Electron Cyclotron Resonance in CdS

Electron cyclotron resonance has been observed in single-crystal CdS platelets at temperatures below 4.2^∘{}K. The single resonance seen in all orientations is consistent with a single-ellipsoid conduction-band model for CdS. The cyclotron effective masses measured with the crystal c axis parallel and perpendicular to the magnetic field are m*cIIBmₒ=0.171 and m*_c⊥Bmₒ=0.162, implying that the constant-energy surfaces near the conduction-band minimum are oblate spheroids having transverse and longitudinal effective masses mₜ*mₒ=0.171 and mₗ*mₒ=0.153. The effective mass values determined from cyclotron resonance are 15% lower than those measured in other experiments. The difference cannot be due to depolarization or optical polaron effects, but can be accounted for in terms of an electron self-energy correction resulting from the piezoelectric electron-phonon interaction in CdS. Electron collision times of order 10^-11 sec were calculated from the 70-Gc/sec cyclotron resonance data taken between 1.25 and 4.2^∘{}K. The magnitude and temperature dependence of the collision times are best described by the theoretical predictions for piezoelectric scattering along with possibly a small neutral-impurity scattering contribution.