Quantum Microscopy Lab

The Quantum Microscopy Lab is located on the ground floor of the Solid State Institute and houses two advanced microscopes for material characterization:

A scanning tunneling microscope (STM) equipped with an optical channel.
A cathodoluminescence microscope (CLM) with time-resolved capabilities.
Both instruments are capable of cooling the sample into cryogenic temperatures using liquid nitrogen (down to ~77K) as well as liquid helium (as low as ~4K).

 

The STM is capable of scanning the tunnelling current between the tip and the sample to resolve atomic structures under ultra-high vacuum (UHV) conditions, reaching pressures as low as 2 × 10⁻¹⁰ torr. The instrument holds three chambers:

Load lock chamber – for loading samples and tips.
Preparation chamber – for surface preparation under UHV conditions, including annealing, electron bombardment, and support for additional modules.
Observation chamber – for performing measurements.
In addition to measuring tunnelling current, the system is equipped with two parabolic mirrors, aligned with the tip apex. These mirrors enable laser excitation and detection at the tip apex, facilitating various advanced measurements such as near-field imaging, Raman spectroscopy, and nonlinear interactions.

The setup also supports state-of-the-art atomic force microscopy (AFM) using the “Q-Plus” technique, achieving subatomic resolution (Q-factor > 10,000) for non-conducting, as well as conducting samples.

 

We utilize this microscope for two-color experiments, in which attosecond pulses are directed at the tip to track the trajectories of ejected electrons at the tip–sample junction. Additionally, we plan to measure quantum states in perovskite materials and analyze the density of states at atomic-scale defects.

 

The CLM is based on the scanning electron microscopy (SEM) technique, under high vacuum conditions (down to 3 × 10⁻⁷ torr); an accelerated electron beam (1 kV–10 kV) hits with the sample surface and scatter secondary electrons (SE) into the SE detector, which characterizes surface morphology. This SE excitation also brings quantum systems into their excited states, resulting in photon emission. The instruments allows for spectrally resolving these photons (visible and infra-red detectors) as well as measuring time correlations g(t) and g2.

Additionally, the microscope includes a time-resolved cathodoluminescence (TRCL) module. In this mode, the sample surface is excited by electron pulses generated through picosecond laser excitation of the electron source tip. A similar effect is achieved using fast, modulated beam-blanking. The scattered light can be measured using a streak camera, enabling single-shot measurements with a high temporal resolution, on the order of ~1 ps, with a single-photon sensitivity.

 

This microscope is primarily used to identify crystals and nanoscale defects. Our next goal is to leverage it for characterizing “superfluorescence” in perovskites — a collective and coherent emission from a group of adjacent nanocrystals. We have already observed this phenomenon under laser excitation and now aim to demonstrate it using electron-pulse excitation, achieving both nanometer spatial and picosecond temporal resolution.