| Summary: | 博士 === 國立中興大學 === 電機工程學系所 === 99 === Research efforts devoted to organic based microelectronic and optoelectronic devices have grown significantly in recent years. The advantages of organic based devices are low processing temperature which is compatible with the plastic substrates, simple processing procedure that is potentially low cost, and solution process that could be produced in large area.
In this thesis, a low voltage pentacene organic thin film transistor (OTFT) was accomplished by using a random copolymer, poly(styrene-co-methyl methacrylate) (PS-r-PMMA) as the gate dielectric. The thickness of PS-r-PMMA polymer can be controlled in the range of 2–14 nm by thermal process. By utilizing this copolymer as gate dielectric, pentacene based organic thin-film transistor could be operated at 5V. Furthermore, the coating, annealing and removing sequential process of ultrathin PS-r-PMMA ensure that this technique is potentially compatible with the large area printing methods such as inkjet printing and doctor blade coating. The random copolymer dielectric is therefore a good candidate for OTFT in large area printed flexible electronic applications.
In addition, we utilized the PS-r-PMMA as a surface modification layer of hafnium oxide which exist hydroxyl groups on the surface. Due to the reduction of interface states, not only low voltage operation but also improved OTFT properties were obtained by the use of PS-r-PMMA. OTFT with low PS-r-PMMA formation temperature, 130°C, was carried out to prove the compatibility with the general plastic substrate. The hysteresis behavior of the high k based OTFT was also discussed in detail. In chapter 5, we demonstrated an organic complementary inverter composed of p channel Pentacene and n channel PTCDI-C13 organic thin film transistors. By stacking an ultra-thin PS-r-PMMA onto hafnium oxide as dielectrics, two types of transistors exhibit balanced performance. The inverter has good performance with switching voltage around half of supply voltage, signal gain of 45 V/V and high noise margin at 10V, that indicates it is suitable for flexible logic application.
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