Electrical, optical, and structural properties of indium tin oxide thin films for organic light-emitting devices

خواص الکتریکی ، نوری، و ساختاری غشاهای نازک اکسید قلع ایندیوم در دستگاه های ساطع کننده نور آلی

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Electrical, optical, and structural properties of indium tin oxide thin films for organic light-emitting devices

High-quality indium tin oxide ~ITO! thin films ~200–۸۵۰ nm! have been grown by pulsed laser
deposition ~PLD! on glass substrates without a postdeposition annealing treatment. The structural,
electrical, and optical properties of these films have been investigated as a function of target
composition, substrate deposition temperature, background gas pressure, and film thickness. Films
were deposited from various target compositions ranging from 0 to 15 wt% of SnO2 content. The
optimum target composition for high conductivity was 5 wt% SnO2195 wt% In2O3. Films were
deposited at substrate temperatures ranging from room temperature to 300 °C in O2 partial pressures
ranging from 1 to 100 mTorr. Films were deposited using a KrF excimer laser ~248 nm, 30 ns full
width at half maximum! at a fluence of 2 J/cm2. For a 150-nm-thick ITO film grown at room
temperature in an oxygen pressure of 10 mTorr, the resistivity was 431024 Vcm and the average
transmission in the visible range ~400–۷۰۰ nm! was 85%. For a 170-nm-thick ITO film deposited
at 300 °C in 10 mTorr of oxygen, the resistivity was 231024 Vcm and the average transmission in
the visible range was 92%. The Hall mobility and carrier density for a 150-nm-thick film deposited
at 300 °C were 27 cm2/V s and 1.431021 cm23, respectively. A reduction in the refractive index for
ITO films can be achieved by raising the electron density in the films, which can be obtained by
increasing the concentration of Sn dopants in the targets and/or increasing deposition temperature.
Atomic force microscopy measurements of these ITO films indicated that their root-mean-square
surface roughness ~;5 Å! was superior to that of commercially available sputter deposited ITO
films ~;40 Å!. The PLD ITO films were used to fabricate organic light-emitting diodes. From these
structures the electroluminescence was measured and an external quantum efficiency of 1.5% was
calculated.

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