| AVS 58th Annual International Symposium and Exhibition | |
| Applied Surface Science Division | Tuesday Sessions |
| Session AS-TuA |
| Session: | Imaging and 3D Chemical Analysis - Part II |
| Presenter: | Scott Lea, Pacific Northwest National Laboratory |
| Authors: | A.S. Lea, Pacific Northwest National Laboratory M.S. Taubman, Pacific Northwest National Laboratory M.C. Phillips, Pacific Northwest National Laboratory M. Raschke, University of Colorado, Boulder |
| Correspondent: | Click to Email |
Molecular nanostructures, polymer and supramolecular assemblies, proteins, biomembranes, correlated systems, and many other natural and synthetic materials gain their unique functionalities from intra- and intermolecular interaction and electron correlations on mesoscopic length scales of 10’s of nm. Gaining a molecular level understanding of the materials structure and function has remained a major experimental challenge. This is due to the lack of experimental techniques that can routinely provide a chemically specific spectroscopic identification with simultaneous nanometer spatial resolution on the relevant length scale associated with the size and interactions of the molecular building blocks: within the 10 – 100 nm range. We have developed an instrument for spectroscopic infrared vibrational near-field nanoimaging capable of ultrahigh spatial resolution down below 10 nm, vibrational spectral information in the 14 to 2 um range, sensitivity down to the molecular level, and applicability under ambient and environmental conditions. There are few instruments that can provide near field IR nanoimaging at high resolution, but except for the aforementioned instrument, none are broadly tunable over a large spectroscopic range nor has resolution that approaches 10nm.
We are integrating a Quantum Cascade Laser to the new instrument as a complementary IR light source to the femtosecond OPO chain. QCLs are a monopolar semiconductor laser devices that can be fabricated to cover significant regions of the mid IR spectrum, specifically 3.5 to 20 microns. Moreover, these devices work extremely well in the molecular fingerprint region (8 to 12 microns), which will be of particular use in this instrument as this is where many fundamental vibrational bands are found, where MCT IR detectors work best, and the region is relatively free from water interference. The rapid scanning capabilities of External Cavity QCLs (ECQCLs) in the 100s of Hz, will allow IR spectra to be taken point by point across the sample, allowing rapid spectral data coverage. This is to be compared with the Hz-rate scanning of the OPO chain. The second significant advantage of QCL incorporation will be its ease of use (permitting wide-spread usage), low cost and ruggedness. This presentation will cover the integration of an ECQCL into the existing scattering-type IR scanning near-field optical microscope and demonstrate its ability to provide spatially resolved IR spectroscopic signatures on a sub-100nm scale. Ultimately, we anticipate this instrument will be able to provide chemical binding information of molecular adsorbates on nanostructured materials.