The Role of Substrate Temperature on Defects, Electronic Transitions, and Dark Current Behavior of ZnO Films Fabricated by Spray Technique
Materials Chemistry and Physics
Volume 239, 1 January 2020, Article number 122065

We have studied structural, electrical, and optical properties of ZnO thin films deposited by a spray technique. The samples were deposited by varying the deposition temperature from 200 °C (S200) up to 500 °C (S500). As the results, using X-ray diffraction and Raman scattering experiments, improvement in crystalline is observed by increasing the deposition temperature as indicated by the intensity enhancement of (002) plane and the E2-high vibration mode. From I–V curves, the photosensitivity of the films also increases up to 37 times (S500) with increasing the temperature. We reveal that strong UV absorption in S500 plays a significant role in the enhancement of sensitivity. On the other hand, the low dark current in S300 is due to the high density of oxygen vacancies, leading to higher mid-gap transitions, green emission, and Schottky barrier height. In the same time, the narrowing effect of the band gap from 3.28 to 3.20 eV is observed with the decrease of the temperature, which is related to the defect states from oxygen vacancies. Our study is essential to design and massively fabricate ZnO-based optoelectronic devices using a simple technique.
Researcher: Dr. Grandprix T. M. Kadja