Tip-induced heating in apertureless near-field optics

Tip enhanced Raman spectroscopy is considered a promising technique for imaging with nano scale lateral resolution. However, its developments and use face many problems. In this paper we provide insight into the level of sample heating by the laser light in the presence of a metal-coated atomic force microscope (AFM) tip. The heating is attributed to the presence of an optical field enhanced by the tip. Sample temperatures were estimated using measurements of the ratio of the Stokes and anti-Stokes signals from a thin 50-nm sample on an Al substrate. A correlation between the heating and optical properties of the tips is established. The results demonstrate significant tip-induced heating (100 K and more) even at very low laser power.