Ru-implanted WS2 nanosheet gas sensors to enhance sensing performance towards CO gas in self-heating mode

Abstract

Ru-implanted (low-dose: 2 ×10 13 ions/cm 2 and high-dose: 2 ×10 14 ions/cm 2 ) p -type WS 2 nanosheet (NS) gas sensors were investigated for CO gas sensing in self-heating mode. X-ray photoelectron spectroscopic analysis showed that the implanted Ru existed as Ru 3+ (~38 at%) and Ru 4+ (~62 at%). A decrease of the resistivity after Ru implantation was attributed to the substitution of W 4+ with Ru 3+ . The enhanced sensor response of the Ru-implanted (2 ×10 14 ions/cm 2 ) WS 2 was attributed to the enhanced adsorption of oxygen onto the sulfur vacancies after Ru ion implantation. Decoration of Au nanoparticles (NPs) onto this gas sensor not only led to an enhancement of the response to CO gas but also improved the selectivity and dynamics of the gas sensor. The related sensing mechanism was explained in terms of the catalytic effect of Au and the spillover effect. The optimized gas sensor showed good response to CO in the presence of humidity ( R g / R a = 3 to 50 ppm CO at 60% relative humidity, where R a is the resistance of the sensor in air and R g is its resistance in the presence of the target gas). • Ru ions were implanted into WS 2 to improve its gas-sensing properties. • Improved oxygen adsorption due to sulfur vacancies enhanced sensor response. • Ru implantation lowered the resistivity by substituting Ru 3+ for W 4+ . • CO gas sensing in self-heating mode was studied under applied voltages up to 5 V. • Au decoration enhanced CO selectivity and the response even when humidity is present.