Zur Lumineszenz des Zinkoxyds

The temperature dependance of efficiency and decay of the ultraviolet and green luminescence bands at UV- and cathode ray-excitation is investigated. In addition to earlier results the Riehl-effect is only observed when excited by cathode rays. The UV-band decays hyperbolically at all temperatures while the decay of the green band depends on kind and intensity of the excitation as well as on temperature. The results can be interpreted by considering the increasing number of electrons in the conduction band under different kinds of excitation and the variation of conductivity with temperature. Furthermore, the glow curves of various ZnO-samples (untreated and annealed in reducing atmosphere) show one or two peaks respectively, thus revealing two trap depths. As the light sum increases with the efficiency it is assumed that by reduction both activators and traps are created. The occurrence of thermoluminescence with many conduction electrons being present leads to the assumption of hole traps.