| AVS 64th International Symposium & Exhibition | |
| Scanning Probe Microscopy Focus Topic | Tuesday Sessions |
| Session SP+AS+MI+NS+SS-TuM |
| Session: | Probing Chemical Reactions at the Nanoscale |
| Presenter: | Aisha Ahsan, University of Basel, Switzerland |
| Authors: | T.A. Jung, Paul Scherrer Institut (PSI), Switzerland A. Wäckerlin, University of Basel, Switzerland S. Fatayer, University of Basel, Switzerland T. Nijs, University of Basel, Switzerland S. Nowakowska, University of Basel, Switzerland S.F. Mousavi, University of Basel, Switzerland O. Popova, University of Basel, Switzerland A. Ahsan, University of Basel, Switzerland C. Wäckerlin, Paul Scherrer Institut (PSI), Switzerland |
| Correspondent: | Click to Email |
We present a conceptually new approach for the formation of 2D chessboard patterns of molecules which is, unlike the other approaches, not dependent on the molecules being functionalized for self-assembly. The deposited Phthalocyanines (Pcs) are sorted in alternating sequence into the 2D layer by their site-specific interaction with the native reconstruction of the bismuth thin-film. The square p-(10 x 10) layer of bismuth on Cu(100) is characterized by the periodic arrangement of shallow pockets which are separated by rims and nodes which originate from the limited registry between Bi and Cu(100). The symmetry and the pitch of 1.8 nm of the Bi/Cu(100) substrate matches with the 4-fold symmetry of the Pc molecules and the pitch of a Pc chessboard arrangement.
We attribute the sorting mechanism to the site-specific interactions between the Bi layer and the out-of-plane 3d states of Mn- and CoPc leading to preferred adsorption sites. The 3d states also allow for the identification of the molecular components in the STM data: Mn and CoPc exhibit a bright contrast on the central metal atom, while Cu in CuPc in absence of such a d-state close to EF is depicted as a depression.
Due to this characteristic difference in the 3d states, MnPc + CuPc and CoPc + CuPc sort into chessboard arrays. In these arrays, the molecules with out-of-plane 3d states (CoPc and MnPc) adsorb on the Bi-nodes and the one without (CuPc) adsorbs on the Bi-pores. If both molecules have out-of-plane 3d states around the Fermi level (CoPc + MnPc mixture), the selectivity of adsorption is insufficient and no chessboard layer is formed.
References:
[1] A. Wäckerlin, et al., Nano Letters 17, 1956 (2017)