Nanodisc Decorated W–WO x Suspended Nanowire: A Highly Sensitive and Selective H2S Sensor

Abstract

In this paper, we report room temperature synthesis of plasma oxidized, suspended tungsten-tungsten oxide (W-WOx) core-shell nanowire for sensing ppb level H 2 S. The electric field modulation at the W-WOx interface of the core-shell nanowire strongly influences the sensing performance and brings down the operating temperature all the way down to 50 °C, compared to completely oxidized (WO x ) nanowire. The optimum interface ratio (W/WOx) of the nanowire shows response of 90.4% (1 ppm) with six months of response stability and excellent selectivity. The limit of detection of 10 ppb with response and recovery time of 4 and 46 s, respectively, is achieved. To enhance the response further, we utilize nanostructuring on top of nanowire, using nanodiscs of 20, 50, and 100 nm diameter and 10 nm height. The nanowire with nanodiscs of 20 nm diameter shows high repeatable response of 12529% (1 ppm) at 150 °C and fast response and recovery times of 12 and 19 s with detection limit of 0.5 ppb. As we switch from unpatterned to patterned nanowire, the observed change in H 2 S sensing characteristics indicates that the core-shell nanowire behavior makes a transition from p-type to n-type. Extensive material characterization is done using UV-Vis spectroscopy, XPS, and TEM.