17 December 1999 Transparent conducting electrode materials grown by pulsed laser deposition for organic light-emitting devices
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Abstract
Two transparent conducting oxides (TCO) thin films including tin-doped indium oxide (ITO) and aluminum-doped zinc oxide (AZO) were grown on glass substrates by pulsed laser deposition (PLD). The structural, electrical and optical properties of these films were investigated as a function of target composition and film growth temperature. Films were deposited using a KrF excimer laser (248 nm, 30 ns FWHM) at a fluence of 2 J/cm2 at growth temperatures ranging from 25 degrees Celsius to 400 degrees Celsius in oxygen pressures ranging from 1 to 100 mTorr. For a 300 nm thick ITO film deposited at 300 degrees Celsius in oxygen pressure of 10 mTorr, the resistivity was 2 X 10-4 (Omega) -cm and the average transmission in visible range (400 - 700 nm) was 85%. The Hall mobility and carrier density for a 150 nm thick ITO film deposited at 300 degrees Celsius were 27 cm2/V-s and 1.4 X 1021 cm-3, respectively. For a 100 nm thick AZO film deposited at 200 degrees Celsius in an oxygen pressure of 5 mTorr, the resistivity was 3.8 X 10-4 (Omega) -cm and the average transmission in visible range (400 - 700 nm) was 90%. The Hall mobility and carrier density for the same AZO film were 18 cm2/V-s and 9.1 X 1020 cm-3, respectively. AFM measurements indicated that the RMS surface roughness of the ITO films (approximately 5 angstrom) was slightly lower than that of the AZO films (approximately 7 angstrom). XPS measurements showed that the work function of ITO films grown at 250 degrees Celsius was 4.51 plus or minus 0.05 eV, which is higher than that (4.05 plus or minus 0.05 eV) of the AZO films grown at 200 degrees Celsius. The PLD ITO films were used to fabricate organic light-emitting diodes (OLEDs). The electroluminescent (EL) performance was measured and the luminous power efficiency was calculated to be 0.6 lm/W, which is comparable to that measured with commercially available sputter-deposited ITO anodes.
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Huengsoo Kim, Huengsoo Kim, Alberto Pique, Alberto Pique, James S. Horwitz, James S. Horwitz, Charles D. Merritt, Charles D. Merritt, Ruediger Schlaf, Ruediger Schlaf, Zakya H. Kafafi, Zakya H. Kafafi, C. M. Gilmore, C. M. Gilmore, Douglas B. Chrisey, Douglas B. Chrisey, "Transparent conducting electrode materials grown by pulsed laser deposition for organic light-emitting devices", Proc. SPIE 3797, Organic Light-Emitting Materials and Devices III, (17 December 1999); doi: 10.1117/12.372722; https://doi.org/10.1117/12.372722
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