Environmental Chamber
The Kelvin probe is situated in an environmental chamber so that experiments may be carried out in a controlled atmosphere. The chamber is equipped with gas inlets and gas outlet so that gas atmosphere can be changed during the experiment. The electrolyte inside the chamber can be saturated with the gas of choice using a manipulator. The chamber is constructed so that it may be operated at the room temperature. However it may be also equipped with Peltier – Element for cooling a sample, with IR- LEDD`s for heating a sample and with temperature /humidity control circulation unit so that it may be operated in the range 5-40°C. In order to assure the electric contact of a sample with electronic devices outside of the chamber, special water proof feed through are installed on the chamber walls. The lights on the top and on the sample stage facilitate the sample observation. In order to increase the quality of the sample monitoring the chamber can be provided with a digital camera with a special macro zoom objective (6.5- times magnified). Chamber window is made from double glass (1mm) coated with transparent conducting film such as Indium Tin Oxide (ITO) so that the tip is shielded from interfering signals.
Kelvin Probe Head (Driving Element and highly integrated Signal Acquisition System)
Driving element of Kelvin probe head consist of double coil, vibrating axis with permanent magnet and the reference probe. Suspension static displacement allows to work without resonance, what guaranties very stable measurement parameter (amplitude, frequency) even if the ambient condition change (temperature, moisture, interfering signals). This system assures a precise and stable axial position of the probe and a very good linearity for DC/Coil controlled height regulation. Height control is achieved by a combination of the double magnetic coils and a stepping positioner on which the KP head assembly is mounted. Fine height control of the head is accomplished by adding a DC voltage to the AC coil voltage. If the DC voltage on the coils exceeds a set limit, the distance is compensated by stepping the positioner motor High accuracy of the height measurement- under 1µm. The first stage of the signal acquisition is carried out using the preamplifier, which is integrated with the vibrating system so that the distance between the tip and the preamplifier is extremely reduced. It reduces significantly the noise and the influence of the parasitic capacitance.
The high selectivity digital and analog filters system increases the dynamic of the Kelvin probe measurements.
Translation System
The 3-Axis translation system is made up of translation stages that are actuated by brushless DC motors. This system guaranties the high resolution (0.1µm), high accuracy and low noise performance. The scan size is up to 100mmx100mm.
Kelvin Probe Control and Data Acquisition
Completely integrated software is included with the system, which allows working with user friendly, intuitive graphical interface. A combination of LabVIEW- based user interfaces allows for the movement of translation stages, monitoring of instrument performance. For calibration of the Kelvin probe, as well as the Volta potential difference measurement and many other routine procedures a number of subprograms have been designed as a part of the user interface. This software allows performing the experiments with many samples. The Kelvin Probe is able to find automatically the start points for scans on different samples, if the points are defined by the user before the experiment list is activated. The software is also suited for the potentiostatic and potentiodynamic experiments. The software includes the built in tools for data acquisition, instrument control and measurement configuration.