Metal-Assisted Transfer Strategy for Construction of 2D and 3D Nanostructures on an Elastic Substrate.

Compared with conventional rigid devices, the elastic substrates integrated with functional components offer various advantages, such as flexibility, dynamic tunability, and biocompatibility. However, the reliable formations of 2D nanoparticles, nanogaps, and 3D nanostructures on elastic substrates are still challenging. The conventional transfer method plays an important role in the fabrication of microstructures on elastic substrates; however, it could not fabricate structures with feature size less than a few micrometers. In this article, we have developed a flexible technique based on the "metal-assisted transfer" strategy. The key concept is to introduce a metal film as an assistant layer between nanostructures and silicon substrates to help the fabrication of nanostructures which cannot be successfully transferred in the conventional transfer method. Various 2D nanostructures, which are difficult to achieve on elastic substrates, could be reliably defined using this approach. The desired gap distances and even sub-10 nm metal gaps between adjacent nanoparticles can be controllably achieved. Moreover, 3D nanostructures can be directly assembled from the prestrained 2D precursors based on the developed technique. Comparing with the previous reports, our fabrication method contains only a one-step transfer process without selective bonding or a second transfer process. Significantly, the 3D nanostructures presented here are 2 orders of magnitude smaller than the state-of-the-art mechanically assembled 3D structures in unit cell size. The proposed method may become a mainstream technology for the nano-optics and ultracompact optoelectronic devices due to its multifunctionalities and superior advantages in achieving tunable nanoparticles as well as 3D nanostructures.