Van der Pauw method

The van der Pauw Method is a technique commonly used to measure the resistivity and the Hall coefficient of a sample. Its strength lies in its ability to accurately measure the properties of a sample of any arbitrary shape, as long as the sample is approximately two-dimensional (i.e. it is much thinner than it is wide), solid (no holes), and the electrodes are placed on its perimeter. The van der Pauw method employs a four-point probe placed around the perimeter of the sample, in contrast to the linear four point probe: this allows the van der Pauw method to provide an average resistivity of the sample, whereas a linear array provides the resistivity in the sensing direction. This difference becomes important for anisotropic materials, which can be properly measured using the Montgomery Method, an extension of the van der Pauw Method (see, for instance, reference). From the measurements made, the following properties of the material can be calculated: The resistivity of the material The doping type (i.e. whether it is a P-type or N-type material) The sheet carrier density of the majority carrier (the number of majority carriers per unit area). From this the charge density and doping level can be found The mobility of the majority carrier The method was first propounded by Leo J. van der Pauw in 1958.