Highly oriented indium tin oxide thin films for organic light-emitting diodes

Abstract

Transparent conducting indium tin oxide (ITO) tin films were grown by pulsed-laser deposition (PLD) on glass and single crystal yttria-stabilized zirconia (YSZ) substrates. The structural, electrical and optical properties of these films were investigated as a function of substrate deposition temperature and background gas pressure. Films were deposited using a KrF excimer laser (248nm, 30 ns FWHM) at a fluence of 1.2 J/cm². Films were deposited at substrate temperature of 300 degree(s)C in mixed gases (12 mTorr of argon and 1-50 mTorr of oxygen). X-ray diffraction, scanning electron microscopy and atomic force microscopy were used to characterize the structure and morphology of the deposited films. UV/VIS/NIR spectroscopy and Hall effect measurements were used to characterize the optical and electrical properties of the films. ITO films (300 nm thick), deposited by PLD on YSZ at 300 degree(s)C in a gas mixture of 12 mTorr of argon and 5 mTorr of oxygen, exhibit a low electrical resistivity (1.6 x 10^-4(Omega) -cm) with a high transparency (~74%) at 550 nm. ITO films deposited by PLD on both glass and YSZ substrates have been used as an anode contact in organic light-emitting diodes. A comparison of the device performance for the two substrates shows that the device fabricated on the ITO/YSZ has a higher external quantum efficiency than that of the device fabricated on the ITO/glass.