Breakdown Voltage Research of Penning Gas Mixture in Plasma Display Panel

Plasma Science Technology, VoL7, No 6, Dec. 2005Breakdown Voltage Research of Penning Gas Mixture inPlasma Display PanelGuo bingang(郭滨刚), Liu chunliang(刘纯亮), Song Zhongxiao(宋忠孝)2Fan Yufeng(范玉锋), Xia Xing(夏星), Liu liu(刘柳), Fan Duowang(范多旺)2Key Laboratory for Physical Electronics and Devices under Ministry of Education, Xi'anJiaotong University, Xi'an 710049, China2 Key Laboratory of Opto-Electronic Technology and Intelligent Control under Ministry ofEducation, Lanzhou Jiaotong University, Lanzhou 730070, ChinaAbstract Paschen law and equations, which ignore the influence of the Penning ionizationon the electron ionization coefficient (a), are always used as the approximation of the breakdownning gas mixture in current researches of discharge characteristics of theplasma display panel(PDP). It is doubtful that whether their results match the facts. Based on theTownsend gas self-sustaining discharge condition and the chemical kinetics analysis of the Penninggas mixture discharging in PDP, the empirical equation to describe the breakdown of the Penninggas mixture is given. It is used to calculate the breakdown voltage curves of Ne-Xe/MgO andNe-Ar/MgO in a testing macroscopic discharge cell of Ac-PDP. The effective secondary electronemission coefficients(yef )of the MgO protective layers are derived by comparing the breakdownvoltage curves obtained from the empirical equation with the experimental data of breakdownvoltages. In comparison with the results calculated by the Paschen law and the equation whichignore the influence of the Penning ionization on a, the results calculated by the empiricalequation have better conformity with experimental data. The empirical equation characterizesthe breakdown of the Penning gas mixture in PDP effectively, and gives a convenient way testudy its breakdown characteristics and the secondary electron emission behaviorsKeywords: plasma display panel(PDP), Penning gas mixture, breakdown voltage, theffective secondary electron emission coefficientPACS:5280.Sm,51.50.+v1 Introductionsure and d is the gap distance between electrodes. It canbe used as the breakdown voltage criterion for a singlePlasma display panel(PDP)is one of the leading gas in the uniform electric field in PDP. Though mostdevices for large-size, high-brightness flat panel dis- filling gases in actual PDP products are Penning gasplays, suitable for high-definition television(HDTV). mixtures ( many scholars still use the Paschen law orThey have many advantages, e. g, high resolution, fast other equations, which ignore the influence of the Penresponse, wide viewing angle, low weight, and sim- ning ionization on the electron ionization coefficient aple manufacturing process for fabrication. The fact as the approximation of the breakdown voltage crite-that PDPs will be the next generation of TV display rion for the Penning gas mixture in their studies 3-10is evident in the remarkable recent progress of PDP It is doubtful that whether their results match the factstechnology development and manufacturing The Therefore, it needs a theoretical or modeling clarifica-voltage characteristics of the filling gas in PDP are of tion of the equation to describe the breakdown of theparamount importance for getting better PDP perfor- Penning gas mixture in PDPmance. They are closely related to the product costOn the basis of the Townsend gas self-sustand the luminous efficiency. PDP cells can operatcharge condition and the chemical kinetics analysis ofonly if the applied voltage is held within certain lim- the Penning gas mixture discharging in PDP, the em-voltage define the margin of the panel a, These limits ning gas mixture is given in this paper. The breakdownare determined by the breakdown voltage. Thereforeoltathe filling gas breakdown voltage investigation is very sion中国煤化工 ndary electron emis-gO and Ne-Ar/Mgoimportant for PDP research and developmentCNMHGcell of acpdpThe Paschen law defines the relationship between the calculated by this empirical eqbreakdown voltage and(Pd), where P is the gas pres- with the results calculated by the Paschen law and byThe project supported by Science and Technology Research