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Issue 33, 2011
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Effect of surface chemical composition on the work function of silicon substrates modified by binary self-assembled monolayers

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Abstract

It has been shown that the application of self-assembled monolayers (SAMs) to semiconductors or metals may enhance the efficiency of optoelectronic devices by changing the surface properties and tuning the work functions at their interfaces. In this work, binary SAMs with various ratios of 3-aminopropyltrimethoxysilane (APTMS) and 3-mercaptopropyltrimethoxysilane (MPTMS) were used to modify the surface of Si to fine-tune the work function of Si to an arbitrary energy level. As an electron-donor, amine SAM (from APTMS) produced outward dipole moments, which led to a lower work function. Conversely, electron-accepting thiol SAM (from MPTMS) increased the work function. It was found that the work function of Si changed linearly with the chemical composition and increased with the concentration of thiol SAMs. Because dipoles of opposite directions cancelled each other out, homogeneously mixing them leads to a net dipole moment (hence the additional surface potential) between the extremes defined by each dipole and changes linearly with the chemical composition. As a result, the work function changed linearly with the chemical composition. Furthermore, the amine SAM possessed a stronger dipole than the thiol SAM. Therefore, the SAMs modified with APTMS showed a greater work function shift than did the SAMs modified with MPTMS.

Graphical abstract: Effect of surface chemical composition on the work function of silicon substrates modified by binary self-assembled monolayers

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Publication details

The article was received on 02 Mar 2011, accepted on 26 May 2011 and first published on 21 Jul 2011


Article type: Paper
DOI: 10.1039/C1CP20590K
Citation: Phys. Chem. Chem. Phys., 2011,13, 15122-15126
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    Effect of surface chemical composition on the work function of silicon substrates modified by binary self-assembled monolayers

    C. Kuo, C. Liu, S. Lee, H. Chang, W. Lin, Y. You, H. Liao and J. Shyue, Phys. Chem. Chem. Phys., 2011, 13, 15122
    DOI: 10.1039/C1CP20590K

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