Metal-nanogap-metal strain, temperature, and infrared sensors

A large mechanical sensitivity can be achieved by a mechanically tunable quantum tunneling barrier. The tunneling resistance across the nanometer-sized gap can be changed by several orders of magnitude through a sub-angstrom-scale displacement. Here, we demonstrate the performance of a strain sensor formed from pre-stretched Platinum (Pt) on PDMS, where perturbation of the thickness of the nanogap cracks due to strain change the resistance of the device. A gauge factor >500 is realized in a device that is mechanically stabilized by self-assembled monolayer (SAM). Then, we extend the application of the nanogap based strain sensor to temperature and infrared detection. Fabricated proof-of-concept metal/SAM/metal suspended bolometers yield a temperature coefficient of resistance (TCR) between -0.006 K^-1 and - 0.085 K^-1, and theoretical predictions show that with further optimization the TCRs could be improve to as much as -2.7 K^-1, which is more than one order of magnitude better than the state-of-the-art VO_x bolometers. Furthermore, this work quantifies the 50 Hz to 10 kHz noise performance of suspended metal/nanogap/metal bolometers and compares the noise spectrum of devices with and without SAM, as well as 10 nm Pt channel vs. 30 nm Pt channel devices. Finally, early stage 830 nm optical measurements show that the device sensitivity of a 10nm Pt / air nanogap / 10 nm Pt peaks at low bias (< 1V, <20 pA) and that the 3dB point of the sensor extends past 10 kHz. The experimental results of this work suggest that nanogap-based sensor architectures exhibit a high sensitivity and may also enable fast response time detectors.