10–25 NM piezoelectric nano-actuators and NEMS switches for millivolt computational logic

This paper reports, for the first time, on the design, fabrication, and measurement of piezoelectric nano-actuators and novel stress-compensating NEMS switches based on 10-25 nm thick aluminum nitride (AlN) films. These ultrathin, highly c-axis oriented, and low-stress AlN films were synthesized over very thin platinum layers using reactive sputtering. The extracted d₃₁ piezoelectric coefficients are -1.73 pC/N and -1.77 pC/N for the 10 nm and 25 nm films, respectively (90% and 92% of their microscale counterpart). Thanks to the scaling of the piezoelectric film thickness and the proposed switch design, the switch exhibits a threshold voltage of 0.2 mV and a subthreshold slope of 0.033 mV/decade - the smallest ever reported for a mechanical transistor. Overall, the NEM relay exhibits a switching energy of ~ 0.01 aJ, making it a very promising candidate for ultra-low power digital computing and memory applications.