The Kelvin Probe can measure contactless the work function of the material. The measurements are based on a changing the capacitance, the one plate of the capacitance is the surface of the sample; the other plate is the Kelvin probe itself. The Kelvin probe plate is vibrating modulating the capacitance. If there is the potential difference between sample and probe, AC current flowing through capacitance. Changing DC potential of vibrating plate allows compensating AC current. In the compensating condition the applied DC voltage directly gives the surface potential of the material and by scanning the surface with the Kelvin Probe the surface potential distribution can be extracted. Because surface potential depends on chemical environment, it can be used for measurement the chemical response of the sample material. High temperature Kelvin scanner together with gas system was designed for developing new materials for the gas sensing application. The main idea is collecting the chemical image from the large area sample, which is coated with the areas with the different sensing materials. Because Kelvin method is non-contact it is possible to acquire the gas response from many different sensing materials in one time and without device bonding. Kelvin scanner was designed together with Semilab inc. Hungary and was assembled on Semilab's facilities. System allows to acquire the chemical image from the sample up to 100*100mm in the controllable gas atmosphere at temperature range 20-450oC. Those parameters together were not reached by any other installation for this application. In Fig.1 the surface potential map of Si sample coated by Au and particularly Pt is shown. Rectangular figure on the image corresponds the area coated by Pt.

Kelvin map of Pt 15x 30 mm rectangular pattern on Au surface.

Gas system for Kelvin scanner consists from 2 separate parts: One generates gas mixture from compounds, which are in liquid phase at room temperature. Airflow goes through evaporator where liquid injected by motorized syringe. Gas concentration is determined by injection speed. Special humidity generator controls humidity. Another part of gas system for compounds, which are in gas phase at room temperature. It is computer-controlled system, which can operate in wide range of gas concentration. All necessary safety equipment makes it compatible with aggressive gases (COCl2, HCN), which can be interesting for development sensor materials for wide range of industrial application.