Angle-resolved photoemission spectroscopy system ultra-high vacuum connected to advanced thin film growth for in-situ characterization

Keng-Yung Lin^1*, Hsiao-Yu Lin², Sheng-Wen Huang², Cheng-Maw Cheng³, J. Raynien Kwo², Minghwei Hong¹

¹Graduate Institute of Applied Physics and Department of Physics, National Taiwan University, Taipei, Taiwan
²Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
³National Synchrotron Radiation Research Center, Hsinchu, Taiwan

* Presenter:Keng-Yung Lin, email:f02222024@ntu.edu.tw

Angle-resolved photoemission spectroscopy (ARPES) is an advanced technique in experimental condensed matter physics. The ability to resolve photoelectron kinetic energy and emission angle simultaneously allows the study of electronic band dispersion and Fermi surface of the materials of interests, including nano-scaled semiconductors, topological materials and superconductors, etc. Besides the characterization instruments, equally important are the sample preparation tools for providing high-quality samples for achieving a solid understanding of a new research work. Connection of ARPES system to practical molecular beam epitaxy (MBE) and atomic layer deposition (ALD) growth chambers with ultra-high vacuum (UHV) sample transfer modules is a must. We have employed MBE and ALD in growing highly pure and ordered thin films of the research topics mentioned above. We have earlier constructed a multi-chamber UHV system consisting of five MBE growth chambers, two ALD reactors, a sputtering and an evaporation growth chamber, an X-ray and ultraviolet photoemission spectroscopy system and a scanning tunneling microscopy (STM) chamber.
In this work, we have extended this UHV system with a newly built APRES system. The horizontal sample transfer mechanism is compatible with the existing multi-chamber system using two-inch sample holders. We have designed this ARPES system, and assembled all the parts on-site including μ-metal chamber, excitation source, hemispherical electron analyzer, manipulator and system frame, etc, which were constructed in different countries. The base vacuum pressure is held below 5×10^-10 torr. Our excitation source is a high intensity helium lamp using electron cyclotron resonance (ECR) effect with a toroidal grating for monochromatic He I and He II ultraviolet sources. The hemispherical electron analyzer is Scienta R3000 with a ±10^o angular acceptance range. Our manipulator is custom-designed with five degrees of freedom (linear motions: x, y, z and rotational motions: theta, tilt) and is motorized. The sample temperature range varies from 20 K to 400 K. An on-site sample-cooling test showed that the minimum achievable wafer surface temperature is 73.9 K and 19.7 K using liquid nitrogen and liquid helium, respectively, with exhaust pumping. The construction of such in-house ARPES system is advanced and powerful to enable the combined abilities of thin film and hetero-structure growth as well as other UHV characterization methods. The current research topics under investigation focus on emergent topological materials such as (Bi, Sb)₂Te₃ and α-Sn thin films. Our ARPES/MBE/ALD/STM/XPS enables many other exciting scientific studies.

Keywords: electronic properties, thin films, surfaces, interfaces, condensed-matter field