PULL-TEST MEASUREMENTS OF DIAMOND-LIKE CARBON-FILMS ON SILICON-CARBIDE, SILICON-NITRIDE, ALUMINUM-OXIDE, AND ZIRCONIUM-OXIDE

Hydrogenated amorphous carbon or diamondlike carbon (DLC) films were f ormed by 400 eV methane (CH4) ion bombardment of various smooth and ro ugh ceramics, as well as ceramics coated with a layer of Si or Ti. Adh esion was measured by a bonded-pin method. Excellent adhesion was meas ured for smooth SiC and Si3N4, but adhesion of DLC to smooth Al2O3 and ZrO2 was negligible. The use of a Si bonding interlayer produced good adhesion to all the substrates, but a Ti layer was ineffective due to poor bonding between the DLC film and Ti. Bulk thermodynamic calculat ions are not directly applicable to bonding at the interface because t he interface is two dimensional and the compositions of interfacial ph ases are generally not known. If the standard enthalpy DELTAH-degrees for the reaction between CH4 and the substrate material is calculated under the assumption that a carbide phase is produced, a relationship is seen between the reaction enthalpy and the relative adhesion. Large positive enthalpies are associated with poor adhesion; negative or sm all positive enthalpies are associated with good adhesion. This relati on between enthalpy and adhesion was also observed for DLC deposited o n Si. The lack of adhesion to the Ti was attributed to inadvertent for mation of a surface oxide layer that rendered the enthalpy for the rea ction with CH4 positive.