Solution Combustion Synthesis of Hafnium-Doped Indium Oxide Thin Films for Transparent Conductors.

Indium oxide (InO)-based transparent conducting oxides (TCOs) have been widely used and studied for a variety of applications, such as optoelectronic devices. However, some of the more promising dopants (zirconium, hafnium, and tantalum) for this oxide have not received much attention, as studies have mainly focused on tin and zinc, and even fewer have been explored by solution processes. This work focuses on developing solution-combustion-processed hafnium (Hf)-doped InO thin films and evaluating different annealing parameters on TCO's properties using a low environmental impact solvent. Optimized TCOs were achieved for 0.5 M% Hf-doped InO when produced at 400 °C, showing high transparency in the visible range of the spectrum, a bulk resistivity of 5.73 × 10 Ω.cm, a mobility of 6.65 cm/V.s, and a carrier concentration of 1.72 × 10 cm. Then, these results were improved by using rapid thermal annealing (RTA) for 10 min at 600 °C, reaching a bulk resistivity of 3.95 × 10 Ω.cm, a mobility of 21 cm/V.s, and a carrier concentration of 7.98 × 10 cm, in air. The present work brings solution-based TCOs a step closer to low-cost optoelectronic applications.