Hydrogen content of C₆₀ fullerenes, measured by elastic recoil detection

The hydrogen content of thin films of C₆₀ fullerenes, measured by elastic recoil detection (ERD), is investigated. In ERD analysis a new method for particle identification is employed using the ion‐induced electron emission from thin carbon foils. Since the electron emission yield depends on the nuclear charge of the penetrating particle, recoiled H ions and scattered He projectiles can be separated. The reliability and the sensitivity of the technique were checked by analysing a series of ion‐implanted H profiles in silicon. The sensitivity is better than 0.1 at.% H. In as‐grown fullerene films a hydrogen content of about 3 at.% has been found throughout the film. After doping of the fullerene films by ion implantation of K the hydrogen content increased up to 6 at.% in the implanted region.