dna - The Electrical Effects of DNA as the Gate Electrode...

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The Electrical Effects of DNA as the Gate Electrode of MOS transistors M. W. Dashiell 1 , A. T. Kalambur 2 , R. Leeson 1 , K.J. Roe 1 , J. F. Rabolt 2 , and J. Kolodzey 1 1 Department of Electrical and Computer Engineering, University of Delaware, Newark, DE 19716 2 Department of Materials Science and Engineering, University of Delaware, Newark, DE 19716 Correspondence should be addressed to J. Kolodzey (email: kolodzey@ee.udel.edu) Abstract The gate conductor material affects the threshold voltage of metal-oxide- semiconductor (MOS) transistors through the influence of the electrochemical work function and electric charge. Measurements of the threshold voltage from current voltage characteristics may therefore provide a method to estimate the electronic properties of biomolecules located on the gate electrode. We have deposited DNA from the corn genome onto the gate oxide of Si nMOS transistors and measured the effects on the current-voltage characteristics. We found that the DNA decreased the drain-source current compared to devices with clean gate oxides and pure buffer solutions. The threshold voltage was extracted by current-voltage measurements in the linear operating region and was found to increase by +1.9 volts after application of the DNA specimen, a value consistent with the expected negative charge density. This large change suggests that MOS devices may be useful as sensitive bioelectronic detectors. Introduction Currently there is interest in the development of high-speed, integrated techniques for rapid processing of biologically important molecules and neurological cells [1-3]. The industrial maturity of high-speed and high-density CMOS technology makes the silicon field effect transistor (FET) a natural contender for applications in this relatively new field. The purpose of our investigation was to analyze the response of Si FETs to the presence of DNA samples suspended in solution, which is placed directly upon the transistor gate oxide. The DNA-solution acts as the transistor gate electrode, replacing the conventional metal electrode IEEE Lester Eastman Conf., August 2002
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which is anticipated to interfere with direct coupling of the bio-material with the Si channel [4]. Figure 1 shows the conceptual design of our bio-FET design. Our approach was to measure the transistor characteristics and to extract device parameters including the threshold voltage, which depends on the electrochemical work function and electric charge of the DNA sample. We offer preliminary results illustrating the effects of biomolecular modification of the gate area on the transistor characteristics. We provide support that further investigation is warranted if this effect can be reliably used as a rational basis for detecting biomolecule specificity.
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dna - The Electrical Effects of DNA as the Gate Electrode...

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