Scattering-type scanning near-field optical microscopy with Akiyama piezo-probes

Abstract

A scattering-type scanning near-field optical microscope at cryogenic temperatures (cryo-SNOM) configured with Akiyama probes for studying low energy excitations in quantum materials present in high magnetic fields. The s-SNOM is provided with atomic force microscopy (AFM) control, which predominantly utilizes a laser-based detection scheme for determining the cantilever tapping motion of metal-coated Akiyama probes, where the cantilever tapping motion is detected through a piezoelectric signal. The Akiyama-based cryo-SNOM attains high spatial resolution, good near-field contrast, and is able to perform imaging with a significantly more compact system capable of handling simultaneous demands of vibration isolation, low base temperature, precise nano-positioning, and optical access. Results establish the potential of s-SNOM based on self-sensing piezo-probes, which can easily accommodate near-IR and far-infrared wavelengths and high magnetic fields. Using a tuning fork-based Akiyama probe provides nano-imaging capability at room and low temperatures and is used for near-field photocurrent mapping.

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