Piezoresistive Properties of Reduced Strontium Titanate

Abstract

The piezoresistance effect has been investigated in reduced single-crystal strontium titanate in the temperature range from 4.2 to 296°K. At 296°K, the elastoresistance coefficients ($m_{11}-m_{12}$), $m_{44}$, and ($m_{11}+2\mathrm{}{m}_{12}$) have been evaluated in samples having a wide range of electron concentrations. The piezoresistance results indicate that the conduction-band edge consists of two types of energy minima separated by several hundreths of an eV with the minimum at $k=0\mathrm{}$ being the lowest in energy. Below approximately 110°K, the piezoresistance effect becomes very anisotropic and for certain crystallographic directions, a saturation of the piezoresistance is observed at stress values between 1×${10}^8$ and 2×${10}^8$ dyn/${\mathrm{cm}}^2$. The low-temperature piezoresistive properties appear to be a result of the cubic-to-tetragonal phase transition and it is postulated that these effects are due to a stress-induced alignment of the tetragonal domains.