Questions on Rs measurement by four point probe device

In summary, the conversation discusses the challenges of measuring the sheet resistance of a CuO thin film using an Agilent B1500 device. The film is deposited using a two-step annealing process and has varying resistance values at different current points. The speaker is seeking help in understanding why this is happening and references other scientific articles that report similar results. They also mention the fragility of CuO and the potential effects of probe materials on the measurement.
  • #1
Hanyuri
1
0
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.
 
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  • #2
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 .
 

1. What is the purpose of using a four point probe device for Rs measurement?

The four point probe device is used to measure the sheet resistance (Rs) of a material. This is a non-destructive technique that can accurately determine the electrical resistance of thin films, semiconductors, and other materials. It is commonly used in material research and quality control processes.

2. How does a four point probe device work?

The four point probe device works by applying a known current through two outer probes, while the inner probes measure the voltage drop across the material. This allows for accurate measurement of the sheet resistance, as the inner probes are not affected by the resistance of the outer probes.

3. What factors can affect the accuracy of Rs measurement using a four point probe device?

Several factors can affect the accuracy of Rs measurement using a four point probe device, including the probe spacing, probe diameter, contact resistance, and material properties such as surface roughness and homogeneity. It is important to carefully calibrate and maintain the device to ensure accurate measurements.

4. Are there any limitations to using a four point probe device for Rs measurement?

While the four point probe device is a commonly used and accurate method for measuring Rs, it does have some limitations. It is not suitable for measuring highly resistive materials or materials with a thickness greater than the probe spacing. It also cannot measure the resistivity of materials with a non-uniform thickness or composition.

5. Can a four point probe device be used for other types of measurements?

Yes, a four point probe device can be used for other types of electrical measurements, such as measuring the resistivity of bulk materials or determining the electrical conductivity of liquids. It can also be used in conjunction with other measurement techniques to obtain more comprehensive data about a material's properties.

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