Jacobs Ian E, Bedolla-Valdez Zaira I, Rotondo Brandon T, Bilsky David J, Lewis Ryan, Ayala Oviedo Alejandra N, Gonel Goktug, Armitage John, Li Jun, Moulé Adam J
Department of Materials Science and Engineering, University of California Davis, One Shields Avenue, Davis, California 95616, United States.
Optoelectronics Group, Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge CB3 0HE, U.K.
ACS Nano. 2021 Apr 27;15(4):7006-7020. doi: 10.1021/acsnano.1c00070. Epub 2021 Mar 18.
Doping-induced solubility control (DISC) patterning is a recently developed technique that uses the change in polymer solubility upon doping, along with an optical dedoping process, to achieve high-resolution optical patterning. DISC patterning can produce features smaller than predicted by the diffraction limit; however, no mechanism has been proposed to explain such high resolution. Here, we use diffraction to spatially modulate the light intensity and determine the dissolution rate, revealing a superlinear dependence on light intensity. This rate law is independent of wavelength, indicating that patterning resolution is not dominated by an optical dedoping reaction, as was previously proposed. Instead we show here that the optical patterning mechanism is primarily controlled by the thermal profile generated by the laser. To quantify this effect, the thermal profile and dissolution rate are modeled using a finite-element model and compared against patterned line cross sections as a function of wavelength, laser intensity, and dwell time. Our model reveals that although the laser-generated thermal profile is broadened considerably beyond the profile of the laser, the highly temperature dependent dissolution rate results in selective dissolution near the peak of the thermal profile. Therefore, the key factor in achieving super-resolution patterning is a strongly temperature dependent dissolution rate, a common feature of many polymers. In addition to suggesting several routes to improved resolution, our model also demonstrates that doping is not required for optical patterning of conjugated polymers, as was previously believed. Instead, we demonstrate that superlinear resolution optical patterning should be attainable in any conjugated polymer simply by tuning the solvent quality during patterning, thus extending the applicability of our method to a wide class of materials. We demonstrate the generality of photothermal patterning by writing sub-400 nm features into undoped PffBT4T-2OD.
掺杂诱导的溶解度控制（DISC）图案化是一种最近开发的技术，它利用掺杂时聚合物溶解度的变化以及光学去掺杂过程来实现高分辨率光学图案化。DISC图案化可以产生小于衍射极限预测尺寸的特征；然而，尚未提出任何机制来解释这种高分辨率。在这里，我们利用衍射在空间上调制光强度并确定溶解速率，揭示了对光强度的超线性依赖关系。该速率定律与波长无关，这表明图案化分辨率并不像先前提出的那样由光学去掺杂反应主导。相反，我们在此表明光学图案化机制主要由激光产生的热分布控制。为了量化这种效应，使用有限元模型对热分布和溶解速率进行建模，并将其与作为波长、激光强度和驻留时间函数的图案化线条横截面进行比较。我们的模型表明，尽管激光产生的热分布比激光轮廓大幅展宽，但高度依赖温度的溶解速率导致在热分布峰值附近发生选择性溶解。因此，实现超分辨率图案化的关键因素是强烈依赖温度的溶解速率，这是许多聚合物的共同特征。除了提出几种提高分辨率的途径外，我们的模型还表明，如先前认为的那样，共轭聚合物的光学图案化并不需要掺杂。相反，我们证明，只需在图案化过程中调节溶剂质量，任何共轭聚合物都应能实现超线性分辨率光学图案化，从而将我们方法的适用性扩展到广泛的材料类别。我们通过在未掺杂的PffBT4T - 2OD中写入小于400 nm的特征来证明光热图案化的通用性。
