The Behavior of Cyclic Voltammetry Stripping (CVs) with Tin-Doped Indium Oxide in 0.3M Hydrochloric Acid
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The Behavior of Cyclic Voltammetry Stripping (CVs) with Tin-Doped Indium Oxide in 0.3M Hydrochloric Acid K. C. Li, C. A. Huang, G. C. Tu1 and W. S. Wang1 Dept. Mechanical Engineering, Chang-Gung University, Taoyuan, Taiwan, R.O.C. 1 Dept. Materials Science and Engineering, Chiao-Tung University, Hsinchu, Taiwan, R.O.C. ABSTRACT The cyclic voltammetry stripping (CVs) behavior of the tin-doped indium oxide (ITO) on SiO2 in 0.3M HCl is reported. The CVs result showed an obvious reduction-current peak that occurred during the first cathodic potential scanning. Smaller reduction current and more negative potential of the reduction-current peak were also observed for the ITO that was annealed at 500 OC. The result was attributed to the replenished oxygen-deficient site and the oxygen anion density is decreased in the ITO. The present study has proved that CVs is a useful method to differentiate the carrier concentration in ITO film controlled by different pretreatments. Many spherical In-Sn particles were formed on the ITO when the reduction current took place. During precipitation of these spherical particles, the grain boundaries of the ITO were dissolved and the ITO surface nearby the grain boundaries offered a preferred nucleation site for the formation of these spherical In-Sn particles. Based on the microstructure observed and the result derived from the short potential range scanning, the formation mechanism of the spherical particle is proposed. Key words: tin-doped indium oxide (ITO), cyclic voltammetry stripping (CVs), and oxide reduction, In-Sn particle INTRODUCTION Tin-doped indium oxide (ITO), also known as the degenerate n-type semiconductor [1], is an oxide-film composed mainly of In2O3 with minor addition of SnO2. While the donors of ITO is contributed principally from oxygen vacancies, the oxygen vacancies and the substitutional tin-dopants formed in the lattice of indium oxide during the growing process of the material will lead to the degenerated characteristic of ITO [2]. ITO, noted for its high optical transmittance (more than 80%–90% at 550 nm wavelength) and low sheet resistivity (lower than 2×10-4Ω-cm), is an important optoelectronic material. Popular applications of the material are found in electronic and photoelectric devices, such as the electrical conducting element, liquid crystal display (LCD), light emitted diode (LED) and organic electroluminescent display (OLED) [3-6]. The electronic and structural properties as well as the electrochemical behavior of ITO film have been investigated for some time. Many researchers have reported their studies on the electrochemical behaviors of ITO film or TCE (Transparent Conductive Electrodes) [7-12]. Bruneaus et al. [7] pointed out that the very slow transfer kinetics for oxide was dependent on the redox potential and the chemical species in the solution while the oxide was used as TCEs in photoelectrochemical cell. In addition, Bressers [8] et al. studied the ITO electrodes in propylene carbonate solutions containing lithium ions using x-ray di
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