Effects of cumulative ion bombardment on ITO films deposited on PET and Si substrates by DC magnetron sputtering

Abstract

Transparent conducting indium tin oxide (ITO) thin films are deposited on polyethylene terephthalate (PET) and silicon (Si) substrates by DC magnetron sputtering at room temperature. The electrical and optical properties of the ITO films are then investigated as a function of the cumulative sputtering gas; a parameter newly proposed in this study and defined as the product of the gas (argon) flow rate and the deposition time. The results show that the ITO films deposited on the PET substrates have an amorphous structure, while those deposited on the Si substrates have a microcrystalline structure. For both ITO films, a critical value of the cumulative sputtering gas parameter exists at which the minimum resistivity occurs due to a corresponding increase in the carrier density. For the ITO films deposited on the Si substrates, the carrier mobility is insensitive to the cumulative sputtering gas. However, for the ITO films deposited on the PET substrates, the carrier mobility reduces as the cumulative sputtering gas increases. For the ITO film on the PET substrate, the average transmittance in the visible range increases with an increasing argon flow rate given a constant deposition time. The optical band gap of the ITO films on the PET substrates located in the visible range reduces the transparency of these samples. Finally, for the ITO films deposited on PET substrates, a low resistivity can be obtained without any significant reduction in the transmittance of the ITO film by using the critical cumulative sputtering gas value as a deposition guideline in determining suitable values of the gas flow rate and deposition time.