Nitrogen-Vacancy Engineering for Controlled Phase Transitions in CrN(111) Epitaxial Films
Nitrogen-Vacancy Engineering for Controlled Phase Transitions in CrN(111) Epitaxial Films
物理学晶体学
XiaoXu Zhang,Yang Li,Yu Shang,MingYue Zhao,GuoKe Li,Li Ma,DeWei Zhao,CongMian Zhen,DengLu Hou.Nitrogen-Vacancy Engineering for Controlled Phase Transitions in CrN(111) Epitaxial Films[EB/OL].(2025-03-25)[2025-10-25].https://arxiv.org/abs/2503.19725.点此复制
The phase transition in CrN epitaxial films is substantially suppressed by
epitaxial constraint. Here, we propose that nitrogen (N) vacancies can be taken
as a knob to regulate the phase transition of CrN(111) epitaxial films. To
validate this concept, a series of CrN(111) films with controlled N
concentrations (approximately from 0.0 to 5.0 at.%) were epitaxially grown on
Al2O3(0001) substrates. Experimental characterization reveals that higher N
vacancy concentrations significantly facilitate the out-of-plane contraction of
the films at 273 K (0.8%), reaching up to 60% of the contraction magnitude of
CrN powders (1.2%) without compromising the stability and reproducibility of
the phase transition. Reducing N vacancy concentrations diminishes the lattice
contraction, lowers the phase transition temperature to 193 K, and triggers a
metallic to insulator transition in electrical behavior. First-principles
calculations corroborate these findings, showing that N vacancies decrease the
internal tensile stress within triangular Cr atomic layers, which enhances the
out-of-plane contraction, elevates phase transition temperatures, and promotes
bandgap closure. These results establish N vacancies as a critical factor
governing phase transition dynamics in CrN systems and provide a practical
strategy for successively engineering thermally responsive phase transitions in
CrN films, advancing their potential for functional device applications.
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