Synthesis of metal oxides by reactive cathodic arc evaporation
In these investigations, an attempt has been made to correlate the deposition parameters of the reactive cathodic arc evaporation with processes at the surface of the composite Al—Cr targets and the nucleation and phase formation of the synthesized Al—Cr—O layers. The oxygen partial pressure and the pulsed operation of the arc current influence the formation of intermetallic phases and solid solutions at the target surface. The nucleation of the ternary oxides at the substrate site appears to be, to some extent, controllable by the intermetallics or solid solutions formed at the target surface. A specific nucleation process at substrate site can therefore be induced by the free choice of target composition in combination with the partial pressure of the oxygen reactive gas. It also allows the control over the oxide island growth at the target surface which occurs occasionally at higher oxygen partial pressure. This hypothesis is supported by the X-ray diffraction analysis of the layers as well as of the target surface.
1. A method for synthesizing layers on a substrate comprising steps of:
placing a composite target in a chamber and evacuating the chamber;
prior to the synthesizing of the layers on a substrate, conditioning a surface of the composite target to form a conditioned composite target by transforming constituents of the composite target to regions containing intermetallic compounds and solid solutions by:
exposing the surface of the composite target to a reactive gas consisting of oxygen, the reactive gas introduced into the chamber during an arc operation to melt the surface of the composite target in the presence of the reactive gas, wherein a pulsed power supply is applied to the composite target during the arc operation, and
varying a flow rate of the reactive gas into the chamber to alter a cohesive energy of the composite target and to transition the surface of the composite target from a non-stationary state to a fully oxidized state, wherein during the non-stationary state, an incorporation of solid solutions or intermetallics occurs, the flow rate of the reactive gas selected to achieve an oxygen partial pressure that results in the fully oxidized state of the surface of the composite target and vaporizing of a high melting point material or any solid solution or intermetallics as an oxide before the surface of the composite target is melted, thereby forming the conditioned composite target; and
synthesizing the layers on the substrate by reactive cathodic arc evaporation using the conditioned composite target.
2. The method according to claim 1 , characterized in that during the reactive cathodic arc evaporation a substrate temperature of 550° C. is selected.
3. The method according to claim 1 , characterized in that the synthesizing includes a substrate bias of −60 V.
4. The method according to claim 1 characterized in that the flow rate of the reactive gas is controlled by a flow controller.
5. The method according to claim 1 characterized in that the composite target is a powder metallurgical produced target.
6. The method according to claim 1 characterized in that the composite target comprises Al—Cr.