Tip-Enhanced Raman Microscopy: Theory, Practice, and Applications for Nanomaterials Visualization and Characterization

Tip-enhanced Raman scattering (TERS) microscopy enables high-resolution optical visualization and analysis of materials at the nanoscale. Although TERS shares similarities with surface-enhanced Raman scattering (SERS), it offers unique advantages, particularly through the utilization of plasmonic TERS tips. This chapter provides an overview of TERS techniques, focusing on the physics of TERS tips as optical antennas and their fabrication techniques. Special emphasis is placed on the theoretical aspects of plasmonic tip behavior, including surface plasmon resonances and localized modes of plasmon resonances on nanostructures. Practical considerations in the fabrication of multi-grain TERS probes, such as optimizing the arrangement of nanoparticles and the effects of deposition parameters, are discussed. Experimental results on the enhancement and resolution of multi-grain TERS probes are presented through comparisons with other probe morphologies, along with TERS imaging of carbon nanotubes (CNTs). Applications of TERS microscopy in characterizing nano-materials such as CNTs, graphene, semiconductor crystals, and twisted bilayer graphene (TBG) are showcased. Additionally, the utilization of deep ultraviolet (DUV) TERS, which extends the capabilities of TERS microscopy to analyze materials with wide-bandgap properties or specific molecular vibrations, is discussed. DUV plasmon resonance in metal nanostructures, such as aluminum and indium, is explored theoretically and experimentally. This comprehensive discourse underscores the potential of TERS microscopy for nanoscale molecular identification and imaging applications.