Research Objectives and Approaches: The objective of this research is to develop an integrated instrument for the fabrication and characterization of plasmonic nanostructures and nanodevices. The approach combines a scanning electron microscope with imaging, localized etching and deposition, and lithography capabilities, with optical spectroscopies, cathodoluminescence, and electrical characterization.
Intellectual Merit:
The proposed platform integrates structural, optical, and electrical characterization to a level substantially above any current commercial or custom-built system. This system will allow the development of active plasmon-based structures and devices, with direct fabrication and characterization. The developmental challenge in this project is the integration of the variety of techniques into one platform and the leveraging of this combined capability to achieve new strategies for developing active plasmonic systems.
Broader Impact:
The availability of this platform will greatly enhance current experimental capabilities in plasmonics, nanoscale photonics and optoelectronics, advancing our understanding of the physical principles upon which their behavior is based. This will enable new applications of plasmonic systems currently limited by joint challenges in the fabrication and characterization of active plasmonic nanostructures.
Rice currently supports an IGERT program in Nanophotonics, a professional master?s program in Nanoscale Physics and an undergraduate REU program ?Conjunto? aimed at underrepresented minority students. The availability of the proposed instrument would provide an unmatched opportunity for all students to participate in research in nanophotonics. The cathodoluminescence capability is not available even as a standalone instrument in the Houston area. This experimental system will be welcomed by the growing nanophotonics research community in southeast Texas.
We have developed a unique state of the art platform for realizing new plasmonic nanostructures and evaluating their optical and electrical properties. The platform is built on a FEI Quanta 650 FEG ESEM. There are three different ways to design and fabricate the nanostructures in the ESEM. The first is by electron beam induced deposition of metals (EBID). The chamber is currently equipped to deposit gold and platinum, but can support upto 4 materials at a time. The second is using a nanomanipulator needle to push nanoparticles on a substrate, together into directed clusters. This is a useful tool to investigate how the properties of a nanocluster change as the size of the cluster changes or the gap between the nanoparticle changes. The third technique to fabricate structures relies on using the e beam of the SEM to pattern a photoresist. This is followed by steps (outside the SEM chamber) to deposit metal and remove the photoresist and create the desired patterns. To characterize the plasmonic nanostructures we have two detectors on the ESEM. This system permits correlated scanning micrographs composed of both photoemission from the sample, and secondary electron emission measured with the integrated Everhart-Thornley detector. This allows for greater resolution and structural information especially of 3D structures. In addition we have acquired a Gatan MonoCL4 Elite cathodoluminescence system that allows us to map the local density of states (LDOS) of the nanostructure and correlate it to the morphology. We will soon also have a fiber coupled Coherent Chameleon tunable laser. The laser sits outside the ESEM on an optical bench and light is coupled at one end to the fiber. The other end of the fiber is attached to the nanomanipulator needle and can be manipulated via the nanobot to within nanometer distance to the sample to excite the sample and collect the scattered light. The first results from this system have demonstrated the impact on our understanding of the plasmonic properties and how they correlate with morphology. The system has also allowed us to directly correlate theory and experiment. This direct correlation has allowed us to verify the theoretical simulations with known nanostructures, and explore the parameter space of complex structures with confidence. This is an extremely powerful and time and cost saving design paradigm. In summary we now have the first ESEM capable of both electrical and optical characterization of plasmonic nanostructures. The CL system is the first in the greater Houston area and has a wavelength range suitable for most plasmonic systems in the near UV, visible and near IR regime.
