A 1.7 nm resolution chemical analysis of carbon nanotubes by tip-enhanced Raman imaging in the ambient.

Surface morphology of materials is routinely analysed by an atomic force microscope and scanning tunneling microscope (STM) down to subnanometer precision. However, it is still challenging to investigate the surface chemistry simultaneously, which requires specific capability of force or tunneling spectroscopy in ultrahigh vacuum environment and liquid Helium temperature. Here we demonstrate the simultaneous chemical and structural analysis of individual carbon nanotubes (CNTs) by STM-based tip-enhanced Raman spectroscopy (STM-TERS) with 1.7 nm spatial resolution in the ambient. Raman contrast over different types of CNTs, local defects, diameters and bundling effect are all visualized in real space. Disengaging from ultrahigh vacuum and cryogenic environment, our ambient STM-TERS imaging is powerful in analysing local chemistry for CNTs and also suitable for analysing as-made and soft materials, which cannot be seen with general electron microscopy techniques.