Boosting the sensitivity of solid-state gas sensors is often achieved by incorporating nanostructured materials as the sensing element. However, interfacial effects at nanoparticles, grains or contacts can lead to non-linear responses, high electrical resistance or electrical noise. A possible way to overcome such drawbacks, using a one-atom thin layer of platinum on silicon carbide, has been reported by a team of researchers, led by scientists at Chalmers University of Technology (Gothenburg, Sweden; www.chalmers.se), and recently published in Advanced Material Interfaces.
These electrically continuous Pt layers are prepared by physical vapor deposition on the “carbon zero layer” (buffer layer) of silicon carbide. The buffer layer is a graphene-like 2-D electrical insulating layer grown epitaxially on the silicon terminated face (0001) of 4H-SiC. This layer enables the 2-D growth of Pt, and also serves to detect the onset of electrical conductivity of the surface as the metal deposits. The 3–4-Å thin Pt layer is found to be “super sensitive to its chemical environment,” explains Kyung Ho Kim, postdoctoral fellow at the Quantum Device Physics Laboratory at the Dept. of Microtechnology and Nanoscience at Chalmers, and lead author of the article. “Its electrical resistance changes significantly when it interacts with gases.”
“Atomically thin platinum could be useful for ultra-sensitive and fast electrical detection of chemicals. We have studied the case of platinum in great detail, but other metals like palladium produce similar results,” says associate professor Samuel Lara Avila.
The researchers used the sensitive chemical-to-electrical transduction capability of atomically thin Pt to detect toxic gases at the parts-per-billion level. They demonstrated this with the detection of benzene, a compound that is carcinogenic even at very small concentrations, and for which no low-cost detection apparatus exists. The 2-D system opens up a route for resilient and high-sensitivity chemical detection and can be the path for designing new heterogeneous catalysts with superior activity and selectivity.