Direct imaging of molecular orbitals of metal phthalocyanines on metal surfaces with an O2-functionalized tip of a scanning tunneling microscope

Abstract

High-resolution scanning tunneling microscope images of iron phthalocyanine and zinc phthalocyanine molecules on Au(111) have been obtained using a functionalized tip of a scanning tunneling microscope (STM), and show rich intramolecular features that are not observed using clean tips. Ab initio density functional theory calculations and extended Hückel theory calculations revealed that the imaging of detailed electronic states is due specifically to the decoration of the STM tip with O 2 . The detailed structures are differentiated only when interacting with the highly directional orbitals of the oxygen molecules adsorbed on a truncated, [111]-oriented tungsten tip. Our results indicate a method for increasing the resolution in generic scans and thus, have potential applications in fundamental research based on high-resolution electronic states of molecules on metals, concerning, for example, chemical reactions, and catalysis mechanisms.

Laser-Combined STM and Related Techniques for the Analysis of Nanoparticles/Clusters

“…In a similar way, voltage-induced chemical contrast in an STM image was reported using chemically modified tips with hydrogen-bond donors [57]. Moreover, molecular orbitals of metal phthalocyanines on metal surfaces have been clearly imaged with an O 2 -functionalized STM tip, where the observations were supported by theoretical calculations [58].…”

Chemically modified STM tips for atomic-resolution imaging of ultrathin NaCl films

“…Various experiments with controlled functionalization of the STM tips have been reported previously [1,2,24]. To obtain such tips, it was required to introduce "impurity" molecules, such as CO, O 2 , and H 2 , on the sample, which can be picked up by the STM tip to achieve functionalization and enhanced resolution.…”

Effect of orbital symmetry of the tip on scanning tunneling spectra of Bi2Sr2CaCu2OSuominen1, Nieminen2, Markiewicz3 et al. 2011Phys. Rev. B

“…However, some insight can be obtained by considering a study such as that of Ref. 17, which discusses the effects of attaching O 2 functionalizing molecules to a tungsten tip for investigating a metal phtalocyanine monolayer on an Au(111) surface. Ref.…”

“…In various experimental studies [9][10][11][12][13][14][15][16][17] , the tip properties have been deliberately modified for better spatial or chemical selectivity by picking up a molecule, e.g. CO, O 2 or N 2 , from the surface to the apex of the tip after which the plain tip results have been compared to the results with a functionalized tip.…”