Applied Physics

Infrared Detection

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Science  05 Jan 2001:
Vol. 291, Issue 5501, pp. 15
DOI: 10.1126/science.291.5501.15a

The detection and characterization of carrier flow is invaluable in microelectronics. For macroscopic circuitry and materials, the response of a material to infrared (IR) radiation is a useful signature of the subsurface carrier conductivity. However, as feature sizes are reduced below the wavelength of the IR light, it can no longer be used as a direct probe.

Knoll and Keilmann show that this resolution limit can be overcome by incorporating the IR probe light into a scanning near-field optical microscope (SNOM), in which the effective resolvable size can be smaller than one one-hundredth of the wavelength of the probe light. Using probe light 9.2 to 10.7 micrometers in wavelength, they demonstrate the ability to image regions of enhanced conductivity only 250 nanometers wide at a resolution of 30 nm. The applicability of this technique across a wide range of tunable wavelengths suggests that it could be extended readily to specific observations on a wealth of nanoscale systems, such as potential modulation along nanotubes and nanowires, Cooper-pair breaking in superconductors, and two-dimensional electron gases. — ISO

Appl. Phys. Lett.77, 3980 (2000).

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