Sol-gel preparation of poly(ethylene glycol) doped indium tin oxide thin films for sensing applications

Indium tin oxide (ITO) thin films were deposited on glass or oxidized silicon substrates by sol-gel process. The sol was prepared by mixing the anhydrous indium trichloride in acetylacetone and tin (IV) chloride in ethanol. Ten percent by weight Sn-doped indium oxide (ITO) films with variation of the amount of polymer poly(ethylene glycol), PEG, added as additives were prepared by heat treatment in air at different temperature and different time intervals. The morphological, structural, optical, and electrical properties of the resulted ITO films were investigated. X-ray diffraction (XRD) results showed that the introduction of PEG lowered the intensity peaks as compared to that of the undoped ones. The SEM and AFM investigations indicated that the PEG doped thin films also result in a flatter surface compared to the undoped. The electrical and optical testings revealed that the doping of PEG could lead to increased optical transmittance rate (∼3% to 5%) with wavelength 350-700 nm and decreased sheet resistance. The ITO thin films prepared under low temperature had been employed as gas sensitive material for poisonous gas detection.