MBE + ARPES

The MBE+ARPES platform integrates twin molecular beam epitaxy (MBE) systems for the growth of transition-metal oxides and chalcogenides with a dedicated high-resolution ARPES chamber for in situ spectroscopy. The MBE activity, led by Ke Zou’s group, enables layer-by-layer synthesis in ultra-high vacuum with fine control of composition, surfaces, and interfaces, while the ARPES chamber developed in our group allows direct momentum-resolved measurement of the electronic structure immediately after growth. This architecture is designed for the study of air-sensitive quantum materials, ultrathin films, and heterostructures whose electronic properties depend critically on interface quality and cannot be reliably accessed after exposure to air.

The ARPES chamber is a custom high-resolution system for polarization-dependent photoemission studies of bulk crystals and thin films, including samples transferred in situ from the attached MBE platform. It is built around a SPECS Phoibos 150 CCD hemispherical analyzer and a SPECS UVS 300 helium-lamp source coupled to a custom rotatable polarizing monochromator. The source provides He I and He II excitation at 21.2 and 40.8 eV, respectively, with a ~500 μm beam spot and more than 90% linear polarization that can be rotated under vacuum. The system incorporates XPS and LEED for chemical and structural characterization, and a six-axis pumped-^4He cryogenic manipulator for low-temperature measurements with in situ sample transfer from the MBE chamber. It delivers energy and angular resolution of 1 meV and 0.1°, respectively, and operates over a sample temperature range from 2.7 K to 300 K.