The characteristics of the plasma in a powder sputtering rig

The powder sputtering rig was specifically designed for the sputtering of loosely packed blended powder targets. The rig incorporates a single unbalanced magnetron with an additional unpowered dummy magnetron used only to provide a closed magnetic field. Sputtering took place mainly in the pulsed direct current (DC) mode, with continuous DC operation also investigated for comparison purposes. The variations in substrate self-bias potential and substrate ion current with substrate-target separation and target current were studied for varying magnetron configurations. The voltage waveforms at the targets were diagnosed, and the effect of pulse parameters on the deposition rate was investigated. The term ‘dead time’ has been introduced to explain, in part, the observed decrease in deposition rate with increasing pulse frequency. To demonstrate the advantages of the powder rig, the structure and properties of aluminium-doped zinc oxide coatings deposited under various magnetron configurations and power delivery modes were compared. The results showed that the closed-field configuration and the use of the pulsed DC power supply were two essential factors in this system, which produced defect free, dense columnar coatings with good electrical and optical properties.