Rutherford backscattering analysis of thin films and superlattices with roughness

Knowledge on the thickness, composition, and interfaces of thin films and m ultilayers is, in many systems, fundamental for the understanding and optim ization of their properties. One of the techniques often applied to such st udies is Rutherford backscattering (RBS). However, it has been very difficu lt to account for the effects of interface roughness in the data obtained, and the alternative has been to develop dedicated data analysis codes for p articular problems where roughness plays a determinant role. In this work, the effect of roughness is taken into account in the data analysis by calcu lating the effect of roughness on the apparent energy resolution as a funct ion of depth. This depends on the exact type of roughness, and three differ ent models have been implemented: inhomogeneous layer thickness, corrugated sample, and rough substrate surface. Interfacial mixing in multilayers can also be analysed with the method developed. Automatic fits to the data can be performed in this way, where the roughness parameters are derived durin g the fit, providing a new tool for RBS analysis. The code is applied to se veral systems in order to test its validity and applicability. Systems whic h are hard to analyse by RBS have been chosen: Si/VS/Si0.65Ge0.35 300 nm/Si 0.2Ge0.8 4 nm/Si0.65Ge0.35 15 nm/Si 3 nm thin films, where VS stands for a linearly composition-graded virtual substrate; and MgO/ (Fe 25 Angstrom /Co 20 Angstrom)(10) multilayers.