LOW-TEMPERATURE PROPERTIES OF RuO2-BASED RESISTORS

Abstract

Thick film RuO2 -glass resistors were studied. They were laboratory made, so their composition is well known. The measurements of resistance and 1/f excess noise as a function of temperature in the range of 30 mK - 300 K were performed. Also as a function of magnetic field in the range 0 – 5 T. The RuO2 -glass resistors can be used as a cryogenic temperature sensors due to their high sensitivity and low magnetoresistance. A comparison of these parameters with the parameters of commercial sensors shows that they are the same class instruments. The resistors studied exhibit a large increase of excess noise level in the range of cryogenic temperatures, thus the temperature measurement resolution is limited. The noise measurements allowed to determine the actual measurement resolution of resistive temperature sensors. A critical analysis of conduction mechanisms frequently used to describe RuO2 resistors has also been performed. Measurements of temperature dependence of resistance allow to reject variable range hopping conductivity model for this type of resistors. On the other hand, the noise measurements give a good agreement with a theory within this model of conductivity. For the samples studied in the work a critical concentration of the metallic component in the resistive layer has been defined at which the metal-insulator transition occurs.