Multifunctional nanomaterial proposed by Rice could enhance solar energy, quantum computing

An atypical two-dimensional sandwich has the tasty part on the outside for scientists and engineers developing multifunctional nanodevices.

An atom-thin layer of semiconductor antimony paired with ferroelectric indium selenide would display unique properties depending on the side and polarization by an external electric field.

The field could be used to stabilize indium selenide’s polarization, a long-sought property that tends to be wrecked by internal fields in materials like perovskites but would be highly useful for solar energy applications.

Calculations by Rice materials theorist Boris Yakobson, lead author and researcher Jun-Jie Zhang and graduate student Dongyang Zhu shows switching the material’s polarization with an external electric field makes it either a simple insulator with a band gap suitable for visible light absorption or a topological insulator, a material that only conducts electrons along its surface.

Turning the field inward would make the material good for solar panels. Turning it outward could make it useful as a spintronic device for quantum computing.

The lab’s study appears in the American Chemical Society journal Nano Letters.

– See more at Rice News

A spot of pressure enables chemical conversion to hardened 2D material

Marrying two layers of graphene is an easy route to the blissful formation of nanoscale diamond, but sometimes thicker is better.

While it may only take a bit of heat to turn a treated bilayer of the ultrathin material into a cubic lattice of diamane, a bit of pressure in just the right place can convert few-layer graphene as well.

The otherwise chemically driven process is theoretically possible according to scientists at Rice University, who published their most recent thoughts on making high-quality diamane — the 2D form of diamond — in the journal Small (featured on the inside Front Cover).

The research led by materials theorist Boris Yakobson and his colleagues at Rice’s Brown School of Engineering suggests a pinpoint of pressure on few-layer graphene, the atom-thin form of carbon known for its astonishing strength, can nucleate a surface chemical reaction with hydrogen or fluorine.

– See more at Rice News

Nature paper reports making and moving large-scale hexagonal boron nitride

Step by step, scientists are figuring out new ways to extend Moore’s Law. The latest reveals a path toward integrated circuits with two-dimensional transistors.

A Rice University scientist and his collaborators in Taiwan and China reported in Nature today that they have successfully grown atom-thick sheets of hexagonal boron nitride (hBN) as two-inch diameter crystals across a wafer.

Surprisingly, they achieved the long-sought goal of making perfectly ordered crystals of hBN, a wide band gap semiconductor, by taking advantage of disorder among the meandering steps on a copper substrate. The random steps keep the hBN in line.

Brown School of Engineering materials theorist Boris Yakobson is co-lead scientist on the study with Lain-Jong (Lance) Li of the Taiwan Semiconductor Manufacturing Co. (TSMC) and his team. Yakobson and Chih-Piao Chuu of TSMC performed theoretical analysis and first principles calculations to unravel the mechanisms of what their co-authors saw in experiments.

– See more at Rice News

Department of Energy’s Office of Science (BES) highlights our work with ORNL

Image courtesy of Oak Ridge National Laboratory

… Scientists use chemical vapor deposition to deposit WS₂ films on substrates that have first been lithographically patterned with three-dimensional features such as trenches and tori (donut shapes).

The team has developed a model that explains that the accelerated crystal growth caused by the strain is because of an increase in the number of sites at which new particles are deposited during film growth (nucleation). When the height of the donut or trench is too high (above 40 nm), the strain becomes too high, and the films crack to release the strain.

– See more at energy.gov

Related:

• Rice News: Microscopic ‘donuts’ a treat for quantum tech
• K. Wang et al., “Strain tolerance of two-dimensional crystal growth on curved surfaces”, Sci. Adv. 5, eaav4028 (2019)

Boris I. Yakobson, the Karl F. Hasselmann Chair of Engineering, Professor of Materials Science & NanoEngineering and of Chemistry, has been named a Highly Cited Researcher for 2019 in the Materials Science award category.

Highly Cited Researchers are among those who have demonstrated significant and broad influence reflected in their publication of multiple papers, highly cited by their peers over the course of the last decade.

These highly cited papers rank in the top 1% by citations for a chosen field or fields and year in Web of Science. Of the world’s population of scientists and social scientists, the Web of Science Group’s Highly Cited Researchers are one in 1,000.

The Highly Cited Researchers 2019 list from the Web of Science Group contributes to the identification of that small fraction of the researcher population that contributes disproportionately to extending the frontiers of knowledge and gaining for society innovations that make the world healthier, richer, more sustainable, and more secure.

The Rice Engineering Magazine features our work on 2D materials for single photon emission

The Fall 2019 issue of the Rice Engineering Magazine [1] features our recent work on 2D materials for single photon emission (SPE).

Single photon emission by a solid-state source requires presence of a distinct two-level quantum system, usually provided by point defects. In a recent Nano Lett., we note that a number of qualities offered by novel, two-dimensional materials, their all-surface openness and optical transparence, tighter quantum confinement, and reduced charge screening—are advantageous for achieving an ideal SPE. On the basis of first-principles calculations and point-group symmetry analysis, we have proposed a strategy  to design paramagnetic defect complex with reduced symmetry, meeting all the requirements for SPE: its electronic states are well isolated from the host material bands, belong to a majority spin eigenstate, and can be controllably excited by polarized light. The defect complex is thermodynamically stable and appears feasible for experimental realization to serve as an SPE-source, essential for quantum computing, with Re_MoV_S in MoS₂ as one of the most practical candidates.

[1] M. Williams, “Making light work of computing”, Rice Eng. Mag. (Fall 2019), 34-35 (2019)

– See more at Rice News

Rice, Oak Ridge scientists study potential of synthetic strain engineering in 2D materials

Dedicating dollars to “donuts,” scientists at Rice University are helping a national laboratory bring about a revolution in electronics and, perhaps, quantum computing.

By patterning nanoscale donuts into a two-dimensional crystal, researchers at Oak Ridge National Laboratory and their colleagues, including theoretical scientists at Rice’s Brown School of Engineering, have achieved a new level of control over its electrical and optical properties.

As researchers eye nanoscale materials for applications like quantum information processing, a method to tailor them from the bottom up will make them more practical.

The research team, which includes Rice materials theorist Boris Yakobson and graduate students Nitant Gupta and Henry Yu, published its results in Science Advances.

– See more at Rice News