IR Microscope Images Materials at nm-Scale

MARTINSRIED, Germany, May 14 -- Researchers at the Max Planck Institute for Biochemistry have developed a microscope to identify material composition on a nanoscale using infrared (IR) vibrational absorption and a scanning metal tip. The scientists describe their findings in a letter appearing in this month's issue of Nature.
In the experiment, the metal tip approaches a polymer film composed of different compounds and records the surface topography in standard atomic force microscope manner. An IR beam simultaneously illuminates the metal tip, which acts as an antenna and concentrates the beam at the very apex of the tip, where it senses the local absorption of the nearby sample. The compiled infrared image overlays the topographical map, allowing researchers to pinpoint the location of the darker, more absorbent surface substances and to identify their chemical composition based upon the IR wavelength absorbed. The IR image changes contrast when a different infrared wavelength is employed.
While infrared spectroscopy has long been a standard means for identifying macroscopic samples, this research breaks new ground by combining the long-wavelength technique with a scanning tip microscope, enabling study of nanoscale structures. Researchers hope these findings will lay the foundation for the development of a generally usable IR microscope with resolution of at least 100 nm.