Four Point Probe Measurement Help for 500 nm Ni Coating

In summary, physicistX deposited 500 nm of Ni on glass substrate to check out the equipment they bought and when they measured the sheet resistance the display showed 13.56 mohm/sqare for 5 mA current. To check out the measurement they multiplied the sheet resistance with the coating thickness which gave about 1/10 of Ni's bulk resistivity. However, it's possible the film is actually much thicker and they need to measure at smaller currents and establish linearity.
  • #1
physicistX
3
0
Hi,

I am new to four point probe measurements and I have a question.

I've deposited 500 nm of Ni on glass substrate to check out the equipment we bought. When I measured its sheet resistance the display showed 13.56 mohm/sqare for 5 mA current.

To check out the measurement I multiplied the sheet resistance with the coating thickness which gave about 1/10 of Ni's bulk resistivity (96.3 nohm.meter). I couldn't figured it out if it's a faulty measurement or is there a logic I am missing. Any help would be appreciated.

thanks.
 
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  • #2
Hi physicistX, welcome to PF. A few questions: is your test equipment set to analyze a thin conductive layer (instead of a bulk sample)? Are the length and width of the Ni film much larger than the spacing between the probes? Are you sure of the thickness?

You could also confirm the current and voltage with a multimeter. In fact, a four-point-probe measurement is quite easy to do yourself; the only advantage of the tool is the precise spacing of the probes.

Are you familiar with the equation used to turn current, voltage, and geometry into sheet resistance? See http://www.ecse.rpi.edu/~schubert/Course-Teaching-modules/A37-Four-point-probe-measurement-of-semiconductor-sheet-resistance.pdf" , for example.
 
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  • #3
Could it be that your film is actually much thicker?

Have you measured at smaller currents and established linearity?

I don't see an error in your logic. The film resistivity for 500nm should be pretty close to the bulk value... possibly a little bigger.
 
  • #4
Hi Mapes,

Thank you for your answer. I am quite sure of the thickness although I did not check it out after the deposition process but it was deposited with magnetron sputter equipped with a thickness monitor. The thickness monitor is healty and calibrated. So I am sure it is 500 nm. I checked the linearity of the resistance by using different currents. The current value I used is the current value where I could get stable voltage and sheet resistance.
 
  • #5
Then I think a useful next step is to try the measurement yourself: hold four electrodes in contact with the sample (perhaps with a friend to help) and apply current, measure voltage, apply equation. Also, use a multimeter to confirm what your prober is doing. Finally, check the prober manual to see if you've set it up right. Good luck!
 

1. How does a four point probe measurement work?

A four point probe measurement is a technique used to measure the resistivity or conductivity of a material. It involves passing a small current through four evenly spaced probes onto the material's surface, and measuring the voltage drop between the inner two probes. This voltage drop is then used to calculate the resistivity of the material.

2. Why is four point probe measurement important in the study of materials?

Four point probe measurement is important because it allows for accurate and precise measurements of a material's resistivity or conductivity. This information can provide insights into the material's electrical and structural properties, which is crucial in the development and improvement of electronic devices and materials.

3. What is the significance of the 500 nm Ni coating in four point probe measurement?

The 500 nm Ni coating is important because it serves as the material being measured in the four point probe technique. It is a relatively thin coating, which allows for a more accurate measurement of the material's resistivity. Additionally, nickel is a commonly used material in various electronic applications, making it a relevant material to study using this technique.

4. How can one interpret the results of a four point probe measurement?

The results of a four point probe measurement can be interpreted in terms of the resistivity or conductivity of the material being measured. A lower resistivity value indicates a higher conductivity, while a higher resistivity value indicates a lower conductivity. These values can then be compared to known values for similar materials or used to determine the effectiveness of a specific material for a desired application.

5. Are there any limitations to four point probe measurement?

Yes, there are some limitations to four point probe measurement. One limitation is that it can only measure the resistivity or conductivity of a material in a specific direction, which may not be representative of the material's overall properties. Additionally, the technique is most accurate for homogenous materials and may not provide accurate results for materials with varying compositions or structures.

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