Scanning Kelvin Probe to investigate electrical surface states of the sample

Dedicated to measure electron work function of the semiconductor sample surface.


The Scanning Kelvin Probe allows to measure CPD (Contact Potential Difference) value and evaluate a work function of  semiconducting and conducting materials. The measurements may be performed not only in a single point of a sample surface but the whole surface may be scanned.

Measurements of work function is particularly useful in semiconductor physics as it provides the position of Fermi level of examined material.

The Kelvin Probe equipped with the light source makes it possible to examine  surface states of electrons of the sample. Surface states of electrons play significant role in the electric charge transfer,  which is especially important for photovoltaic materials and in photoelectrochemistry.

Possibility of scanning the sample surface and to examine its electrical properties enables precise assessment of the quality of the material, and its homogeneity.  The series of data gathered during the experiment may be used to evaluate work function more precisely.

Electrostatic Voltmeter

Scanning Kelvin Probe allows to specify the electrostatic charge distribution on the examined sample surface – including dielectrics! (up to several kV). The measurement method applied and the design of the instrument makes the instrument unique and peerless in testing charged dielectric surfaces. The system enables to specify the electrostatic charge (up to several kV!) distribution on the sample surface.


kelvin probe modules

The instrument consists of the probe on the stand, the electronic control system and the Faraday’s cage.


  • The sample is located on the XY table, on one of the two provided stands. Motorized table enables to move the sample in range of 5 cm in both: X and Y directions.
  • Each time the probe approaches the sample being examined, an accurate distance between the sample surface and the probe is measured with 50 µm precision. In the method applied, the vertical axis precision is not important for the determination of work function.
  • The probe is equipped with a laser pointer that illuminates a spot the probe will hoover above during measuremnt.
  • The light source helps see the sample under the Faraday cage.
  • Above the probe, the optical fiber adapter is mounted. The optical fiber allows to illuminate the sample with light from a monochromator or from a LED revolver.
  • During a sample handling, the probe is hidden under a metal cover which prevents the probe from being accidentally damaged.


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The probe tip

The probe tip is the component fully designed and manufactured by Instytut Fotonowy Sp. z o.o. It provides:

  • Large signal even from a distance of 0.5 mm above the sample. Thus it does not matter if the sample surface is rough or polished.
  • Transparency that lets the light through. This way the sample can be illuminated by a perpendicular light beam.

The tip oscillations are generated with an electromagnet.

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Sample holders

The Kelvin Probe set includes two types of sample stands:

  • for thin film samples

  • for freely shaped solid state samples

Faraday Cage

The whole measurement instrument is covered with Faraday cage which shields the system from the surroundings. The grounding socket is situated on the cage.

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The following specification may be changed in terms of further process of appliance development.


Voltage range-5 V .. 5 V
Voltage measurement nominal resolution0.15 mV
Measurement technology2-channel lock-in amplifier
Sample holdermotorized translation stage X-Y,
Sample standstand for sample layer/ stand for solid state sample
Range of stage movement5 cm x 5 cm
Min sample move step1 µm
Tip typeAu, mesh, dia. 2.5 mm
Tip Z positioningmotorized Z stage
Positioning with respect to a samplelight barrier
Tip Z positioning resolution10 µm
Spectral range for wave guides200 nm .. 2000 nm (depending on a waveguide)
Liquid waveguides selection (Lumatec)Wybór światłowodów Lumatec
Auxiliary sensorshumidity and temperature
Internal Faraday cage illuminationwhite LED
X-Y positioning aidlaser sample placement indicator
PC connectivityUSB 2.0
Size40 x 40 x 45 cm
Weight10 kg

Exemplary results

Aluminium surface

Distribution of the electric potential on the sample surface:

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Ambient temperature during measurement:

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Air humidity during measurement:

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Metal surface sample with periodic holes

Evaluated CPD values on surface:

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Preview during ongoing measurement

Distribution of the electric potential on the sample surface:

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Ambient temperature during ongoing measurement:

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Air humidity during ongoing measurement:

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Charge distribution on the dielectric surface

PTFE on alluminium foil – Electric potential from the surface charge of the sample

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    Zgodnie z przepisami Ustawy z dnia 29 sierpnia 1997 r. o ochronie danych osobowych wyrażam zgodę na przetwarzanie moich danych osobowych przez Instytut Fotonowy Sp. z o.o. dla potrzeb kontaktu w sprawie oferowanych usług.

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