Ding Tao, Chikkaraddy Rohit, Mertens Jan, Baumberg Jeremy J
Nanophotonics Centre, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, United Kingdom.
ACS Photonics. 2017 Jun 21;4(6):1292-1297. doi: 10.1021/acsphotonics.6b01000. Epub 2017 May 25.
Under UV illumination, polymer films can undergo chain scission and contract. Using this effect, tightly focused laser light is shown to develop runaway near-field concentration that drills sub-100 nm pits through a thin film. This subwavelength photolithography can be controlled in real time by monitoring laser scatter from the evolving holes, allowing systematic control of the void diameter. Our model shows how interference between the substrate and film together with near-field focusing by the evolving crevice directs this formation and predicts minimum pit sizes in films of 100 nm thickness on gold substrates. The smallest features so far are 60 nm diameter pits using 447 nm light focused onto polystyrene through a ×100 objective (NA = 0.8). Such arrays of pits can be easily used as masks for fabricating more complex nanostructures, such as plasmonic nanostructures and biomicrofluidic devices. This demonstration shows the potential for harnessing near-field feedback in optical direct-writing for nanofabrication.
在紫外线照射下，聚合物薄膜会发生链断裂并收缩。利用这一效应，已证明紧密聚焦的激光会产生失控的近场聚焦，从而在薄膜上钻出亚100纳米的小孔。这种亚波长光刻技术可通过监测不断演变的小孔的激光散射来实时控制，从而实现对空隙直径的系统控制。我们的模型展示了基底与薄膜之间的干涉以及不断演变的缝隙所产生的近场聚焦如何引导这种形成过程，并预测了在金基底上100纳米厚的薄膜中的最小小孔尺寸。迄今为止，使用通过×100物镜（数值孔径=0.8）聚焦到聚苯乙烯上的447纳米光所产生的最小特征是直径为60纳米的小孔。这样的小孔阵列可轻松用作制造更复杂纳米结构（如等离子体纳米结构和生物微流体装置）的掩模。这一演示展示了在纳米制造的光学直写中利用近场反馈的潜力。
