Chemical imaging beyond the diffraction limit using photothermal induced resonance microscopy

Photothermal induced resonance recently attracted great interest for enabling chemical identification and imaging with nanoscale resolution. Here, the PTIR working principles are reviewed along with the main results from a recent publication aimed at assessing the PTIR lateral resolution, sensitivity and linearity. For this purpose nanopatterned polymer samples were fabricated using electron beam lithography directly on 3D zinc selenide prisms. Results show that the PTIR lateral resolution for chemical imaging is comparable to the lateral resolution obtained in AFM height images, up to the smallest feature measured (100 nm). Spectra and chemical maps were produced from the thinnest sample analyzed (40 nm). Notably, we show that the PTIR signal increases linearly with thickness for samples up to ≈ 1 μm (linearity limit); a necessary requirement to use the PTIR technique for quantitative chemical analysis at the nanoscale. The analysis of thicker samples provides evidence that the previously developed PTIR signal generation theory is correct. We believe that our findings will foster nanotechnology development in disparate applications by proving a basis for quantitative chemical analysis with nanoscale resolution.