p-Co3O4/n-ZnO, Obtained by PECVD, Analyzed by X-ray Photoelectron Spectroscopy

The present work focuses on the X-ray Photoelectron Spectroscopy (XPS) and X-ray Excited Auger Electron Spectroscopy (XE-AES) of a Co3O4/ZnO nanosystem. The composite material was obtained via a two-step Plasma Enhanced-Chemical Vapor Deposition (PECVD) process in Ar/O2 mixtures, consisting in the initial deposition of ZnO and the subsequent growth of Co3O4 onto the pristine matrices. Zn(ketoimi)2 (ketoimi=[CH3O(CH2)3NC(CH3)=C(H)C(CH3)=O]) and Co(dpm)2 (dpm=2,2,6,6-tetramethyl-3,5-heptanedionate) were used as zinc and cobalt precursors, respectively. In particular, strongly <001> oriented ZnO was grown at 300°C, followed by the deposition of Co3O4 at 200°C, applying a radio-frequency (RF) power of 20 W. Structural, morphological and compositional investigations were performed by Glancing Incidence X-ray Diffraction (GIXRD), Field Emission-Scanning Electron Microscopy (FE-SEM) and Energy Dispersive X-ray Spectroscopy (EDXS). Surface XPS and XE-AES analyses were carried out to study in detail the system O 1s, Zn 2p3/2, Zn 3p and Co 2p core levels, as well as the Zn and Co Auger peaks. The obtained results evidenced the formation of a composite material, in which ZnO and Co3O4 preserved their chemical identity.