Deposition temperature effect on properties of electrosprayed ZnO thin films

Zinc oxide (ZnO) thin films are the subject of extensive investigation because of their outstanding physical characteristics that make ZnO thin films highly suitable for a broad range of applications such as optoelectronic systems, transparent electronic devices, gas sensing technologies, solar energy conversion, and biosensing platforms.

The performance of ZnO-based thin films is closely influenced by the selected deposition methods and the specific conditions under which the films are grown. Various methods have been developed for the deposition of ZnO thin films, among which electrospray has emerged as a versatile and scalable technique that enables tunable film properties through straightforward variation of deposition parameters. One particularly important parameter is the substrate temperature, which governs droplet mobility on the substrate surface and significantly influences film morphology and crystallinity.

In the present study, ZnO thin films were deposited by electrospraying at relatively low substrate temperatures ranging from 120 °C to 150 °C. The surface morphology, roughness, crystallinity, water contact angle, and film thickness were systematically investigated, and their dependence on substrate temperature was analyzed. The potential application of the films as ammonia gas sensors was evaluated using the quartz crystal microbalance (QCM) method, for which the films were deposited onto quartz crystal resonators and their frequency responses were monitored during ammonia exposure.

The results demonstrate that the properties of ZnO thin films can be effectively tuned by adjusting the substrate temperature, enabling optimization for gas-sensing applications.

Acknowledgement

The support of the Bulgarian National Science Fund Project KP-06-COST/29 (2024) and COST action CA21159 are highly appreciated. Research equipment of Distributed Research Infrastructure INFRAMAT, part of Bulgarian National Roadmap for Research Infrastructures, supported by Bulgarian Ministry of Education and Science was used in this investigation.