Foundation of the Ministry of Education, China( No 0205-[200278)Plasma Science Technology, Vol7, No 6, Dec. 2005the equation which ignores the influence of the PenningThe secondary electrons escaping from the cathodeionization on a, the results calculated by the empiri- surface are mainly induced by the impacting ions andcal equation have better conformity with experimental metastable particles, which are generated only in thedata.The empirical equation characterizes the break- first three processes. Consequently, coefficient a shoulddown of the Penning gas mixtures in PDP effectively, be calculated according to the first three processes. Itdown characteristics and the secondary electron e k.and provides a convenient way to study their breaincludes both the ionization and excitation processesIn terms of the fundamental pre-assumptions of thesion behaviorsTownsend self-sustaining discharge condition and thesimultaneous consideration of the effects of deioniza-2 The equation to describe thetion, deexcitation and electron backscattering on a, theequation to describe the breakdown of the Penning gasbreakdown of Penning gasmixture can be derived as Eq.(1)from the gas dis-mixture in PDPcharge chemical kinetics shown aboveOn the basis of the Townsend self-sustaining dis-feff+ICPrd·k1Ucharge condition, yef(ead-1)=l, the equation todescribe the breakdown of the Penning gas mixturePrdcan be derived from it simultaneously with the equa--CPd. k2Uytion that represents the relationship between the electronic ionization coefficient a and the breakdown volt-age. The electronic ionization coefficient a is directlyCPd.kUCdetermined by the processes of chemical kinetics of thePenning gas mixture discharging in PDP. The chemicalkinetics of the Penning gas mixture discharging in PDP-CPd.kAUCincludes several processes shown as follows. The generation of new electrons is described by corresponding-CPd ksUCa.Ionization impacted by an electron( direct ionization, cumulative ionization)CPd. ksCe+X→X++2e,e+X*→X++2e,e+X*→X++2e-cpld.k7U(xi)).nr+e+x2→x++2eUrCPd. ksUCcumulative excitationCPd.kgU(xb. Excitation impacted by an electron(direct exci-tion, cumulative excitatione+X→X*+e,CPd…k0(e+x→x*+e,CPrd·k1Uye+X2→X2+e.expc. Penning ionizationX*+X*→X++X+e,-CPTd k2UX*+Y(YorY“)→Y++X+e,X*+Y→(XY)++e,X**+X**→X++X+e-CPd.klUxX…+Y(Y"orY)→Y++X+e,X+Y→(XY)++e,CPrd·k2Uwhere y is a gas atom whose ionization energy is lessthan the excitation energy of xd. Deionization impacted by an electron(r-cP d- k3(A-).na+中国煤化工e. Deexcitation impacted by an electronf. Formation of excimersCNMH+g. Charge transferh. Excitation transferi. Radiative transition-COrd.krU(x:)")n3128Guo Bingang et al.: Breakdown Voltage Research of Penning Gas Mixture in Plasma Display PanelCPd kgCcord.knUx).Prx(X").m+CPdk12Uy).Pr(Y*)·m+UFig 1 Schematic diagram of testing macroscopic dischargeell of ac-pdpexp/-CPrdk13Ux) Prv(X").n+exp/ -cpr. k13Ux.Pr.(X")·mn+CPld k13UP-CPTdklUx.roxy(X)'m+Pd/ Pa-mCPTd k15Ux…Prx…(X)m1+Ne+1% Xe/MgOCPrd·k16U之Pry…(Y…)·m2+CPd kisUPr(X*)·m+CPdh5Ux")·Pry(x”)m+CPd·k15UPry…(X)·m1+1%A/Mg0Fig 2 Calculated curves of breakdown voltage vs Pd for-CPrd·k14UxUrPrix(x").m,(1) of break down voltage ne data ponts are measwhere P is the filling gas pressure, d is the electrodes' tion results. The Penning ionizations caused bygap distance, Yeff is the effective secondary electron metastable atoms are counted in the third item inemission coefficient, C and ki(i= 1, 2, ., 14)are ex- Eq(2)perimental constants, which relate to gas species, gascomposition and the electron energy distribution, Uix)is the ionization potential of particle X, Uix) is the ex-crain let=exp(=cP d,kiv)citation potential of particle X, Uix) is the cumulativeCPd·K2U-CPd. K3Uexcitation potential of particle X, Prix (y)is the ion- exppization probability of particle X impacted by particlY, and ni(i=1, 2,., 10)are parameters which charac(2)terize collision probability of one kind of particles im- 3 Results and disscussionpacted by an electron. r is a exponential which repre-sents the damage effects on an electron ionizing colliThe breakdown voltages are examined in a testingsion caused by deionization, deexcitation and electron macroscopic discharge cell of AC-PDP filled with thebackscattering.These damage effects on ionization be- Penning gas mixture. Fig. I shows the schematic dia-come severe with the increasing gas pressure P for moregram of the macroscopic testing discharge cell of AC-particle collisionsPDP. The electrodes gap distance d is 1 mm. The elec-Because too many parameters need to be determined, trodes are covered by 600 nm +50 nm MgO film. ACit is conducive to great computational complexity of pulsethe discharging calculation directly using Eq.