Apparatus for Measurement of Piezoresistivity of Low Resistivity Materials

Publisher Website
Google Scholar
Abstract
This paper describes a highly sensitive system which has been used to measure seven of the eight independent components of the piezoresistivity tensor of bismuth. The apparatus employs a 35 Hz alternating stress with dc applied to the sample, and is capable of resolving piezoresistive voltages as small as 1 nV. The increased sensitivity, which is required for low resistivity materials, is obtained primarily by the suppression of noise. The signal‐to‐noise ratio was improved by a balanced connection of sample voltage directly to a low noise stepup transformer which was followed successively by a bandpass preamplifier, 60 Hz rejection filter, selective amplification, and phase detection at 35 Hz. Although common mode 35 Hz noise was reduced by the balanced configuration, further suppression was possible by active cancellation using a phase balanced bridge prior to the selective amplifier. The sensitivity achieved makes this system useful for precise piezoresistivity measurements on materials with resistivities as low as 10 μΩ cm.

This publication has 5 references indexed in Scilit: