Tailoring of optical, hydrophobic, and anti-icing properties of Ca-Mg co-doped ZnO thin films via sol-gel method

Ice formation on solid surfaces may originate serious problems in various fields such as aircraft, electrical lines etc. Hydrophobic coatings and surfaces can have potential applications with anti-icing properties via excessive repellency of water. Zinc oxide (ZnO) is a material with great importance in many technological applications. Recently, co-doping with different elements in zinc oxide is collecting research interest for hydrophobicity. In this work, calcium co-doped with magnesium in zinc oxide (CaMgZnO) thin films were deposited by sol-gel spin coating method. The doping percentage for calcium was x = 0, 1, 2.5, 4 at% as (CaxMg0.025Zn0.975-x). X-ray diffraction results revealed that all the films had hexagonal wurtzite structure and preferred (002) plane dominance with no secondary phase. Crack free surface was found for all the samples by SEM images. All the deposited films had average transmission of greater than 80%. Maximum band gap value of 3.43 eV revealed for max doping level. Furthermore, optical constants, complex dielectric functions, energy loss functions, and photoluminescence study were also explored. Hydrophobic behavior was evaluated for all the samples and more hydrophobicity with the water contact angle (WCA) of 104.06 degrees produced by the sample having equal amount of calcium and magnesium. De-icing properties like freezing on-set and freezing delay was -15.1 degrees C and 900 s with the temperature set-point -5 degrees C respectively. Likewise, maximum freezing delay with temperature set-point -10 degrees C was 630 s.