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Questions on Rs measurement by four point probe device

  1. Jul 24, 2015 #1
    Hi all,
    I am working on electronics material (using metal oxide as an active layer in TFTs). Currently, I'm trying to measure the sheet resistance (Rs) of CuO thin film (~100nm in thickness). My lab uses Agilent B1500 device for measuring the Rs. I met some problems when carrying out the measurement:

    For my case, CuO nanoparticle solution is deposited and is annealed by 2 step annealing ( in inert gas first and then is oxidized in very low % O2). At the first step, the samples has very low and specific Rs, which showed as a metallic material (Cu), but after the second step, the Rs is not clearly. The Rs drop at every different current points are varied widely and not specific from a few ohms/sq. (I~1-100mA) to Gohms/sq. (I~1-100nA). If they are insulating, there should be no voltage drops between the probes. I wonder why it happened like that and whether there is any wrong in my measurement.

    I alse referred some other scientific articles. They reported that CuO thin film has Rs ~ tens of kohm/sq (the deposition method is RF sputtering).

    This measurement is very important for my research. I hope that some of you have done this measurement before.
    I will greatly appreciate if somebody can help me for this case. Please feel free to contact me if you nees any further information.
     
    Last edited: Jul 24, 2015
  2. jcsd
  3. Jul 25, 2015 #2

    Nidum

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    Science Advisor
    Gold Member

    CuO is mechanically very weak . It is very easy to punch right through it or at least reduce local thickness with probes .

    Pointed probes are particularly problematic . Small diameter spherical end probes give a variable contact area and indentation depending on applied load .

    Copper oxide can react with some probe metals to produce a small voltage .
     
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