characterization of surface electronic states ; the electronic states are origins of the interaction force between tip and sample in the nc-AFM. The interaction is mainly composed of van der Waiils force, chemical bonding force and exchange repulsive force, which have different characteristics with respect to a separation between tip and sample. The separation controlled by nc-AFM feedback circuits and applied bias voltage between tip and sample determine the dominant force to produce the image contrast.Samples were Si(111)7x7 and Ge-deposited Si(lll) surfaces. Using a home-made nc-AFM, atom-resolved images of nc-AFM and damping were successfully observed. The damping images showed atomic contrast much stronger than that in nc-AFM images under particular imaging conditions. A model explaining the contrast in damping images caused by a strong attractive interaction was proposed, based on the decrease in averaged velocity of a cantilever under conditions of a constant frequency shift and a constant amplitude of the cantilever.The bias voltage dependence of the contrast was also examined. Although at sample bias voltages less than 1 V the contrast difference between faulted and unfaulted half was less, at sample bias voltages negatively higher than 2 V, corner adatoms on the faulted half were depicted as spiky protrusions, and the damping decreased much over these adatoms. This indicates that the bias voltage change can lead to tip stably approaching much closer to the sample surface and a strong attractive interaction over specified surface atoms as the electron resonance is induced. A slight change in frequency shift caused a faint change in contrast of the spiky.protrusions in nc-AFM and damping images ; the intermixing between Si and Ge on the film growth was possibly evidenced.

这项研究的目的是建立一种利用超高真空中的非接触原子力显微镜（NC-AFM）来建立一种新方法，以表征表面电子状态。电子状态是NC-AFM中尖端和样品之间相互作用力的起源。该相互作用主要由范德尔·韦尔斯（Van der Waiils）力，化学键合力和交换排斥力组成，这些键相对于尖端和样品之间的分离具有不同的特征。由NC-AFM反馈电路控制的分离和尖端和样品之间施加的偏置电压决定了产生图像对比度的主要力。样本为Si（111）7x7和Ge-Deposed Si（LLL）表面。使用自制的NC-AFM，成功观察到了NC-AFM和阻尼的原子分辨图像。阻尼图像显示的原子对比度比在特定成像条件下的NC-AFM图像中强得多。基于在恒定频移和悬臂的恒定幅度下，悬臂的平均速度下降，提出了一个模型，该模型提出了由强烈的吸引人相互作用引起的阻尼图像。尽管在小于1 v的样品偏置电压下，断层和不欠不欠的一半之间的对比度差异较小，在样本偏置电压上，偏置电压高于2V，断层一半上的角adtoms被描述为尖刺的突起，而阻尼在这些adatoms上的减少大大减少。这表明偏置电压变化会导致尖端稳定接近样品表面，并且随着电子共振的诱导，在指定表面原子上的相互作用很强。频移的略有变化导致尖峰形成对比的微弱变化。在电影生长上，Si和GE之间的混合可能证明了。

项目成果

Toyoko Arai: "Simultaneous imaging of tunneling current and damping energy by noncontact-AFM in ultrahigh vacuum"Appl. Phys. A. 72. S51-S54 (2001)

Toyoko Arai：“超高真空中非接触式原子力显微镜同时成像隧道电流和阻尼能量”Appl。

T.Arai, M.Tomitori: "Simultaneous imaging of tunneling current and damping energy by noncontact-AFM in ultrahigh vacuum"Appl. Phys. A. 72. S51-S54 (2001)

T.Arai，M.Tomitori：“超高真空中非接触式原子力显微镜同时成像隧道电流和阻尼能量”Appl。

Toyoko Arai: "Bias dependence of Si(111)7x7 images observed by noncontact atomic force microscopy"Applied Surface Science. 157. 207-211 (2000)

Toyoko Arai：“通过非接触原子力显微镜观察到的 Si(111)7x7 图像的偏差依赖性”应用表面科学。

T.Arai, M.Tomitori: "Germanium islands grown on a Si(111)7x7 surface observed by noncontact atomic force microscopy with simultaneous imaging on damping"Applied Surface Science. (in print).

T.Arai、M.Tomitori：“通过非接触原子力显微镜观察 Si(111)7x7 表面上生长的锗岛，同时对阻尼进行成像”应用表面科学。

T.Arai: "Simultaneous imaging of tunneling current and damping energy by noncontact-AFM in ultrahigh vacuum."Appl.Phys.A. (in print.). (2001)

T.Arai：“在超高真空中通过非接触式 AFM 对隧道电流和阻尼能量进行同步成像。”Appl.Phys.A。