Structure, microstructure and electronic characterisation of the Al2O3/SiO2 interface by electron spectroscopies

Al2O3 has been deposited by evaporation and post-oxidation of Al on a flat SiO2 substrate. The obtained films have been analysed by X-ray photoemissio n spectroscopy (XPS) and reflection electron energy loss spectroscopy (REEL S). It has been found that the modified Auger parameter of Al varies by sim ilar to 2.2 eV between a low coverage situation (below an equivalent monola yer) and the bulk material. This change has been attributed to variations i n the coordination state of the aluminium atoms. Some minor contributions d ue to bonding and polarisation effects are also detected. Valence band photoemission and REELS have shown that the band gap energy of the deposited Al2O3 increases as the coverage decreases. These effects are discussed in terms of the bonding interactions between the SiO2 and Al2O3 at the interface between the two oxides. Sandwich structures formed by approximately one equivalent monolayer of Al2 O3 intercalated between SiO2 present Auger parameter and band gap energy va lues which are larger than those of a monolayer-like Al2O3 thin film suppor ted on SiO2. Also, it has been shown that the energy of the plasmon losses behind the AlKLL Auger peak can be used as a fingerprint to discriminate be tween supported Al2O3 thin films or layers of this material embedded within a sandwich structure of two SiO2 layers. (C) 2000 Elsevier Science B.V. Al l rights reserved.