Antenna Effect in Large Area Palladium-Coated Electrostatically Formed Silicon Nanowire for Ppb Level Hydrogen Sensing

An electrostatically formed nanowire (EFN) with an electrostatically formed channel is a highly sensitive and selective sensor for detecting various gases and volatile organic compounds. We report here on a specially designed large-area sensing antenna EFN that improves the response of the conventional EFN by several orders of magnitude, thus allowing the sensing of very low analyte concentrations. We have fabricated an EFN with a large area (∼3500 μm²) palladium sensing layer and show that its response in a dry air atmosphere to 30 ppb H₂ is ∼90% at 60 °C. We show that this unprecedented sensitivity is due to the antenna effect, which causes the charged H₂ species to drift to the region right above the EFN transistor channel. Electrostatic modeling shows good agreement with the measured antenna effect and predicts that this design paves the way to an ultrasensitive very-large-scale integration (VLSI) based gas sensing platform.