Elastic recoil detection analysis for the determination of hydrogen concentration profiles in switchable mirrors

Switchable mirrors [J.N. Huiberts, R. Griessen, J.H. Rector, R.J. Wijngaard en, J.P. Dekker, D.G. de Groot, N.J. Koeman, Nature 380 (1996) 231; J.N Hui berts, J.H, Rector, R.J. Wijngaarden, S. Jetten, D. de Groot, B. Dam, N.J.. Koeman, R. Griessen, B. Hjorvarsson, S Olafsson, Y.S. Cho, J. Alloys and C ompounds 239 (1996) 158; F.J.A. den Breeder, S.J. van der Molen, M. Kremers , J. N. Huiberts, D.G. Nagengast, A.T.M. van Gogh, W.H. Huisman, N. J. Koem an, B. Dam, J.H. Rector, S. Plota, M. Haaksma, R.M.N. Hanzen, R.M. Jungblut , P.A. Duine, R. Griessen, Nature 394 (1998) 656] made of thin films of Y, La or rare-earth (RE) metals exhibit spectacular changes in their optical a nd electrical properties upon hydrogen loading. The study of these material s :has indicated that the occurring phenomena are highly sensitive to the a ctual hydrogen concentration in these materials. In this paper elastic recoil detection analysis (ERDA) is used as a tool to measure hydrogen concentrations on a micrometer scale. The measurements ha ve been performed using a He-4(2+) ion beam from a 1.7 MV Pelletron acceler ator. The ion beam can be focused routinely to a spot size of approximately 10 mu m(2). The experimental set-up enables the simultaneous measurement o f Rutherford backscattering spectrometry (RBS) as well as particle induced X-ray emission (PIXE) spectra, which provide complementary information. The results of ERDA measurements on laterally diffused YHx (0 < x < 3) samp les with a qualitatively known hydrogen concentration profile are presented and discussed. The calibration of the microbeam set-up and possible improv ement of the measurement technique are described. (C) 1999 Elsevier Science B.V. All rights reserved.