Transparent, amorphous and organics-free ZnO thin films produced by chemical solution deposition at 150°C

We have studied the low-temperature processing of ZnO by chemical solution deposition. A transparent, stable precursor solution prepared from zinc-acetate dihydrate dissolved in 2-methoxyethanol was spin-coated on SiO x /Si, soda-lime glass and polymer substrates and heated at 150°C. Selected thin films deposited on SiO x /Si were additionally heated at 450°C. Microstructural and chemical analyses showed that the thin films heated at 150°C in air were amorphous, contained no organic residues and had a root mean square roughness of 0.7 nm. The films deposited on SiO x /Si and heated at 450 o C were crystallised and consisted of randomly oriented grains with a diameter of about 20 nm. All thin films were transparent, exhibiting a transmission of over 80 % in the visible range. The resistivity of the 120 nm thick ZnO films processed at 150 o C was 57 MΩcm and upon heatineg at 450 o C it decreased to 1.9 kΩcm.