Molecular Alignment and Electric Characteristics for Thin Films on Planar and Nano-Structured Substrates

• Main Authors: Jou-An Liao, 廖柔安
• Other Authors: Yu-Tai Tao
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/73960871587371142462

碩士 === 國立臺灣科技大學 === 化學工程系 === 102 === The discotic liquid-crystals (DLCs) systems are appealing in organic electronics because of their solution-processibility and controllable inter-molecular ordering. Generally, these orderings are induced by the strong inter-planar π-π interactions and result in columnar self-assembly with hexagonal arrangement. These systems are expected to gives rise to better semiconducting properties with the charges hopping along stacks of π-conjugated planes. Therefore, to control the orientation of the column stakes between two electrodes would be an important issue in designing semiconducting devices, such as field-effect transistors. In the first part of this study, the orientations and structures of several discotic liquid crystals on surface were characterized using reflection-absorption infrared spectroscopy (RAIRS), powder X-ray diffractometer, polarizing microscope (POM) and atomic force microscope (AFM) to investigate the film structure. In the second part, in order to understand the semiconducting properties and packing behaviors of DLCs in different environments, the film structure on planar substrate and nanopillar-templated substrate were examined. Less morphological imperfections were observed when DLC films were formed on nanopillar-templated surfaces, compared to that on a planar surface. The sidewalls of nanopillars appear to assist the growth of DLCs into columnar alignment with their long-axis parallel to the nanopillar and against the substrate. FET devices are also fabricated for these materials. The mobility was measured in TC4TBC based lateral transistor devices and reached 7.59E-4 cm2V-1s-1. Field effect mobilities were measured for all four materials in vertical transistor configuration.