Elastic recoil detection analysis for large recoil angles (LA-ERDA) I. Bogdanovi  c Radovi  c a,b, * , E. Steinbauer a , O. Benka a a Institut f ur Experimentalphysik, Johannes Kepler-Universit at Linz, Altenbergerstraûe 69, A-4040 Linz, Austria b Rud  er Bo skovi c Institute, P.O. Box 180, 10002 Zagreb, Croatia Received 29 December 1999; received in revised form 15 February 2000 Abstract In this paper, elastic recoil detection (ERD) measurements at recoil angle of 60° using ion-induced electron emission (IEE) for particle identi®cation are presented. In our IEE system for particle identi®cation, recoiled target atoms and scattered projectiles penetrate a set of thin carbon foils before their energy is analyzed in a solid state detector. Particle identi®cation is based on the fact that the total number of electrons emitted from the foils depends on the particle nuclear charge. This method is characterized by its low minimum detectable energy, which stimulated us to study ERDA at 60°. Due to collision kinematics and due to the angular dependence of the scattering cross-sections, it is expected that the sensitivity can be signi®cantly improved. In this work, the detection eciency of the IEE particle identi®cation system for H recoils at energies below 1 MeV was determined. LA-ERDA measurements were performed with 4 He and 12 C projectiles using two dierent types of samples with a well-known amount and depth distribution of H atoms near the surface. Sample 1 consisted of a 50 lg/cm 2 melamine layer evaporated on a ¯at Si substrate, sample 2 was a Si wafer with implanted H. Sensitivity and depth resolution were measured using LA-ERDA with a recoil angle of 60° and ERDA with recoil angles of 30° and 45°. The results for dierent recoil geometries and projectiles are discussed and compared with theoretical predictions. Ó 2000 Elsevier Science B.V. All rights reserved. PACS: 34.50.)s; 07.81.+a; 68.55.Jk Keywords: Large angle elastic recoil detection analysis; Sensitivity; Depth pro®ling 1. Introduction One of the most useful ion-beam techniques developed for quantitative analysis and depth pro®ling of light elements in surface layers and thin ®lms is elastic recoil detection analysis (ERDA). In contrast to Rutherford backscatter- ing, where only backscattered projectiles can reach the energy detector, in ERDA both scattered projectiles and recoiled target atoms are simulta- neously detected in the forward direction. In the last two decades, dierent methods for separating scattered projectiles from the recoiled atoms based on particle identi®cation or discrimination have been developed [1±5]. The most simple and widely used is ERDA with a stopping foil. Nuclear Instruments and Methods in Physics Research B 170 (2000) 163±170 www.elsevier.nl/locate/nimb * Corresponding author. Tel.: +385-1-4561-161; fax: +385-1- 4680-239. E-mail address: iva@rudjer.irb.hr (I. Bogdanovic  Rad- ovic Â). 0168-583X/00/$ - see front matter Ó 2000 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 - 5 8 3 X ( 0 0 ) 0 0 0 7 7 - X