Electroluminescent Lines in ZnS Powder Particles

Abstract

Existing theories of ZnS-powder-EL are shown to be unable to explain the new findings of electroluminescent striations or lines described in Part I of this work. Several new hypotheses are discussed. Among these, a model seems to be likely which is based on simultaneous bipolar field-emission from opposite ends of conducting imperfection lines into the insulating crystallite, with trapping of injected holes in activator centers, and recombination with mobile electrons at field-reversal. This model, which is shown to be consistent with facts, is discussed in detail. A new impact ionization model is also described which is very similar to that of the field-emission model. At present, it is experimentally indistinguishable from the field-emission model.1 This is tentative because the semllog nature of the plots and the range of the results do not allow a precise determination of the exponent of V.

Microstructure and electroluminescence of ZnS:Cu,Cl phosphor powders prepared by firing with CuS nanocrystallites

“…On the basis of the previous studies [12,13] and results shown above, EL has been attributed to the ionization of activators by the impact of charge carriers accelerated by the high electric fields between Cu x S precipitates and ZnS:Cu,Cl matrix. It is believed that both the amount as well as the physical properties of Cu x S precipitates would influence the recombination rate and the following EL intensity.…”

“…According to the bipolar field emission model proposed by Fischer [12,13], conductive impurities such as cuprous sulfides (Cu x S) are necessary for luminescent ZnS particles to intensify the electric field, and to allow holes and electrons to recombine with radiation in luminescent centers. Therefore, by referring to the XRD analysis shown above, we can also predict that the samples fired at 900 • C with Cu Figure 3 shows the EL emission spectra of ZnS:Cu,Cl powders with various amount of Cu addition.…”

Synthesis and characterization of Zn1−xCdxS:Cu, Cl red electroluminescent phosphor powders

“…The mechanism of high-field EL was proposed to result from the intensification of the electric field near a ZnS-Cu x S contact, and the induction of the tunneling charge carriers to activate the luminescence centers, e.g. Cu, Mn [2,3]. The precipitated Cu x S phase, which has been observed by Ono et al [4] and our group [5] by electron microscopy and optical analysis, is crucial to EL emission.…”

“…According to the bipolar field emission model proposed by Fischer [2,3], conductive impurities such as Cu x S are necessary for luminescent ZnS particles to intensify the electric field, and to allow holes and electrons to recombine with radiation in the luminescent centers. Nien et al have also shown that Cu x S is crucial for EL phosphor powders [5,11].…”

Luminescence of ZnS:Cu,Cl Phosphor Powder Excited by Photons, an Electric Field and Cathode Rays

“…2, the average size of the phosphor powder was approximately 5µm, indicating that the whole powder particle can be excited by photons with a wavelength of 343nm. However, according to the bipolar field emission model proposed by Fischer [16] and our previous studies [7][8][9], conductive Cu x S precipitates are necessary for luminescent ZnS particles to intensify the electric field and to allow tunneling electrons to recombine with radiation in luminescent centers. This is shown per the dependence of emission intensity on the electric field shown in Fig.…”