Thin Film Fabrication and Characterization of Layered Rock Salt LiCoO2 on Quartz Glass Spray-Coated with an Aqueous Ammonia Solution Involving Metal Acetates

Abstract

A LiCoO2 thin film on a quartz glass substrate was fabricated by a wet process involving heat treatment of a precursor film spray-coated with an aqueous ammonia solution containing LiCH3COO and Co(CH3COO)2. The precursor film formed onto the substrate at 180 °C in air, and was heat treated at 500 °C in air for 0.5 h. The obtained film was spin-coated further with an ethanol-based precursor solution containing identical metal acetates, and heat treated at 500 °C in air for 0.5 h. The X-ray diffraction pattern of the resultant film showed only peaks assignable to the layered-rock-salt LiCoO2. Raman spectroscopy measurements revealed vibrational modes assignable to layered rock salt LiCoO2, with minor content of less than 5 mol% of spinel-type Co3O4. The field emission scanning electron microscopy images indicated that the resultant film was 0.21 μm thick, had no voids, and was a combination of small rounded grains measuring 18 nm in diameter and hexagonal grains larger than 0.2 μm in length. The Hall effect measurements indicated that the resultant thin film was a p-type semiconductor with electrical resistivity of 35(2) Ω·cm and a carrier concentration and carrier mobility of 8(2) × 1016 cm−3 and 2(1) cm2·V−1·s−1, respectively.