In situ Raman growth monitoring of indium/copper phthalocyanine interfaces

Abstract

Interface formation between indium and copper phthalocyanine (CuPc) is investigated using in situ Raman spectroscopy. CuPc and indium are deposited onto hydrogen passivated Si (111) surfaces via molecular beam deposition under ultra high vacuum (UHV) conditions. The 647.1 nm excitation wavelength of the Krypton laser fulfils resonance conditions for the CuPc molecules and provides a reasonable signal‐to‐noise ratio for thin films in the nanometer regime even for accumulation times below one minute. Indium clusters are formed at the interface and the surface enhanced Raman spectroscopy (SERS) effect is observed. A comparison of the spectra with results of density functional theory (DFT) calculations do not support a formerly proposed structure of CuPc/indium mixed layers with covalent‐like bonds [1]. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Indium on a copper phthalocyanine thin film: Not a reactive system

“…We note that our recent study on the identical system by Raman spectroscopy also suggested a nonreactive behav- ior of indium on CuPc. 44 The evolution of the In 4d spectrum may thus be rationalized by means of the varying size distribution of indium nanoclusters; "nonmetallic" nanoclusters prevail at low indium coverages, whereas the increasing indium deposition leads to the increase in the cluster size-and therewith the gradually vanishing effect of the final state-up to the indium thicknesses, where nanoclusters with their size sufficient to exhibit metallic behavior dominate the surface. Given the photoemission detection limit about 1%, it is conceivable that a fractional in diffusion cannot be excluded; still, our data justify to infer that the determining effect is the clustering and not the in diffusion.…”