Impact of aliovalent La-doping on zinc oxide – A wurtzite piezoelectric

The development of high-performance low-cost electroactive films for energy conversion and electronic device applications is a key goal of current advanced materials and condensed matter physics research. Here, using solution-based scalable chemical spray pyrolysis, high-quality electroactive lanthanum-doped zinc oxide (i.e., Zn_1-xLa_xO) thin films are grown on silicon substrates, and the impact of aliovalent lanthanum doping is investigated using a suite of microstructural, optical and nanoscale scanning probe microscopy techniques. The synthesized polycrystalline thin films show hexagonal wurtzite crystal structure with an increased unit cell volume, crystallite size, and conductivity with lanthanum doping up to 4 at.% beyond which the thin films (6 at.%), however, exhibit a change in dominant crystalline orientation from (101) to (002) plane. Concurrently, at this optimal dopant concentration of 4–6 at.%, the electromechanical performance is enhanced by about 20 %, and polarity-dependent nanoscale electronic transport behaviour is revealed. Our study, therefore, provides key insights into the impact of the rare earth aliovalent lanthanum dopant on the electroactive and electronic properties of low-cost, functional thin films for sustainable energy and sensing applications.