| Summary: | 碩士 === 國立嘉義大學 === 電子物理學系光電暨固態電子研究所 === 105 === In this study, Gallium-doped zinc oxide (GZO) thin films have been grown on glass substrates by Pulsed laser deposition (PLD) at various substrate temperatures. The composition, structure, electrical and optical properties of GZO thin films were analyzed by X-ray photoelectron spectroscopy (XPS), X-ray Diffraction, Hall-Effect measurement, Full Spectroscopic Reflectometer and UV-VIS spectrum, respectively.
The results of XRD indicated that GZO films were hexagonal wurtzite type structure with strong (002) c-axis orientation, when the GZO thin films were deposited at the various substrate temperature. For the GZO thin films deposited at over 200 °C, (103) orientation was strongly observed by X-ray diffraction analysis, which is attributed to the substitution of Ga elements into Zn site.
The Hall measurement shows that the higher conductivity is due to the increase in the carrier concentration and mobility of carriers with increasing substrate temperature. The resistivity of GZO thin films decreased rapidly with the increasing the substrate temperature. The lowest resistivity is about 1.1473×10-4 Ω-cm at 300℃substrate temperature. The optical transmission of GZO thin films were over 80% in the visible range. The optical band gap energy of GZO thin films reduced from 3.9eV to 3.6eV with decreasing substrate temperature by PLD.
GZO thin films have shown high conductivity and transparent properties. GZO thin films enable a wide variety of applications on electro-optic devices. In this study, GZO thin films were prepared by PLD as the transparent conductive oxide layer (electrode) in polymer light-emitting diodes (PLED). The I-V curve, L-V curve and E-L curve of the PLED were measured by Keithley 2400 Source Meter, BM-7A Luminance Meters and HR4000 Spectrometer. The results of L-V curve showed that the luminance of PLED becomes better bright when the substrate temperature rises. It is indicated that the intensity of XRD (103) will be enhanced with increasing substrate temperature. The orientation of (103) is favorable to the improvement of the luminance efficiency of the PLED. The photoluminescence (PL) spectra emitted from the F8BT polymer in the range of 500 to 650 nm using 266 nm as the excitation source at RT. The EL spectrum of PLED with GZO electrode show the same emission band of green and yellow light. A PLED lifetime testing capability was established to measure the change in PLED light output by drive at constant voltage. When GZO thin film was deposited under 150 ℃substrate temperature, the XRD pattern show that the GZO thin has the (002) prefer orientation. The durability of PLED device with (002) GZO electrode can reach over 550 minutes. Therefore, the lattice orientation of the (002) lattice can improve the durability of the PLED.
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