On the synthesis of ultra smooth ITO thin films by conventional direct current magnetron sputtering

Highly transparent, conductive Sn-doped In2O3 (ITO) thin films with a characteristic root mean square surface roughness RMS below 1 nm were obtained from deposition of amorphous ITO and subsequent annealing treatment. ITO thin films with ultra flat surface were produced by (i) controlling crystallization mechanisms (nucleation and growth) of amorphous ITO through optimization of hydrogen content and temperature profile during sputtering and annealing process and (ii) preventing formation of agglomerated atoms/clusters in the gas phase and hence reducing large surface particles through fine tuning the sputtering rate and process pressure. Characterization of the coatings revealed specific resistivities below 2.5 × 10− 4 Ω cm and transparencies above 90% in the visible range of light.