Revealing the nanoscale secrets through spectroscopic imaging  


figure_1_website          Domains of a block copolymer revealed with 10 nm spatial resolution by the PFIR microscopy.

Microscopy opens many possibilities for understanding the composition, organization, and interaction of inhomogeneous materials. In our group, we develop spectroscopic microscopy techniques to study functional nano-materials in order to decipher their chemical, electric, and mechanical properties.

One challenge of optical microscopy is the diffraction limit of light, which is approximately half of light’s wavelength. Nano-materials often have features smaller than the half wavelength that is not resolvable by traditional optical microscopy. To overcome this challenge, we work on two types of super-resolution infrared microscopies:

1. Scattering-type scanning near-field optical microscopy (s-SNOM) that measures the scattering signal from the near field of the sample through a metallic probe in atomic force microscope (AFM) at 10~20 nm spatial resolution. It provides spectroscopic imaging on heterogeneous materials with strong contrast in the dielectric functions, including those that support surface plasmon or polaritons.

2.  Peak force infrared (PFIR) microscopy that measures the transient infrared induced the mechanical response of the sample with a sharp AFM probe at < 10 nm spatial resolution. It provides simultaneous infrared and mechanical properties for organic and inorganic materials with high sensitivity.

We are interested in studying materials that may be nanoscale heterogeneous, such as certain types of polymers,  protein aggregates, polaritonic nanostructures, urban aerosols, and photovoltaics.