When working with SKP probes of small diameter it is important to keep in mind that the fringing effect can be detrimental to the lateral resolution possible from these probes. Smaller probe diameters are more susceptible to fringing effects than larger probes. The probe diameter is also known to influence the fringing in the SKP measurement. Therefore, working at the smallest practical probe to sample distance, typically 100 µm, and maintaining this distance throughout the measurement, reduces the fringe effect and improves the SKP measurement quality. the probe and the sample, the fringe effect is reduced, Fig. With the decreasing distance between the capacitor electrodes, e.g. When the fringing effect is large, relative to the probe size, the lateral resolution of SKP can be reduced, and therefore efforts should be taken to minimize fringing for the highest quality measurements. The extension of the electric field beyond the edge of the plane of the SKP probe means regions beyond those directly below the probe tip will influence the signal measured in SKP. The dashed lines represent the electric field between the electrodes.įringing can have a significant effect on the SKP measurement. įigure 2: The fringing effect between two electrodes of finite, unequal length, as is the case for an In an SKP experiment, the capacitor electrodes are unequal in length, with the probe typically much smaller than the sample electrode, giving rise to a significant fringing effect as illustrated in Fig. 1 illustrates the fringing effect when the electrodes of a capacitor are equal, or similar, in length, this is not the case in SKP. The dashed lines represent the electric field between the electrodes. Note this is a simplified illustration showing the fringing only of the parallel surfaces as would occur at the SKP probe where care is taken to stop the electric field at the sides of the probe.įigure 1: The fringing effect between two electrodes of finite, and equal length is illustrated. Fringing at a parallel plate capacitor is illustrated in Fig. It is this extension of the electric field beyond the edges of the electrodes which is referred to as fringing. At this point, the electric field can be seen to bend beyond the edges of the electrodes. Between the two electrodes, a uniform electric field exists, however, at the edges of the electrodes the field becomes non-uniform and extends out into the surrounding space. Understanding the fringing effect and its role in Scanning Kelvin Probe (SKP)įringing is a phenomenon that occurs for capacitors of finite length.

Fringe field effect