| Summary: | 碩士 === 國立交通大學 === 電子工程系所 === 93 === Recently, organic thin film transistors (OTFTs) were researched widely for low-cost, low-temperature and flexible application. In this paper, organic thin film transistors based on poly (3-hexylthiophene) (P3HT) with the “bottom contact” structure, SiO2 as insulating layer, organic active layer grown with spin-coating have successfully been demonstrated.
In chapter 2, we use Cr, Ni or Pt as S/D contact materials of OTFTs. The work function of they are all larger than the work function of P3HT. Because of the stability of Pt, it can form better ohmic contact with P3HT than others. The crowding effect was occurred at the small drain bias for Ni as S/D contact material of OTFTs. Cr form Schottky contact with P3HT because of the chemical reactivity. We improved the characteristics of OTFTs with Ni as S/D contact material by capping thin Pt film on S/D contact. We adjusted the thickness of adhesion metals and found that don’t affect the performance significantly of OTFTs.
In chapter 3, we tested the electric reliability of P3HT OTFTs. The field-effect mobility and gate leakage current did not be affected significantly after hot-carrier stress. The threshold voltage shift is attributed to polarization effect. Next, we investigated the polarization phenomenon P3HT OTFTs. Threshold voltage shift ratio saturated after a span and the last value is as large as the gate bias. The polarization will release when addition electric field remove in P3HT OTFTs but cannot return to initial characteristics.
In chapter 4, we used LPD(liquid phase deposition) method to deposit the SiO2 as insulator in P3HT OTFTs. The performance of P3HT OTFTs with LPD SiO2 as insulator is comparable with that with PECVD SiO2 except the gate leakage current. We used the isolation dielectric under the S/D contact materials to reduce the gate leakage current and that is reduced about one order successfully.
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