Stopping power of thin GaAs films for Si and P ions M. Nigam a,b, * , J.L. Duggan a , M. El Bouanani a,c , C. Yang a,d , G.V. Ravi Prasad a,e , E.D. Sosa c , S. Matteson a , F.D. McDaniel a a Ion Beam Modification and Analysis Laboratory, Department of Physics, University of North Texas, P.O. Box 311427, Denton, TX 76203, USA b Center for Applied Isotope Studies, University of Georgia, 120 Riverbend Road, Athens, GA 30602, USA c Department of Material Science and Engineering, University of North Texas, Denton, TX 76203, USA d Micro Analytical Research Center, The University of Melbourne, Parkville, Vic. 3052, Australia e Institute of Physics, Bhubaneswar 751005, Orissa, India Abstract Stopping powers of energetic Si and P ions are measured in thin GaAs films. A new technique derived from molecular beam epitaxy (MBE) was developed to prepare near stoichiometric GaAs films on thin carbon layers for use in transmission ion beam experiments. The GaAs films were characterized using X-ray photoelectron spectroscopy (XPS) and particle induced X-ray emission (PIXE). Stopping power data are presented for the first time for Si and P in GaAs. Ó 2004 Elsevier B.V. All rights reserved. Keywords: GaAs; Stopping powers; Thin films 1. Introduction Accurate knowledge of stopping powers is essential for quantitative analysis and surface characterization of thin films using ion beam analysis (IBA). These values are also of interest in radiobiology and radiotherapy and in ion- implantation technology, where shrinking feature sizes puts high demands on the accuracy of range calculations. A commonly used database that predicts the stopping powers is the SRIM/ TRIM program developed by Ziegler and coworkers [1]. However, researchers report that at times, TRIM calculations differ significantly from experimental values by as much as 20– 25%. In the case of stopping cross-sections for compound targets, the additivity rule, i.e. Bragg’s law [2] is assumed in almost all cases. Lennard et al. [3] have made a stoichiometric study using MeV energy 4 He ions backscattered from Si, SiO 2 and Si 3 N 4 . Using the RUMP simulation package [4] to model the data, they comment upon the accuracy of Ion Beam methods in the absence of accurate stopping cross-sections, especially for compound targets. Rajatora et al. [5] report the * Corresponding author. Address: Center for Applied Iso- tope Studies, University of Georgia, 120 Riverbend Road, Athens, GA 30602, USA. Tel.: +1-706-542-5579; fax: +1-706- 542-6106. E-mail address: mnigam@uga.edu (M. Nigam). 0168-583X/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2004.01.067 Nuclear Instruments and Methods in Physics Research B 219–220 (2004) 273–277 www.elsevier.com/locate/nimb