Multiband and Ultrahigh Figure-of-Merit Nanoplasmonic Sensing with Direct Electrical Readout in Au-Si Nanojunctions

Nanoplasmonic sensors are heralding exciting advances as clinical diagnostics as they facilitate label-free, real-time, and ultrasensitive monitoring in a small footprint. But in essence, almost all of them still largely rely on expensive and bulky spectroscopy/imaging instrumentation and methodology, which has become the major impediment for point-of-care (POC) testing implantation. In this context, an ultracompact optical sensor is achieved with direct electrical read-out capacity by combining plasmonic sensing resonance and optical-signal-transducing into a unity integrated device. Benefiting from the convergence of high figure-of-merit (∼190) resonance and hot electron enhanced photoelectric conversions on the near-flat Au-Si nanotrench framework, the device is demonstrated to yield a detection limit on the order of 10^-6 RIU in a broadband operating wavelength window (700-1700 nm). Such a compact, silicon process compatible, and ultrasensitive optoelectronic sensing platform holds great potentials for future clinical POC detection and on-chip microspectrometer applications.