A comparative study of the optical, electrical, and wettability properties of amorphous and nanocrystalline ITO/Cu/ITO multilayer thin films prepared by DC pulsed magnetron sputtering
摘要
Two ITO/Cu/ITO multilayer thin film systems (amorphous and crystalline) were prepared using DC pulsed magnetron sputtering with varying Cu interlayer thicknesses. The amorphous ITO/Cu/ITO multilayer thin films were deposited at room temperature, whereas the crystalline ones were prepared at a working temperature of 400 °C for both ITO bottom and top layers. The ITO bottom and top layers were deposited at a thickness of 70 ± 2 nm, while the thickness of interlayer Cu was altered from 4 nm to 16 nm for both the amorphous and crystalline ITO/Cu/ITO systems. The optical, electrical and wettability properties of both systems were analyzed and discussed. The optical bandgap (Eg) for a single amorphous ITO layer recorded 4.07 eV, and it decreased from 4 eV to 3.85 eV as the thickness of Cu sandwich layer increased from 4 nm to 16 nm. In the crystalline system, the Eg for a single ITO layer recorded 3.46 eV, and it decreased from 3.55 eV to 2.33 eV as the thickness of Cu embedded layer increased from 4 nm to 16 nm. The amorphous ITO/Cu (16 nm)/ITO film exhibited the lowest resistivity (3 × 10−4 Ω cm) compared to other samples in both two sets. The measured water contact angle for the amorphous films recorded 93o, 90o, 80o, 75o and 75ο for Cu interlayers thickness of 0, 4, 8, 12 and 16, respectively. For the crystalline ITO/Cu/ITO multilayer films, the recorded water contact angles are 60°, 34°, 114°, 125°, and 130° for Cu interlayer thicknesses of 0, 4, 8, 12, and 16 nm, respectively. The crystalline ITO/Cu (4 nm)/ITO structure exhibits a FOM (1.4 × 10−4 Ω−1), which is slightly higher than that of the crystalline ITO single layer and significantly higher than those of all other tested samples, making it the most suitable ITO/Cu/ITO configuration for TCO applications.