Studies Of Magnetic Atoms And Molecules On Various Surfaces With Scanning Tunneling Microscopy/Spectroscopy

Scanning tunneling microscope (STM) can not only obtain high-resolutionimages of the surface and surface adsorption system in real space, but also probethe scanning tunneling spectroscopy (STS) of them, and can manipulate thesurface-adsorbate. In the nearly three decades, as an important scientific analyticalinstrument, STM has been widely utilized in physical science, chemical and materialscience, biology. In this thesis, we use ultra-high vacuum low temperature scanningtunneling microscopy (UHV LT-STM) to study the electronics properties of theadsorbate on monolayer graphene/Ru(0001), Highly Oriented Pyrolytic Graphite(HOPG) and Ru(0001) surface.The Chapterâ… is the basis of this thesis, we briefly introduced the invention,development and simple fundamental principle of STM, in addition, and theinstrument structure and work mode of the UHV LT-STM used in our experiment.In Chapterâ…¡, the epitaxial monolayer and bilayer graphene (MG and BG) onRu(0001) surface was studied comparatively. We found that the local density of states(LDOS) of the high sites of MG is the same with that of the BG in a wide energyrange, and there is a Dirac point on the high regions of MG as BG at about 0.5 Vbelow Fermi energy. In addition, it is found that the local work function (LWF) ofMG is around 3.5 eV, and the LWF difference between the high and low sites of MGis about 100 to 200 meV. But LWF of BG is larger than that of MG. We concludedthat the LWF of MG surface is too small value and periodic distribution is due to theexistence of periodic surface dipole moment.In Chapterâ…¢, we mainly studied the cobalt phthalocyanine (CoPc) adsorbed onMG/Ru(0001) surface. We found that there is an obvious rectification effect inthe central Co ion of the CoPc molecules. Through the comparative studies ofthe CoPc molecules adsorbed on Ru(0001) surface, and combined with the theoreticalcalculations of these two systems, we found that the interaction between the CoPcmolecules and Ru(0001) surface become much weaker due to the decoupling effect ofthe MG. And the asymmetry of the d orbital of the central Co ion relative tothe Fermi energy results in the rectification effect on the central Co ion.In Chapterâ…£, highly oriented pyrolytic graphite (HOPG) was chosen asthe substrate to study the interaction between CoPc molecules and the substrate further. Combined with the STM/STS and the first principles calculation, we foundthat the interaction between the CoPc molecules and the substrate is very weak, soa double barrier tunneling junction (DBTJ) is formed, the two tunnel barriers in thejunction are the vacuum gap between the STM tip and the molecule, and the vacuumgap between the molecule and HOPG. By analyzing the double barrier tunnelingthrough the LUMO orbital of CoPc molecules, we find that the quantum correctionsshould be introduced to the capacitance of this two tunnel barriers.In Chapterâ…¤,we mainly studied the Kondo effect of single cobalt (Co) atomsand clusters in Ru(0001) surface. Combined with the lateral manipulation andSTM/STS, we found that the width of Kondo peaks is almost unchanged fromsingle Co atoms to dimer then linear trimer, only their line shape is little changed. Butwhen the Co atoms form a triangle compact trimer or larger compact clusters,the Kondo peak disappear. We can obtained tips with Kondo resonance by the use ofvertical manipulation, use these tips to detect the Kondo resonance of the single Coatoms on Ru(0001) surface, the new Kondo resonance is mainly contributed bythe Kondo resonance on the tip.