Electronic states of AgCl nanocrystals embedded in crystalline KCl studied by95−GHzoptically detected magnetic resonance spectroscopy

The properties of shallow electron centers (SEC), self-trapped holes (STH), and self-trapped excitons (STE) are investigated in nanocrystals of AgCl embedded in a crystalline KCl matrix. Time-resolved photoluminescence (PL) measurements reveal a behavior different from that in bulk AgCl: an inhomogeneous distribution of the properties of the recombination centers is revealed by the spectral dependence of the decay rates. In time scales from nano- to microseconds, slower rates are systematically observed at the low-energy side of the emission range. In high-frequency $\left(95\mathrm{GHz}\right)$ optically detected magnetic resonance (ODMR) measurements, the transitions of SEC and STH centers are only observed in the extreme-low energy tail of the PL emission and they exhibit a broad and asymmetric $g$-value distribution (width $\delta g\approx 0.07$), ranging up from the respective bulk $g$-values. A complex behavior of the ODMR spectrum in the STE region is revealed, showing different spectra at $1.8\mathrm{K}$ and at higher temperature, and, different from the bulk AgCl case, exhibiting a strong dependence upon variation of the detection photon energy. Analysis of the measurements at $4.6\mathrm{K}$ yields a zero field splitting in the STE triplet state in good agreement with the bulk value, while the $g$-values are slightly increased relative to bulk, which is ascribed to the nanocrystal environment.