A quantum mechanical transport phenomenon demonstrated for the first time in synthetic, atomically-thin layered material at room temperature could lead to novel nanoelectronic circuits and devices, according to researchers at Penn State and three other U.S. and international universities.
The quantum transport effect, called negative differential resistance (NDR), was observed when a voltage was applied to structures made of one-atom-thick layers of several layered materials known as van der Waals materials. The three-part structures consist of a base of graphene followed by atomic layers of either molybdenum disulfide (MoS2), molybdenum diselenide (MoSe2), or tungsten diselenide (WSe2).
NDR is a phenomenon in which the wave nature of electrons allows them to tunnel through any material with varying resistance. The potential of NDR lies in low voltage electronic circuits that could be operated at high frequency.
“Theory suggests that stacking two-dimensional layers of different materials one atop the other can lead to new materials with new phenomena,” says Joshua Robinson, a Penn State assistant professor of materials science and engineering whose student, Yu-Chuan Lin, is first author on a paper appearing online today, June 19, in the journal Nature Communications. The paper is titled “Atomically Thin Resonant Tunnel Diodes Built from Synthetic van der Waals Heterostructures.”
Achieving NDR in a resonant tunneling diode at room temperature requires nearly perfect interfaces, which are possible using direct growth techniques, in this case oxide vaporization of molybdenum oxide in the presence of sulfur vapor to make the MoS2 layer, and metal organic chemical vapor deposition to make the WSe2 and MoSe2.
“This is the first time these vertical heterostructures have been grown like this,” Robinson says. “People typically use exfoliated materials that they stack, but it has been extremely difficult to see this phenomenon with exfoliated layers, because the interfaces are not clean. With direct growth we get pristine interfaces where we see this phenomenon every time.”
What caught Lin and Robinson’s attention was a sharp peak and valley in their electrical measurements where there would normally be a regular upward slope. Any unexpected phenomenon, if it is repeatable, is of interest, Robinson says. To explain their results, they consulted an expert in nanoscale electronic devices, Suman Datta, who told them they were seeing a 2D version of a resonant tunneling diode, a quantum mechanical device that operates at low power.
“Resonant tunnel diodes are important circuit components,” says Datta, a coauthor on the paper and Penn State professor of electrical engineering. “Resonant tunneling diodes with NDR can be used to build high frequency oscillators. What this means is we have built the world’s thinnest resonant tunneling diode, and it operates at room temperature!”
Coauthor Robert Wallace of the University of Texas at Dallas says this collaborative work represents an important achievement in the realization of useful 2D integrated circuits. “The ability to observe the resonant behavior at room temperature with synthesized 2D materials rather than exfoliated, stacked flakes is exciting as it points toward the possibilities for scalable device fabrication methods that are more compatible with industrial interests. The challenge we now must address includes improving the grown 2D materials further and obtaining better performance for future device applications,” says Wallace. The UT-Dallas coauthors provided the detailed atomic resolution materials characterization for the resonant tunneling diodes discovered at Penn State.
Datta credits a theoretical understanding of the electron transport in the 2D layered materials to his post-doc, Ram Krishna Ghosh, whose calculations show close correspondence to the experimental results. Datta cautions that the new resonant tunnel diode is just one element in a circuit and the next step will require building and integrating the other circuit elements, such as transistors, in 2D. “The take home message,” he says, “is that this gives us a nugget that we as device and circuit people can start playing around with and build useful circuits for 2D electronics.”
Other coauthors include Sarah Eichfield at Penn State, Rafik Addou, Ning Lu, Hui Zhu, Xin Peng, and Moon Kim, all at UT-Dallas, Ming-Yang Li at Institute of Atomic and Molecular Sciences, Taiwan, and Lain-Jong Li, at King Abdullah University of Science and Technology, Saudi Arabia. The work was performed in conjunction with the Center for Two-Dimensional and Layered Materials (2DLM) at Penn State and supported by the Semiconductor Research Corporation and DARPA through the Center for Low Energy Systems Technology. Work at UT-Dallas was also supported through the Southwest Academy on Nanoelectronics sponsored by the Nanoelectronics Research Initiative and NIST.
About the Center for Two Dimensional and Layered Materials at Penn State
The 2DLM Center conducts multidisciplinary research in the fast emerging field of atomically thin layered materials. Based in Penn State’s Materials Research Institute, the Center works with industry partners, national labs, and academic collaborators to discover and predict new properties that arise when novel materials are created one atomic layer at a time. Visit the website at http://www.mri.psu.edu/centers/2dlm/
Associate Editor Publications
Walter Mills | newswise
One in 5 materials chemistry papers may be wrong, study suggests
15.12.2017 | Georgia Institute of Technology
Scientists channel graphene to understand filtration and ion transport into cells
11.12.2017 | National Institute of Standards and Technology (NIST)
DNA molecules that follow specific instructions could offer more precise molecular control of synthetic chemical systems, a discovery that opens the door for engineers to create molecular machines with new and complex behaviors.
Researchers have created chemical amplifiers and a chemical oscillator using a systematic method that has the potential to embed sophisticated circuit...
MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.
Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...
Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...
Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.
To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...
The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.
Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...
11.12.2017 | Event News
08.12.2017 | Event News
07.12.2017 | Event News
15.12.2017 | Power and Electrical Engineering
15.12.2017 | Materials Sciences
15.12.2017 | Life Sciences