Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Stenciling with atoms in 2-dimensional materials possible

02.05.2017

The possibilities for the new field of two-dimensional, one-atomic-layer-thick materials, including but not limited to graphene, appear almost limitless. In new research, Penn State material scientists report two discoveries that will provide a simple and effective way to "stencil" high-quality 2D materials in precise locations and overcome a barrier to their use in next-generation electronics.

In 2004, the discovery of a way to isolate a single atomic layer of carbon -- graphene --opened a new world of 2D materials with properties not necessarily found in the familiar 3D world. Among these materials are a large group of elements -- transition metals -- that fall in the middle of the periodic table.


A Raman image of the Nittany Lion shows the possibilities of large-area patterning of 2-D transition metal dichalcoginides.

Credit: Eichfeld, Penn State

When atoms of certain transition metals, for instance molybdenum, are layered between two layers of atoms from the chalcogenide elements, such as sulfur or selenium, the result is a three-layer sandwich called a transition metal dichalcogenide. TMDs have created tremendous interest among materials scientists because of their potential for new types of electronics, optoelectronics and computation.

"What we have focused on in this paper is the ability to make these materials over large areas of a substrate in precisely the places we want them," says Joshua Robinson, associate professor of materials science and engineering. "These materials are of interest for a variety of next-generation electronics, not necessarily to replace silicon, but to augment current technologies and ultimately to bring new chip functionality to silicon that we never had before."

In order to integrate TMDs with silicon in transistors, chip companies will need to have a method to place the atoms precisely where they are needed. That method has not been available until now. In their 2D Materials paper, "Selective-area Growth and Controlled Substrate Coupling of Transition Metal Dichalcogenides," Robinson and his group demonstrate, for the first time, a simple method for making precise patterns of two-dimensional materials using techniques familiar to any nanotechnology lab.

"It turns out the process is straight forward," Robinson explains. "We spin photoresist on the sample in the cleanroom, as if we are going to start making a device. It can be any of a number of polymers that are used in nanofabrication. We then expose it to ultraviolet light in the desired areas, and we develop it like a photograph. Where the polymer was exposed to light, it washes away, and we then clean the surface further with standard plasma-etching processes. The 2D materials will only grow in the areas that have been cleaned."

A second simple discovery described in this work that could help advance the field of TMD research involves overcoming the strong effect a substrate has on the 2D materials grown on top of the substrate. In this case, molybdenum disulfide, a highly studied semiconductor TMD, was grown on a sapphire substrate using typical powder-based deposition techniques. This resulted in the properties of the sapphire/molybdenum disulfide interface controlling the desired properties of the molybdenum disulfide, making it unsuitable for device fabrication.

"We needed to decouple the effects of the substrate on the 2D layer without transferring the layers off the sapphire," says Robinson, "and so we simply tried dunking the as-grown material into liquid nitrogen and pulling it out into air to 'crack' the interface. It turned out that was enough to separate the molybdenum disulfide from the sapphire and get closer to the intrinsic performance of the molybdenum disulfide."

The process is gentle enough to weaken the bonds connecting the 2D material to the substrate without completely setting it free. The exact mechanism for loosening the bonds is still under investigation, because of the complexity of this "simple process," said Robinson. The two materials shrink at different rates, which could cause them to pop apart, but it could also be due to the bubbling of the liquid nitrogen as it turns into gas, or even contact with water vapor in the air that forms ice on the sample.

"We're still working on understanding the exact mechanism, but we know that it works really well, at least with molybdenum disulfide," Robinson says.

###

The three co-lead authors on the paper are doctoral students Brian Bersch and Yu-Chuan Lin, and research associate Sarah Eichfeld. Also contributing to this work are Robinson's doctoral student Keohao Zhang and his former doctoral. student, Ganesh Bhimanapati, now at Intel, undergraduate student Aleksander Piasecki, and Materials Research Institute staff scientist Michael Labella. Robinson is co-director of the Center for Atomically Thin Multifunctional Coatings and the Center for Two-Dimensional and Layered Materials, and director of user programs for the Penn State 2D Crystal Consortium, all part of the Penn State Materials Research Institute.

The work was supported by the Center for Low Energy Systems Technology, one of six Semiconductor Research STARnet centers of the Semiconductor Research Corporation; the Defense Threat Reduction Agency; and the National Science Foundation.

Media Contact

A'ndrea Elyse Messer
aem1@psu.edu
814-865-9481

 @penn_state

http://live.psu.edu 

A'ndrea Elyse Messer | EurekAlert!

More articles from Materials Sciences:

nachricht In borophene, boundaries are no barrier
17.07.2018 | Rice University

nachricht Research finds new molecular structures in boron-based nanoclusters
13.07.2018 | Brown University

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Pollen taxi for bacteria

18.07.2018 | Life Sciences

Biological signalling processes in intelligent materials

18.07.2018 | Life Sciences

Study suggests buried Internet infrastructure at risk as sea levels rise

18.07.2018 | Information Technology

VideoLinks
Science & Research
Overview of more VideoLinks >>>