On avalanche processes in electroluminescence of single ZnS-Cu crystals

The electrical, photoelectrical and luminescent properties of single crystals (30 to 50 microns in size) of commercial ZnS-Cu electroluminophore with green emission have been investigated. The dependencies of dark current, photocurrent and luminescence brightness on the applied voltage have been found to reveal a greater complexity than those obtained for polycrystal samples.When the d.c. voltage applied to the crystal rose above 4 volts the dark and photo electrons were observed to multiply, this being accompanied by emission. The observed dependence of the multiplication coefficient on the applied voltage resembles in shape the curves obtained for other substances (Ge, Si, ZnO).     

The electroluminescence of ZnS-Cu,Mn

The brightness waves of ZnS-Cu, Mn phosphor were investigated and it was found that their shape changes from that characteristic for copper-activated phosphors to that characteristic for manganese-activated phosphors as a function of the magnitude of the voltage applied, the length of the pulses and the temperature. In order to explain the results it is assumed that simultaneously with the mechanism of electroluminescence, accepted for ZnS-Cu (ionization of activators; recombination and radiation delayed in phase compared with voltage), there exists an immediate recombination of the Cu activators in the barriers, which is accompanied by radiation in phase with the voltage.

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ZnS-Cu, Mn

ZnS-Cu, Mn. , , , , , , , , . , , ZnS-Cu ( ; , ), : Cu , , .

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In conclusion, the authors thank Dr. M. Trlifaj for valuable discussions and M. Skala for supplying the electroluminescent phosphor of ZnS-Cu, Mn.     

The photodielectric effect in ZnS-Cu monocrystals

The frequency dependence of the photodielectric effect, transition-process kinetics, and peculiarities of IR light action on tan are studied. It is shown that a photodielectric effect of the first type occurs not only in ZnS-Ag crystals but also in ZnS-Cu crystals.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 40–43, January, 1976.     

Relaxation of the space charge in the electroluminescence of ZnS-Cu phosphors

The relaxation of the space charge originating in the electroluminescence of ZnS-Cu phosphors excited by a pulse voltage is investigated by the method of electrical sounding after excitation is removed. It is shown that the main characteristics of the brightness wave for a periodic pulsed excitation are determined by the quantity of electrons and holes locked in the phosphor at the time the previous pulse acted, as well as by the rate of resorption of the space charge.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 16, No. 9, pp. 90–93, September, 1973.     

Microscopic observations of electroluminescence of ZnS-Cu single crystals

Inhomogeneous emission in a field perpendicular to thec-axis was investigated and an attempt made to explain this effect by the existence of linear regions of increased conductivity or of an increased dielectric constant, which are bounded by places of a strong electric field. An experimental proof of delayed recombination is given.     

Thermally stimulated and photo-stimulated conductivity in ZnS-Cu single crystals

The development of thermally stimulated and photo-stimulated conductivity in zinc-sulfide phosphors has been studied. The sign of the charge carriers in the single crystal samples inspected has been determined. The effect of infrared light in the region 1–3.5 m upon previously excited crystals has been investigated and the temperature dependence of the photostimulated conductivity established.In conclusion, the authors express their deep gratitude to E. S. Bespalovaya for the samples and also to K. Arun for his help in measuring the Hall constant.