Nanoscale Optical Imaging Research Articles

Nanoscale optical imaging of pigment particles in paint with near-field scanning optical microscopy

The distribution of pigment at the nano to micron scale illuminates the length scale of failure in paint samples. The authors use optical and topographical images from near-field scanning optical microscopy (NSOM) to compare a high quality paint sample with one that fails a standard quality control test based on visual inspection. NSOM provides the required nanometer to micrometer mesoscopic regime resolution and range, combined with simultaneous topographic and optical information. Features such as pigment clumping and pigment density fluctuations are simultaneously analyzed. The two types of samples are distinguished by fluctuations at different length scales. The authors observed individual pigment particles near the polymer surface of both samples.

Nanoscale optical imaging of single-walled carbon nanotubes

In this contribution, we apply a microscopic technique that relies on the enhanced electric field near a sharp, laser-irradiated metal tip that acts as a highly confined light source. The tip is used for the local excitation of the optical response of single-walled carbon nanotubes (SWNT) deposited on glass. We demonstrate photoluminescence and Raman imaging of the same SWNTs with a spatial resolution of about 10 nm.

Nanoscale Optical Imaging of Excitons in Single-Walled Carbon Nanotubes

We present simultaneous near-field photoluminescence (PL) and Raman imaging of single-walled carbon nanotubes (SWNTs) with a spatial resolution better than 15 nm. Highly localized excitation is used to visualize the spatial extent of the contributing excited states. For SWNTs on glass, we typically observe highly confined PL from short segments of about 20 nm in length. The PL from micelle-encapsulated SWNTs on mica is extended along the tube up to several hundreds of nanometers. We find that near-field enhancement is much stronger for photoluminescence than for Raman scattering, an observation that is explained by the low intrinsic quantum yield of SWNTs.

Development of an Apertureless Near-Field Optical Microscope for Nanoscale Optical Imaging at Low Temperatures

We have developed an apertureless scanning near-field optical microscope (apertureless SNOM) operating at low temperatures. The apertureless SNOM system is based on the atomic force microscope using a frequency modulation detection technique. The SNOM images reflect local optical properties of the sample surface, and optical images of a ferroelectric material are successfully obtained at low temperatures below a Curie temperature. The SNOM system developed in this work is a powerful tool to image local fields on the sample surface and to study phase transitions under high spatial resolution.

A cryogenic scanning near-field optical microscope with shear-force gapwidth control

We present a scanning near-field optical microscope designed for nanoscale optical imaging and spectroscopy as well as simultaneous tuning fork shear-force topographic imaging at cryogenic temperatures. The whole setup is immersed in superfluid helium (T=1.8 K). In this medium we observe resonance frequency fluctuations of the tuning fork sensor with an amplitude of Δν≈5%–10% of the full width at half-maximum of the resonance. Possible reasons for the occurrence of the frequency fluctuations are discussed. A stable gapwidth feedback can still be achieved if the set value of the frequency shift is chosen slightly larger than the fluctuation amplitude. As an example we demonstrate shear-force topographic imaging of a silicon grating in superfluid helium.

Nanoscale optical imaging on an electroluminescent polymer by conducting atomic force microscopy

We demonstrate optical imaging with a resolution of around 50 nm on an electroluminescent polymer by conducting atomic force microscopy. The results indicate that brighter light emission occurs from asperities on the polymer surface. By comparing surface morphologies of the polymer and the indium tin oxide substrate, it is found that similar asperities exist on both surfaces and the polymer becomes thinner on these locations. Therefore, stronger luminescence intensity from asperities is caused by higher electric field due to reduced polymer thickness. The present method can also be extended to obtain simultaneous optical and electrical transport properties.

Nanoscale optical imaging of chromosomes with apertureless microscopy.

Near-field optical structure of the centromere region of undyed polytene chromosomes has been observed using an apertureless near-field optical microscope that detects the intensity of light scattered from an atomic force microscope tip under laser illumination. The centromere is of primary importance to the functioning of the chromosome in the cell during cell division. It is also particularly interesting for structural/optical studies since its DNA repeat sequences are highly conserved among organisms and it is possible that they play a part in the centromere self assembly (Clark and Wall 1996).