Piezoresistive microcantilevers from ultrananocrystalline diamond

This paper reports on the temperature-dependent electrical resistivity and piezoresistive characteristics of boron-doped ultrananocyrstalline diamond (UNCD) and the fabrication of piezoresistive microcantilevers using boron-doped and undoped UNCD. The devices consist of 1-μm} -thick doped UNCD on either 1- or 2-μm}-thick undoped UNCD. The electrical resistivity of doped UNCD is 0.1 Ω ̇ cm at room temperature, which is five orders of magnitude smaller than the electrical resistivity of undoped UNCD. Over the temperature range of 25 ° C-200° C, the doped UNCD has a temperature coefficient of electrical resistance of (-1.4 × 10^-3) per ° C. The doped UNCD exhibits a significant piezoresistive effect with a gauge factor of 7.53 ± 0.32 and a piezoresistive coefficient of 8.12 × 10^-12\ Pa^-1 at room temperature. The piezoresistive properties of UNCD are constant over the temperature range of 25 ° C-200° C. Microcantilevers having a length of 300μ have a deflection sensitivity of 0.186 mΩ/Ω per micrometer of cantilever end deflection. These measurements of electrical and piezoresistive properties of doped UNCD could aid the design of future diamond microsystems.