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

Ru-implanted (low-dose: 2 ×10¹³ ions/cm² and high-dose: 2 ×10¹⁴ ions/cm²) p-type WS₂ 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 Ru³⁺ (~38 at%) and Ru⁴⁺ (~62 at%). A decrease of the resistivity after Ru implantation was attributed to the substitution of W⁴⁺ with Ru³⁺. The enhanced sensor response of the Ru-implanted (2 ×10¹⁴ ions/cm²) WS₂ 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 = 3–50 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).