Study of ion beam mixing in C/Si multilayers by X-ray absorption spectroscopy K. Asokan a,b, * , S.K. Srivastava a , D. Kabiraj a , S. Mookerjee a , D.K. Avasthi a , J.C. Jan b , J.W. Chiou b , W.F. Pong b , L.C. Ting b , F.Z. Chien b a Nuclear Science Center, Aruna Asaf Ali Marg, New Delhi 110 067, India b Department of Physics, Tamkang University, Tamsui 251, Taiwan Abstract The C/Si multilayers were prepared by electron beam evaporation in a cryo-pumped vacuum deposition system. ThesewerecharacterizedbyX-raydiffractionbeforeandafterhigh-energyheavyion,120MeVAu,irradiation.SoftX- ray absorption spectra in the C K-edge region were measured using synchrotron radiation to identify the chemical bonding states of the Si and C. This study indicates that ion beam mixing induces SiC phase and carbon clusters. A significant increase in the intensity of pre-edge peak of C K-edge, assigned to p  , is observed in the irradiated C/Si multilayersample.Itisintriguingtonotesuchsharpincreaseinintensityafterirradiationthatmaybeassociatedwith theeffectoflargeelectronicexcitationenergytransferredbyenergeticAuions. Ó 2002ElsevierScienceB.V.Allrights reserved. PACS: 61.10.Ht; 61.80.Jh; 61.82.Fk Keywords: Ion beam mixing; XANES; Multilayers; Silicon carbide 1. Introduction Ion irradiation has been one of the powerful techniques to synthesize metastable phases in thin film form from multilayered elemental structures for a variety of applications [1]. This process in- volves ion irradiation induced mass-transport popularly known as ion beam mixing (IBM) and phase transformations. IBM is a local rearrange- ment of atoms across the interface induced by en- ergetic ions [2]. In the low energy regime, the mechanism of mixing at interface is well under- stood as the energy transfer to material by elastic collisionsthatcausethetargetatomstomovefrom their lattice positions and generate defects and subsequent atomic mobility across the interface [3,4]. On the other hand, IBM induced by elec- tronicexcitationsinthehigh-energyregimeisbeing intensively investigated to understand the mecha- nism and to exploit it for novel applications. Re- cently, swift ion beam induced mixing has been investigated in Cu/W, Tb/Fe, Co/Si and many other combinations [1,5–7]. SiC is a difficult semi- conductortosynthesizeandmanytechniqueshave been used to overcome the high stability of lattice defects and requirement of high temperature of Nuclear Instruments and Methods in Physics Research B 193 (2002) 324–328 www.elsevier.com/locate/nimb * Corresponding author. Present address: Department of Physics, Tamkang University, Tamsui 251, Taiwan. Fax: +91- 11-689-9666/3666/+886-2-2621. E-mail address: asokan@nsc.ernet.in (K. Asokan). 0168-583X/02/$ - see front matter Ó 2002 Elsevier Science B.V. All rights reserved. PII:S0168-583X(02)00799-1