Comparative analysis of FDTD intensity profile of 2D and noble materials for TERS application

Abstract

Imaging technique with high-sensitivity and high-spatial-resolution at single molecular level is always a desired aspect to the researchers. In association with scanning probe microscopy and Surface-Enhanced Raman Spectroscopy (SERS), a new technology has shown the light of hope to achieve what was thought as unachievable earlier, named Tip-Enhanced Raman Spectroscopy (TERS). An essential tip is used in TERS to disseminate the information of the morphology of the target molecule by scanning probe technique and concurrently can magnify the Raman signal largely without any special sample preparation. Between this metal tip and surface, a 'hot-spot' is formed when the laser beam is applied. TERS has many applications in nanotechnology, biophotonics, and sensing etc. Generally, noble materials are used in the operation of TERS. Recently, 2D materials are showing great potential in parallel with the noble materials in producing sensors, measurement devices, conductive films, printed electronics and many more due to their extraordinary properties like strength, thermal conductivity, high electrical conductivity etc. In this paper, we will compare the enhancement factor of noble and 2D materials at the vicinity of the metallic tip of TERS. Finite-Difference Time-Domain (FDTD) simulation method has been opted to find out the enhancement factor. For this simulation, tip radius was varied from 5 nm to 30 nm with 5 nm interval and distance between tip and substrate was varied from 1 nm to 5 nm with 1 nm interval and incident wavelength was kept constant at visible wavelength (300nm-700nm).