XPS, AES and EELS studies of Al surfaces

XPS, AES and EELS spectroscopies are used to study the surface and near-sur face composition of ambient-exposed Al metal. Large-area averaged XPS analy sis shows that after prolonged etching the sample consists of Al metal and anhydrous, virtually stoichiometric Al2O3. The intensities of the first bul k plasmon and surface plasmon signals lying below the Al2p peak are used to observe the incoherence of the alumina overlayer, as well as derive estima tes of both its coverage and thickness. An Anger parameter, alpha (A1)(2), involving the ALVV transition is considered which marks the difference betw een Al-0 and Al2O3 with a chemical shift which is more than twice as great as that associated with the AlKLL-related Auger parameter used in the liter ature for characterizing the aluminum chemistry. Both AES and EELS highligh t lateral chemical heterogeneities over the surface at different depths of analysis, with AES proving a more powerful indicator of chemical state chan ges. EELS-to-AES signal intensity ratios, calculated as a function of prima ry electron energy and analyzer resolution, are considered as a reference f or anticipating the contrast obtainable in chemical imaging of Alo-containi ng surfaces by reflected electron energy loss microscopy and scanning Auger microscopy. (C) 2001 Elsevier Science Ltd. All rights reserved.