Method for producing implantable electrode coatings with a plurality of morphologies

Abstract

An implantable electrode comprising a substrate supporting microscopic surface structures such as columnar titanium nitride and further having nanoscopic surface structures on titanium nitride deposited on the exposed surface of the microscopic columnar structures is described. This is done through physical vapor deposition (PVD) and is based upon a relatively abrupt change in the surface mobility of the depositing material with a consequential variation in nucleation site density and surface mobility. At low mobility, there are increased nucleation sites and the condensation features are more numerous and finer. As mobility of the deposited species increases, the nucleation sites in the condensate film become fewer with coarser features. Consequently, the change from a relatively coarse microscopic surface structure to a relatively fine nanoscopic surface structure is accomplished by abruptly changing the total gas pressure in the processing chamber within a relatively short period of time of about ten seconds, or less.