InAs Nanowire-Based Twin Electrical Sensors Enabling Simultaneous Gas Detection

Epitaxially grown InAs NWs are relevant for electrical sensing applications due to the Fermi level pinning at the NW surface and are highly sensitive to the surrounding environment. While a single NW growth batch consists of millions of virtually identical replicas of the same NW, real samples display subtle differences in NW size, shape, and structure, which may affect detection performance. Here, electrical gas detection is investigated in two nominally identical or twin devices fabricated starting from the same NW growth batch. Two individual wurtzite InAs NWs are placed onto a fabrication substrate at a 2 μm distance with a 90° relative orientation, each NW is electrically contacted, and the nanodevices are exposed to humidity and NO₂ flux diluted in synthetic air. Electrical signal versus time is measured simultaneously in each nanodevice upon exposure to different gases and concentrations. The observed detection limit is 2 ppm for NO₂ and 20% for relative humidity. Correlation analysis methods are exploited by calculating autocorrelation and cross-correlation functions for the experimental signal pairs, indicating lack of cross-correlation in the signal noise of the two nanodevices, suggesting that signal differences between the twins could be ascribed mainly to nonidealities in the fabrication protocol and nanoscopic differences in the two nanostructures, rather than to different environmental conditions. While InAs nanowires are used here as demonstrators of simultaneous gas sensing, the approach is general and virtually applies to any nanoscale material suitable for the realization of two-terminal electronic devices.