Single digit nanofabrication for photonics at nanoscale (Conference Presentation)

We use the term “single-digit nanofabrication” (SDN) to describe the structuring and characterization of materials whose key features are defined and resolved on a scale of 10 nm or less. Achieving single-digit nano resolution in synthesis and fabrication is a central challenge for the development of next-generation functional nanoscale and mesoscale materials Single digit nanostructured materials have special properties with regard to the control and flow of energy. Energy can take, for example, electronic, magnetic, thermal or photonic forms. We will focus on how material components can be structured with high accuracy and precision in classical lithographic processes 2D and how we can achieve new or improved properties in 3D fabrication. One of the field that requires such precision, resolution and control of materials is nanophotonics. Nanophotonics covers light interactions with dielectric materials and plasmonic effects in metallic structures. In addition, we have emerging efforts in exciton transport in organized nanomaterials. PLASMONIC LIMITS Gap Plasmonic antennas are of great interest due to their ability to concentrate light into small volumes. Smaller the volume higher is the enhancement until the gap is so closed that other effect start to became more important. Theoretical studies, considering quantum mechanical effects, have predicted the optimal spatial gap between adjacent nanoparticles to be in the subnanometer regime in order to achieve the strongest possible field enhancement. We developed a technology [1] to fabricate gap plasmonic structures with subnanometer resolution, high reliability, and high throughput using collapsible nanofingers. The systematic investigation of the effects of gap size are consistent with previous findings as well as with a straightforward theoretical model that is presented here. LARGE AREA METASURFACES Metasurfaces have facilitated the replacement of conventional optical elements with ultrathin and planar photonic structures. Previous designs of metasurfaces were limited to small deflection angles and small ranges of the angle of incidence. We have created two types of Si-based metasurfaces, [2] working both in transmission and reflection modes, to steer visible light to a large deflection angle. These structures exhibit high diffraction efficiencies over a broad range of angles of incidence. We have demonstrated metasurfaces based on conventional thin film silicon processes that are suitable for the largescale fabrication of high-performance devices. EXCITONIC PROPERTIES OF DIRECTED ASSEMBLY PEROVSKITE NANOCRYSTALS Colloidal nanomaterials display a broad range of unique chemical and physical properties that make them prime candidates as nanoscale building blocks for the development of future technologies. Towards this goal, one of the main challenges resides in developing methods to manipulate these materials with a level of precision comparable with their small size. We studied the effects of topography and surface chemistry on the assembly behavior of perovskite nanocrystals PNC [3] with outstanding optical properties and great potential for applications in optoelectronics and photonics. Arranging PNCs in 1D-like features allows careful studies of the collective mechanisms of exciton diffusion and recombination in PNCs assemblies, which in turn determine the optoelectronic behavior of the system and offer fundamental guidance in engineering new optoelectronic devices made of PNCs. Work was supported by the Office of Science,Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. [1] Boxiang Song et al “Probing Gap Plasmons Down to Subnanometer Scales Using Collapsible Nanofingers”; ACS Nano, June 2017 [2] Dianmin Lin et al ”Optical metasurfaces for high angle steering at visible wavelengths”; Scientific Reports 7, Article number: 2286 (2017) [3]L. Protesescu et al. Nano Letters 15 (2015) 3692-3696