Research out of New York University’s Tandon School of Engineering has found a new method for developing electronics at the atomic scale - and it’s difficult to get much smaller than that.
Scientists and engineers have previously tried developing electronics using two-dimensional or monolayer electronic materials like graphene to make transistors, but found that the material’s lack of an energy band gap poses difficulties for semiconductor applications.
The new research by assistant professor of electrical and computer engineering Davood Shahrjerdi and doctoral student Abdullah Alharbi, has shown that using a monolayer of tungsten disulfide might be the key to unlocking the potential in nano-scale electronics.
"You can't turn off the graphene transistors," explained Shahrjerdi. Unlike graphene, tungsten disulfide has a sizeable energy band gap.
While monolayer materials can show unmatched flexibility, strength and conductivity, developing practical applications for them has been challenging due to imperfections in the materials themselves and structural disorders that can compromise the movement of charge carriers in the semiconductor, a phenomenon known as carrier mobility.
Shahrjerdi noted that comprehensive testing of the monolayer tungsten disulfide revealed the highest values recorded thus far for carrier mobility. "It's a very exciting development for those of us doing research in this field," he said.
It also displays other useful properties: when the number of atomic layers increases, the band gap becomes tunable, while at monolayer thickness it can strongly absorb and emit light, making it ideal for applications in optoelectronics, sensing and flexible electronics.
Creating these single-atom layer sheets takes a special touch as well.
"We developed a custom reactor for growing this material using a routine technique called chemical vapor deposition,” said Shahrjerdi. “We made some subtle and yet critical changes to improve the design of the reactor and the growth process itself, and we were thrilled to discover that we could produce the highest quality monolayer tungsten disulfide reported in the literature."
"It's a critical step toward enabling the kind of research necessary for developing next-generation transistors, wearable electronics, and even flexible biomedical devices, Shahrjerdi added."
For more information, read Electronic properties of monolayer tungsten disulfide grown by chemical vapor deposition, where Alharbi and Shahrjerdi published their findings.