有机场效应晶体管“双斜率”效应产生机理的实验研究

In recent years, the novel “double-slope” effect, namely the linear transfer curves or square root of the saturation transfer curves exhibit a higher slope at low gate voltage Vg but a lower slope at high Vg was observed in organic field-effect transistors. This effect has brought difficulties in accurately calculating the device mobility and thus has been a deep concern to the community. How to properly understand the mechanism causing “double-slope” effect remains an open question. In this project, we aim to clarify the physics behind “double-slope” effect by systematic experimental studies. We will employ scanning Kelvin probe microscopy (SKPM) to accurately characterize the gate dependence of contact resistance and channel resistance in OFETs, and study its correlation with “double-slope” effect. In addition, the gate dependence of contact resistance and channel resistance in OFETs fabricated with different dielectrics will be inspected to see how the semiconductor/dielectric interface traps influence the “double-slope” effect. The work will yield importance experimental evidences for clarifying the mechanism of “double-slope” effect, provide guidance to answering the scientific questions caused by “double-slope” effect, deepen the understanding of device physics in OFETs, and also promote the synthesis as well as the applications of high-mobility organic semiconductors.

近年来，有机场效应晶体管（OFET）中出现新奇的“双斜率”效应：线性区转移特性曲线或饱和区转移特性曲线的根方在低栅压区域呈现高斜率而在高栅压区域呈现低斜率。它给迁移率的准确计算带来困难，因而引起整个领域的极大关注。如何正确地理解这种“双斜率”效应的产生机理仍然是一个难题。本项目以阐明“双斜率”效应的产生机理为目标，拟从实验上系统深入地研究该效应的产生机理。计划利用开尔文扫描探针显微镜（SKPM）准确测量OFET中接触电阻和沟道电阻的栅压依赖特性，探讨其与“双斜率”效应之间的内在联系。并通过表征用不同介电层制备的OFET中接触电阻和沟道电阻的栅压依赖特性来探究半导体/介电层界面处的缺陷如何影响“双斜率”效应。本项目将为阐明“双斜率”效应的产生机理提供重要的实验基础，为解答由“双斜率”效应引发的科学问题提供指导，加深人们对OFET器件物理的认识，并促进高迁移率有机半导体的合成及应用。

有机场效应晶体管（OFET）中的“双斜率”效应给迁移率的准确提取带来困难，是近年来本领域重点关注的问题。为了深入理解 “双斜率”效应，阐明其产生机理，本项目开展了“双斜率”效应产生机理的实验研究，在项目执行期内，主要研究了以下内容： 1. 研究了有机场效应晶体管（OFET）中线性区与饱和区迁移率差别的产生机理，因为该现象与“双斜率”效应密切相关；2. 研究了基于铁电介电层的OFET器件的制备及表征。通过分别探究接触电阻、界面缺陷以及体缺陷对线性区和饱和区迁移率差异的影响，发现导致迁移率差异的主要因素是接触电阻。相比之下，界面缺陷主要影响迁移率的数值大小，对迁移率的相对差异影响则较小。为了研究消除“双斜率”效应的方法，我们采用PVDF-TrFE铁电材料作为介电层，在该器件中得到了接近理想情况的转移特性曲线，为消除“双斜率”效应提供了思路。相关工作发表SCI论文12篇，其中通讯作者论文11篇，包括2篇Adv. Funct. Mater., 1篇Small, 3篇Adv. Electron. Mater., 2篇J. Mater. Chem. C。本项目的研究成果为阐明OFET 中“双斜率”效应的产生机理，深刻认识影响迁移率的因素提供了重要的实验基础。