Transparent, amorphous and organics-free ZnO thin films produced by chemical solution deposition at 150 degrees 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 SiOx/Si, soda-lime glass and polymer substrates and heated at 150 degrees C. Selected thin films deposited on SiOx/Si were additionally heated at 450 degrees C.

Microstructural and chemical analyses showed that the thin films heated at 150 degrees C in air were amorphous, contained no organic residues and had a root mean square roughness of 0.7 nm. The films deposited on SiOx/Si and heated at 450 degrees 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 degrees C was 57 M Omega cm and upon heating at 450 degrees C it decreased to 1.9 k Omega cm. (c)