Sputtering Deposition With Low Cost Multi-Element Powder Targets

Compared to solid target, powder target is low cost and can be varied in wide range of elemental combinations. Transparent and conductive aluminum-doped zinc oxide (AZO) thin films were prepared by sputter deposition using a mixed powder target consisting of zinc oxide and aluminum oxide powders at 98:2 wt%. The bulk density of the powder target can be varied depending on the pressing pressure. Therefore, AZO thin films were prepared on Si and sapphire substrates using powder targets with different bulk densities (
ρ_powder
) ranging from 0.898 to 3.00 g/cm
³
. The fabricated structural, electrical, and optical properties of the AZO thin films were examined, and the relationships between the target bulk density and film properties were investigated. X-ray diffraction measurements revealed c-axis ZnO (002) diffraction peaks, corresponding to crystallite growth oriented perpendicular to the substrate. Hall effect measurements showed n-type conductivity, with carrier density and Hall mobility increasing as the bulk density of the powder target increased. At
ρ_powder
= 3.00 g/cm
³
, the AZO thin film on the Si substrate showed the lowest resistivity of 1.35 × 10
⁻³
Ω·cm. UV-visible spectroscopy measurements showed that the average transmittance in the visible light region exceeded 80% for the AZO thin films on the sapphire substrates. The figure of merit was calculated as a measure of the potential application in optoelectronic devices, resulting in 6.37 × 10
⁻³
Ω
⁻¹
for
ρ_powder
= 3.00 g/cm
³
. This research contributes to Nagasaki University's goal of “planetary health”.