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.

A two-dimensional periodically corrugated silver surface prohibits the propagation of the surface plasmons in all lateral directions. And band gaps are generated in the dispersion relation, named plasmonic band gaps. At the edge of this band gap, surface plasmons are laterally confined as standing waves. We investigate this phenomenon for lasing action by the use of a dye film deposited on a corrugated silver surface. Fluorescence of the dye was strongly enhanced. Indeed, we obtained an enhancement factor 150 for a methyl-red doped poly (methylmethacrylate) film and 3 for an evaporated 4-dicyanomethylene-2-methyl-6-p-dimethyl-aminostyryl-4H-pyran film. We also discuss the conditions under which lasing action may occur.

The local optical field enhancement which can occur at the end of a nanometer-size metallic tip has given rise to both increasing interest and numerous theoretical works on near-field optical microscopy. In this article we report direct experimental observation of this effect and present an extensive study of the parameters involved. Our approach consists in making a “snapshot” of the spatial distribution of the optical intensity in the vicinity of the probe end using photosensitive azobenzene-containing films. This distribution is coded by optically induced surface topography which is characterized in situ by atomic force microscopy using the same probe. We perform an extensive analysis of the influence of several experimental parameters. The results are analyzed as a function of the illumination parameters (features of the incident laser beam, exposure time, illumination geometry) as well as the average tip-to-sample distance and tip geometry. The results obtained provide substantial information about the tip’s field. In particular, they unambiguously demonstrate both the nanometric spatial confinement of the tip field and the evanescent nature of the nanosource excited at the tip’s end. Most of the experimental results are illustrated by numerical calculations based on the finite element method and commented using the literature on the subject. Additionally, we discuss the origin of the optically induced topography on a nanometer scale and present some preliminary results of the apertureless near-field optical lithography based on local field enhancement. Our approach constitutes a useful tool to investigate the near-field of apertureless probes and should enable the optimization of the nanosource for any experiment requiring local optical excitation of the matter.

We report the direct observation of the optical near-field enhancement at the nanometric extremity of a metallic probe for apertureless scanning near-field optical microscopy. Our approach consists in making the “snapshot” of the spatial distribution of the optical intensity in the vicinity of the probe end via a photosensitive polymer. This distribution is coded by polymer surface topography which is characterized in situ by atomic force microscopy using the same probe. Results clearly reveal nanometric dots corresponding to local field enhancement below the tip end. The field enhancement is shown to be crucially dependent on the polarization state of the incident laser beam as well as the tip material and geometry. The experimental results are found to agree with the results of preliminary calculations. This experiment both constitutes a useful tool for investigating field enhancement below apertureless probes and has potential applications in nanophotolithography.