Effect of Pulsed Plasma Processing on Controlling Nanostructure And Properties of Thin Film/Coatings

Abstract

The benefits of pulsed plasma processing, including pulsing both cathode and substrate in physical vapour deposition (PVD) processes (magnetron sputtering and cathodic arc evaporation (CAE)) and the pulsed plasma enhanced chemical vapour deposition (P-PECVD) process were demonstrated by correlating the pulsed plasma process parameters, microstructure and properties. Five coating systems were developed for structural, electronic, functional and tribological applications. These are: pulsed reactive magnetron sputtering of TiO thin films; alumina deposition with pulsed plasma in closed field unbalanced magnetron sputtering; deposition of thin film silicon using P-PECVD; high energy pulsed bias assisted CAE of Cr–N graded coatings on 7075-T6 Al substrates; and sputter deposition of nickel anode on protonic BaCe0.9Y0.1O3–a electrolyte under pulsed dc biasing of substrate. Pulsed plasma was found to change particle energies and plasma composition in both PVD and CVD processes. Through controlled ion bombardment (ion energies and relative abundances of plasma species) by varying pulse frequency, pulse duration and bias voltage, film growth and therefore film properties can be tailored. The films became denser and nanostructured. The interface structure was graded, allowing superior adhesion. Better film performance (e.g. wear resistance, fracture toughness and efficiencies of solar cells and fuel cells) was achieved because of the modified film microstructure and architecture. These results clearly indicate the significant effects of the plasma species and their energies on modification of both the structure and properties of thin films. In several of these examples, the properties could not have been achieved in continuous dc magnetron sputtering. SE/518