Thickness dependent physical and photocatalytic properties of ITO thin films prepared by reactive DC magnetron sputtering

Transparent and conducting indium tin oxide (ITO) thin films were deposited on glass substrates by reactive DC magnetron sputtering at room temperature. The effect of thickness (165-1175 nm) on the physical (structural, optical, electrical) and photo catalytic properties of ITO thin films were investigated systematically. It is observed that with increasing thickness (i) the films turn from amorphous to polycrystalline with a preferential orientation along (4 4 0) direction, (ii) the average grain size and RMS roughness increases from 35 nm to 100 nm and 2.3 nm to 8.6 nm respectively, (iii) the optical band gap decreases from 3.65 eV to 3.45 eV and (iv) the relative density (calculated from the refractive index data) decreases. Four probe and Hall effect measurements show a low resistivity (4.5 × 10-4 Ω cm), mobility (26 cm2/V s) and high carrier concentration (5.3 × 1020 cm-3) values for film with a thickness 545 nm. The work function of ITO films measured by Kelvin probe method varies with thickness. The photocatalytic activity (PCA) of ITO thin films was studied by the degradation of Rhodamine B in water; highest PCA is shown for the films of 545 nm thickness. Present work shows that the ITO is a promising photocatalytic material for the degradation of organic compounds.