PHASE-TRANSITIONS AND MULTIPHASE SYSTEMS IN MAGNETRON SPUTTERED HARD COATINGS

Microstructures and macroscopic properties of magnetron sputtered hard protective coatings depend strongly on the plating energy e.U(pl) and on the ratio J(pl)/J(sb) of the fluxes of the plating ions and the film forming neutral particles. In usual equipment the arrival ratio J(pl)/J(sb) can easily be tuned within the range from 0.01 to 100. For hard coatings prepared of WC, Cr3C2, SiC and amorphous carbon phase transitions have been induced by the variation of e.U(pl) and J(pl)/J(sb). For two component multilayer systems consiting of Cr3C2, SiC and Al2O3 it is shown, that strong variations of the mechanical properties can occur, if the thickness of a single layer is in the order of 10 to 20 nm. This size effect in metal-semiconductor multilayers is caused by an extended space charge (electronic interface) at the very narrow atomic interface, from which free electrons can move into the semiconducting material and compensate unsaturated dangling bonds. As a consequence the multilayer system shows properties which are similar to those of a film with metallic bonding.