An improved method for preparing an abrasive SiO.sub.x coating wherein 1.ltoreq.x.ltoreq.2. The method includes the steps of submitting SiH.sub.4 and N.sub.2 O to glow discharge and depositing the SiO.sub.x product of the glow discharge onto a substrate. The improvement includes the additional step of adjusting the refractive index and thickness of the SiO.sub.x coating by means of the glow discharge deposition process parameters so as to maximize the abrasiveness of the SiO.sub.x coating.
An improved method of preparing a coating by subjecting gaseous precursors to a glow discharge and an apparatus suitable for carrying out such a method are disclosed. The improvement includes mounting a substrate onto a plate of ferromagnetic material which enhances the deposition rate of the coating within the electrode area.
Enhanced micromachining rates are observed when lapping discs with standard SiO.sub.x lapping coatings are doped with trivalent or pentavalent additives, such as boron or phosphorous. Doping can be accomplished by subjecting the SiO.sub.x material to a "post glow", i.e., an argon plasma in the presence of a source of the dopant.
