Self-Assembled Molecular Junction Bolometers for Mid Infrared Detection*

A tremendous 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 a suspended metal/self-assembled monolayer (SAM)/metal nanostructure to implement such a mechanically tunable tunneling barrier and use it as an ultra-sensitive bolometric mid-infrared (IR) detector. Fabricated proof-of-concept metal/SAM/metal bolometers yield a temperature coefficient of resistance (TCR) of up to 0.2 K^-1, and theoretical predictions show that with further optimization the TCRs could be improved to as much as 5 K^-1, which is more than one order of magnitude better than the state-of-the-art VO_x bolometers. Strain, transport, noise and mid-IR scanning photocurrent microscopy measurements are performed to show the full functionality of the devices.