The characterization of Electronic state from Surface to Several Nanometer Region on MgO:Si Thin Film
- PDF / 223,701 Bytes
- 6 Pages / 432 x 648 pts Page_size
- 21 Downloads / 174 Views
The characterization of Electronic state from Surface to Several Nanometer Region on MgO:Si Thin Film Mikihiko Nishitani, Mutsumu Fukada, Yukihiro Morita, Masaharu Terauchi, Tessei Kurashiki, Hiroki Tsuchiura* , Yasushi Yamauchi** Co-operation Laboratory of Panasonic, Osaka University Department of Applied Physics, Tohoku University* National Institute for Material Science** ABSTRACT We report the properties of MgO:Si film as a protective cathode material on the electrical discharge, and the electronic state of the outer-most surface on MgO:Si film characterized by helium Meta-stable De-excitation Spectroscopy (MDS) and that of several nanometer region from the surface evaluated by X-ray Photoelectron Spectroscopy (XPS). Both of the spectra are discussed focusing on the dependence upon the amount of Si in the MgO film for understanding discharge phenomena. The analyses of the experimental data imply that the discharge properties are not improved due to surface degradation with the increase of Si in MgO films. However, an in-situ discharge experiment, in which MgO:Si films are not exposed for the atmosphere after its deposition, shows that the introduction of Si up to about 1 atomic% has the potential to enhance the secondary electron emission coefficient.
INTRODUCTION MgO thin film bas been commercialized in Plasma display panels (PDPs) as a protective cathode material. Until now the study on the MgO protecting layer has been focused on how to decrease the discharge voltage and time lag by increasing the secondary electron emission coefficient. It has been known that various physical and chemical properties of MgO film such as surface roughness, density, stoichiometry, and defect level affect the discharge properties of a PDP cell [1]. On the other hand, we have tried to characterize the electronic state around the outer-most surface of the protective cathode material on PDP, using the conventional XPS, extreme UV photoelectron spectroscopy (EUPS)[2] and meta-stable de-excitation spectroscopy (MDS) [3] for understanding of the secondary electron emission process. Recently, it is reported that the secondary electron emission coefficient is improved by optimizing the amount of Si (about 0.03 at %) in MgO film [4,5]. In those papers, it has not come to clarify the mechanism though the relation between the secondary electron emission coefficient and the preferred orientation of the film measured by XRD was discussed. In this paper, we aim to clarify the effect of Si doping into MgO film for the improvement of the secondary electron emission coefficient, applying the surface characterization of the films with the analysis of the measurement of the electrical discharge property. To prove the experimental data, a theoretical research was also carried out. THEORETICAL APPROACH It has been widely recognized that the secondary electron-emission from the MgO surface can be enhanced by introducing in-gap defect states in which electrons can occupy [6]. Here we study the electronic states around a Si atom substituted for Mg on
