Abstract

Dielectric coatings play an important role in the overall design of active layers for magneto-optic recording. When coated to the thickness required to establish an antireflection condition, an enhancement of the shot noise limited carrier to noise ratio is possible, and significant reduction in the rate of oxidation of the Rare Earth/ Transition Metal (RE-TM) layer is achieved by sandwiching this layer between adjacent layers of certain dielectrics. Even though many dielectrics offer excellent properties in terms of low permeability to oxygen and water vapor, in some cases (for example SiO₂) degradation of the RE-TM layer can still proceed via oxidation of the rare earth element, occurring at the RE-TM/dielectric interface⁽¹⁾. In this respect, amorphous C:H coatings would seem to have an advantage advantage, and in this paper we describe a study of the optical properties, surface passivation characteristics and effect on dynamic disk recording performance of amorphous C:H films deposited into active layer structures with TbFe and TbFeCo alloys. The amorphous C:H films were produced by RF plasma deposition from CH₄ in a conventional diode reaction chamber. Relatively high deposition rates of 90Å/min are readily achieved. The physical structure and properties of a-C:H films are widely reported, but in particular they are known for their high hardness, low electrical conductivity (σ=10^-9 ohm^-1 cm^-1), high refractive index (n=2.1) and are often termed "diamond like carbon" in the literature. Such films are also optically transparent in the IR, chemically stable, inert, homogeneous (i.e. low pin hole density) and have found wide application elsewhere in the field of optical coatings in the IR.

© 1987 Optical Society of America