(1). It is betw中国煤化工 quency of125kHdispensable to simplify it. After the error testing ofCNMHGethod, we can pointhe breakdown voltages( between the experimental data out that breakdown voltage curves measured in the ex-and calculation results), the equation to determine the periments fit the empirical Eq.(2)well. Fig. 2 givesbreakdown voltage of the Penning gas mixture can be the calculated breakdown voltage curves, which are ofsimplified as empirical Eq(2)with satisfying calcula- the lowest mean square fitting errors compared withPlasma Science Technology, Vol7, No 6, Dec. 2005Table 1. Calculation parameters and mean square error S of different equationsGas/Mgo EquationExperimental constantsn or T1A=52.2B=20.050323.4774Ne+1%XeITC=16DNe=24Dx。=0.480990.120325.5750IC=1319K1=24K=24K3=2.504320.90.0340.4327A=39.6B=2.40.025191.3701Ne+1% Ar II C=1.7 DNe=1.87DAr=0.1709900801955285IIC=387K1=458K2=452K3=4540.4662.20.1080.3788the experimental voltage results, of the Penningmixtures: Ne+1%Xe/MgO and Ne+1%Ar/MgOdata points are measured values of the breakdown voltge. The three breakdown voltage curves areculated by three different equations: I: PaschenU= APd/ln(BPd/In(1+1/eff)7, II: Yer(exp(ad)1]=1,a=maN+(1-n)axe/Ar(0≤n≤1a= C'Pexp(-DP/E]6, 10, and III: empirical Eq(2)A, B, C and D are experimental constants.The lowest mean square error $(S=n-ixb2扌自78§EUUfi-cal-Ufi-mea)2)of least squares fitting betweenthe calculated breakdown voltage values and the mea-sured breakdown voltage values and other parametersare given in Table 1. Compared with the breakdownvoltage curves calculated by equation I and equationI l, curve III calculated by empirical Eq.(2)has beter conformity with the experimental data and muchlower S. As a parameter result, the Jeff can be de-rived by least squares fitting. The corresponding yefvalues in the three different equations are also given inTable 1. Calculated index r is less than 1. It revealsB: Ne+Xe/ MgOthat there are damage effects on electron ionizing colli- Fig. Breakdown voltage as a function of pd for Penningsion caused by deionization, deexcitation and electron gas mixtures, the data points are measured values of breakbackscattering in gas discharging. We can also see that down voltage in experimentsm1=0.9 1 of Ne +1%Xe/ MgO and n = 2.2> 1 ofXe/ Mgo decreases with increasing Xe% from 0.1% totion could be considered as an increase in the collision 4% continuously. It indicates that there is no evidentprobability in empirical Eq.(2)Penning effect on Ne-Xe/Mgo discharging in this ratioThe dosage of impure gas has a great effect on rangethe breakdown voltage and Yef. Fig 3 displays theThe range of Ar% and Xe% discussed in thisbreakdown voltage curves measured in the experi- is 0.1% w 4%. Whether different Yeff variationsments. Fig 3a is for Ne+Ar/MgO, and Fig 3boutside of this range, especially in the range of afor NeXe/ MgO. In Fig 3a, the breakdadosing ratio, is an interesting subject. Further studiescurve is depressed with increasing Ar% from 0. 1%to are in progress in order to obtain better yeff results with1%. Then, the curve rises with increasing Ar% from higher Ar% and Xe%1% to 4%. However, there is a different result forTable 2 also provides a comparison of the calcuNe+xe/MgO shown in Fig. 3b. The breakdown volt- lated Yef values with the y values in the literatureage curve rises with increasing Xe% from 0.1% to 4% of Ne-Xe/MgO. y values in reference [7, ll] are mea-continuously. Table 2 gives the Yeff results derived by sured by FIB techniques. Because the ion energy in theleast squares fitting using empirical Eq(2). The calcu- Townsend discharging is very low[ 12, 13), we choose ylated yef s show a reversed variation in U curves with values when the ion