Free-electron-like dispersion in an organic monolayer film on a metal substrate

Indirect coupling of an organic semiconductor to ad-orbital surface state

“…This is already different than expectations for direct molecule-metal interaction that would shift the state in energy such as observed for PTCDA on Ag(111). 23 Although the surface state is not shifted, it is broader than for the clean Cr(001) surface indicating a more subtle electronic interaction. There is also an additional peak located at -370meV.…”

“…This is assigned as the result of charge transfer into the lowest unoccupied molecular orbital (LUMO) of PTCDA by direct analogy with similar molecular states for PTCDA on Ag surfaces. 23,24 In Figure 2 This is effect is shown in more detail in Figure 3 as a plot of Lorentzian linewidth for a large collection of local spectra measured at different distances from the centers of a population of PTCDA molecules (74 total molecules considered). Within the span of the distance from the center to the edge of the molecule, the width is approximately constant and then starts to decay toward the clean surface value.…”

“…We begin by noting the interesting metal-molecule interactions found in the coupling of PTCDA to the sp-derived Shockley surface state on Ag(111) [23][24][25] . In this adsorption system, the strong acceptor PTCDA takes charge from the bulk sp band of the Ag substrate in a manner that is essentially traditional direct orbital coupling.…”

“…25 The adsorbate modification of the bulk bands correspondingly modifies the sp-derived Shockley surface state by significantly shifting its energy (by ~ 0.4eV) and slightly changing its effective mass. 23 We focus attention on a related but more subtle interaction between PTCDA adsorbates and a This indirect and long-range surface state modification is distinct from the more direct and strongly localized modification of sp Shockley surface states seen for PTCDA on Ag(111). Most importantly, it is distinct from the direct coupling often invoked as a mechanism for spin injection into organic materials.…”

Energy Dissipation in Dynamic Force Spectroscopy of PTCDA on Ag-Si(111) .RAD.3*.RAD.3

“…A large field of research has emerged, studying the structural and electronic properties of various molecules on solid surfaces [15][16][17]. Scanning probe methods (SPM) have proven to be powerful tools for these studies [18][19][20]. In particular, NC-AFM offers the possibility of studying the energy dissipation above organic molecules.…”