In situ Electrical Characterization of the Thickness Dependence of Organic Field-Effect Transistors with 1-20 Molecular Mono layer of Pentacene
In situ Electrical Characterization of the Thickness Dependence of Organic Field-Effect Transistors with 1-20 Molecular Mono layer of Pentacene
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DOI：
10.1021/am1003377
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发表时间：
2010-08-01
影响因子：
9.5
通讯作者：
Chen, Chin-Ti
中科院分区：
文献类型：
--
作者：
Liu, Shun-Wei;Lee, Chih-Chien;Chen, Chin-Ti
利用原位电特性研究了五苯基有机场效应晶体管（ofet）的场效应迁移率(p)与分子单层（ML）数目的关系，极大地提高了ofet电特性的准确性和可重复性。在真空条件下，观察到了平均厚度为1 ML （7-1.57 nm）的并五烯OFET的空穴面积。在薄膜厚度小于饱和厚度（do）的区域，并五苯OFET的mu随着表面覆盖率的增加而迅速增加，本文研究的并五苯OFET的mu约为3.2 ML。我们已经观察到，并五苯分子层对半导体通道中载流子的输运几乎没有贡献。并五苯fet的阈值电压（lir）具有可变的厚度依赖性，在并五苯厚度约为3.2 ML时，其最小值类似于17 V。对并五苯fet的漏极电流和通/关电流比进行了类似的验证。并五苯层的原子力显微镜（AFM）图像证实了并五苯在SIO2衬底上的层加岛（Stranski-Krastanov模式）生长机制。并五苯薄膜在3.2 ML左右开始出现梯田状堆积结构。从AFM图像来看，在达到最大畴尺寸约1 0 ML后，最上面的几层并五苯阶地堆叠层的尺寸变小。我们的实验结果表明，衬底上最初几层并五苯阶地堆叠层的生长质量强烈地影响了更厚薄膜的形貌、封装结构和OFET的电特性，包括改变载流子迁移率。
Field-effect mobility (p) of pentacene-based organic field-effect transistors (OFETs) is studied as a function of the number of molecular monolayer (ML) by in situ electrical characterization, which greatly improves the accuracy and reproducibility of electrical characteristics of OFETs. The hole mu of pentacene OFET with an average I ML (7-1.57 nm) thickness has been observed under a vacuum. The mu of pentacene OFET rapidly increases with increasing surface coverage in the region of film thickness less than saturation thickness (do), which is about 3.2 ML for pentacene OFETs studied herein. We have observed that pentacene molecular layers beyond do have little contribution to the carrier transport in the semiconducting channel. The threshold voltage (lir) of pentacene OFETs has a variable thickness dependence having minimum similar to 17 V at pentacene thickness around 3.2 ML. Similar do was verified for both drain current and on/off current ratio of pentacene FETs. The atomic force microscopy (AFM) images of the pentacene layer confirm the layer-plus-island (Stranski-Krastanov mode) pentacene growth mechanism on SIO2 substrate. Terrace-like stacking structure begins to be disernable around 3.2 ML of pentacene thin film. From AFM images, top few layers of pentacene terrace stacking become smaller in size after reaching the largest domain size around i 0 ML. Our experimental results have demonstrated that the growth quality of the first few pentacene MLs on substrate strongly influences the morphology of the thicker film, packing structure, and electrical characteristics of OFET, including change-carrier mobility.