Fe3+in Cubic and Axial Fields in Cubic ZnSe

Abstract

Cubic zinc selenide crystals were grown by vapor-phase deposition with a charge containing LiOH. The electron-paramagnetic-resonance (EPR) spectrum at 77\ifmmode^\circ\else\textdegree\fi{}K consisted of an intense isotropic line at $g=2.0464\ifmmode\pm\else\textpm\fi{}0.0004$, and a group of angular-dependent lines, each of which varied between ${g}_{\ensuremath{\parallel}}=2.072\ifmmode\pm\else\textpm\fi{}0.004$ and ${g}_{\ensuremath{\perp}}=6.1\ifmmode\pm\else\textpm\fi{}0.1$, depending on crystalline orientation. The intense line is attributed to the central (\textonehalf{}\ensuremath{\rightarrow}-\textonehalf{}) transition of ${\mathrm{Fe}}^{3+}$ in a zinc substitutional site. The less intense angular-dependent lines are attributed to ${\mathrm{Fe}}^{3+}$ in a crystalline field with a strong axial component. The axial component has the symmetry of a nearest-neighbor site. The large zero-field splitting due to a selenium vacancy or substitution leaves a spin doublet lowest in energy and only a transition within this doublet is observed. This leads to a single EPR line with ${g}_{\ensuremath{\parallel}}\ensuremath{\cong}2$ and ${g}_{\ensuremath{\perp}}\ensuremath{\cong}6$, with the parallel direction lying along a $〈111〉$ direction. The four possible sites are not equivalent. This is explained on the basis of the stack-faulted nature of the crystals. The optical properties related to the imperfections giving rise to the EPR signals have also been investigated.