Identification of the Silicon Vacancy Containing a Single Hydrogen Atom by EPR

The electron paramagnetic resonance spectrum of float-zone silicon recorded after implantation with protons contains a strongly temperature dependent signal from a vacancy-type defect. The signal displays monoclinic-I symmetry below 65 K and trigonal symmetry above 100 K. This symmetry change, together with a hyperfine splitting from a single proton, allows an unequivocal identification with ${\mathrm{VH}}^0$, the neutral charge state of a vacancy containing a single hydrogen atom. The striking similarity between the properties of ${\mathrm{VH}}^0$ and ${\mathrm{VP}}^0$ (the $E$ center) corroborate our identification.