IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 51, NO. 8, AUGUST 2004 1241 The Effect of the Discharge Aging Process on the Surface State of MgO Film in AC PDPs Kyung Cheol Choi, Hee-Joong Kim, and Bhum Jae Shin Abstract—This paper reports on the change in the surface condi- tion of the MgO thin ﬁlm in an ac plasma display panel during the discharge aging process. The superﬁcial layer on the MgO thin ﬁlm was created during the discharge aging process, which was related to the minimum sustain voltage and the light intensity emitted from the Neon Xenon gas mixture discharge. The superﬁcial layer on the MgO thin ﬁlm was observed using a transmission electron mi- croscope. The X-ray diffractometer pattern of the MgO thin ﬁlm after the discharge aging process was different from the pattern at the beginning of the discharge aging process. Index Terms—MgO, plasma display panel (PDP), superﬁcial layer. I. INTRODUCTION A C PLASMA display panels (PDPs) are the leading display devices for 40- and above-40-in ﬂat panel displays. How- ever, the phenomena related to the small display pixels in an ac PDP are still not well known. Especially, the interaction between the plasma and the surface of the display cell is not well known. In an ac PDP, MgO thin ﬁlm is used as a protective material over the dielectric layer as well as the secondary electron emissive layer. There is an interaction between the plasma and the MgO thin ﬁlm layer during the aging process and sustain discharge period. The display characteristics, aging process time, and the reliability of an AC PDP are all related to the surface properties of the MgO ﬁlm, which are mainly affected by the discharge aging process and actual display period [1]. While preparing the panel, the MgO thin ﬁlm layer of the display cell should be subjected to annealing and discharge aging process. There was a study related to the annealing process of MgO thin ﬁlm in ac PDP [2]. Also, research on the aging process had been done [3], [4]. Usually, it takes 8–24 h for the discharge aging process, which is used for stabilizing the discharge. The surface state of MgO has some kind of relationship with the discharge charac- teristics during the discharge aging process. However, there is no end point detection possible because the effect of the dis- charge aging process on the surface of an MgO ﬁlm is not well known. Accordingly, the current study investigates the surface condition of the MgO ﬁlm during the discharge aging process, which can be used for determining the optimal aging time. Fig. 1 shows a schematic diagram of the test ac PDP. The front test plate has 48 sustain electrodes. Usually, one display pixel Manuscript received April 6, 2004; revised April 27, 2004. This work was supported by Sejong University under the IT Research Center Project. The re- view of this paper was arranged by Editor J. Hynecek. K.C. Choi and B.J. Shin are with the Department of Electronics Engineering, Sejong University, Seoul 143-747, Korea (e-mail: kyungcc@sejong.ac.kr). H.–J Kim is with PDP Division, LG Electronics Industries, Gumi, Korea. Digital Object Identiﬁer 10.1109/TED.2004.831367 has two sustain electrodes to maintain the surface discharge. The distance between the two sustain electrodes in one display pixel was 100 m. Fig. 1 shows only the two sustain electrodes of total 48 of the test panel. The experimental panel was subjected to thermal annealing in the aging chamber for 2 h with the base pressure of about 1.0 torr at a temperature of 300 C to activate the MgO surface. Thereafter, the aging chamber was ﬁlled with the Ne Xe(4%) gas at the pressure of 435 torr. The pulses of 220 V and 25 kHz were applied to the sustain elec- trodes for the discharge aging process. When the pulses of 220 V and 25 kHz were applied to the two sustain electrodes, the sur- face discharge occurred between the two sustain electrodes. In order to examine the effect of the discharge aging process on the surface of the MgO thin ﬁlm, the sustain voltage, discharge cur- rent, and light emitted from the Ne Xe gas mixture discharge were investigated. The surface condition of the MgO thin ﬁlm was observed with the transmission electron microscope (TEM) and the XRD. II. RESULTS AND DISCUSSION First, we investigated the discharge characteristics during the discharge aging process. Fig. 2 shows the maximum and min- imum sustain voltage of the 4-in experimental panel as a func- tion of the discharge aging time. Within 1 h, the maximum and minimum sustain voltage decreased steeply and became satu- rated. This is a well-known phenomenon. It was expected that the minimum sustain voltage would start to increase after 10 h. Usually, the discharge characteristics are dependent on the gas composition and the surface condition of the MgO thin ﬁlm in an ac PDP. During the discharge aging process, it was pos- sible for the gases inside the panel to be contaminated, and the light intensity could vary as a result. The main purpose of the current work is to investigate the relationship between the dis- charge characteristics and the surface state of the MgO thin ﬁlm. After the gases were replenished at each detecting time to avoid the effect of gas contamination, the light intensity was investi- gated as a function of discharge aging time according to the gas pressure, as shown in Fig. 3. The driving conditions were all the same for each gas pressure. The behavior of the light intensity is similar for each gas pressure. The light intensity from the Ne Xe( 4%) gas discharge changed only slightly during the 16 h and then suddenly decreased after – h. The behavior of the minimum sustaining voltage and the light intensity in the vacuum chamber were almost the same as those of the sealed panel during the discharge aging process. After the 4-in AC PDP was subjected to the discharge aging, the surface condition of the MgO thin ﬁlm was investigated by using the TEM cross-sectional images and XRD. Fig. 4 shows 0018-9383/04$20.00 © 2004 IEEE