Facility

The CAU STM Laboratory is located on the first floor of the R&D Building at Chung-Ang University (CAU). The lab comprises three soundproof rooms, a measurement area, a sample preparation zone, and a service area housing pumps and an uninterruptible power supply (UPS). Two of the soundproof rooms are dedicated to low-temperature STM systems and feature specially constructed double walls with acoustic absorption layers to minimize ambient noise transmission. A helium reliquefier is installed in a separate space on the same floor maintain the cryogenic temperature required for STM operation while minimizing vibrational and electrical interference.

Home-built low-temperature STM, typically operating at 4K, has been integrated with a glove box and a specially designed sample stage. The glove box, directly connected to a load-lock chamber of STM system, enables the transfer and measurement of samples without exposure to ambient air, minimizing contamination and oxidation. The sample stage, designed with dual pockets and micron-level positioning capability, facilitate in-situ tip conditioning and precise navigation to small 2D flakes. The synergistic integration of these components ensures reliable, high-resolution STM/STS measurements, enabling comprehensive investigations into the electronic properties of a wide range of 2D materials.

Detailed design and the performance specfication are presented in

"Design of a scanning tunneling microscope integrated with a glove box for measuring two-dimensional material flakes" Measurement Science and Technology (2025) LINK

A Dewar type low-temeprature STM operating at 4 K is equipped with a 6 T vertical axis superconducting magnet. The Unisoku system is optimized for measuring a layered materials that can be cleaved at both room and cryogenic temperature. 

The helium liquefier system comprises the following components:

An atmospheric-pressure gas bag, A helium compressor and high-pressure gas cylinder, A helium gas purifier, and A pulse tube liquefier.

The entire system is installed on the first floor of the R&D building. Helium gas from the  LT STMs is collected into the gas bag via a 2-inch pipeline. The liquefier has a production capacity of approximately 30 liters of liquid helium per day.

A general-purpose atomic force microscope is mounted on an actively damped granite table housed within a soundproof enclosure to minimize environmental noise and vibration.

Non-contact mode is used to measure the thickness and assess the quality of 2D flakes with high precision.

Contact mode enables surface cleaning and mechanical manipulation, such as tearing of the 2D flakes

The home-built 2D flake stacking system includes: 

A long working distance optical microscope, A temperature-controlled vacuum chuck, and Motorized motion stages for precise positioning.

The stamping handle consists of multiple polymer layers adhered to a glass slide, which is mounted on a vertically motorized positioner. Alignment between the stamp and the pre-patterned substrate is achieved using the optical microscope.

Stamping conditions—such as speed, applied pressure, and substrate temperature—can be precisely controlled to optimize transfer quality.