Very high frequency (VHF) self-sensing nanoscale cantilevers and their mass sensing applications in ambient conditions.

We report the development a new class of self-sensing, nanometer-scale cantilevers with fundamental-mode mechanical resonances up to very high frequencies (VHF). The sensors employ integrated piezoresistive displacement transducers; we show that, at the nanoscale, these are optimally realized using thin, metallic-density films. Our approach enables detection of VHF cantilever vibrations, to date as high as 127 MHz, at the thermomechanical noise limit. Displacement sensitivity of 39 fm/Hz$^{1/2}$ and extremely low 1/f noise are attained. Our smallest devices have lateral dimensions approaching the mean free path at atmospheric pressure; hence their high quality factors are preserved in ambient. Measurements of molecular chemisorption onto polymer-coated nanocantilevers yield unprecedented mass resolution below 1 attogram (10$^{-18}$ g) level at atmospheric pressure and room temperature.