energy is less than 100 eV.yvaluesthe increasing gas dosage. Yeff of Ne-Ar/MgO rises ob- in reference [12] are estimated by comparing the breakviously when Ar% increases from 0.1%to 1%. There is dowrL+-i--dk. quid simulations anea maximum %eff value when Ar% is 1%. When Ar% is by ex中国煤化工 here is a good numer-larger than 1%, eff decreases with increasing Ar%. It icalCNMHG[7, 11], and therindicates that there is an obvious Penning effect on Ne- alsoueucies will creasing Xe% of eff,Ar/Mgo discharging. The same result has also been m(7, 11I and y [121. It suggests that the results calculatedgiven by Xu Xueji in reference[14]when Ar/(Ne+Ar) by empirical Eq(2)characterize the breakdown of theatio increases from 10-3 to 10-. However, Yeff of NePenning gas mixtures effectively. Empirical Eq. (2)3130Guo bingang et al.: Breakdown Voltage Research of Penning Gas Mixture in Plasma Display PanelTable 2. Calculated %eff values under different gas dosing ratiosGas/Mgo (%)0.0310.0470.050Ne+x%Xey710.03~0.0350.03~0.040.035~0.0460.03~0.1250.03~0125Ne+x%Ar0.1080.1010098gives a convenient way to study the breakdown charac- Referencesteristics of the Penning gas mixtures and the secondaryelectron emission behaviors in PDP1 Boeuf J P. J. Phys. D: AppL. Phys., 2003, 36: R53-4 Conclusions2 Meunier J, Belenguer Ph, Boeuf J P J Appl. Phys1995,78:731~745The equation to determine the breakdown voltage 3. Park Chung-Hoo, Lee Woo-Geun, Kim Dong-Hyun,etof the Penning gas mixture can be given by empiri-al. Surface and Coating Technology, 1998, 110: 128cal Eq(2). In comparison with the Uf and y valuescalculated according to the Paschen law and the equa4 Yu Zhi-Nong, Seo Jong-Wook, Yu Soon-Jae, et altion which ignore the influence of Penning ionizationSurface and Coating Technology, 2002, 162: 11 N 18on a, the results of Ur and feff calculated by empirica5 Hu Wenbo, Sun Jian. Calculation of the BreakdownCq.(2)have better conformity with the experimentalVoltage of Gas Mixture Discharge Occurring in Colordata. It indicates that the results calculated by empir-AC-PDP, ASIDo0, PB-18, Xi'an Jiaotong UniversityP. R. China. 2000ical Eq(2)characterize the breakdown of the Penninggas mixtures effectively. The equation gives a conve- 6 Yasushi Matsunaga, Tomokazu Kato, Tadatsugu Ha-ori,etal.J.Apl.Phys,2003,93(9):5043~5052nient way to study the breakdown characteristics of 7 Lee Won Tae, Im Seoung Jae, Han Jeon Geon, etalthe Penning gas mixtures and the secondary electronpn. J. Appl. Phys., 2002, 41, PartI(11A):6550emission behaviors in PDPThe calculated Yefts show a reversed variation in Uf 8 Yuichi Harano, Kunio Yoshida, Heiju Uchike IEICEurves with an increasing gas dosage. Ur curve of Ne-Trans. Electron, 1997, E80-C(8 1091 N 1094Ar/MgO falls and Yeff rises when Ar% increases from 9 Kunio Yoshida, Heiju Uchiike, Masahiro Sawa. IEICE0.1% to 1%. There are a bottom U curve and a maxi-Trans. Electron, 1999, E82-C(10): 1798 1803mum eff value when Ar% is 1%. When Ar% increases 10 Boeuf J P, Punset C, Hirech A, et al. J. Phys. IVfrom 1% to 4%, Ur curve rises and Yeff decreases withFrance,1997,7,C43C414increasing Ar%. However, the Ur curve of Ne-Xe/Mgo 11 Uhm Han S, Choi Eun H, Lim Jae Y Applied Physicsrises and Yef decreases with increasing Xe% from 0. 1%Letters,2002,80(5):737~739to 4% continuously. It indicates that there is an obvious 12 Hur Min Sup, Lee Jae Koo, Kim Hyun Chul, et alPenning effect on Ne-Xe/MgO discharging in the ralPenning effect on Ne-Ar/Mgo discharging, but no cleaIEEE Trans. on Plasma Science, 2001, 29 (5):86113 Yoon Sean J, Lee Insook, Lee Jong-Wan, et al. Janrange 0. 1% 4%. The calculated index r is less than 1.J.Appl.Phys,2001,40:809~812It reveals that there are damage effects on the electronXu Xueji, Zhu Dingchang. Gas Discharge Physicsnizing collision caused by deionization, deexcitationShanghai: Fudan University Press, 1996, 18(in Chiand electron backscattering in the Penning gas mixturedischarging. That n1=0.9 1 of Ne+1%Xe/MgO andm=2.2> 1 of Ne +1%Ar/MgO in Table 1-III suggests(manuscript received 21 November 2004)that the Penning ionization could be considered as an E-mail address of Guo Bingincreasing collision probability in empirical Eq (2guobingang@ipedxjtu.edu.cn中国煤化工CNMHG3131