High sensitivity variable-temperature infrared nanoscopy of conducting oxide interfaces.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Studying buried interfaces in two-dimensional electron systems (2DES) requires high-resolution, non-invasive methods across wide temperature ranges.
• The LaAlO3/SrTiO3 interface is a key system for exploring emergent electronic properties.

Purpose of the Study:

• To investigate scattering-type scanning near-field optical microscopy (s-SNOM) for probing local transport properties of the 2DES at buried interfaces.
• To establish s-SNOM as a viable technique for analyzing the LaAlO3/SrTiO3 heterostructure from room temperature to cryogenic conditions.

Main Methods:

• Utilized s-SNOM to study the conducting LaAlO3/SrTiO3 interface from 300 K down to 6 K.
• Developed a model correlating the near-field optical signal (phase) with plasmon-phonon modes and 2DES transport properties.
• Employed atomic force microscopy (AFM) with a voltage-biased tip to image conducting nano-channels.

Main Results:

• The near-field optical signal phase demonstrated high sensitivity to the 2DES transport properties.
• Quantitative correlation was achieved between optical signal variations and changes in 2DES properties due to temperature and electrostatic gating.
• High spatial resolution imaging of conducting nano-channels was demonstrated.

Conclusions:

• s-SNOM is a powerful non-invasive tool for characterizing local transport in 2DES at buried interfaces.
• The technique's sensitivity to coupled plasmon-phonon modes enables quantitative analysis of electronic properties.
• s-SNOM offers high spatial resolution for nanoscale imaging of electronic structures.