Photoemission study of the Si(111)-native SiO2/copper phthalocyanine (CuPc) ultra-thin film interface

The Ultraviolet and X-ray Photoemission Spectroscopy (UPS, XPS) investigation was done to examine the interface formation between deposited copper phthalocyanine (CuPc) thin films and covered with native oxide n-and p-type silicon Si(111) substrates. The UPS results indicated the existence of small interface dipole effect for very first layer of CuPc deposited on both types of substrates. The dipoles were oriented differently depending on silicon conductivity type. In this paper we present that near the inorganic/organic interface the phthalocyanine's molecular orbital levels shift downwards 0.20 +/- 0.05 eV in the case of n-Si substrate and upwards 0.25 +/- 0.05 eV for p-Si indicating the different displacement of the negative charge within the interface region. This tendency was also confirmed by conducted XPS study of the core levels. It is highly probable that band bending-like shift is provoked by the continuous change of CuPc molecule orientation induced by interface polarization layer. (C) 2012 Elsevier B.V. All rights reserved.