Excess Noise in Thick Film Resistors: Volume Dependence

An investigation of the excess noise in thick film resistors as a function of the sample volume Ω has been performed. The results obtained on two different resistive series, based on bismuth ruthenate and ruthenium dioxide respectively, make clear that the excess noise follows an inverse relationship with Ω (and thus the slope of NI vs log Ω plots is equal to -10, NI being the noise index). Previously observed deviations from this behaviour are ascribed to inhomogeneity of composition in the resistive film, resulting from its interactions with the substrate and/or the terminations, as well as in changes of the resistors' thickness.