Fluctuating phenomena in resistive materials and devices

Abstract

Noise properties of thick-film resistors made of various resistive and conductive materials, including Pb-rich and Pb/Cd-free, have been studied. Power spectral density of voltage fluctuations has been measured using different methods which have been described and discussed, including ac and dc bridge configuration, cross-correlation technique and low-frequency noise spectroscopy (LFNS). In temperature range from 0.3 up to 350 K, for all studied samples 1/f noise resulting from resistance fluctuations has been found to be dominated noise component. Using LFNS thermally activated noise sources (TANSs) have been detected. Their interesting properties have been described and activation energies of TANSs have been extracted, which occurred to be below 1eV. Second spectra analysis has been applied revealing non-Gaussian noise components in 1/f noise. On the other hand, it has been found that noise intensity in TFRs, including devices designed for temperature sensing, increases rapidly when temperature drops below a few K. Model of conduction transport, involving hopping mechanism and electro-thermal feedback, has been used for explanation of noise suppression by excitation power, what was observed in temperatures below 1K, in the framework of inhomogeneous heating. Integral measure of noise has been introduced which was then used for qualitatively description of bulk noise generated by resistive layer and noise of contacts. Detailed comparison of material noise intensities obtained for various resistive materials has been shown. Conclusions concerning TFRs optimization with respect to noise have been given. Compatibility criteria for materials used for thick-film technology have been formulated and systems of compatible materials have been evaluated. The conclusions might be useful in further improvement of materials systems for thick-film technology in order to fabricate low-noise, reliable and stable resistors.