Papers by Author: Do Geun Kim

Abstract: Ga-doped ZnO films were deposited on polyethylene terephthalate (PET) substrate by dc magnetron sputtering using a high density GZO target (doped with 6.65 wt% Ga2O3) without substrate heating. We investigated electrical, structural, and mechanical properties of GZO films deposited under various total gas pressures (Ptot). GZO films deposited at Ptot of 2.0 Pa showed the lowest resistivity (2.91 x 10-2 7cm), which could be attributed to higher crystallinity of the film. Also, this GZO film showed the lowest change in resistance (8 R/R0 = 0.3) for the dynamic bending test.

Abstract: The electrical, optical and mechanical properties were investigated for the In-Sn-Zn-O films deposited using ITO and ZnO targets, without substrate heating. Three types of ITO target, which are 90wt.% In2O3 : 10wt.% SnO2, 93wt.% In2O3 : 7wt.% SnO2, and 95wt.% In2O3 : 5wt.% SnO2, were used. The power of DC cathode equipped ITO target was fixed at 70W and the power of RF cathode equipped ZnO target was changed from 20W to 60W. The lowest resistivity (2.95x10-4 2cm) was obtained for the In-Sn-Zn-O films deposited under DC power of 70W of ITO (93wt.% In2O3 : SnO2 7wt.%) and RF power of 40W of ZnO target. It is confirmed that surface uniformity, electrical property, and mechanical durability were improved by introduction of Zn atom for all the ITO targets.

Abstract: Electrical, optical, and structural properties of amorphous indium zinc oxide (IZO) anode films grown on flexible polycarbonate (PC) substrate were investigated. The x-ray diffraction (XRD) result shows that the IZO film grown at room temperature is complete amorphous structure due to low substrate temperature. A sheet resistance of 34.1 ,/
, average transmittance above 88.9% in visible range, and root mean spare roughness of 3.5~10.5 Å were obtained even in the amorphous IZO anode film grown on PC substrate at room temperature. It is shown that the Ir(ppy)3 doped-flexible organic light emitting diode (OLED) fabricated on the amorphous IZO anode exhibit comparable current-voltage-luminance characteristics as well as external quantum efficiency and power efficiency to OLED fabricated on conventional ITO/glass substrate. These findings indicate that the IZO anode film is a promising anode material for the fabrication of flexible OLEDs.

Abstract: Tin doped indium oxide (ITO) films were deposited on plastic films by RF superimposed DC magnetron sputtering method using an In2O3 – 10 wt.% SnO2 target without intentionally heating substrates. We have investigated the effects of an RF superimposed DC power system on the electrical, optical, and mechanical properties of the ITO films by using Four-Point Probe, Hall Effect Measurement, UV-Vis-NIR Spectrophotometer, XRD, and Residual Stress Measurement. With increasing the amount of RF power superimposed on DC power, the sputtering discharge voltages of DC power supply were decreased from –290 V to –100 V, i.e., plasma impedance decreased with an increase of the amount of RF power. The resistivity of the samples drastically decreases with increasing RF power, and shows the lowest value of 3.8×10-4 8·cm. Hall effect measurements explain that the increase of carrier mobility is strongly related with the enhancement of the resistivity of ITO films even though there is no difference on its concentration. The RF power superimposed on DC power also reduces the residual stress of the samples up to the stress level of ~ 200 MPa at optimum values of RF power.