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

The piezoresistive effect of p-type crystalline materials under uniaxial st ress was analyzed by the deformation-potential theory and the valence-bands split-off model. The calculation formula of the gauge factor under the con dition 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 b etween 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 p iezoresistive effect of the p-type polycrystalline material was also discus sed from the Mayadas-Shatzkes model. The results showed that the piezoresis tive effect of polycrystalline materials is related to both the valence-ban ds split off and the grain-boundary scattering. The grain-boundary scatteri ng played a role of decreasing the piezoresistive effect, which made the po lycrystalline materials have a smaller gauge factor than the crystalline ma terials. (C) 1999 American Institute of Physics. [S0021- 8979(99)02021-6].