Evaluation of improved efficiency with a diamond coating for a plasma display panel electrode

Abstract

Application of diamond to electrode coating of a plasma display panel (PDP) is evaluated, since we expect diamond to emit much secondary electron due to the Auger neutralization induced by Xe ions. In a conventional magnesium oxide-xenon (MgO/Xe) system, the most abundant Xe+ produced in the discharge does not effectively cause the secondary electron emission, because the condition of the Auger neutralization is not satisfied. In order to increase the efficiency of ultraviolet (UV) radiation, being especially important for engineering, we should avoid such inefficiency. Under suitable conditions in diamond/Xe system the Auger neutralization can occur. Further, if the electron affinity χ is negative, i.e., negative electron affinity (NEA), the condition of the Auger neutralization in diamond/Xe system is sufficiently satisfied. First, we calculate the coefficients of the secondary electron emission on diamond of clean surface or of hydrogenated surface where the dangling bonds are terminated, on the basis of the Hagstrum model. If the NEA with the electron affinity χ=−0.5 is realized, the high ion-induced secondary electron coefficients such as γXe=0.25 and γNe=0.32 are obtained. Next, we carry out a one-dimensional fluid simulation of the electric discharge in which the two secondary electron emission coefficients of Ne and Xe obtained theoretically are set. Results are presented with changing the sustaining voltage, the fraction of Xe, and the duration of the zero-voltage phase. For 10%Xe mixture, it is shown that the efficiency of UV radiation in the diamond coating increases two times higher than that in the MgO coating. An unnecessarily spontaneous breakdown during the zero-voltage phase, which is peculiar to high secondary electron emission materials, is observed. A mechanism of the breakdown is discussed and means to suppress it are proposed. Taking the zero-voltage phase short and increasing the fraction of Xe up to 50%, in comparison with MgO, a maximum improvement of 3.5 times in the efficiency of UV radiation can be performed. The high secondary electron emission due to Xe ion brings about a decrease in the sustaining voltage, and the sustaining voltage can be further lowered by shortening the duration of the zero-voltage phase. The operation with an increase of Xe fraction becomes attainable. The feasibility of the high performance operation on the ac type PDP by utilizing the materials including diamond with high secondary electron emission for Xe is quantitatively shown.

Current status of microplasma research

“…For this reason a thin MgO film is commonly used to overcoat the dielectric layer above the ITO electrodes in a commercial PDP [8], and new materials such as (Sr,Ca)O have also been developed [25]. There have been several other trials to use as electrode materials diamond (or diamondlike carbon) films [26] and carbon nano-tubes [27], which have larger field emission coefficients. However, some method to enhance the durability against ion bombardment must be developed simultaneously for their practical use.…”

Secondary electron emission and glow discharge properties of 12CaO·7Al2O3electride for fluorescent lamp applications

“…For example, it has been known that the luminous efficiency is improved by changing the cathode material from Ni to Mo, as a result of the reduction in the cathode fall voltage. Improvement was also achieved by depositing a film of doped diamond or MgO on the surface of a metal electrode, thereby lowering the electron emission threshold [30][31][32][33][34][35][36][37][38][39], although the lifetime of the lamp was not satisfactory.…”

Field Emission and Electric Discharge of Nanocrystalline Diamond Films

“…15,17,18 Polycrystalline diamond films, which have a high FE efficacy, emit many secondary electrons upon ion bombardment, resulting in a low breakdown voltage. 37,38 The NCD films, which have high electron emission efficiency, also exhibit a correlation between the FE and electric discharge behaviors.…”

“…Diamond films have high c i values and low breakdown voltages in gas discharge. 37,38 The low electron affinity of diamond surfaces is responsible for high secondary electron emission upon bombardment by ions, following the Auger neutralization process. 37,38 In comparison, DLC and tetrahedrally coordinated amorphous carbon has lower c i and higher breakdown voltages than diamond films.…”

“…37,38 The low electron affinity of diamond surfaces is responsible for high secondary electron emission upon bombardment by ions, following the Auger neutralization process. 37,38 In comparison, DLC and tetrahedrally coordinated amorphous carbon has lower c i and higher breakdown voltages than diamond films. 37 The variation in breakdown voltages in the breakdown region herein suggests that the NCD films have a range of c i values.…”