Y.-R. Ma

Translation, rotation and removal of C60 on Si(100)-2 × 1 using anisotropic molecular manipulation

We have investigated the interactions of C60 molecules adsorbed on Si(100)-(2 × 1) through their response to manipulation induced by a scanning tunneling microscope operating at room temperature. Intramolecular features are resolved which vary as a molecule is displaced showing that C60 undergoes rotation during tip-induced displacement. For translation to and from certain bonding sites, the apparent size of a molecule may change following lateral manipulation. Furthermore, reversible changes in dimer buckling are observed as a molecule is moved across the surface. Our experimental observations show that the C60Si(100)-(2 × 1) interaction is dominant over the C60C60 interaction and attempts to move a molecular pair result in the transfer of one molecule across a dimer row due to barrier lowering by the intermolecular interaction. We also show that transfer of a molecule from sample to tip (or vice versa) changes both the imaging and manipulation properties of the tip.

C60 adsorption on the Si(110)-(16 × 2) surface

Abstract The interaction of C 60 with the Si(110)-(16 × 2) surface has been studied using a scanning tunnelling microscope (STM). For a submonolayer coverage isolated C 60 molecules are observed with no evidence for a preferential adsorption site. As the coverage is increased, a disordered monolayer is observed and at still higher coverage disordered aggregates are observed which ripen into hexagonally ordered islands. These islands could be disrupted by the STM tip and were desorbed by annealing. Our results show that the interaction between the disordered layer and C 60 islands is weak. However, the first monolayer is strongly bonded to the Si surface and forms a passivating layer which is stable to exposure to atmosphere.

Adsorption of Sb on GaAs(111)B studied by photoemission and low energy electron diffraction

Abstract The surface structures resulting from the deposition of Sb on the GaAs(111)B-(2 × 2) surface at room temperature followed by annealing, have been studied by high-resolution soft X-ray photoemission (SXPS) and low energy electron diffraction (LEED). For depositions at room temperature with no subsequent anneal and for annealing temperatures up to 300°C, Sb islands are formed between which the As trimer-based (2 × 2) substrate reconstruction of the clean GaAs surface is observed. Annealing to temperatures between 350 and 475°C leads to the creation of Sb chain pairs coexisting with regions of Sb trimers. At 500°C an ordered surface is produced, associated with Sb trimers and an As vacancy.

Probing the interactions of on Si(100)- using anisotropic molecular manipulation

We have investigated the response of molecules adsorbed on to manipulation induced by a scanning tunnelling microscope. Our results show that the interaction is greater than the interaction. Attempts to move a molecular pair result in the transfer of one molecule across a dimer row due to barrier lowering caused by the intermolecular interaction. Our results suggest that is chemisorbed and this is confirmed by Si 2p core-level photoemission spectra.

Investigation and manipulation of C60 on a Si surface using a scanning tunneling microscope

Abstract We have demonstrated that the tip of a scanning tunnelling microscope (STM) may be used to position individual C60 molecules on a Si(111) surface. This work is reviewed together with more recent results on STM modification of C60multilayers. The chemical passivation of Si(111) by a C60 monolayer is also discussed.