Dynamics of positively charged muonium centers in indium nitride

Abstract

Muon spin depolarization measurements performed on powdered InN with zero applied magnetic field reveal several positively charged diamagnetic muonium centers. At low temperatures, the ${\mathrm{Mu}}^{+}$ ground state is weakly relaxing with the characteristics of local tunneling motion, which changes to thermally activated diffusion above $350\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. Additional signals imply stationary metastable ${\mathrm{Mu}}^{+}$ centers, which undergo successive activated transitions into the ground state at temperatures ranging from $250\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}400\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. Above $450\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, the ${\mathrm{Mu}}^{+}$ diffusion is interrupted by trap and release events. The high-temperature trapped state is different from any of the low-temperature sites. The energies associated with metastable-to-stable site changes, detrapping transitions, and thermal diffusion are extracted and possible sites for the observed ${\mathrm{Mu}}^{+}$ signals are discussed as a model for interstitial protons, ${\mathrm{H}}^{+}$.