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2007
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In the Laboratory
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Flat-Band Potential of a Semiconductor: Using the Mott–Schottky Equation
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K. Gelderman, L. Lee, and S. W. Donne
Discipline of Chemistry, University of Newcastle, Callaghan, NSW 2308, Australia
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April 2007
Vol. 84 No. 4
p. 685
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| Abstract |
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Semiconductors are an important category of materials involved in many applications in modern society. One such application revolves around the search for efficient sustainable forms of energy, in this case the use of semiconductors to assist in the conversion of light to electrical energy. Related to a semiconductor's behavior in such an application is its flat-band potential. In this article we have described an experiment suitable for fourth-year undergraduate or graduate students that involves determination of the flat-band potential of a semiconductor using electrochemical impedance spectroscopy (EIS) and the Mott–Schottky equation, which relates semiconductor–electrolyte interfacial capacitance to voltage. To demonstrate this approach we used a polycrystalline ZnO electrode in an electrolyte of 7 x 10-4 M K3[Fe(CN)6] (1 M KCl). EIS, with a suitable equivalent circuit, was used to extract interfacial capacitance data (C), which was then compared with the electrode voltage via the Mott–Schottky equation (C-2 versus V). From the x-axis intercept the flat-band potential was determined to be -0.316 ± 0.033 V versus SCE. For descriptive purposes, some fundamentals of band theory have been included in the Supplemental Material, as has the derivation of the Mott–Schottky equation.
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| Supplement |
Instructions for the students, including pre- and postlab questions and the complete derivation of the Mott–Schottky equation, and notes for the instructor are available.
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| More Information |
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Citation |
Gelderman, K.; Lee, L.; Donne, S. W. J. Chem. Educ. 2007, 84, 685.
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Keywords |
Electrochemistry; Graduate Education / Research; Hands-On Learning / Manipulatives; Laboratory Instruction; Physical Chemistry; Semiconductors; Upper-Division Undergraduate
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History |
Created:
Last Updated: |
3/6/2007
3/8/2007
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 Caution! | | Experiments, laboratory exercises, lecture demonstrations, and other descriptions of the use of chemicals, apparatus, instruments, computers, and computer interfaces are presented in the Journal of Chemical Education as illustrative of new or improved ideas or concepts in chemistry instruction and are directed at qualified teachers. Although every effort is made to assure and encourage safe practices and safe use of chemicals, the Journal of Chemical Education cannot assume responsibility for uses made of its published materials. Many chemicals are hazardous. Precautions for the safe use of hazardous chemicals and directions for their proper disposal are described in the Material Safety Data Sheets and on the labels. We strongly urge all those planning to use materials from our pages to make choices and to develop procedures for laboratory and classroom safety in accordance with local needs and situations. |
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