Laser processing of indium tin oxide thin film to enhance electrical conductivity and flexibility

This work reports a method that uses a KrF excimer laser to enhance the electrical and mechanical properties of amorphous indium tin oxide (ITO) thin films on flexible substrates. Irradiation with nanosecond laser pulses induces thermal crystallization of ITO, and thereby increases the electrical conductivity and flexibility of film deposited on polyethylene terephthalate substrates. The shallow optical (~45 nm) and thermal penetration (~100 nm) of the laser beam confines the thermal effect to within the ITO layer without damaging the substrate. The laser treatment changed the crystallinity of ITO film from amorphous to poly-crystalline; as a result, its electrical-conductivity increased by 20-25%. Moreover, the treatment decreased the critical bending radius to avoid loss of electrical property from 8 mm to 5 mm. The adhesion strength and transparency of the ITO film were not affected significantly by the laser treatment. This work suggests that laser treatment can be an effective tool to enhance the crystallinity, of sputtered ITO thin film, and its electrical and mechanical properties on flexible substrate.