Antenna Effect in\nLarge Area Palladium-Coated Electrostatically\nFormed Silicon Nanowire for Ppb Level Hydrogen Sensing

Abstract

An electrostatically formed nanowire (EFN) with an electrostatically\nformed channel is a highly sensitive and selective sensor for detecting\nvarious gases and volatile organic compounds. We report here on a\nspecially designed large-area sensing antenna EFN that improves the\nresponse of the conventional EFN by several orders of magnitude, thus\nallowing the sensing of very low analyte concentrations. We have fabricated\nan EFN with a large area (∼3500 μm²) palladium\nsensing layer and show that its response in a dry air atmosphere to\n30 ppb H₂ is ∼90% at 60 °C. We show that this\nunprecedented sensitivity is due to the antenna effect, which causes\nthe charged H₂ species to drift to the region right above\nthe EFN transistor channel. Electrostatic modeling shows good agreement\nwith the measured antenna effect and predicts that this design paves\nthe way to an ultrasensitive very-large-scale integration (VLSI) based\ngas sensing platform.