Low-temperature deposition of meta-stable β-MoO₃(011) epitaxial thin films using step-and-terrace substrates

We demonstrated the epitaxial growth of meta-stable β-MoO₃(011) thin films on SrTiO₃(100), NdGaO₃(110), and NdGaO₃(001) substrates, using dc reactive magnetron sputtering. Low-temperature deposition at ~ 200 °C resulted in the suppression of the formation of thermodynamically stable α-MoO₃, and we observed the growth of a β-MoO₃ phase with mixed orientation. In contrast, depositions on substrate surfaces with a step-and-terrace structure resulted in uniaxially oriented β-MoO₃(011) epitaxial thin films. The step-and-terrace structures were found to play an important role in controlling the epitaxial growth behavior of β-MoO₃ thin films. - Highlights: • Meta-stable β-MoO₃(011) thin films are fabricated using dc magnetron sputtering. • Depositions on step-and-terrace substrates realize the β-MoO₃(011) epitaxy. • The step-and-terrace structure is a key to control the growth behavior.