ZnS (Cu, Mn, Cl) 蒸着EL薄膜の直流および交流特性

抄録

Two kinds of electroluminescent ZnS (Cu, Mn, Cl) vacuum-deposited thin film, heat-treated and untreated, both being operative under dc and ac excitation conditions, are investigated with regard to their chemical and electrical properties. When the excitation is by dc supply, the intensity and stability of luminescence depend on the polarity of applied voltage: with untreated films, the emission is stronger when the polarity of electrode (aluminum) is negative than when it is positive; with heat-treated films, this relation is reversed. In general, untreated films are unstable when the polarity of electrode is positive and their luminescence accompanies sparks. When the excita-tion is by ac supply of low frequency, the above characteristics are also observed, suggesting that the mechanism of luminescence by dc excitation and that by low frequency ac excitation are the same. From the observation of dc luminescence, the emission is inferred to occur near the anode. In dc current vs. voltage relation, there are cases in which the films show a negative characteristic at a certain voltage, beyond which the emission increases rapidly, and raising and lowering of voltage gives a hysteresis loop.
From these obtained results, a conclusion is drawn that the luminescence is caused by the influx of carriers through heterojunctions found between aluminum electrode or NESA electrode and ZnS phosphor base.