While graphene has been on a nearly decade long surge of research, its two-dimensional (2D) rival molybdenum sulfide (MoS2) has enjoyed an equal rush of interest over a mere two-and-a-half years. Ever since researchers at Ecole Polytechnique Federale de Lausanne’s (EPFL) Laboratory showed it could be used in replacing silicon in transistors in early 2011, the competitive landscape for 2D materials has gotten a little crowded. Despite the growing competition between 2D materials, MoS2 still holds a special place among the competition because it can be used to further enable graphene or work on its own in the next generation of nanocircuits.
Now researchers Kansas State University have raised the prospects of MoS2 a little bit higher by combining it with gold nanoparticles. The researchers believe that the incorporation of gold nanoparticles with MoS2 will open greater possibilities for the material in diverse applications such as transistors and biochemical sensors.
The research, which was published in the journal NanoLetters ("Controlled, Defect-Guided, Metal-Nanoparticle Incorporation onto MoS2 via Chemical and Microwave Routes: Electrical, Thermal, and Structural Properties"), focused on the surface structure of MoS2. The team decided that MoS2's strong chemical bond with noble metals, like gold, could be an avenue for investigation.
They were not disappointed. They quickly discovered that once a bond had been established between the MoS2 and gold nanostructures, the bond behaved like a highly coupled gate capacitor. Following on this discovery, the Kansas State team was able to further enhance the transistor characteristics of MoS2 by manipulating it with the gold nanostructures.
"The spontaneous, highly capacitive, lattice-driven and thermally-controlled interfacing of noble metals on metal-dichalcogenide layers can be employed to regulate their carrier concentration, pseudo-mobility, transport-barriers and phonon-transport for future devices," Vikas Berry, a professor at Kansas State and a leader of the research, said in a press release (though it does stretch the bounds of credulity to imagine him actually speaking these words aloud without pausing numerous times for breath).
Among the transistor characteristics of MoS2 that the researchers were able to manipulate with the gold was its power requirements. The team also demonstrated a direct route for attaching electrodes to a MoS2 tunneling gate.
"The research will pave the way for atomically fusing layered heterostructures to leverage their capacitive interactions for next-generation electronics and photonics," Berry said. "For example, the gold nanoparticles can help launch 2-D plasmons on ultrathin materials, enabling their interference for plasmonic-logic devices."
In further research, the team intends to create more complex nanoscale structures with MoS2, leading to the building of logic devices and structures.
With MoS2 having the advantage of an inherent band gap—unlike graphene—and the recent flood of research that’s turning up new ways to work with, it may have a slight advantage over graphene at the moment for transistor applications.
Image: Vikas Berry
Dexter Johnson is a contributing editor at IEEE Spectrum, with a focus on nanotechnology.