Studyofthechemicaltransformationsinducedatthe surfaceofbulkironbyprotonsand a beams C.Pirlot a,c, * ,G.Deniau b ,P.Viel b ,G.L ecayon b ,G.Demortier c , J.Delhalle a ,Z.Mekhalif a a Laboratoire Interdisciplinaire de Spectroscopie Electronique, Facult es Universitaires Notre-Dame de la Paix 61, Rue de Bruxelles, B-5000 Namur, Belgique b Commissariat  a l'Energie Atomique, DSM-DRECAM-SPCSI, b^ at. 466, F-91191 Gif-Sur-Yvette Cedex, France c Laboratoire d'Analyses par R eactions Nucl eaires, Facult es Universitaires Notre Dame de la Paix 61, Rue de Bruxelles, B-5000 Namur, Belgique Abstract In this work the chemical transformations induced by protons and a beams 10 17 ion cm 2 ) at the surface of polycrystallineironareanalysedbyX-rayPhotoemissionSpectroscopyXPS).Spectroscopicchangesforbothincident particles are globally dierent. We show that helium particles contribute to etch away the oxygen leaving the iron surface in a metallic state. In contrast, hydrogen ions do not remove, at least completely, the iron oxidised species presentatthesurface,butchangeitsoxidationstatebyreducingFe 2 O 3 andFe 3 O 4 toFeO. Ó 2001ElsevierScienceB.V. Allrightsreserved. Keywords: Bulkiron;H  irradiation; a irradiation;XPS 1. Introduction Due to their limited and to some extent con- trollable depth of penetration, ions are ideal for surface alteration without modifying the proper- tiesoftheunderlyingbulk.Inthepastthreeyears, we have studied the chemical transformations inducedbyprotonbeams5±20keV)onpolyacr- ylonitrile PAN) ®lms deposited on various sub- strates [1±3]. We have observed that a signi®cant depletion of the N-containing species in the ®rst layers and a general increase in unsaturated structures appear. After exposure to air, limited oxygen incorporation is noted, which seems to aect mostly the ®rst layers [2]. These modi®ca- tionssuggestadirectrelationwiththehydrogenin a tothenitrilefunction[3].Inthecaseofthin®lms <0.200 lm), where the protons reach the poly- mer/iron interface Fig. 1a)), enhanced adhesion isnoted[4].Asimilarsituationalsoseemstohold when a bare polished iron substrate is subjected toprotonirradiation®rstandthenquicklydipped in the PAN solution, the ®lm resulting from the evaporation of the solvent Fig. 1b)). If repro- ducible and controllable, this opens the prospect NuclearInstrumentsandMethodsinPhysicsResearchB1852001)71±76 www.elsevier.com/locate/nimb * Correspondingauthor. 0168-583X/01/$-seefrontmatter Ó 2001ElsevierScienceB.V.Allrightsreserved. PII:S0168-583X01)00759-5