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.

本研究的目的是建立一种新的方法，利用非接触原子力显微镜（nc-AFM）在真空中表征表面电子状态，电子状态是nc-AFM针尖和样品之间的相互作用力的来源。这种相互作用主要由货车力、化学键合力和交换排斥力组成，它们对针尖与样品之间的分离具有不同的特性。由nc-AFM反馈电路控制的分离和施加在针尖和样品之间的偏置电压决定了产生图像对比度的主导力。利用自制的纳米原子力显微镜，成功地观察到纳米原子力显微镜和阻尼的原子分辨图像。在特定的成像条件下，阻尼图像显示出比nc-AFM图像更强的原子对比度。基于悬臂梁的平均速度在恒定频率偏移和恒定振幅条件下的减小，提出了一个解释强吸引相互作用引起的阻尼图像对比度的模型，并研究了对比度对偏置电压的依赖性.虽然在样品偏置电压小于1 V的故障和未故障的一半之间的对比度差是较小的，在样品偏置电压负高于2 V，角吸附原子的故障的一半被描绘为尖锐的突起，和阻尼降低了很多超过这些吸附原子。这表明，偏压的变化可以导致尖端稳定地接近更接近样品表面和强烈的吸引力的相互作用，在指定的表面原子的电子共振诱导。频率偏移的轻微变化导致nc-AFM和阻尼图像中的尖峰突起的对比度的微弱变化;可能证明了Si和Ge之间的混合对膜生长的影响。

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。

荒井 豊子: "NC-AFM像の印加電圧依存症と画像化技術"応用物理. 70(10). 1205-1207 (2001)

Toyoko Arai：“NC-AFM 图像和成像技术的应用电压依赖性”应用物理学 70(10)。