The growth of vertically aligned carbon nanotubes using a direct current plasma enhanced chemical vapor deposition system is reported. The growth properties are studied as a function of the Ni catalyst layer thickness, bias voltage, deposition temperature, ${\mathrm{C}}_{\mathrm{2}}{\mathrm{H}}_{\mathrm{2}}{\mathrm{:NH}}_{\mathrm{3}}$ ratio, and pressure. It was found that the diameter, growth rate, and areal density of the nanotubes are controlled by the initial thickness of the catalyst layer. The alignment of the nanotubes depends on the electric field. Our results indicate that the growth occurs by diffusion of carbon through the Ni catalyst particle, which rides on the top of the growing tube.

We determine the effect of defects induced by ion bombardment on the Raman spectrum of single-layer molybdenum disulfide. The evolution of both the linewidths and frequency shifts of the first-order Raman bands with the density of defects is explained with a phonon confinement model, using density functional theory to calculate the phonon dispersion curves. We identify several defect-induced Raman scattering peaks arising from zone-edge phonon modes. Among these, the most prominent is the $\mathrm{LA}\left(M\right)$ peak at $\sim 227\mathrm{c}{\mathrm{m}}^{-1}$ and its intensity, relative to the one of first-order Raman bands, is found to be proportional to the density of defects. These results provide a practical route to quantify defects in single-layer $\mathrm{Mo}{\mathrm{S}}_2$ using Raman spectroscopy and highlight an analogy between the $\mathrm{LA}\left(M\right)$ peak in $\mathrm{Mo}{\mathrm{S}}_2$ and the $D$ peak in graphene.

This review provides a detailed overview of the state of the art in tip-enhanced Raman spectroscopy (TERS) and focuses on its applications at the horizon including those in materials science, chemical science and biological science. The capabilities and potential of TERS are demonstrated by summarising major achievements of TERS applications in disparate fields of scientific research. Finally, an outlook has been given on future development of the technique and the mechanisms of achieving high signal enhancement and spatial resolution.

Chemical mapping of a photocatalytic reaction with nanoscale spatial resolution is demonstrated for the first time using tip-enhanced Raman spectroscopy (TERS).

Excitonic processes in single-layer MoS₂ are mapped for the first time using tip-enhanced photoluminescence and Raman microscopy with 20 nm spatial resolution.