Pulsed laser deposition of ITO nanorods in argon and OLED applications

Indium tin oxide (ITO) nanorods were deposited in argon gas environment on glass substrate at 250 °C by a pulsed Nd:YAG laser, with laser parameters of 10 Hz, 355 nm and 2–3 J/cm2. The formation of ITO nanorods was found to depend strongly on argon pressure and deposition duration, of (4–7) Pa and (30–60 min) respectively. At the initial growth stage, a large number of nucleation sites were first formed which eventually evolved into pin-needle types of nanorods. For extended period of deposition, oval-shaped lumps were seen to be formed among the nanorods. The growth of spherical tips in nanorods suggests the vapor–liquid–solid (VLS) mechanism. The XRD patterns show that ITO with In2O3 bixbyite structure is strongly orientated in <111> direction. The presence of ITO nanorods, however, was found to improve the organic light emitting diodes (OLED) performance with higher brightness and lower turn-on voltage, as compared to OLED fabricated with commercial ITO. ITO samples were also deposited in N2 but nanorod was not observed and its OLED failed to operate.