Measurement of hydrogen content in ultrathin diamond-like carbon films using low-energy elastic recoil detection analysis

We performed direct measurement of hydrogen content in diamond-like carbon (DLC thin films using elastic recoil detection analysis (ERDA) of hydrogen atoms forward-scattered by a 2 keV beam of helium ions. DLC films were prep ared in an electron cyclotron resonance (ECR) microwave plasma chemical vap or deposition (CVD) system. Use of a low-energy beam in conjunction with a small incidence angle allowed measurements of hydrogen content in the surfa ce region of films of various thickness (2.4, 5 and 100 nm). Analysis of re sultant spectra indicates that a higher negative substrate bias voltage pro duces lower hydrogen content; these findings are consistent with those obta ined on thick DLC films using high-energy (2-3 MeV) ERDA. Accordingly, this confirms the suitability of using the low-energy ERDA system described to measure hydrogen content in ultrathin (< 5 nm) DLC films. The relationship between film hardness and hydrogen content in such films is also discussed, as is the effect of film thickness on hydrogen content. (C) 2000 Elsevier Science S.A. All rights reserved.