Four point probe manual

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Related Audiobooks Free with a 30 day trial from Scribd. Elizabeth Howell. Parameters such as film thickness, sheet resistance, and bulk resistivity can be evaluated using the Four-Point Probe. Equal to m Substrate The material of which something is made. In this case, a Si wafer or glass slide. Wafer A thin slice of semiconductor such as silicon used as a base for an electronic component, or substrate.

The schematic representation of the Four-Point Probe is shown in Figure 1. The theory behind this is a fixed current is injected into the wafer through the two outer probes, and a voltage is measured between the two inner probes.

The approximation used in the above equations is easily met for shallow layers in silicon. Figure 1 — Four-Point Probe schematic left and actual right. The probes must be able to make ohmic contact with the material. Gallium Arsenide cannot be probed with this particular model. To ensure you are getting the most accurate results possible, please allow 30 minutes for the system to warm up before taking measurements.

Place the sample onto the vertical translation sample stage, ensuring that is it centred beneath probes. For rectangular samples, the longer edge should be aligned parallel to the probes. Using the micrometer, raise the stage to make contact between the probes and the sample.

When the probes have retracted most of the way into their casing, there should be good contact with the sample. If the probes are not in contact with the centre of the sample, the sample should be repositioned before performing the measurement.

Do not attempt to reposition the sample whilst the probes are in contact, as this may cause damage to both the sample and the probes themselves. First, lower the stage so that contact is broken, then reposition the sample and re-establish contact. Start up the Ossila Sheet Resistance Lite software and wait for the window to open. Set the geometry for the sample in the software. This must be provided so that the appropriate geometric correction factor can be calculated. Correction factors account for increased resistances that will be measured for samples with dimensions lower than 40 times the probe spacing These larger resistances arise from the limitation of current pathways when the probes are close to boundaries.

However, samples thicker than this require additional correction factors , so the thickness must be entered to ensure accurate measurements. The system will attempt to pass a current through the sample between the outer probes, starting with the highest current range and working downwards if a stable current cannot be achieved.

Once a stable current has been achieved the software will measure the voltage between the inner probes and use it along with the outer probe current and geometric correction factors to calculate the sheet resistance and display it in the software.

If the sample thickness is provided, then the average resistivity and conductivity will also be displayed. If the system cannot apply a current between the outer probes the measurement will stop with a warning. While the measurement is running, the data can be saved. Choose how many measurements you want to save in the 'Readings to Save' box, then click the save icon. You will be prompted to choose a directory and save file name.

The software will save the specified number of measurements to a comma-separated value. The mean and standard deviation of the sheet resistance and resistivity and conductivity if a thickness is provided is also saved below the raw data. An example data file is shown below in Figure 5. This guide is intended for those who have used the Four-Point Probe System previously and need a reminder on the steps involved in a measurement.

By clicking the 'Use Advanced Settings' check box you can access some advanced features of the software, as well as see the voltage and current between the outer probes, and the voltage between the inner probes.

For a more in-depth explanation, please see our application note: Sheet Resistance Measurements of Thin Films. As the system measures the sheet resistance of a sample, a general range of measurable resistivities or conductivities cannot be given. This is because the measurable resistivity range depends on the thickness of the sample being tested.

The resistivity of a sample can be calculated from its sheet resistance and thickness using the following equation:. Below is a table of the resistivity and conductivity ranges of the system for samples with thicknesses of different orders of magnitude:. Currently we offer a single probe layout, i. This allows us to maintain the affordable price of the Four-Point Probe System, whilst still providing reliable and accurate measurements of sheet resistance.

The result of this equation must further be multiplied by a geometric correction factor based upon the shape, size, and thickness of the sample. This accounts for limitations to the possible current pathways through the sample, which affects the values that are measured. A more in-depth explanation of the theory behind sheet resistance, geometric correction factors, and the four-point probe technique can be found in our Guide to Sheet Resistance Theory.

This guide explains the theory behind sheet resistance, an electrical property of thin films of materials, and demonstrates how the four-probe method can be used to measure it. This guide gives an overview of how to use the Ossila Four-Point Probe System, as well as some general tips and tricks for measuring sheet resistance. Sheet resistance or surface resistivity is an important property of many materials, quantifying the ability for charge to travel along uniform thin films.

These resources cover the underpinning theory behind our products and their intended applications. An intuitive and user-friendly standalone PC program is used to control the four-point probe measurement, enabling rapid characterisation of materials without the need for the user to write any code themselves.

This PC software calculates appropriate geometrical correction factors for the given sample geometry, ensuring accurate results. It can also calculate the resistivity and conductivity of the sample, if the thickness is provided, to allow for extensive electrical characterisation of materials. The software saves data to comma-separated value.

Advanced settings give you greater control over the measurment, allowing you to set voltage and current limits, perform negative polarity measurements, or use probes with different spacings. To the best of our knowledge the information provided here is accurate.

However, Ossila assume no liability for the accuracy of this page. The values provided are typical at the time of manufacture and may vary over time and from batch to batch. All products are for laboratory and research and development use only, and may not be used for any other purpose including health care, pharmaceuticals, cosmetics, food or commercial applications.

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Four-Point Probe Software Manual. VAT click to shop in. Quality assured. Ossila Sheet Resistance Lite 1. Quick and accurate characterisation for a wide range of materials Experience effortless sheet resistance measurements with the system's easy-to-use PC software Overview Specifications Software Part of the Institute of Physics award-winning Ossila Solar Cell Prototyping Platform , the Ossila Four-Point Probe System is an easy-to-use tool for the rapid measurement of sheet resistance, resistivity, and conductivity of materials.