Highly Conducting, Transparent Rhombic/Cubic Indium Tin Oxide Nanocomposite Thin Films

Abstract

Polycrystalline tin-doped indium oxide (ITO) films were deposited at growth rates up to 0.8 nm/s on glass using pulsed nebulization CVD. The precursor solutions were nebulized into droplets with a modal size significantly smaller than predicted by theory. Rhombohedral distortion of the structure was observed in a number of films leading to nanocomposites of the rhombic/cubic structures. The rhombic phase is rarely observed without applying high pressure. The average mobility (carrier concentration) for the partially rhombic films was 27 cm2/(V s) (5.7 × 1020 per cm3), whereas for the purely cubic films it was 11 cm2/(V s) (4.0 × 1020 per cm3). These values are higher than for sputtered films. The significantly improved mobility is explained by lower strain/disorder in the presence of the rhombic phase. The higher carrier concentration may relate to increased tin solubility in rhombohedral phase. Median film optical transparency was 89%, and the median rms roughness value was 6 nm, comparable to sputtered films.