Spectral study of Ne^{+}-bombarded crystalline MgO

Abstract

Optical-absorption spectra are presented from 3.8 to 7.4 eV of the coloration produced in crystalline MgO by bombardment with 3-MeV ${\mathrm{Ne}}^{+}$ convering a fluence range from ${10}^{14}$ to ${10}^{17}$ ions ${\mathrm{cm}}^{\ensuremath{-}2}$. Dose dependence of absorption at 5.0, 5.8, and 7.0 eV and of the integrated intensity of the ${F}^{+}$-center ESR pattern are shown. Spatial profiles of coloration at 5, 6, and 7 eV are similar to the shape of the nuclear stopping power predicted by Lindhard, Scharff, and Schiott, suggesting that much of the coloration is related to displacement-type lattice damage. Normalized spectra show at high dose additional absorption on the high-energy side of the $F$-type band and absorption on the low-energy side of the first exciton-type transition. The latter is discussed in terms of perturbed excitons. Annealing to 600 \ifmmode^\circ\else\textdegree\fi{}C removes the intense $F$-type band and reveals a band at 5.8 eV. This band accounts for most of the additional, high-fluence-induced absorption observed on the high-energy side of the $F$-type band. The room-temperature-measured intensity of the $F$-type band is enhanced 2.5 times when irradiations are performed near 80 \ifmmode^\circ\else\textdegree\fi{}K. A brief comparison is made with spectra obtained from 3-MeV-proton-bombarded MgO and from fast-neutron-irradiated MgO.