# Ion Scattering for in-situ Characterization of the Composition of La$_{2-x}$Sr$_x$CuO$_4$ Films

Ion scattering techniques in the 5--50~keV range have the potential to yield quantitative information on the composition of high-$T_{\rm c}$ films [1,2]. To demonstrate this we have designed and built an ion scattering spectrometer, compact enough for in-situ use, as an analytical tool for vacuum deposition processes. Data collected from La$_{2-x}$Sr$_x$CuO$_4$ films demonstrate the excellent mass resolution available using heavy incident ions. Modelling of the data has been carried out using both a simple empirical method and a full Monte--Carlo code. In addition to stoichiometric information, the contribution of light recoiled elements to the spectrum is determined. The estimated composition based on these models is compared with the composition obtained using high energy Rutherford Backscattering Spectrometry to verify the quantitative capabilities of the technique.