Single-crystal gold tip for tip-enhanced Raman spectroscopya)

The authors have investigated the structures of gold tips suitable for tip-enhanced Raman spectroscopy (TERS) fabricated by the electrochemical etching technique [C. Williams and D. Roy, J. Vac. Sci. Technol. B 26, 1761 (2008)]. This work attempts to find an answer to why some of the chemically etched tips do not produce TERS signal and suggests possible ways of improving the reproducibility of the enhancement factor by fabricating single-crystal tips. TERS tips with single crystalline tip ends and polycrystalline tip ends were studied by electron-backscattered diffraction. Influences of defects and grain boundaries on surface plasmon resonance energy are invoked to explain why some tips do not produce appreciable TERS signals.