THERMAL CONDUCTIVITY OF ELECTRON-IRRADIATED CdS.

Measurements were made of the change in low-temperature thermal conductivity of high-resistivity sulfur-compensated single-crystal CdS upon electron irradiation and annealing. Samples oriented parallel and perpendicular to the hexagonal $c$ axis of CdS were irradiated with 2-MeV electrons below 25\ifmmode^\circ\else\textdegree\fi{}K to fluences $\ensuremath{\Phi}$ totaling 7.8 \ifmmode\times\else\texttimes\fi{} ${10}^{17}$ electrons/${\mathrm{cm}}^{2}$. The increase in the additive thermal resistivity at 11 \ifmmode^\circ\else\textdegree\fi{}K on irradiation was found to be independent of the orientation of the sample, and $\frac{1}{K}\ensuremath{-}\frac{1}{{K}_{0}}=(5.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}){\ensuremath{\Phi}}^{0.5}$ cm deg/W. Isochronal annealing measurements show almost complete annealing out of the additive thermal resistivity below room temperature, and recovery begins as low as 35 \ifmmode^\circ\else\textdegree\fi{}K. There are three major annealing stages centered near 45, 75, and 225 \ifmmode^\circ\else\textdegree\fi{}K. Annealing above 60 \ifmmode^\circ\else\textdegree\fi{}K produces an anisotropic thermal conductivity for subsequent measurements below 20 \ifmmode^\circ\else\textdegree\fi{}K. The anisotropic additive thermal resistivity is much greater if the temperature gradient is perpendicular to the $c$ axis than if it is parallel. The anisotropic phonon scattering is attributed to the formation and temperature-dependent orientation of anisotropic defects. It is concluded that the defect orientation parallel to the $c$ axis has the lowest energy, and measurements of the temperature dependence of the thermal conductivity parallel and perpendicular to the $c$ axis give the equilibrium energy difference for reorientation to be $\ensuremath{\approx}1.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ eV.