Nano-scale tribology study of organic adlayer-metal interface using quartz crystal microbalance combined with scanning tunneling microscopy

摘要

A quartz crystal microbalance combined with scanning tunneling microscopy (STM-QCM) was used to investigate the interactions between organic adlayers (C_6H_6 and C_6H_5I) on Cu surfaces and a metallic STM tip. STM images of C_6H_6 covered Cu surface improved when the QCM was simultaneously oscillated during the imaging. In contrast, STM images of C_6H_5I covered surfaces became noisy when the sample was oscillated. The two systems moreover exhibited frequency changes of opposite signs in response to STM tip contact, indicative of different physical phenomena at the surface. The dependence of the STM image quality and the frequency shift were interpreted in terms of the adsorbate-substrate chemical and physical interactions, and different levels of frictional heating at the interface.