Effect of chelating agents on the surface parameters and optical constant of CZO thin films by sol–gel process

Abstract

3 mol% Cu-doped ZnO (CZO) transparent p-type thin films were deposited on glass substrates by sol–gel dip coating technique, and the influence of various chelating agents such as monoethanolamine (MEA), diethanolamine (DEA) and triethanolamine (TEA) on structural, morphological, optical, and electrical properties of CZO thin films was investigated. The XRD results showed that CZO-DEA and CZO-TEA samples have hexagonal Wurtzite structure which homogenously grown in all direction while CZO-MEA thin film was highly oriented along the (002) direction. In addition, the grain size of thin films is about 16.2–19.4 nm, which the smallest grain size belongs to CZO-MEA. FESEM images showed the wrinkled like morphology of the CZO-MEA thin film consists of spherical nanograins in compared with spherical shape of other samples. The electrical measurements revealed the p-type conductivity of samples. Also, CZO-MEA sample exhibited the highest mobility and carrier concentration values of 26.2 cm2/Vs and 2.32 × 1014 cm−3, respectively. Based on optical studies, the superior optical transmittance of CZO-MEA related to the lowest roughness parameters and better growth along c-axis. Moreover, CZO-TEA thin film showed the lowest band gap (3 eV). The PL spectra showed the CZO-MEA sample has the highest visible emission. CZO-MEA thin film illustrated the more contact angle (hydrophobic behavior). Besides, the most change of contact angle observed in CZO-MEA sample under UV-irradiation.