Nanoimprint lithography is an emerging technology to form patterns and features in the nanoscale. Production of nanoscale patterns is challenging particularly in the sub-50 nm range. Pre-stressed polymer films with embedded microscale pattern can be miniaturized by shrinking induced due to thermal stress release. However, when pre-stressed films are thermally nanoimprinted with sub-micron features and shruken, they lose all the topographical features due to material recovery. Here we report a new approach that prevents recovery and allows retention of shrunken patterns even at the scale of <50 nm. We have discovered that when the shrinking process is mechanically constrained in one direction, the thermal treatment only relieves the stress in the orthogonal direction leading to a uniaxial shrinkage in that direction while preserving the topographical features. A second step, with the constraint in the orthogonal direction leads to biaxial shrinkage and preservation of all of the topographical features. This new technique can produce well defined and high resolution nanostructures at dimensions below 50 nm. The process is programmable and the thermal treatment can be tuned to shrink features to various dimension below the original imprint which we use to produce tunable and gradient plasmonic structures.

纳米压印光刻是一种新兴技术，可在纳米尺度上形成图案和特征。纳米级图案的生产具有挑战性，特别是在亚 50 nm 范围内。带有嵌入微尺度图案的预应力聚合物薄膜可以通过热应力释放引起的收缩而小型化。然而，当预应力薄膜被热纳米压印成亚微米特征并收缩时，由于材料恢复，它们会失去所有的地形特征。在这里，我们报告了一种新方法，即使在 <50 nm 的尺度上，它也可以防止恢复并允许保留收缩的图案。我们发现，当收缩过程在一个方向上受到机械约束时，热处理仅减轻正交方向上的应力，导致该方向上的单轴收缩，同时保留了地形特征。第二步，在正交方向上的约束导致双轴收缩并保留所有地形特征。这种新技术可以在低于 50 nm 的尺寸上产生明确定义的高分辨率纳米结构。该过程是可编程的，并且可以调整热处理以将特征缩小到原始印记以下的各种尺寸，我们用来产生可调和梯度等离子体结构。这种新技术可以在低于 50 nm 的尺寸上产生明确定义的高分辨率纳米结构。该过程是可编程的，并且可以调整热处理以将特征缩小到原始印记以下的各种尺寸，我们用来产生可调和梯度等离子体结构。这种新技术可以在低于 50 nm 的尺寸上产生明确定义的高分辨率纳米结构。该过程是可编程的，并且可以调整热处理以将特征缩小到原始印记以下的各种尺寸，我们用来产生可调和梯度等离子体结构。