紫外光於PMMA有機薄膜電晶體之光響應提昇研究

Abstract

在本研究中，以加熱固化的方式，將可溶性的甲基丙烯酸甲酯製作成有機薄膜電晶體的閘極介電層。並利用紫外光，對甲基丙烯酸甲酯－閘極介電層進行改質。根據觀察，經過紫外光改質後的閘極介電層，有機薄膜電晶體的臨界電壓將會降低、次臨界幅擺增加、而載子的場效飄移率則沒有顯著的變化。在光照射有機薄膜電晶體的實驗中，以波長為460奈米的光線對元件進行照射。經過紫外光改質後的元件，光照射時會觀察到一個較大的臨界電壓飄移與光響應。若對元光照特性進行時間相依的分析，則發現紫外光改質後的元件有較短的飽和時間與較長的回復時間。為找出紫外光改質影響元件特性差異的原由，我們藉著材料分析與介電層的漏電分析，各自排除紫外光改質後影響有機半導體膜內部結構與介電層內產生捕捉缺陷，而主導特性差異的可能性。最後，我們推測元件電特性的差異可能是來自於半導體與介電層間、因紫外光改質而產生介面的捕捉缺陷態所主導。並以一系列的時間常數特性來加以驗證提出的假設。

In this study, with the thermal solidification method, the soluble Polymethylmethacrylate (PMMA) was used as the gat-dielectric of organic thin film transistors (OTFTs). Furthermore, we treated the PMMA gate-dielectric with the UV-light treatment. According to our observation, the OTFTs with UV-light treatment on gate-dielectric, the threshold voltage will be reduced, the subthreshold swing will be increased, however, no significant change in field-effect mobility was observed. In the OTFT experiments under light-irradiation, the devices was irradiated with a ray at a wavelength about 460nm. Among the OTFTs with UV-light treatment on gate-dielectric, when the light-irradiation was turn on, a larger threshold voltage shift and phonic responsivity will be found. If we further analyzed the time-dependent OTFT characteristics after the light-irradiation, the OTFTs with UV-light treatment will show a shorter saturation time and a longer recovering time. In order to find out the origin of UV-light treatment on OTFT property variation, we tried to introduce the material analysis and dielectric-leakage analysis to rule out the effects of UV-light treatment on organic semiconductor inertial structure and the traps inside the dielectric film, respectively. Finally, we presumed the OTFT property variation should be dominated by the interface traps between the organic semiconductor film and the dielectric film, which may be created by the UV-light treatment. The proposed assumption is also verified by a serious time-constant analysis.