Achieving high mobility ZnO:Al at very high growth rates by dc filtered cathodic arc deposition

Achieving a high growth rate is paramount for making large-area transparent conducting oxide coatings at a low cost. Unfortunately, the quality of thin films grown by most techniques degrades as the growth rate increases. Filtered dc cathodic arc is a lesser known technique which produces a stream of highly ionized plasma, in stark contrast to the neutral atoms produced by standard sputter sources. Ions bring a large amount of potential energy to the growing surface which is in the form of heat, not momentum. By minimizing the distance from cathode to substrate, the high ion flux gives a very high effective growth temperature near the film surface without causing damage from bombardment. The high surface temperature is a direct consequence of the high growth rate and allows for high-quality crystal growth. Using this technique, 500–1300 nm thick and highly transparent ZnO : Al films were grown on glass at rates exceeding 250 nm min⁻¹ while maintaining resistivity below 5 × 10⁻⁴ Ω cm with electron mobility as high as 60 cm² V⁻¹ s⁻¹.