title: Modifying the STM tip for the ' ultimate ' imaging of the Si(111)-7×7 surface and metal-supported molecules.
abstract: We report on high-resolution STM measurements with modified probe tips. First, both the rest atoms and adatoms of a Si(111)-7×7 surface are observed simultaneously. The visibility of rest atoms is dependent upon the sample bias voltage (less than -0.7 V) and is enhanced  by sharpening the tip, which is rationalized by first-principles calculations. Second, a tip with a perylene molecule adsorbed at its apex is used to discriminate the molecular states and the metal states of the underlying Ag(110) surface, which is attributable to a mismatch between the energy  levels of the functionalized tip and the adsorbates on silver. Lastly, high-resolution images of iron phthalocyanine (FePc) and zinc phthalocyanine (ZnPc) molecules on Au(111) are obtained by using an O(2)-terminated tip, and the images reveal rich intramolecular features arising  from molecular orbitals that are not observed when using clean metallic tips.
authors.affiliation: Chinese Academy of Sciences, Institute of Physics, Beijing 100190, China. ylwang@iphy.ac.cn.
authors.forename: Ye-Liang
authors.initials: YL
authors.lastname: Wang
authors.forename: Zhi-Hai
authors.initials: ZH
authors.lastname: Cheng
authors.forename: Zhi-Tao
authors.initials: ZT
authors.lastname: Deng
authors.forename: Hai-Ming
authors.initials: HM
authors.lastname: Guo
authors.forename: Shi-Xuan
authors.initials: SX
authors.lastname: Du
authors.forename: Hong-Jun
authors.initials: HJ
authors.lastname: Gao
mesh_terms: D000327:Adsorption; D005296:Ferrous Compounds / Q000737:chemistry*; D007211:Indoles / Q000737:chemistry*; D054833:Isoindoles; D016252:Microscopy, Scanning Tunneling; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*; D012825:Silicon / Q000737:chemistry*; D012834:Silver / Q000737:chemistry*; D013499:Surface Properties; D017967:Zinc Compounds
chemical_list: D005296:Ferrous Compounds; D007211:Indoles; D054833:Isoindoles; D009942:Organometallic Compounds; D017967:Zinc Compounds; C493990:iron phthalocyanine; C052159:Zn(II)-phthalocyanine; D012834:Silver; D010100:Oxygen; D012825:Silicon