Two-wire transmission-line tip-enhanced Raman microscopy

Obtaining both chemical and morphological information at nanometer scales is of vital importance in nano-science and technology. Tip-enhanced Raman scattering (TERS) microscopy is a promising surface sensitive technique that combines two concept, i.e. chemical finger printing by Raman spectroscopy and high spatial resolution atomic/molecular imaging of scanning problem microscopy (SPM), such as scanning tunnelling microscopy (STM) and atomic force microscopy (AFM). In the TERS measurement, a laser beam is focused onto a sharpened metal or metal-coated tip. Excitation of localized surface plasmons resonance (LSPR) at the tip apex causes confinement and enhancement of Raman scattering (ca. Surface enhanced Raman scattering: SERS). As a result, chemical information of a surface cab be obtained underneath the SPM tip at nanometer scales. Interesting target is bio-materials, such as DNA and proteins. However, Raman cross-sections of biomolecules are often low and researchers have often met controversy in interpreting results due to the low sensitivity. The objective of this project is to develop a noble TERS tip equipped with plasmon waveguiding effect using metal nanowires. The disadvantage of plasmon waveguide is its high absorption loss, which significantly reduce the propagation length (~ 3μm). This project will employ two-wire transmission line configuration to overcome the disadvantage.