Picowatt gas sensing and resistance switching in tunneling nano-gap electrodes

Functionalized engineered nanogap electrodes (pair of electrodes separated by a gap of a few nanometers) are utilized as tunneling chemoresistors for gas sensing and resistance switching at the molecular scale. The nanogap device consists of two gold electrodes vertically separated by a very thin spacer of 2 nm of α-Si and ~4 nm of dielectric (SiO
₂
or Al
₂
O
₃
). A ~10 nm wide sidewall air gap is formed by etching the spacer along the edge of the electrodes followed by linker functionalization. After exposure to a gaseous chemical target (1,5-Diaminopentane), the target gas molecules adsorb onto the linker-coated surface bridging the two electrodes and establish an electrically conductive path. Preliminary electrical measurements indicate a nearly reversible decrease of electrical resistance between five to seven orders of magnitude when exposed to the target. The large change in resistance and the high value of resistance in air makes this device suitable as a candidate for a gas-triggered on-off switch with pW standby power consumption.