Description
Tantalum–germanium (Ta–Ge) alloys have recently emerged as a promising materials platform for superconducting
quantum devices due to their compatibility with Ge-based semiconductor architectures
and demonstrated superconductivity. Understanding the atomic-scale structure and thermal stability of
these alloys is essential for developing high-quality superconductor–semiconductor interfaces.
Here, we investigate the surface structure and thermal evolution of a molecular beam epitaxy (MBE)-
grown Ta–Ge alloy film on Ge(001) using scanning tunnelling microscopy (STM) and synchrotronbased
soft X-ray photoelectron spectroscopy (XPS). A series of annealing steps between 673 and
873 K smoothed the initially corrugated surface and enabled atomic-resolution STM. At 873 K, STM
revealed spatially heterogeneous surface structures, including well-ordered three-fold symmetric domains,
square-lattice regions consistent with Ta(100), and more corrugated areas. Further temperature
increases result in increased surface roughening and reduced imaging stability. Complementary
synchrotron XPS measurements indicate a gradual enrichment of Ge at the surface following high-temperature
annealing, suggesting diffusion of Ta into the bulk.
These preliminary results map out how thermal processing affects the Ta-Ge surface and will guide
strategies to obtain cleaner, sharper superconductor-semiconductor interfaces.
| I am the presenting author | Yes |
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