Tuning the Sheet Resistance, Ferromagnetism, and H₂O₂ Sensitivity of ITO Film by Introducing Tunable Pores

Abstract

An ethanol-assisted etching route using Zn powder as reductant was developed to prepare the tunable pores in ITO films for modifying the sheet resistance, ferromagnetism, and H2O2 sensitivity. Both XRD and XPS revealed that ITO is initially reduced into metal In and Sn by Zn and then dissolved by HCl aqueous solution diluted by ethanol, which makes the etching reactions controllable and homogeneous. By adjusting the amount of Zn and/or ethanol, the pore size and density were continuously tuned in the ranges of 20–280 nm and 49–213/μm2, respectively. With enlarging the pore region, the ITO sheet resistance and ferromagnetism gradually enhance. The pore formation decreases the ITO crystalline integrity and carrier density and mainly contributes to the increase of sheet resistance. The enhanced ferromagnetism arises from the increase of oxygen vacancies induced by pores. Contrarily, the ITO ferromagnetism can be greatly depressed by irradiating ITO with UV light to reduce oxygen vacancies. By optimizing the pore structures and sheet resistance, the porous ITOs made here increase the detection sensitivity of H2O2 up to 16.4 times in comparison to the commercial ITO films.