Experimental comparison between microscopic energy dissipation and inelastic molecular scattering from surfaces

本研究的目的是通过实验比较非接触式原子力显微镜（nc-AFM）观察过程中的微观机械能耗散与表面分子非弹性散射的特征，并最终阐明微观能量耗散的起源，在碳材料-部分沉积Pt（111）表面进行了成功的评价与nc-AFM配备了一个振幅稳定的悬臂梁激发自动补偿之间的接触电位差，针尖和样品表面，诱导电能耗散。另一方面，为评估的能量耗散与分子束散射技术，采用甲烷超声辐照制备了高取向单层石墨（MG）覆盖的Pt（111）表面。在经典硬立方体模型的框架内，除非散射过程中激发了分子的转动态，否则可以很好地解释Ne、Ar、甲烷和乙烷分子在干净和MG覆盖的Pt（111）表面上的角速度分布。这表明，微观能量耗散分布图像的对比度是由于表面材料的有效质量的差异。然而，从两种方法得到的能量耗散的绝对值被发现有很大的不同。理论研究需要定量地阐明微观能量耗散的起源。

The purpose of this study is to experimentally compare the microscopic mechanical energy dissipation during the observation with a non-contact atomic force microscope(nc-AFM) and the feature of the inelastic scattering of molecules from surfaces, and eventually to clarify the origin of the microscopic energy dissipation, which can be utilized to locally control the surface chemical reaction.The microscopic mechanical energy dissipations on a carbon material-partially deposited Pt(111) surface are successfully evaluated with a nc-AFM equipped with an amplitude stabilized catilever excitation by automatically compensating the contact potential difference between tip and sample surfaces which induces electric energy dissipation.On the other hand, for the evaluation of the energy dissipation with molecular beam scattering techniques, the highly oriented monolayer graphite (MG)-covered Pt(111) surface is prepared by a supersonic methane beam irradiation. The angular and velocity distributions of supersonic Ne,Ar,methane and ethane molecules scattered from clean and MG-covered Pt(111) surfaces are well explained within the framework of the classical hard cube model unless the rotational states of molecules are excited during scattering. This suggests that the contrast of the microscopic energy dissipation distribution image is due to the difference in the effective mass of the surface materials. However, the absolute values of the energy dissipations obtained from two methods are found to be largely different. The theoretical study is required to quantitatively clarify the origin of the microscopic energy dissipation.