Atmospheric-Pressure Epitaxial System

Fig. S. The initial part of a decay curve; (a) ZnS:Cu,A1, (b) ZnS:Ag,C 1, and (c) ZnS:Ag,Ga,C1. The measurement was made by the pulsed line method9 just after the cessation of an electron-beam pulse. The fast decay is observed for different activators and host materi-als. It has been confirmed for ZnS:Mn 2 ' and InBO3:Tb 3' that the fast component has a broad spectral distribution covering the visible and near UV regions. As a candidate of such a transition, relaxation of hot electrons has been pro-posed. The integrated intensity of this fast component is typically 10-5 as high as the intensity of the activator lumi-nescence. It will not provide, therefore, any visual effect o an observer. It does, however, make the definition of time constant ambiguous, if the definition is made in terms of 9 1/10 for total luminescence. The renewed definition based on the integrated luminescence intensity is more reasona-ble, since it eliminates this ambiguity. Acknowledgments The authors are indebted to Mr. Masahiro Nishizawa, who designed and built the decay measurement apparatus and to Mr. Takao Ebine, who operated the apparatus. They are also grateful to Dr. Yasuhiko Uehara for his encourage-ment of this work. time was estimated to be less than 35 ns in the latter case (3). Since hot electrons are created by cathode ray excita-tion as well, it is reasonable to assign the fast component to hot luminescence. Conclusion The fast luminescence decay with a time constant of 0.8 4 x 102 ns can be observed when the competing activator luminescence has a long persistence, i.e., a low intensity Manuscript received Feb. 25, 1991. Hitachi Ltd. assisted in meeting the publication costs of this article