抄録
The electron spin resonance spectrum of Fe3+ in hexagonal CdS has been studied at X-band. The spectrum is explained in terms of the usual spin Hamiltonian with the following parameters: g=2.018±0.002, a=(96±2)×10−4cm−1, D=(−49±2)×10−4cm−1, F=(−3±2)×10−4cm−1, at 1.5°K. The resonance signal is observed in as-grown crystals under irradiation with band-gap light and also in heat-treated samples without illumination at liquid helium temperatures. The signal is enhanced by 950 mμ radiation. Light in the region around 650 mμ and also of 1.2∼2 μ causes quenching of the signal. The 650 mμ quenching bands consist of two bands of 630 mμ (1.97 eV) and 680 mμ (1.82 eV), which correspond to the electron excitation from the bonding level (t2b) to the non-bonding one (en). The 950 mμ enhancement is due to the hole transfer from Cd vacancy to Fe2+ via the valence band. The 1.2∼2 μ quenching arises from the recombination of electrons released from electron traps with holes at Fe3+. The observed positive g-shift can be explained by Watanabe’s theory of the g-shift in which electron transfer from ligands to Fe3+ through spin-orbit interaction is taken into account. The ESR signal is also observed at 78°K in a heat-treated sample.
