Cathodoluminescence of Double Layers of Phosphor Particles

Daniel Den Engelsen,Jack Silver,Terry Ireland,Paul Harris

doi:10.1149/2.021404jss

Daniel Den Engelsen, Jack Silver + Show 2 more

Open Access

https://doi.org/10.1149/2.021404jss

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Abstract

We present radiance measurements of particle layers of ZnO:Zn, Y2O3:Eu and Y2O2S:Eu bombarded with electrons at anode voltages between 1 and 15 kV. The layers described in this work refer to single component layers, double layers and two component mixtures. The phosphor layers are deposited on ITO-coated glass slides by settling; the efficiency of the cathodoluminescence is determined by summing the radiances and luminances in the reflected and transmitted modes respectively. The efficiency of a double layer of Y2O3:Eu on top of ZnO:Zn at high electron energy is significantly larger than the efficiency of a corresponding layer in which the two components are mixed. This result is interpreted in terms of the penetration-model, which predicts a larger efficiency for a high-voltage phosphor on top of a low-voltage phosphor. When a layer of the low-voltage phosphor ZnO:Zn is on top of the high-voltage phosphor Y2O3:Eu, we also observe a higher efficiency than that of the corresponding layer with both components mixed. In this case the efficiency increases due to suppression of charging in the Y2O3:Eu layer. Double layers of ZnO:Zn and Y2O2S:Eu did not show enhanced efficiency, because the size of the Y2O2S:Eu particles was too large to evoke the penetration effect.

Highlights

The efficiencies of ZnO:Zn and Y2O2S:Eu do not depend on the coating weight of the phosphor layer; in the case of nano-sized Y2O3:Eu, there is a slight dependence
We have extended CL-measurements of conductive (ZnO:Zn) and non-conductive phosphor (Y2O3:Eu and Y2O2S:Eu) layers to high electron beam energies in order to study the electron penetration mechanism
The efficiency of the nano-sized Y2O3:Eu at 15 kV is lower than that of commercial material measured with an Al backing layer

Summary

Introduction

We have described an idea to enhance the efficiency of cathodoluminescence (CL) of phosphor particle layers by depositing one layer on top of another.[1] Such an enhancement is to be expected when a high-voltage phosphor is deposited on top of a low-voltage phosphor. High-voltage, layer is thin enough to allow electrons of sufficient energy (but not enough to excite the high energy one) to penetrate into the low-voltage phosphor layer enhancement of the luminance may be expected. We published a new measuring method (the “comparison method”) to determine the CL of an insulating phosphor layer.[5] The objective of the work described here, was to investigate the effect of double layers of phosphor particles on the lumen and energy efficiency by using electron beam energies up to 15 kV and applying the comparison measuring method.

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