Growth Phase Map of α and \b{eta} Tantalum as a Function of Growth Temperature and Oxygen Partial Pressure

Tantalum thin films are used in low-loss superconducting quantum circuits, yet the growth conditions governing selection of $α$-Ta(110), $α$-Ta(111), and metastable $β$-Ta on c-plane sapphire remain uncertain. We deposited 100 nm Ta films by dc magnetron sputtering on Al$_2$O$_3$(0001) at 300-900 $^