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Thread: OTFT characterization

  1. #1
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    OTFT characterization

    Hi everyone,

    I'm not sure whether this is the right forum to ask this type of question. All the posts I see on here are discussing companies, but I figured I'd give it a shot anyway. I'm a PhD student studying organic semiconductors, and I'm building an organic thin-film transistor measurement system. I am using a Keithley 2636B SMU to measure the output characteristics of my transistors. I have been able to reproduce standard curves for industrial standard MOSFETs, but when I make my own I get very strange results. My MOSFETs are made on silicon wafers with an SiO2 surface dielectric that is 25 nm - 25 um thick. I have been trying to use P3HT as a standard, where the P3HT layer is spin-cast from a 2% by weight solution (chlorobenzene as the solvent) and is about 200 nm thick. I then deposit 100 nm Ag electrodes in a vacuum chamber. The devices are about 10 mm wide, about 2 mm long, and have a channel length of about 0.5 mm. To make contacts I am using pins on micro-positioners that are connected directly to the keithley system. I make contact to the source and drain, and then I scratch the silicon wafer down to the silicon and make my gate contact where I scratch. When I sweep the drain voltage to, say, -30 V I get a drain current that looks somewhat diodic. As I ramp up the gate voltage to, say, -30 V I don't see any gate activity. The curves are reproduced at all gate-voltages. I know that most organic MOSFETs in research labs are pushed up to +/- 100 V on both the drain and the gate, but mine don't show any activity at these high voltages. Again, I get normal output characteristics on industry MOSFETs, but my own don't work. Any suggestions on:
    1-What is a good organic material to use as a standard?
    2-What device architecture should I be using?
    3-Is it OK to use needles as contacts to such large devices? I am thinking I may need to make the switch to larger, blunt contact pins.
    4-Are there any good resources on setting up and standardizing MOSFET measurement systems? I have scoured the web and can't find anything.

    Thank you for your help.

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  2. #2
    Blogger Daniel Payne's Avatar
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    Sep 2010
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    The experts at Silvaco would probably be able to answer your questions about OTFT characterization.

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    Daniel Payne, EDA Consultant

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