Conductivity of individual particles measured by a microscopic four-point-probe method

We introduce a technique for measuring the conductivity of individual hybrid metal, semiconducting core-shell and full-metal conducting particles by a microscopic four-point probe (μ-4PP) method. The four-point probe geometry allows for minimizing contact resistances between electrodes and particles. By using a focused ion beam we fabricate platinum nanoleads between four microelectrodes on a silicon chip and an individual particle, and determine the particle's conductivity via sensitive current and voltage measurements. Up to sixteen particles can be taken up by each chip, which allows for multiple conductivity measurements by simply multiplexing the electric contacts connected to a multimeter. Although, for demonstration, we used full Au (conducting) and Ag-coated latex particles (semiconducting) of a few micrometers in diameter, the method can be applied to other types of conducting or semiconducting particles of different diameters.