Piezoresistivity in vapor-deposited diamond films

We report the observation of a very large piezoresistive effect in both polycrystalline and homoepitaxial chemical-vapor-deposited diamond films. The gauge factor for polycrystalline p-type diamond at 500 microstrains was found to be only 6 at room ambient, but increased rapidly with temperature, exceeding that of polycrystalline silicon (30) at 35 ‘C, and that of single-crystal Si (120) at 50 “C!. For strain and current flow in the [loo] direction, the gauge factor of a ( lOO)-oriented homoepitaxial diamond film was found to be at least 550 at room temperature. Although the origins and unexpected temperature dependence of piezoresistive effect in diamond are not yet understood, these findings may suggest diamond-based sensors with performance significantly superior to that of their Si counterparts.