ROOM TEMPERATURE MANIPULATION OF INDIVIDUAL GLYCINE MOLECULES ADSORBED ON THE Cu(111) SURFACE
室温下单个甘氨酸分子在Cu(111)表面的操纵研究

Low-energy electron diffraction (LEED) shows that glycine molecules can stick onto the Cu(100) substrate at room temperature forming ordered structures, while their binding to the substrate is fairly weak as evidenced by the quick degradation of the adsorbing structures and in turn the LEED pattern induced by the incident electron beam. Scanning tunneling microscopy (STM) observation shows that the molecules can also adsorb on the Cu(111) substrate at room temperature, and the binding is strong enough to be imaged with not too small a tunnel resistance but is weak enough to be manipulated by the tip with a small tunnel resistance. Careful inspections of the STM images allow us to further conclude the following.(i) At least three adsorption geometries with different apparent heights have been identified, although the details of the molecular images are often dominated by the tip shape.(ii) It is possible to move the molecules without changing their adsorbing geometry. (iii) In manipulation the molecules are pushed forward by the tip.(iv) Each glycine molecule forms at least two bonds with the substrate. During controllable manipulations the molecules remain at least one bond unbroken. (v) Electrostatic forces between the tip and sample do not play an important role in manipulations, as changing bias polarity seems to have almost no influences.(vi) In manipulations the higher the tunnel resistance the better our control on the molecules, as long as the molecules can be moved.