nelipistetutkimusta

Nelipistetutkimusta, a Finnish term, translates to "four-point measurement" or "four-probe measurement" in English. This is a fundamental experimental technique widely used in condensed matter physics and materials science for determining the electrical resistivity of a material. The method is particularly advantageous for thin films and bulk samples where direct contact with electrodes can alter the material's properties or be technically difficult.

The core principle of nelipistetutkimusta involves using four equally spaced probes arranged linearly. Two outer probes are used to pass a known current through the sample, while two inner probes measure the resulting voltage drop across a specific section of the material. By applying Ohm's Law (V=IR) and accounting for geometric factors, the resistivity can be calculated. The key advantage of this configuration is that the contact resistance at the probes, which can be significant and variable, does not affect the voltage measurement. This is because the voltage is measured between the two inner probes, and ideally, no current flows through the voltmeter.

This technique allows for non-destructive measurements and provides accurate resistivity values even for materials with high contact resistances. It is essential for characterizing semiconductor wafers, thin-film coatings, and various conductive or semiconductive materials in research and industrial quality control. The spacing of the probes and the geometry of the sample are crucial parameters that must be considered when calculating the resistivity from the measured current and voltage.