In this paper native and RCA-treated n- and p-doped Si(111) substrates and ultra-thin 16-nm copper phthalocyanine (CuPc) layers deposited thereon were investigated using X-ray Photoemission Spectroscopy and Angle-Resolved X-ray Photoemission Spectroscopy. The oxide layer thickness was determined to be 1.3 nm on the RCA-treated substrates and 0.8 nm on the native ones. The analysis of substrate carbon contamination showed the existence of C-H, C-OH and COOH components on all substrates. The RCA clean removes more readily the carbon components with the OH group from the n-type Si and causes the segregation of the contaminants. The initial carbon species propagate in the evaporated CuPc layer up to a thickness of about 5 nm affecting the shape of the C1s peak. Additionally, the behavior of the binding energy difference between N1s and Si2p peaks upon the CuPc growth shows that there may occur various CuPc molecule adsorption modes on investigated Si substrates. It could be a useful information, from the technological point of view, especially for low dimensional electronic device preparation. (C) 2009 Elsevier B.V. All rights reserved.