A General Method to Accurately Measure the Thin-Film Sheet Resistance for Sensors

The sheet resistance is one of the essential properties of thin-films, and the change of it under different conditions is the basis of various sensor designs. However, the contact resistances between the thin-film materials and the metal electrodes can seriously affect the sensing accuracy. Due to various material properties, the contact resistances are usually difficult to be managed or reduced, and even nonlinear Schottky barriers can form in some cases. A modified four-terminal method is proposed to eliminate the impact of the contact resistances through simple resistance measurements and algebraic calculations, which can be easily integrated into sensors and accurately measure the sheet resistances/resistivities of thin films of different materials under different conditions. The carbon black/polydimethylsiloxane (CB/PDMS) thin film is taken as an example for demonstration of the method. The applications for pressure-sensitive and temperature-sensitive resistance measurement are also demonstrated.