Enhancing the properties of polymer thin-film transistors using a novel atmospheric-pressure plasma technology

• Main Authors: Chih-Hsiang Lin, 林志祥
• Other Authors: Kow-Ming Chang
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/24447429746634181806

博士 === 國立交通大學 === 電子工程系所 === 97 === Organic thin film transistors made by spin-coating from solution- processable conjugated polymers have potential advantages in fabricating low-cost devices with large areas. Since OTFT performance depends strongly on the interface between the semiconductor and the dielectric layer, this study attempts to demonstrate that the characteristics of P3HT-based OTFT are improved by controlling the chemistry of the dielectric/polymer interface. Thermal SiO2 is adopted as the dielectric because of its well-characterized properties and ease of chemical modification. Regioregular P3HT (of which HT linkages represent more than 98.5% of the linkages) is utilized as the active layer, so it exhibits better ordering and crystallinity in the solid state, and substantially improved electroconductivities. The field-effect mobility was markedly improved by modifying the surface of SiO2 with using a hexamethyldisilazane (HMDS) self-assembled monolayer. Before the active layer was deposited, the surface of SiO2 was modified using atmospheric-pressure plasma technique (APPT). APPT is a new process that can be implemented at atmospheric pressure and at low temperature. The steps of APPT are performed below 120°C and at atmospheric pressure, so the approach is very suited to use on a plastic substrate. After the SiO2 surface has been modified by the APPT process with hexamethyldisilazane (HMDS), it exhibits typical I-V characteristics of TFTs. Calculations reveal that its field effect mobility can reach 0.02-0.03 cm2/Vs, which is about 15 times that before the modification, and the threshold voltage is below -10V. The performance is even better than that obtained following the usual surface treatment of the SiO2 surface by spin-coating or evaporation. This work suggests an interesting direction for preparing high-performance OTFTs with high efficiency and low-temperature surface treatment by APPT.