Microstructure and piezoelectric properties of hexagonal MgxZn1−xO/ZnO films at lower Mg compositions

Abstract

We investigate the piezoelectric coefficient (d33) of MgxZn1−xO and MgxZn1−xO/ZnO films with the variation of the Mg concentration. The films are grown on Si (111) substrate using MgO and ZnO as targets by radio frequency magnetron sputtering. The thickness of all the films is fixed at around 500 nm for both MgxZn1−xO and MgxZn1−xO/ZnO films. All the films have high crystallinity with preferred orientation along c-axis and that shows columnar microstructures. Besides, the substitution of magnesium ions at zinc sites is confirmed by X-ray diffraction patterns, X-ray photoelectron spectroscopy and UV–Visible spectroscopy. The d33 values reach 41.7 pm/V and 47.5 pm/V for MgxZn1−xO and MgxZn1−xO/ZnO (x = 0.30) films which is around 3.4 and 3.8 times larger than pure ZnO films (12.4 pm/V). The films may be considered as promising candidate for piezoelectric nanogenerators and piezotronic transistors.