ALD grown undoped ZnO and Al-doped-ZnO thin-film heaters

Abstract

TTFHs require conductive thin-film materials with high transparency in the visible spectrum. Although, ITO is considered as the common material, and alternative materials, such as networks of carbon nanotubes, graphene, silver nanowires, hybrid structures and various oxide thin films, have been studied. Some of the application areas of TTFHs include touch screens and window defrosters. This study aims to demonstrate ALD grown simple binary compound ZnO as a cheap and simple to produce alternative material for TTFHs and compare ZnO and Al doped counterpart performances to each other. For the first time in literature, undoped ZnO thin films grown by ALD are successfully demonstrated as TTHF and record high performances are obtained for AZO TTFHs for 100 nm and below very thin films. The optimized ZnO and AZO thin films showed comparable input power density values in very small thicknesses (∼70–100 nm) with an average optical transmittance of ∼ 90 % in the visible spectra. At a 20 V bias, ZnO heaters reached 52 °C, while AZO heaters achieved 116 °C within 2 min. These temperatures were stabilized within 3 min, and the corresponding input power densities were calculated as 864 and 4276 W/m², and the lowest resistivity values were achieved as 6.79 × 10⁻³ and 3.30 × 10⁻³ Ω cm for ZnO and AZO, respectively.