The non-contact measurement involves oscillating capacitor, one electrode of which is a specimen, the other is oscillating reference electrode made of gold grid. Thus, measured value is referenced to the workfunction of gold (5.1 eV). Resolution of the measurement can reach 0.1 meV with sufficiently long integration time. The Kelvin probe system can be used in various type of surface studies, including: corrosion, adsorption/desorption, surface charging, catalytic activity and others.
For convenience, the probe is equipped with laser pointer and digital microscope. The motorized vertical positioning system allows reproducible of the reference electrode at the same distance from the specimen’s surface (with accuracy of 10 um). X-Y positioning can be installed as an option. The system is also equipped with wide-band light guide that can be coupled with digitally-controlled monochromator and high pressure xenon arc lamp. The wavelength range from 300 to 1000 nm can be used for continuous or pulsed sample illumination. This configuration allows measurement of the workfunction and electrical charging of surfaces, surface photovoltage spectroscopy and other photophysical techniques with photovoltage resolution better than 5 mV (0.1 mV when long integration time is applied). The whole system is accommodated in grounded Faraday cage for reduction of electrical noise and the influence of stray light. This surface photovoltage spectrometer is an essential tool in investigation of photocatalysts, organic and inorganic semiconductors, solar cells and other photoactive materials and devices. With the help of this Kelvin probe/surface photovoltage spectrometer monitoring of photocorrosion of semiconductors, photodesorption and photocatalytic reactions in real time is also possible.
