Study on the piezoresistive effect of crystalline and polycrystalline diamond under uniaxial strains

The piezoresistive effect of p-type crystalline materials under uniaxial stress was analyzed by the deformation-potential theory and the valence-bands split-off model. The calculation formula of the gauge factor under the condition of the strain-induced separation of the heavy- and light-hole bands was obtained. It is found that the great difference of the effective mass between the heavy and light hole in diamond is one of the main factors which are responsible for the piezoresistive effect in the p-type diamond. The piezoresistive effect of the p-type polycrystalline material was also discussed from the Mayadas–Shatzkes model. The results showed that the piezoresistive effect of polycrystalline materials is related to both the valence-bands split off and the grain-boundary scattering. The grain-boundary scattering played a role of decreasing the piezoresistive effect, which made the polycrystalline materials have a smaller gauge factor than the crystalline materials.