Mg doping effects on the microstructure and piezoelectric characteristics of ZnO:Li films deposited at room temperature using an RF sputtering deposition method

In this work, Density functional theory (DFT + U) was used to simulate Mg doped LZO (ZnO:Li 3 mol%) based on an atomic substitution concept. The calculation results indicate the piezoelectric constants e₃₃, e₃₁ and lattice constant a have a tendency to increase significantly due to Mg doping effects. Also, an RF magnetron sputtering system was used to prepare Mg-doped LZO films (ZnO: Li 3 mol%) with Mg doping concentrations of 0, 3, 6, 9 mol% at room temperature. A further analysis shows that when the proposed films are deposited at room temperature, Li atoms will bond with oxygen atoms to form Li₂O₂ to help to enhance the piezoelectric properties of the films. This is also found to be one of the reasons for the error in the simulated lattice constants. In addition, the doping of Mg induces lateral tensile stress in the ZnO structure. This phenomenon can produce lattice distortion and change the asymmetry of the ZnO atomic center at room temperature, thus improving the piezoelectric properties (piezoelectric coefficient d₃₃ is increased from 4.5 to 26.3 pm/V). The reported d₃₃ value is the highest compared to other reports on ZnO-based films deposited at room temperature.