Supplementary document for Ultracompact Vernier-effect-improved sensor by a single microfiber-knot resonator - 6263535.pdf

supplement materia

Supplementary document for Ultracompact Vernier-effect-improved sensor by a single microfiber-knot resonator - 6237197.pdf

supplemental material

Nanoscale Insights into the Hydrogenation Process of Layered α‑MoO₃

The hydrogenation process of the layered α-MoO₃ crystal was investigated on a nanoscale. At low hydrogen concentration, the hydrogenation can lead to formation of H_<i>x</i>MoO₃ without breaking the MoO₃ atomic flat surface. For hydrogenation with high hydrogen concentration, hydrogen atoms accumulated along the <101> direction on the MoO₃, which induced the formation of oxygen vacancy line defects. The injected hydrogen atoms acted as electron donors to increase electrical conductivity of the MoO₃. Near-field optical measurements indicated that both of the H_<i>x</i>MoO₃ and oxygen vacancies were responsible for the coloration of the hydrogenated MoO₃, with the latter contributing dominantly. On the other hand, diffusion of hydrogen atoms from the surface into the body of the MoO₃ will encounter a surface diffusion energy barrier, which was for the first time measured to be around 80 meV. The energy barrier also sets an upper limit for the amount of hydrogen atoms that can be bound locally inside the MoO₃ <i>via</i> hydrogenation. We believe that our findings has provided a clear picture of the hydrogenation mechanisms in layered transition-metal oxides, which will be helpful for control of their optoelectronic properties <i>via</i> hydrogenation