Highly conductive low-temperature combustion-derived transparent indium tin oxide thin film

Abstract

Combustion synthesis is a well-known method for synthesis of transparent metal oxide thin films at low temperature (<400 °C). However, their functional properties are often inferior due to high residual porosity originating from a release of large amounts of gaseous products during combustion reaction. In this paper, indium tin oxide (ITO) transparent conductive oxide thin films are prepared through combustion synthesis at 350 °C and the porosity issue is explored via multilayer deposition. When the thickness of individual layers is downscaled from 12 to 3 nm, the density increases from 5.8 to 7.0 g cm⁻³ and porosity decreases from 20 to 3%. This causes a strong boost of conductivity σ_f from 220 to 620 S cm⁻¹, the latter being one of the highest values ever reported for low-temperature processed ITO films. The effectiveness of this approach is attributed to a large specific surface area of thinner individual layers, which strongly enhances gas transport during the combustion process. We also show that improved crystallinity and a strong increase in tensile in-plane stress strongly contribute to the boost in conductivity.