Perfluoropentacene thin films on Au(111) surfaces: Effect of kinetic energy and vibrational properties

We studied vibrational properties and the effect of beam kinetic energy on perfluoropentacene (PFP) thin films grown by supersonic molecular beam deposition (SMBD) technique on gold surfaces. Though similar growth mechanism was observed for different beam kinetic energies, in the case of low coverage (less than 1 monolayer) films and for low deposition rates significant differences were observed in the properties of films grown by using helium and argon carrier gasses with the former case resulting in higher average grain size. For multilayer films however there were no significant differences between helium and argon grown films. Vibrational properties were investigated by using Infrared Scattering-type Scanning Nearfield Optical Microscopy (s-SNOM) on clean and m-carborane-1-thiol (M1) coated template-stripped gold (TSAu) substrates. For both substrates thick PFP films (15 nm) had similar spectra whereas there were significant differences in the spectra of thin films (1 nm) due to PFP-substrate interactions. Davydov splitting of the IR modes were observed for both 1 nm and 15 nm films indicating similar molecular arrangements in both type of films.