X-ray photoemission Spectroscopy (XPS) results are presented which have given a direct insight into the surface composition of Fe-Al2 O3 "granular" thin films consisting of fine iron particles (? ~ 40-150 Å) dispersed in an insulating alumina matrix. The data are mainly discussed in relation to: (i) the bulk iron content in the sample, (ii) the sample preparation procedure (e.g., by rotation of the sample target) and (iii) the mean iron particle size. At the surface, the iron is in a fully oxidized 3+ state within an alumina-rich partly hydrated region. Depth analysis, achieved by an Ar+ etching procedure, provides evidence of metallic iron and iron aluminate forms. In general, the metallic iron percentage increases with depth and with increasing iron bulk content. Good agreement is found between X-ray photoemission spectroscopy and Mössbauer Spectroscopy data. Fe2+ aluminate forms, which indicate an interaction between the metal particle and the alumina matrix, show increasing percentages with decreasing mean particle sizes. Particular attention is paid to evaluating the accuracy of XPS quantitative results, obtained by use of a first-principles model, and to assessing the importance of the artefacts associated with the Ar+ etching procedure.
SURFACE-COMPOSITION OF FE-AL2O3 GRANULAR THIN-FILMS BY X-RAY PHOTOEMISSION SPECTROSCOPY
PAPARAZZO E;FIORANI D
1985
Abstract
X-ray photoemission Spectroscopy (XPS) results are presented which have given a direct insight into the surface composition of Fe-Al2 O3 "granular" thin films consisting of fine iron particles (? ~ 40-150 Å) dispersed in an insulating alumina matrix. The data are mainly discussed in relation to: (i) the bulk iron content in the sample, (ii) the sample preparation procedure (e.g., by rotation of the sample target) and (iii) the mean iron particle size. At the surface, the iron is in a fully oxidized 3+ state within an alumina-rich partly hydrated region. Depth analysis, achieved by an Ar+ etching procedure, provides evidence of metallic iron and iron aluminate forms. In general, the metallic iron percentage increases with depth and with increasing iron bulk content. Good agreement is found between X-ray photoemission spectroscopy and Mössbauer Spectroscopy data. Fe2+ aluminate forms, which indicate an interaction between the metal particle and the alumina matrix, show increasing percentages with decreasing mean particle sizes. Particular attention is paid to evaluating the accuracy of XPS quantitative results, obtained by use of a first-principles model, and to assessing the importance of the artefacts associated with the Ar+ etching procedure.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
