UHV

The mounting flange for the non-scanning probe is DN40 (CF2.75 inch OD) and CF64, CF100 for our SKP systems. The UHV head stage features a voice coil actuator and user defined flange-to-sample spacing. Please note that our standard tip sizes are 4-8mm diameter and you would achieve 1-3 meV resolution with such tips.
The standard head unit is designed for normal geometry, i.e.; the insertion port is at 90o to the sample plane. The quoted voltage resolution for a 4-8mm diameter tip is 1-3 meV: this is the highest resolution of any commercially available Kelvin probe on the market and sub mV resolution is achievable with the larger tip sizes. Note the actual work function resolution will depend upon the electrical and mechanical noise in the vicinity of the measurement cell.
Some customers monitor the work function change as a function of system pressure or substrate temperature. Accordingly the system software package allows for these other parameters to be recorded using an additional input channel and plotted against the change in work function. This is a digital system the Kelvin Probe frequency, amplitude of oscillation, mean spacing, backing potential and data acquisition parameters can be set by the user.
Further this is an off-null system; i.e. the work function is calculated using two or more signal peak-to-peak measurements performed at backing potentials on either side of balance. Thus the actual Kelvin Probe signal is visible at all times during measurement. In contrast, null-based detection systems require a phase sensitive detector and the Kelvin Probe signal is nulled throughout.