Near-Field Microscopy Maps Nanoscale Material Compositions

Far-field microscopy techniques typically cannot map different types of materials on multicomponent nanostructures because the associated wavelength limit causes blurring of the image.
Researchers at the Max Planck Institut für Biochemie in Martinsried, Germany, have developed a method to distinguish the three main constituents of nanosystems -- metals, semiconductors and dielectrics -- by combining tapping-mode atomic force microscopy with an optical scattering probe to simultaneously map the optical response and tomography of a system.

As reported in the Jan. 7 issue of Applied Physics Letters, the method suppresses background interference by demodulating the detector signal at a harmonic of the microscope's tapping frequency -- thus providing measurements of refractive indices, linked to the different types of materials, at topological resolutions down to 10 nm.