Photoluminescence, Optical Absorption, and Cathodoluminescence in Ion Implanted CdS
Photoluminescence and optical absorption have been measured at 90 K in undoped CdS before and after ion bombardment at 90 K and as a function of isochronal annealing to 350 K. Implantation with Ar+, Cu+, Cl+, He+, or H+ ions at energies sufficient to penetrate the depth of most of the U.V. excitation severely quenches all the luminescence and introduces continuous absorption beyond the absorption edge. These effects are observed for fluences of ~ 2 × 1014 cm-2 for H+ and ~ 5 × 1011 cm-2 for the heavier ions. However, upon annealing to 350 K the ion-induced absorption disappears and the green edge emission at 5200 Å, which is seen initially in almost all samples, partially recovers. A more striking change is the growth of a broad red band at 7200 Å to intensities much greater than observed prior to implant of the above ions. The red emission center is believed to be a relatively simple native defect center which, upon annealing, evolves from the more complex damage introduced initially by the implantation.
Cathodoluminescence measurements were also made on Ar+ implanted CdS as a function of exciting electron energy (1–20 keV). The results indicate that information concerning the depth distribution of ion-induced damage and radiative centers can be obtained with this technique. For example, the emission at 7200 Å exhibited by an implanted and annealed sample is shown to originate in the near-surface region consistent with the predicted depth for an ion-induced defect center.
KeywordsElectron Irradiation Defect Cluster Radiative Center Edge Emission Cathodoluminescence Spectrum
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