Infrared nanoscopy down to liquid helium temperatures.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Near-field microscopy is essential for nanoscale analysis.
• Low-temperature spectroscopy is crucial for studying phase transitions and excitations.
• Existing techniques have limitations at cryogenic temperatures.

Purpose of the Study:

• To introduce and validate a scattering-type scanning near-field infrared microscope (s-SNIM) capable of operation at cryogenic temperatures (down to 5 K).
• To demonstrate the capability of low-temperature s-SNIM for analyzing low-temperature phase transitions and low energy excitations.
• To investigate the impact of local laser heating and apply the technique to multiferroic materials.

Main Methods:

• Development and implementation of a low-temperature (LT) s-SNIM system integrated with a non-contact atomic force microscope (AFM).
• Spectroscopic analysis using CO2-IR excitation and mid-IR to THz free-electron laser-light source (FELBE).
• In situ characterization using complementary AFM techniques like topography profiling, piezo-response force microscopy (PFM), and Kelvin-probe force microscopy (KPFM).

Main Results:

• Successful operation of s-SNIM down to 5 K, enabling near-field analysis and spectroscopy at cryogenic temperatures.
• Quantification of local laser heating effects under the s-SNIM tip apex.
• Demonstration of LT s-SNIM for studying the spectral response and domain structure of the multiferroic material GaV4S8 near its phase transition.

Conclusions:

• The developed LT s-SNIM is a powerful tool for nanoscale investigation of materials at cryogenic temperatures.
• The integration with AFM techniques allows for comprehensive studies of coupled physical properties.
• This technique opens new avenues for exploring low-temperature phenomena in condensed matter systems.