Enabling high-quality transparent conductive oxide on 3D printed ZrO2 architectures through atomic layer deposition

The conformal atomic layer deposition of a transparent conductive oxide composed of Al-doped ZnO (AZO) over three-dimensional (3D) shaped ZrO2 microarchitectures produced using two-photon lithography (TPL) is reported here for the first time. The effect of ZrO2 morphology, surface roughness, and crystallographic phase (tetragonal and monoclinic) on the quality and properties of the deposited ZnO and AZO thin films is investigated. No discontinuities, domains, or areas differing from the desired chemical composition have been found in films grown over the 3D structures. Three different Al dopant concentrations (4.0 %, 4-5 %, and 5.0 % Al doping cycles) are examined and compared to undoped ZnO. AZO and ZnO optical and electrical properties are studied using cathodoluminescence (CL) and Hall effect measurements. The CL study confirms that the observed emissions from the ZnO and AZO films are associated with the near band emission of ZnO and defects, i.e., zinc and oxygen vacancies and interstitial oxygen. The AZO films exhibit n-type semiconductor behavior, and a minimum resistivity of 1.2 x 10-3 Ω cm is achieved. From a broad perspective, AZO deposition on 3D microarchitectures opens a new route towards dimensionally refined optoelectronic devices in which the ZrO2/AZO can serve a key enabling role for the production of electrodes.