SPECIAL ISSUE: NANOSTRUCTURED MATERIALS 2010 Potassium-doped FePc thin-film on metal surfaces: observation of different empty state occupation Marco Angelucci • Pierluigi Gargiani • Carlo Mariani • Maria Grazia Betti Received: 13 September 2010 / Accepted: 21 December 2010 / Published online: 14 January 2011 Ó Springer Science+Business Media B.V. 2011 Abstract Iron-Phthalocyanine molecules deposited on the Cu(119) vicinal surface form molecular chains along the vicinal surface steps, as deduced by the low-energy electron diffraction (LEED) reconstruc- tion pattern. The work-function lowers at the FePc single-layer completion, due to the formation of an interface dipole. Further FePc deposition induces a different growth morphology, as suggested by the slope discontinuity in the work function variation. Upon depositing potassium onto the FePc thin-film prepared on Cu(119), the K-injected electrons fill up the Fe-d-associated and ligand-p-related orbitals, as observed by means of high-resolution ultraviolet photoelectron spectroscopy. Keywords Surface science  Photoemission  Iron phthalocyanine  FePc  Cu(119)  Doping Introduction Metal-containing complex organic molecules like hemoglobin, myoglobin, chlorophyl, constitute effi- cient natural systems for light-harvesting and charge transfer activity. Science and technology try to follow and to develop the path singled-out by the natural processes, with the final purpose of utilizing artificial architectures built-up by simple metallorganic mole- cules for potential optical, electronic and/or magnetic devices at the nanoscale. Within this general context, metal-Phthalocyanines (M-C 32 H 16 N 8 , MPc) consti- tute exemplary molecular biomimetic prototypes (Cook et al. 2009) for studying electron transport in different conditions of solid aggregation, by self- assembling them on single-metal surfaces. MPcs are stable metallorganic molecules constituted by a central metal atom coordinated by four pyrrolic and four benzene rings (see sketch in Fig. 2), where the charge transport and delocalization are due to the p-conjugation, and where the central metal atom determines its magnetic properties (Forrest 2004). Metal phthalocyanines are organic semiconductors with the energy gap typically in the range of visible light. Their highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) occupation can be varied by doping, also depending on the actual molecular arrangement. Electron-doping (n-type doping) through exposition to alkali metals has proved to vary the electronic band diagram and energy gap of MPcs adsorbed on several substrates, by adjusting the occupation of the formerly empty molecular levels (Betti et al. 2007a; Schwieger et al. 2002; Calabrese et al. 2009; Aristov et al. 2010; Gargiani et al. 2010b). In particular, despite continu- ous occupation of the former LUMO, MPc single- layers, and thin-films prepared in controlled ultra-high M. Angelucci  P. Gargiani (&)  C. Mariani  M. G. Betti Dipartimento di Fisica, Universita ` di Roma La Sapienza, Piazzale Aldo Moro 2, 00185 Roma, Italy e-mail: pierluigi.gargiani@roma1.infn.it 123 J Nanopart Res (2011) 13:5967–5973 DOI 10.1007/s11051-010-0202-1