Study of dose effects on Au–Ni bilayers mixing by 300 keV Kr ions D. Datta * , S.R. Bhattacharyya Surface Physics Division, Saha Institute of Nuclear Physics, 1/AF Bidhan Nagar, Kolkata 700 064, India Abstract In order to study ion-beam induced mixing mechanism of immiscible system, Au/Ni bilayer systems were irradiated by 300 keV 84 Kr 2þ ions at a number of ion doses ranging from 1 · 10 14 to 5 · 10 16 ions/cm 2 . A series of Au(40 nm)/Ni(30 nm) bilayer samples were deposited on cleaned Si(1 0 0) substrates using dc magnetron sputtering in Ar atmosphere at a pressure of 5 · 10 3 mbar. Distributions of different species after irradiation and post irradiation annealing were monitored by RBS technique using 2.05 MeV He 2þ beam. Mixing rate was determined as a function of ion doses using RBS spectra. With increasing doses, particularly at higher annealing temperatures, RBS spectra show a tendency to form metastable solid solution at Ni–Au interface. Discrepancy of the theoretical and experimental values of observed mixing rate has been explained by the existing models. Ó 2003 Elsevier B.V. All rights reserved. 1. Introduction Ion beam mixing is a unique method to syn- thesise a wide range of stable and metastable compounds, alloys and solid solution [1]. A solid subjected to energetic ion beam is modified by the significant atomic rearrangements within the range of ions in it. In the same way, atomic intermixing and alloying can take place at the interface of two layers of different materials. The process being known as ion beam mixing, has received great attention for its potential applications as well as for the basic understanding of the mechanism [2]. Due to such mixing, both mass transport and phase transformation occur across the interface of two or more layers of a thin film system. This also induces changes in the crystalline structure, asso- ciated with the appearances of radiation driven vacancies, dislocations etc. The technique of ion beam mixing can be forced even in immiscible system to form metastable phases under appro- priate conditions [3]. In this paper, we report on ion beam mixing of Gold–Nickel thin film system due to irradiation of 300 keV Kr ions at different doses. Apart from fundamental understanding of Au–Ni system, it has important applications in making Ohmic contacts used in LEDs and GaN-based devices [4] and formation of amorphous phase from crystal- line one in the interface due to ion irradiation [5]. The mixing rate obtained from the RBS profiles has been compared with theoretical estimates and the discrepancies are justified with existing models and formalism. * Corresponding author. Fax: +91-33-2337-4637. E-mail address: deba@surf.saha.ernet.in (D. Datta). 0168-583X/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0168-583X(03)01736-1 Nuclear Instruments and Methods in Physics Research B 212 (2003) 216–220 www.elsevier.com/locate/nimb