Computational Study of a:SiC:H Thin Films Deposited on Interdigitated Microelectrodes Using Electrical Impedance Spectroscopy

This work presents the development of a 3D model in COMSOL Multiphysics® for fast study of thin films deposited on interdigitated microelectrodes (IMEs). A reduction in computation time is achieved by simulating only one micrometric piece of the total IME array. The measurement technique was electrical impedance spectroscopy. Hydrogenated amorphous silicon-carbon (a-SiC:H) was selected as a material under study. The electrical conductivity, thickness, and surface topology of the films were varied to know their effects on the corresponding electrical impedance spectra. According to the results, the deposition of the a-SiC:H thin film on the IMEs generates a plateau in the Bode graph at intermediate frequencies, whose impedance is reduced subsequently in frequency by its own capacitive effect. The thickness of the film impacts both on the impedance magnitude of the plateau and on the value of the capacitance associated to the film. The surface topology was modified removing rectangular blocks from the inwards surface of the films. The effects of this modification were inverse with respect to that obtained with the increase in thickness. This 3D model could be used to correlate changes in impedance with the progressive dissolution of films immersed in biological fluids or define design parameters in sensors and biosensors that uses this type of structures.