Near-field images of modulation doped InP nanowires yield pronounced contrasts between the differently doped segments. The topography image shows two, approx. 2µm long wires with a diameter of about 100nm. In the near-field amplitude (color) and phase (gray) image the individual segments can be clearly identified. Comparison of the near-field signals of the segments with model calculations even enables the quantification of the free carrier concentration. A gradient in the free carrier concentration between two adjacent segments can be investigated in detail and spatially mapped, yielding a spatial extension for the gradient of approx. 200nm.
The results demonstrate the application of infrared near-field microscopy for highly sensitive and nanoscale resolved mapping of free carriers in doped semiconductor nanowires.
Further reading:
- J. M. Stiegler, A. J. Huber, S. L. Diedenhofen, J. Gómez Rivas, R. E. Algra, E. P. A. M. Bakkers, and R. Hillenbrand, “Nanoscale Free Carrier Profiling on Individual Semiconductor Nanowires by Infrared Near-Field Nanoscopy”, Nano Lett. 10, p.1387 (2010)
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