Effects of hydrogen doping on the phase structure and optoelectronic properties of p-type transparent SnO

Hydrogen (H) is a ubiquitous impurity, which can significantly affect the phase structure and the optoelectronic properties of oxide semiconductors. To date, a well-established understanding of the effects of H doping on the properties of p-type transparent SnO is still lacking. Here, we present a comparative study to reveal the role of H in SnO films by magnetron sputtering. We find that in as-grown undoped SnO films, in addition to the tetragonal SnO phase, secondary phases of SnO₂ or Sn₃O₄ are present under certain growth temperatures. In contrast, a small fraction of metallic Sn phase is included in the as-grown H-doped SnO (SnO:H) films, attributed to the partial reduction of SnO by the H₂ in the sputtering gas. Effects of post thermal annealing (PTA) on the properties of SnO films are also explored. Results strongly indicate that H doping or PTA facilitates the formation of Sn phase and Sn vacancies related defects, giving rise to the p-type conductivity observed in the undoped or H-doped SnO films. The present study provides a comprehensive understanding of the evolution of phase structures as well as defect properties of SnO films, which is crucial for their future studies and optoelectronic applications.