| Summary: | 博士 === 國立成功大學 === 電機工程學系 === 102 === The control dimension and morphology in Zinc Oxide (ZnO) nanorods are critical issues in the fabrication of electronic nanodevice. This study discusses ZnO nanorods on plastic substrate for Thin Film Transistor (TFTs) applications. The substrate was immersed in a zinc nitrate hexahydrate Zn(NO3)26H2O and hexamethylenetetramine C12H6N4 solution under various deposition conditions. The X-ray diffraction (XRD) pattern showed that the films were composed of ZnO and Zn(OH)2, and that the ZnO crystal had strong x-ray reflection peaks (110) and (002), in which the c-axis was parallel to the substrate.
The films with plasma surface pre-treatment has stronger (110) peak intensity than that without plasma surface pre-treatment. Also, very uniform grain size of the ZnO nanostructures can be seen. The fabricated enhancement mode ZnO TFTs exhibiting good transistor behavior with the drain saturation current of 38.1 A at VGS = 35 V can be achieved.
The ZnO nanorods based TFTs on plastic substrate by solution method under low temperature were successfully fabricated. The pH of solution and the surface rms roughness greatly influenced the structure and morphology of the ZnO nanorods. It can be seen that the electrical properties of ZnO nanorods based-TFTs is depend greatly on the pH value of the solution and the surface rms roughness of ZnO nanorods channel. The best electrical properties of the ZnO nanorods based-TFTs was obtained at pH value of the solution of 7.80 and surface rms roughness value of 0.94 nm in which the ZnO nanorods based-TFTs operates in the enhancement mode, exhibiting the saturation mobility of about 5.74 cm2/V.s, a threshold voltage of 20 V and drain current on-to-off ratio of 1.8x105.
The ZnO nanorods based-TFTs are fabricated under different process such as under strain tensile effect and without mechanical effect. As observed in strain tensile solution process effect, the saturated drain current, field-effect mobility and on/off ratio was changed. The field-effect mobility of 2.5×10−5 cm2/V.s in the obtained ZnO channel layer without mechanical bending effect is increases to 4.5×10−5 cm2/V.s in films without mechanical bending effect. These changes of the electrical performance of ZnO nanorods based TFTs caused by bending of the substrate are likely related to change in the distance between the nanorods. This study is meaningful in that this is the first report on solution-processed flexible ZnO TFTs which are fully functional in the bent state solution process and describes the practical problems that must be solved in order to make ZnO TFTs on plastic substrates through the solution methods of ZnO nanorods.
Pentacene-based organic TFTs (OTFT) with solution-processed barium zirconate titanate dielectric layers are demonstrated. According to the programming/erasing operations, the devices exhibited memory characteristics, such as reversible threshold voltage shifts and nondestructive readout. The reliability of the memory was confirmed by data retention time and repeated switching cycles’ endurance testing. The possible mechanism of the memory effect was also discussed. These results suggest that the devices could potentially be applied to nonvolatile memory applications in organic electronics.
Solution processible poly(4-vinylphenol) is employed as a transistor dielectric material for low cost processing on flexible substrates at low temperatures. A 6,13-bis (triisopropylsilylethynyl) (TIPS) pentacene–graphene hybrid semiconductor is drop cast to fabricate bottom-gate and bottom-contact field-effect transistor devices on flexible and glass substrates under an ambient air environment. The TIPS pentacene–graphene hybrid semiconductor-based OTFTs cross-linked with a poly(4-vinylphenol) gate dielectric exhibit an effective field-effect mobility of 0.076 cm2V−1s−1 and a threshold voltage of −0.7 V at Vgs = −40 V. By contrast, typical TIPS Pentacene shows four times lower mobility of 0.019 cm2V−1s−1 and a threshold voltage of 5 V.
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