Depth profiling high Tc materials with 6.2 MeV He ion elastic backscattering

Abstract

Elastic backscattering of helium ions accelerated to 6.2 MeV has been used to determine the compositional depth profile of thin films of high Tc superconductors. The higher than normal bombarding energy allows separation of the contributions from Cu, Y and Ba in the measured spectra for film thicknesses up to about 5500 A, rather than about 1000 A by standard RBS at 2 MeV. An added benefit of the higher energy is greatly enhanced yield from nuclear elastic scattering by the light elements C and O at backward angles. This non‐Coulomb scattering process increases the scattering cross section by a factor of about 10 for oxygen and 50 for carbon, thereby increasing by a comparable amount the sensitivity for profiling C and O in thin films on useful substrate materials. Quantitative analysis for C and O requires the use of standards to ascertain the enhancement factor for the scattering cross section when compared to the well‐known Rutherford value.