The Kelvin Probe system allows to precisely measure the Contact Potential Difference (CPD) and to determine the Work Function of conducting and semiconducting material.
The non-contact technique of CPD measurements employs the Probe Tip-oscillating reference electrode made of a golden mesh. The examined sample serves as the second electrode in the circuit. The Work Function value is evaluated indirectly from the measured CPD of the sample referenced to the gold tip.
The Kelvin Probe system may be used in various types of studies of the material surfaces such as: corrosion and photocorrosion process, adsorption/desorption, surface charging, catalytic activity and others. Subsequent CPD measurements in adjustable time intervals allows to monitor the changes in real time. The measurement method is accurate for many types of samples: organic and inorganic semiconductors, solar cells, photoactive materials. During the measurement, the instrument is covered with the Faraday Cage to screen the ambient light and electromagnetic fields.
The Kelvin Probe set consists of:
The Kelvin Probe instrument is equipped with:
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The most important part of the Kelvin Probe instrument is the Probe Tip. The reference electrode is made of Au mesh of 2.5 mm diameter. It provides high signal to noise ratio, even from a distance of 0.5 mm above the sample. Thus, it does not matter if the examined sample surface is rough or polished. The tip oscillations are generated with an electromagnet.
The Probe Tip is the component fully designed and manufactured by Instytut Fotonowy Sp. z o.o.
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The standard Kelvin Probe Set includes two types of sample stands:
The entire instrument is covered with the Faraday Cage, shielding the setup from the ambient light and electromagentic fields.
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Scince measurements of the CPD is often sensitive to environmental factors like temperature, humidity, dust and chemical contaminants, Kelvin Probe may be placed inside the hermetic version of the Faraday Cage with the inert gas flow system.
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The Kelvin Probe is equipped with the Laser barrier system. System automatically detects the sample sub-
strate. Each time the probe approaches the sample being examined, an accurate distance between the sample surface and the Probe Tip is measured with 20 µm precision.
The sample may be illuminated during the measurements from the optical fiber situated above the Probe Tip. The Probe Tip lets the light through. The light at optical fiber input may be provided by the LED Revolver, Xenon Lamp combined with the Monochromator or any other type of the light source desired.
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CPD values recorded for a Photodiode. The plot represents the response for a saw tooth type light intensity modulation.
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