Mechanical and electronic measurements based on scanning probe microscopy for single molecules on surfaces using electron resonant interaction

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The purpose of this study is to analyze the structures, binding states and electronic states of functional single molecules with potential for opto-electronic devices fabricated on solid surfaces by bias-voltage non-contact atomic force spectroscopy (bias nc-AFS), invented by ourselves. The bias nc-AFS is a nanomechanical spectroscopy based on scanning probe microscopy (SPM). Our aim is also to establish this method to evaluate nano-structures using the energy shift of Fermi level induced by applying and sweeping the bias voltage between a tip and a sample.Here we developed ultra-high vacuum (UHV) bias nc-AFM/S together with improvement of the method, and aimed at developing of force sensors based on a commercial quartz tuning fork. In addition, we experimentally designed and fabricated a bending type and a stretching type of quartz force sensors in cooperation with a group in Tohoku University.Furthermore, we grew Ge clusters on a clean Si tip as a functionalized AFM tip. The clusters have specified facetted structures owing to a strained growth with lattice mismatch. Then the corner surrounded with the facets becomes sharper that is applicable to a well-defined scanning tip. We tried to obtain AFM images with it using a commercial AFM. Consequently, the spatial resolution was improved by using the Ge cluster tip compared with that using an uncovered Si tip. After wearing the tip we heated the worn Ge cluster tip in UHV, resulting in resharpening the tip apex with remolding a Ge cluster. Since the facet structure of a Ge cluster on Si is very stable, we resharpened it many times by heating, implying that we acquire a way to reproduce a tip having the same electronic states on the tip apex.We deposited it -conjugated molecules of 4,4"-diamino-p-terphenyl (DAT) on Si(111)7x7 in UHV, and examined their adsorption states using SPM.