Spectroscopic scanning near-field optical microscopy with a free electron laser: $\ce{CH2}$┬ábond imaging in diamond films,” et al., Journal of Microscopy 202, 446–450 (2001).


Hydrogen chemistry in thin films and biological systems is one of the most difficult experimental problems in today’s science and technology. We successfully tested a novel solution, based on the spectroscopic version of scanning near-field optical microscopy (SNOM). The tunable infrared radiation of the Vanderbilt free-electron laser enabled us to reveal clearly hydrogen-decorated grain boundaries on nominally hydrogen-free diamond films. The images were obtained by SNOM detection of reflected 3.5 micron photons, corresponding to the C-H stretch absorption, and reached a lateral resolution of 0.2 micron, well below the $\lambda/2$ ($\lambda$ = wavelength) limit of classical microscopy.

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