Temperature-dependent mechanical and electrical properties of boron-doped piezoresistive nanocantilevers

In this paper, the temperature-dependent mechanical and electrical properties of boron-doped silicon piezoresistive nanocantilevers are reported. The surfaces of the 100 nm thick nanocantilevers are doped with boron using a spin-on diffusion method and fabricated using nano-machining technology. The frequency responses of piezoresistive nanocantilevers at room temperature are measured by both optical detection and piezoresistive detection methods. Reduction of the temperature leads to an increase in the resonant frequency and the Q factor. The temperature coefficient of the resonant frequency is found to be as high as 210 ppm K^-1 in the range of 140-240 K. The high temperature coefficient compared to that of single crystal silicon cantilevers originates from the residual stress after boron doping. The increase in the Q factor by decreasing the temperature is considered to be due to some surface dissipation mechanisms. A maximum value for the longitudinal piezoresistance coefficient is observed in the range of 80-90 K, whilst it was considered that the piezoresistive coefficient increases monotonically with decreasing temperature.