Ecofriendly Water-Based Solution Processing: Preliminary Studies of Zn-ZrO2 Thin Films for Microelectronics Applications

This paper demonstrates the high yield and cost effectiveness of a simple and ecofriendly water-based solution processing, to produce Zinc-doped Zirconia (Zn-ZrO2) composite thin films, onto glass substrates, with excellent optical properties that make them of great interest for optical and microelectronics technologies. The effect of Zn variation (given as 10, 15, 20 at.%) on the crystallization, microstructure, and optical properties of ZrO2 film was examined. The addition of Zn did not restructure the ZrO2 lattice, as the results indicated by X-ray diffraction (XRD) and Raman spectroscopy revealed neither any mixed or individual phases; rather, all the films retained the amorphousness. Nonetheless, Zn did control the grain formation at the film surfaces, thereby changing the surface morphology. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) evidenced homogeneous, compact, crack-free, and dense films with surface roughness below 2 nm indicating smooth surfaces. The films were highly transparent (>80%) with tunable optical band gap Eg (5.21 to 4.66 eV) influenced by Zn dopant. Optical constants such as refractive index (n), extinction coefficient (k), and dielectric constant (ε) were obtained from spectroscopic ellipsometry (SE), and a correlation was established with respect to the doping level. A high value of n > 2 value indicated high packing density in these films, and it decreased slightly from 2.98 to 2.60 (at 632 nm); whereas, optical losses were brought down with increasing Zn indicated by decreasing k values. The photoluminescence (PL) spectra showed UV emissions more pronounced than the blue emissions indicating good structural quality of all the films. Nonetheless, added defects from Zn had suppressed the PL emission. The technique presented in this work, thus, manifests as high performance and robust and has the potential comparable to the sophisticated counter techniques. Furthermore, the Zn-ZrO2 films are promising for a low-cost solution to processed microelectronics and optical technologies after reaching high performance targets with regards to the electrical properties.