Multi-color Luminescence from Surface Oxidized Silicon Nanoparticles
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Multi-color Luminescence from Surface Oxidized Silicon Nanoparticles K. Sato*,***, K. Hirakuri*, M. Iwase**, T. Izumi*** and H. Morisaki**** *
Department of Electronic and Computer Engineering, Tokyo Denki University, Ishizaka, Hatoyama, Hikigun, Saitama, 350-0394, JAPAN ** Department of Materials Science, Tokai University, 1117 Kitakaname, Hiratsuka, Kanagawa, 259-1292, JAPAN *** Department of Electronics, Tokai University, 1117 Kitakaname, Hiratsuka, Kanagawa, 259-1292, JAPAN **** Department of Electronic Engineering, The University of Electro-Communications, 1-5-1 Chofugaoka, Chofu, Tokyo, 182-8585, JAPAN ABSTRACT We fabricated the multi-color electroluminescent (EL) device using hydrofluoric (HF) acid solution treated and oxidized silicon (Si) nanoparticles. Strong red luminescence was obtained from the HF treated Si nanoparticles based EL device under a low forward bias of 4.0 V. On the other hand, green and blue luminescence, which could be seen with naked eye under room illumination, was observed for the oxidized Si nanoparitcles based EL device at the forward bias below 9.5 V, because of reduction of size due to oxidation onto the Si nanoparticle surface. Furthermore, the red/green/blue lights showed good stability for aging of a long period of time in air by the formation of oxidized layer on the surface. These results indicate that the EL devices developed in this study can realize as application to future flat panel display. INTRODUCTION Silicon (Si) nanoparticles are useful candidate materials for development of new flat panel displays including electroluminescent (EL) display and field emission display, because it exhibits high efficient photoluminescence [1] and injection-type EL [1] at room temperature. Recently, some research groups have been developed a multi-color EL devices using porous silicon and Si nanoparticles as an application to Si-based display device [2-4]. The EL devices show red/green/blue luminescence in N2 atmosphere [2]. However, they have been demonstrated low efficiency and unstable luminescence in air. The low efficiency and the poor stability for their luminescence is caused by the re-formation of high-density Si dangling bonds, which is a non-radiative recombination center, onto the Si nanoparticle/SiO2 layer interface, because the Si nanoparticle surface has most unstable passivation in air. Moreover, the EL devices require the high voltage above 10.0 V, because of formation of thick oxidized (SiO2) layer on the surface [3,4]. From above feature of the multi-color EL devices, it is necessary to reduce the Si dangling bonds and the SiO2 layer on the surface. They can be improved by the hydrofluoric (HF) acid
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solution and the oxidation techniques. The HF treatment leads to decrease of Si dangling bonds by hydrogen termination. And, the oxidation treatment leads to formation of SiO2 layer as stable passivation, and reduction of size, which is directly related to luminescent color. In this paper, we fabricate the EL devices using HF treated and surface oxidized
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