Assessing multi-variable coupling effects of UV illumination, heat and oxygen on porous ZnO nanocrystalline film through electron concentration and mobility extraction.

Porous ZnO nanocrystalline films have been widely used in optoelectronic and gas-sensing applications. However, the effect mechanisms of the external fields, such as light, heat and atmosphere, are still controversial. In this work, the multi-variable coupling effects of the UV light, heat and oxygen were thoroughly studied by a newly proposed method, the central idea of which was to first isolate each effect of the fields on electron concentration and mobility, and then analyze how the coupling effects were achieved. Our results revealed the important roles of oxygen adsorption-induced interface barriers and photo-assisted thermal ionization first proposed here, because of which the positive coupling effect of UV light/heat and oxygen, as well as the negative coupling effect of UV light and heat was observed. Our work provides inspiration for studies on metal oxides from both the whole idea and the detailed argument.