(DURIP) CONSTRUCTION OF A PLASMONIC SCANNING TUNNELING MICROSCOPE CAPABLE OF OPTICAL IMAGING AND LITHOGRAPHY ON THE ATOMIC SCALE
Abstract
The plasmonic scanning tunneling microscope (PSTM) consists of a nanometrically polished silver tip and a parabolic mirror. The incident visible light couples to the tip surface plasmon which is funneled to the tip apex forming a localized surface plasmon (LSP). In effect, the metal optics through plasmonic focusing provides an atomic light source that dielectric-based refractive lenses cannot offer. The LSP faces the specimen (2-dimensional crystalline film or single molecules adsorbed on the substrate) within the quantum tunneling range. The homemade system integrates an ion polishing device for creating an optimal taper of the tip with the PSTM enabling seamless transfer of freshly prepared tips without contamination under ultrahigh vacuum (UHV) environment. The parabolic mirror controlled by the xyz-piezo motor stack maximizes the collection of scattered photons when aligned precisely to the tip apex and provides an aberrationfree collection optics. The principle of optical microscopy employed in the PSTM is tip-enhanced Raman scattering (TERS). The hyperspectral data obtained from inelastic scattering of the atomically confined photon visualizes molecular/lattice vibrations which carry structural identity information, constitute reaction coordinates of chemical reactions, and couple to electrons giving rise to properties that can be tailored to new functional materials. Using the ultimate spatial resolution of the PSTM, the following research objectives will be addressed: (1) Establishing the principle of atomic-scale Raman scattering. The dual nature of the LSP being electronic polarization coupled to the confined photon raises a fundamental question on how the light-matter interaction takes place. Through imaging simple molecules using TERS, the model of optical tunneling of electrons and evanescent field from the confined photon in the volume of the tip apex will be compared and tested. (2) Fabrication of plasmonic tips based on intelligent design principles. The ideal tip geometry created from the built-in ion milling device will be verified through imaging tests. After polishing the taper for efficient waveguiding, the final tuning of LSP will be done through tip functionalization. In particular, terminating the tip apex with a magnetic atom will add another modality of magneto-optical Raman scattering. (3) Atomic-scale photolithography. The atomically focused light can serve dual purpose of inducing and observing photochemistry such as dehydrogenation and photoisomerization. Patterning a monolayer of photoresist grown on the substrate with atomic widths will be attempted. The successful execution of the proof-of-principle experiment can open a new path for increasing the transistor density in the integrated chip production.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 20, 2023
- Source ID
- FA95502210484
Entities
People
- Joonhee Lee
Organizations
- Air Force Office of Scientific Research
- Nevada System of Higher Education
- United States Air Force