Accurate measurement of enhancement factor in tip-enhanced Raman spectroscopy through elimination of far-field artefacts

摘要

Enhancement factor (EF) is an important measure of the quality of tip-enhanced Raman spectroscopy (TERS) probes. Currently, due to the presence of far-field artefacts, EF is often overestimated in TERS measurements. The origin of this problem is discussed in this article and a methodology for an accurate measurement of the EF using a bilayer sample is presented to characterise TERS tips. EF values measured using the conventional and the proposed methodologies are compared. EF is found to be overestimated by up to an order of magnitude when the conventional methodology is used. Finally, EF values of Ag coated TERS probes prepared from SiO_2 tips and as received Si tips are evaluated using the proposed methodology. Oxidation of the Si tips showed in the range of seven-fold increase in their EF.