Abstract
The frequently observed 3.0-eV emission band in nominally pure KI is shown not to be intrinsic, but to arise from the annihilation of an excitonic state in the vicinity of a sodium ion. Crystal samples containing 1.2, 460, and 4800 ppm (molar parts per million) sodium were investigated by photoluminescence techniques. Merck Suprapur KI was zone refined in order to reduce its sodium content to 1.2 ppm. The other samples were prepared by diffusing sodium into the zone-refined material. At 10 K with excitation in the exciton absorption region (less than band-gap energy) the 3.0-eV emission is present in all crystals. However, it increases monotonically with increasing sodium concentration. As the temperature is raised, the 3.0-eV intensity decreases and the intrinsic, annihilation, 3.3-eV intensity increases. At low temperature the exciton diffuses to the sodium impurity where it is trapped, relaxes, and annihilates. At higher temperature the exciton relaxes and annihilates before reaching an impurity site. To confirm this, copper (3.1 ppm) was diffused into some of the zone-refined material. The temperature-versus-intensity characteristics were the same, within experimental error, for the characteristic copper emission as for the 3.0-eV (sodium-perturbed) annihilation emission.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
