Ion beam deposition of diamond-like carbon films

Abstract

The process of deposition of single-phase diamond-like carbon (DLC) films was studied by employing a device capable of generating beams of mass-separated carbon ions. Structural investigation of the films was accomplished at different values of such variables as the energy of 12C + ions (20–300 eV), substrate temperature (200–350 K) and pressure in vacuum chambers (10 -6-10 -3 Pa). To obtain structural characteristics the atomic density radial distribution function plotting procedure and the interference function simulation method were used. It was demonstrated that the optimal set of process parameter values includes the energy of ions ranging from 20 to 100 eV, a substrate temperature of 310 K and an ion-to-impurity atom flow rate ratio Γ i/Γ a of not less than unity at pressures not less than 10 -4 Pa. Structurally, single-phase DLC films were assemblies of hexagonal regions commonly occurring in the diamond; these regions had the form of ellipsoids with axes equalling 9 and 6 Å and were connected by single tetrahedra. The corresponding theoretical value of the atomic density (calculated by means of related energy loss spectra) was 1.8 × 10 23 cm -3, which appeared to be close to the value for diamond. The fundamental characteristics of single-phase DLC films are listed below. Possible mechanisms for the process of DLC film deposition are discussed.