Tunable microstructures and morphology of zirconium films via an assist of magnetic field in HiPIMS for improved mechanical properties

Abstract

Although HiPIMS technology has been widely studied, its optimization still remains in the adjustment of the experimental parameters acting on the ions, such as impulse mode, due to the inherent complexity of partially magnetized plasma of HiPIMS. Herein, recapture and re-energy of electrons by the assistance of the A-type magnetic field configuration, constructed by field coupling of the cathode magnetron and the auxiliary magnets mounted behind the substrate holder, was proposed. The dynamic behavior of the ions is attempted to be guided by exploiting electron recapture. The studies on the plasma diagnosis by optical emission spectroscopy and magnetic field simulation revealed that when the cathodic discharge remains constant, the characteristics of the deposition plasma in front of the substrate can be altered. Zirconium films were prepared under the a-HiPIMS mode (operated with the A-type magnetic configuration) and the conventional HiPIMS mode. Results showed that the Zr films prepared in the a-HiPIMS mode exhibited smoother surface, denser morphology, finer grains, higher homogenous thickness distribution, higher hardness, enhanced elastic recovery and higher value of the ratios H/E⁎ and H3/E⁎2. The mechanism of microstructure evolution of Zr film was discussed. It demonstrated that the action of the A-type magnetic configuration can densify the Zr film, without the need for high energy ion bombardment. The A-type magnetic field configuration provided an alternative strategy for compensating for the shortcoming of substrate bias in HiPIMS, invalidity to electrical insulating substrates, in terms of the dense film.