King Benjamin, Radford Chase L, Vebber Mário C, Ronnasi Bahar, Lessard Benoît H
Department of Chemical and Biological Engineering, University of Ottawa, 161 Louis Pasteur Pvt., Ottawa, Ontario K1N 6N5, Canada.
Department of Chemistry, University of Saskatchewan, 110 Science Place, Saskatoon, Saskatchewan S7N 5C9, Canada.
ACS Appl Mater Interfaces. 2023 Mar 10. doi: 10.1021/acsami.2c22789.
Understanding the effect of surface chemistry on the dielectric-semiconductor interface, thin-film morphology, and molecular alignment enables the optimization of organic thin-film transistors (OTFTs). We explored the properties of thin films of bis(pentafluorophenoxy) silicon phthalocyanine () evaporated onto silicon dioxide (SiO) surfaces modified by self-assembled monolayers (SAMs) of varying surface energies and by weak epitaxy growth (WEG). The total surface energy (γ), dispersive component of the total surface energy (γ), and polar component of the total surface energy (γ) were calculated using the Owens-Wendt method and related to electron field-effect mobility of devices (μ), and it was determined that minimizing γ and matching γ yielded films with the largest relative domain sizes and highest resulting μ. Subsequent analyses were completed using atomic force microscopy (AFM) and grazing-incidence wide-angle X-ray scattering (GIWAXS) to relate surface chemistry to thin-film morphology and molecular order at the surface and semiconductor-dielectric interface, respectively. Films evaporated on -octyltrichlorosilane (OTS) yielded devices with the highest average μ of 7.2 × 10 cm·V·s that we attributed to it having both the largest domain length, which were extracted from power spectral density function (PSDF) analysis, and a subset of molecules with a pseudo edge-on orientation relative to the substrate. Films of with the mean molecular orientation of the π-stacking direction being more edge-on relative to the substrate also generally resulted in OTFTs with a lower average . Unlike conventional MPcs, films fabricated by WEG experienced no macrocycle in an edge-on configuration. These results demonstrate the critical role of the axial groups on WEG, molecular orientation, and film morphology as a function of surface chemistry and the choice of SAMs.
了解表面化学对介电 - 半导体界面、薄膜形态和分子排列的影响，有助于优化有机薄膜晶体管（OTFT）。我们研究了双（五氟苯氧基）硅酞菁（）蒸发到通过具有不同表面能的自组装单分子层（SAM）和弱外延生长（WEG）改性的二氧化硅（SiO）表面上形成的薄膜的性质。使用欧文斯 - 温特方法计算了总表面能（γ）、总表面能的色散分量（γ）和总表面能的极性分量（γ），并将其与器件的电子场效应迁移率（μ）相关联，结果表明，最小化γ并使γ匹配可得到具有最大相对畴尺寸和最高μ值的薄膜。随后分别使用原子力显微镜（AFM）和掠入射广角X射线散射（GIWAXS）进行分析，以将表面化学与表面和半导体 - 介电界面处的薄膜形态和分子有序性联系起来。在 - 辛基三氯硅烷（OTS）上蒸发的薄膜制成的器件平均μ最高，为7.2×10 cm·V·s，我们将其归因于它具有从功率谱密度函数（PSDF）分析中提取的最大畴长度，以及相对于衬底具有伪边缘取向的分子子集。π堆积方向的平均分子取向相对于衬底更接近边缘的薄膜通常也会导致OTFT的平均 较低。与传统的金属酞菁不同，通过WEG制备的 薄膜在边缘取向配置中没有大环。这些结果证明了 轴向基团在WEG、分子取向和薄膜形态方面作为表面化学和SAM选择的函数所起的关键作用。
