Investigation of thin films by high-energy ERDA

Abstract

Thin film samples were investigated by high-energy elastic recoil detection analysis (HE-ERDA), using heavy-ion beams such as e.g. 420 MeV 127I, which allows detection of all target elements simultaneously. A time-of-flight detection system consisted of channel plate detectors for start and stop. The recoils are finally stopped in a semiconductor detector delivering a total energy signal. The particle's mass is derived by its energy and time-of-flight. Accurate energy loss measurement of all particles up to the highest mass region and for all energies is attainable using the time-of-flight signal. Depth profiles were evaluated using the stopping powers of Biersack, Littmark and Ziegler. Heavy-ion stopping powers are accurate only to about 10%. For high-precision measurements calibration samples were used to correct the high-energy stopping powers of projectile and recoils. Samples of TiN on steel prepared by ion beam aided deposition (IBAD) technique, thin vapor deposited layers of Al and Ni on a Si substrate and a SiC layer on a Si substrate were investigated. The measurements provided absolute values for concentration and depth for all isotopes in the samples. The maximum measurable depth was 2–4 μm, depending on the recoil mass. The attained resolution was comparable to RBS measurements.