Transferable Optical Enhancement Nanostructures by Gapless Stencil Lithography.

Optical spectroscopy techniques are central for the characterization of two-dimensional (2D) quantum materials. However, the reduced volume of atomically thin samples often results in a cross section that is far too low for conventional optical methods to produce measurable signals. In this work, we developed a scheme based on the stencil lithography technique to fabricate transferable optical enhancement nanostructures for Raman and photoluminescence spectroscopy. Equipped with this new nanofabrication technique, we designed and fabricated plasmonic nanostructures to tailor the interaction of few-layer materials with light. We demonstrate orders-of-magnitude increase in the Raman intensity of ultrathin flakes of 2D semiconductors and magnets as well as selective Purcell enhancement of quenched excitons in WSe/MoS heterostructures. We provide evidence that the method is particularly effective for air-sensitive materials, as the transfer can be performed in situ. The fabrication technique can be generalized to enable a high degree of flexibility for functional photonic devices.