Decay kinetics of luminescence and electron emission from MgO crystal powders in ac plasma display panels

Abstract

Decay kinetics of luminescence at 5.2 eV and those of sustained electron emission from MgO crystal powders were investigated in order to understand the mechanism of discharge delay in ac plasma display panels and sustained electron emission from insulator. The decay of UV-luminescence was nonexponential and the decay was enhanced by increasing the temperature after showing negligible temperature dependence at low temperature. Existence of carrier traps was indicated by thermoluminescence measurements. As a possible mechanism, luminescence from a donor-acceptor pair in combination with thermal activation from carrier traps was introduced. The electron emission properties were evaluated by the measurement of statistical discharge delay time in ac plasma display panels as an indicator. By coating MgO crystal powders on the MgO protective film, the intensity of electron emission increased and its time and temperature dependence was reduced. A comparison under the same excitation revealed that the decay of UV-luminescence was steeper than that of electron emission. To explain the experimental data, we proposed the involvement of direct electron emission from electron traps synchronized with measuring voltages in addition to luminescence-associated electron emission.

Accumulation and Decay Characteristics of Exoelectron Sources at MgO Protective Layer Surface in Alternating-Current Plasma Display Panels

“…Recently, the detailed theoretical investigations of exoelectron emission in AC-PDPs using rate equations have been performed. 12,26) The present study revealed that the exoelectron emission due to the recombination between an electron and a hole is enhanced for the positively charged surface. Within the scheme of these proposed models, the recombination reaction rate does not depend on the polarity of accumulated charges.…”

“…The emission of exoelectrons is considered to principally originate from electrons and holes trapped in carrier trap states within the band gap. 1) Recent investigations of the exoelectron emission from MgO protective layers, such as Si-or Ge-doped MgO layers 10,11) and a MgO layer coated with MgO crystal powders, 12) indicate that the carrier traps play an important role in the exoelectron emission that triggers the firing in AC-PDPs. However, there have been no systematic investigations of the effects of wall charges accumulated in the MgO surface on the exoelectron emission in spite of accumulated wall charges being strongly correlated with the exoelectron emission.…”

Improvement in Discharge Delay Time by Accumulating Positive Wall Charges on Cathode MgO Protective Layer Surface in Alternating-Current Plasma Display Panels

“…This enhancement of exoelectron emission observed for a positively charged surface revealed that electrons trapped at shallow energy levels coexist in depth 21,22) and/or in plane with holes on a positively charged MgO surface. Moreover, the findings strongly suggest that the detrapping and retrapping rates of holes are larger within a scheme of the exoelectron emission model recently reported for AC-PDPs, 22,23) and a larger number of exoelectrons are emitted from a positively charged MgO surface.…”

“…This dependence of t s on V wall is attributed to the fact that electrons trapped at shallow energy levels in the band gap coexist in depth 21,22) and/or in plane with holes on a positively charged MgO surface, suggesting that the detrapping and retrapping rates of holes are larger within a scheme of the exoelectron emission model in AC-PDPs recently reported in the literature. 22,23) In addition, t f also shows a dependence on V wall similarly to t s , i.e., the positive wall charges on the cathode MgO surface provide shorter t f . Note that a similar relationship between the applied waveform, the so-called negative waveform, and t s has been reported.…”

Photoexcitation, trapping, and recombination processes of theF-type centers in lasing MgO microcrystals

“…Magnesium oxide is one of the most thoroughly studied metal-oxide materials not only in terms of a simple oxide system with a rocksalt structure but also of structural defects. 1 Recently, structure and properties of defects in MgO have attracted renewed interest in view of their intriguing electronic states, giving rise to a variety of optical, 2-6 magnetic, [7][8][9] and electron-emission [10][11][12][13][14] properties. These renewed findings have revealed that our knowledge about defects in MgO is still incomplete, hence requiring further investigations on their structural and electronic properties.…”