Near-Infrared Transparent Transition-Metal-Doped Indium Oxide Thin-Film Heater for LiDAR

Abstract

The evolving need for all-weather light detection and ranging (LiDAR) sensors and cameras for autonomous vehicles, remote sensing surveillance, and space exploration has spurred the development of transparent heaters. While LiDAR photon sources have shifted from the visible to the near-infrared (NIR) range, the use of transparent conductive oxides (TCOs) for heaters leads to significant optical losses due to their high plasmonic absorption and reflection in the NIR range. Although different TCO compositions can be employed to preserve transparency and electrical conductivity in this range, the choice of dopants, their concentrations, and the underlying mechanisms remain largely unknown. In this study, we present TCOs specifically designed for NIR applications with a focus on identifying new compositions that strike a balance between NIR transparency and electrical conductivity. We present a 4B-6B transition-metal-doped indium oxide thin-film heater that exhibits impressive NIR transmittance (>90%) surpassing that of commonly used indium tin oxide films. By incorporating effective dopants such as titanium, hafnium, and tungsten, we successfully reduced the resistivity and enhanced the electrical conductivity of indium oxide films. To enhance the practical utility of the film, we implemented post-treatments comprising argon plasma treatment and encapsulation with low-molecular-weight poly-(dimethylsiloxane), which resulted in significantly improved performance. The optimized film exhibited a sheet resistance of 520 Omega/sq and excellent optical transmittance at 850 nm (89.1%), 905 nm (89.7%), and 1550 nm (92%). Moreover, we successfully integrated defogging and defrosting capabilities into a commercial LiDAR camera and demonstrated its reliable operation in challenging environments.