Nanomanufacturing and System Integration of Multi-Functional Metallic Pyramidal Probes

University Of Minnesota-Twin Cities, Minneapolis MN

Investigators

Abstract

Optical microscopy and spectroscopy is limited in resolution to roughly half the wavelength of light, generally about 200 to 250 nanometers. Scientists can overcome this limit using a sharp metal tip as an antenna to focus light into the optical near-field, gleaning crucial information about nanoscale light-matter interactions inaccessible by other methods. Current state-of-the-art tips for near field applications are fabricated one at a time, are fragile, and have rough surfaces. These manufacturing inconsistencies limit resolution and often give irreproducible results. The objective of this project is to manufacture, integrate, characterize, and disseminate a new generation of metal probes. Dissemination of reproducible, high-performance, and multi-functional probes will democratize access to high-resolution near-field optical microscopy and spectroscopy and enable its use in user facilities, promoting this technology from the realm of a few experts to general use. The research team will use a high-throughput manufacturing technique known as template stripping for reproducible, wafer-scale production of nanometrically sharp, noble metal pyramidal tips. Crystalline-orientation-dependent wet etching of silicon will be used to define an atomically smooth template, into which gold or silver will be deposited. The metal will then be stripped off, using epoxy, exposing the ultra-smooth, sub-nanometer roughness, backside surface. The resulting ultrasmooth metal pyramids mitigate parasitic random hotspots, endemic to other metallization techniques, and promote optical energy delivery to and concentration at the tip. Robust packaging methods will be developed to integrate these probes with scanning probe microscopy systems. These scanning-probe-affixed metal pyramids will be quality controlled in an atomic force microscope, enhancing spectroscopic signals from standard samples while simultaneously acquiring topographic images. Detailed manufacturing and packaging protocols will be published in peer-reviewed journals and provided to researchers upon request. This will transform near-field microscopy and spectroscopy from a difficult niche technique used by a small number of specialists to a widespread, routine characterization method adopted by many researchers in broad range of disciplines such as nanotechnology, materials science, chemistry, and biology.