3 years ago

Mapping Free-Carriers in Multijunction Silicon Nanowires Using Infrared Near-Field Optical Microscopy

Mapping Free-Carriers in Multijunction Silicon Nanowires Using Infrared Near-Field Optical Microscopy
Tucker M. Mastin, David J. Hill, Earl T. Ritchie, James F. Cahoon, Joanna M. Atkin, Panfilo C. Deguzman
We report the use of infrared (IR) scattering-type scanning near-field optical microscopy (s-SNOM) as a nondestructive method to map free-carriers in axially modulation-doped silicon nanowires (SiNWs) with nanoscale spatial resolution. Using this technique, we can detect local changes in the electrically active doping concentration based on the infrared free-carrier response in SiNWs grown using the vapor–liquid–solid (VLS) method. We demonstrate that IR s-SNOM is sensitive to both p-type and n-type free-carriers for carrier densities above ∼1 × 1019 cm–3. We also resolve subtle changes in local conductivity properties, which can be correlated with growth conditions and surface effects. The use of s-SNOM is especially valuable in low mobility materials such as boron-doped p-type SiNWs, where optimization of growth has been difficult to achieve due to the lack of information on dopant distribution and junction properties. s-SNOM can be widely employed for the nondestructive characterization of nanostructured material synthesis and local electronic properties without the need for contacts or inert atmosphere.

Publisher URL: http://dx.doi.org/10.1021/acs.nanolett.7b02340

DOI: 10.1021/acs.nanolett.7b02340

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