Piezoresistive Microcantilevers From

Abstract—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 un-doped 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 temper-ature. The piezoresistive properties of UNCD are constant over the temperature range of 25 ◦C–200 ◦C. Microcantilevers having a length of 300 µm 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. [2010-0020] Index Terms—Diamond, microcantilever, piezoresistivity. I