Doping and growth of diamond-like carbon films by ion beam deposition

Abstract

Hydrogen-free amorphous carbon films produced by direct deposition of low energy carbon ions exhibit diamond-like properties such as extreme hardness, large band gap and high index of refraction. Using mass separated ion beam deposition, high purity diamond-like carbon (DLC) films were grown under vacuum conditions better than 10 −5 Pa on Si substrates kept at room temperature. The deposition parameters such as the ion energy, vacuum conditions, substrate temperature and ion species can be controlled independently, and thus used to modify the film properties and composition. In this paper we present the first results of doping of DLC films during growth by alternating deposition of 100 eV 12C + ions and dopant ions such as 63Cu +, 27Al +, 11B + or 14N +. For beam currents of up to 100 μA cm −2, DLC films with a thickness of several micrometers were produced. Undoped films were characterized by Raman spectrometry, ellipsometry, electrical measurements, Rutherford backscattering spectrometry (RBS) and proton induced X-ray emission. For these films an energy gap of 2.6 eV, a Vickers hardness of 4500 kg mm −2, an index of refraction n > 2, a resistivity of 10 9 Ω cm and an electrical breakdown strength greater than 10 9 V m −1 were measured. Dopant concentration profiles of copper-doped films were analyzed by RBS. Homogeneous dopant concentrations of several atomic per cent are easily achieved.