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. It is defined as the reciprocal of the resistance in ohms, measured between the opposing faces of 1 cm cube of liquid at a specific temperature.Understanding the fringing effect and its role in Scanning Kelvin Probe (SKP)įringing is a phenomenon that occurs for capacitors of finite length. This standard measure is referred to as specific conductance or conductivity. To have useful meaning for analytical purposes, a dimension needs to be given to the measurement i.e., the physical parameters of the measurement.īy defining the physical parameters of the measurement, a standard measure is created. As the two points move closer together or further apart, this value changes. The conductance of a liquid can be defined by its electrical properties – the ratio of current to voltage between any two points within the liquid. The flow of current through electrolytic conductors is accomplished by the movement of electric charges (positive and negative ions) when the liquid is under the influence of an electrical field. Liquids which carry an electric current are generally referred to as electrolytic conductors. The term Conductance refers to the readiness of materials to carry an electric current.

Fringe field effect