Electroluminescence in Potassium Iodide Single Crystals Containing Potassium Metal Colloids(III)

In order to investigate the phenomenon of electroluminescence,EL,in KI single crystals containing potassium metal colloids it is essential to clarify the formation processes of the colloids during thermal annealing treatment.In the previous report a simple measurement system for the observation of the photoacoutic signal(PAS)was fabricated.Through PAS measurements we could obtain an information about the behavior of potassium metal colloids existing near specimen surfaces in the course of the thermal annealing treatments.The potassium metal colloids existing in the bulk of the speciments,however,may play a dominant role in the electroluminescence phenomenon.In order to make clear the aggregation and / or the dissolving processes of the potassium metal colloids in the bulk of the specimens various measurements of the optical absorption of the specimens subjected to the isothermal annealings were performed.It was found that isothermal annealing treatment at 90℃ for 48 hours of densely colored KI specimen could supply a specimen containing potassium metal colloid of dominant size of about 30nm.Using this specimen detailed EL observations were carried out as a function of the applied field strength.Brief discussion is given concerning the characteristic behavior of the potassium metal colloids from the point of view of defect aggregation processes.|カリウム・コロイドを含むKI単結晶における電界発光の機構を明らかにするために,これまでにコロイドの導入法の確立とその評価法について研究成果の報告を行った。カリウム・コロイドに関する諸物性と関連付けて電界発光現象の機構の詳細を考察するに際して,試料中に存在するカリウム・コロイドの形状・大きさ・分布状態を知る必要がある。本研究では,付加着色法によってF中心を高濃度(～10^18個/cm^3)