Tip-enhanced Raman scattering microscopy is a powerful technique for analysing nanomaterials at high spatial resolution far beyond the diffraction limit of light. However, imaging of intrinsic properties of materials such as individual molecules or local structures has not yet been achieved even with a tip-enhanced Raman scattering microscope. Here we demonstrate colour-coded tip-enhanced Raman scattering imaging of strain distribution along the length of a carbon nanotube. The strain is induced by dragging the nanotube with an atomic force microscope tip. A silver-coated nanotip is employed to enhance and detect Raman scattering from specific locations of the nanotube directly under the tip apex, representing deformation of its molecular alignment because of the existence of local strain. Our technique remarkably provides an insight into localized variations of structural properties in nanomaterials, which could prove useful for a variety of applications of carbon nanotubes and other nanomaterials as functional devices and materials.

The electronic properties of single walled carbon nanotubes (SWNTs) can change with a slight deformation, such as the one caused by the pressure of one SWNT crossing over the other in an "X" shape. The effect, however, is extremely localized. We present a tip-enhanced Raman investigation of the extremely localized semiconductor-to-metal transition of SWNTs in such a situation, where we can see how the Fano interaction, which is a Raman signature of metallic behavior, grows towards the junction and is localized within a few nanometers of its vicinity. After exploring the deconvoluted components of the G-band Raman mode, we were able to reveal the change in electronic properties of a SWNT at extremely high spatial resolution along its length.

Two-dimensional transition metal dichalcogenides are gaining increasing interest due to their promising optical properties. In particular, molybdenum disulfide (MoS) which displays a band-gap change from indirect at 1.29 eV for bulk materials to direct at 1.8 eV for the material monolayer. This particular effect can lead to a strong light interaction which can pave the way for a new approach to the next generation of visible light emitting devices. In this work we show the nanoscale variation of light emission properties by tip-enhanced photoluminescence microscopy and spectroscopy in the MoS monolayer, grown by chemical vapour deposition. The variations of the light emission properties are due to different effects depending on the shape of the MoS single layer, for instance, a different concentration of point defect in an irregularly shaped flake and the presence of a nanoscale terrace in a triangular monolayer. Simultaneously, atomic force microscopy reveals indeed the presence of a nanometric terrace, composed of an additional layer of MoS, and tip-enhanced PL intensity imaging shows a localized intensity decrease.

Nanoscale integration of graphene into a circuit requires a stable performance under high current density. However, the effects of the current density that approach the electronic breakdown limit of graphene are not well understood. We explored the effects of a high current density, close to the electronic breakdown limit of 10 A/cm (∼3.0 × 108 A/cm2), on graphene, using tip-enhanced Raman scattering. The results showed that the high current density induces Raman bands at 1456 and 1530 cm−1, which were assigned to edge-phonon modes originating from zigzag and armchair edges. This led us to conclude that C–C bonds are cleaved due to the high current density, leaving edge structures behind, which were detected through the observation of localized phonons.

A single gold nanostructure is successfully deposited at the tip apex of a silicon probe for atomic force microscopes (AFM) in an electroless and area-selective manner. The tip apex of a commercially available silicon AFM probe is irradiated with a focused ion beam (FIB) to remove the native oxide layer, and then the probe was exposed to chloroauric acid (HAuCl 4 ) aqueous solution containing sodium chloride (NaCl). A single gold nanostructure selectively grows at the FIB-irradiated apex as a consequence of electron transfer from silicon to the solution through the FIB-irradiated silicon surface. This electron transfer is driven by the difference in the electrochemical potential of electrons. NaCl, added to a pure HAuCl 4 aqueous solution, improves the area-selectivity of gold growth and decreases the size of gold, resulting in desired geometry of gold as the tip apex for tip-enhanced Raman spectroscopy (TERS) in terms of the spatial resolution and the enhancement of the electric field. Our probes provide TERS imaging of a carbon nanotube with a spatial resolution of 10 nm, and enhancement factors up to 2.2 × 10 5 for an azobenzene thiol self-assembled monolayer in the gap-mode configuration with a side-illumination optical setup.