Role of Hydrogen in the Formation and Structure of the Si- $\mathit{NL}10$ Thermal Donor

Microscopic evidence of a prominent role of hydrogen in the formation and structure of the Si- $\mathrm{NL}10\mathrm{}$ thermal donor is presented. Hyperfine interactions with the ${}_{}{}^1{}_{}{}^{}H$ nucleus have been detected and analyzed by means of electron-nuclear double resonance (ENDOR) and field-scanned ENDOR. Based on the current results an identification of the Si- $\mathrm{NL}10\mathrm{}$ center as a singly passivated state of the thermal donor in its neutral charge state is proposed.