Category: HIGHLIGHTS

Researchers at NUS Physics, CA2DM and Materials Science and Engineering have created the world’s first atomically thin amorphous carbon film. The amorphous structure has widely varying atom-to-atom distance unlike crystals. This is because of the random arrangement of five-, six-, seven- and eight-carbon rings in a planar carbon network, leading to a wide distribution of bond lengths (in Å) and bond angles

NUS scientists have synthesised the world’s first one-atom-thick amorphous material. Previously thought to be impossible, the discovery of monolayer amorphous carbon (MAC) could finally settle a decades-old debate of exactly how atoms are arranged in amorphous solids, and open up potential applications. 

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In less than 10 years, the Centre for Advanced 2D Materials, initially known as Graphene Research Centre, published over 1000 research papers.

At least 100 of these publications have by now been cited 100 times or more; in other words, CA2DM reached an h-index of 100 in less than 10 years.

Since CA2DM was also one of the first centres in the world dedicated to graphene and two-dimensional materials, we use the “m-quotient”, defined as the h-index divided by the number of years since the first publication, to compare its research impact with similar centres.

Among CA2DM’s highly cited publications are studies on graphene, black phosphorous, transition metal dichalcogenides, van der Waals heterostructures and topological insulators.

CA2DM’s full publication list can be found at here.

Abstract:

The family of 2D and layered materials has been expanding rapidly for more than a decade. Within this large family of hundreds of materials, black phosphorus and its isoelectronic group IV monochalcogenides have a unique place. These puckered materials have distinctive crystalline symmetries and exhibit various exciting properties, such as high carrier mobility , strong infrared responsivity , widely tunable bandgap, in-plane anisotropy and spontaneous electric polarization. Here, we review their basic properties, highlight new electronic and photonic device concepts and novel physical phenomena and discuss future directions.

Key Points:

• The crystalline symmetries of layered black phosphorus and its isoelectronic group IV monochalcogenides play a very important role in the determination of their physical properties.
• Black phosphorus is likely to be the layered semiconductor material with the highest carrier mobility at room temperature, making it promising for high-performance electronic applications.
• Black phosphorus, arsenic phosphorus and other group V alloys may find applications in mid-infrared photonics as alternative material systems owing to their layered nature and moderate bandgap.
• Monolayer group IV monochalcogenides have a broken inversion symmetry and spontaneous in-plane electric polarization. They present a great platform for the exploration of piezoelectricity, ferroelectricity, ferroelasticity and multiferroics.
• In black phosphorus and other group V alloys, the interplay between the crystal symmetry and spin–orbit coupling may lead to the realization of rich topological states.
• Wafer-scale synthesis of this group of materials remains challenging. Future research may leverage the phase transition induced by pressure, temperature or high-intensity light.

Read the full article here: https://www.nature.com/articles/s42254-019-0043-5
For those without a subscription, a read online version is also available at https://rdcu.be/bvAWB

CA2DM researchers transformed recovered carbon black (rCB), a very economical and abundance source of material, into dazzling multicolour fluorescence and visual display, by way of a scanning focused laser treatment. This laser-initiated process is both straightforward and versatile, catering to both micro- and macro-scopic patterning with the sample in ambient or helium environment.

The observed phenomenon is attributed to both chemical and structural induced colouration of rCB powder. Chemically, carbon infusion of oxidised metal occurs when photothermal reaction takes place in ambient. After laser modification with the sample in helium environment, the powder not only fluoresces due to sulphur impurities, control annealing of these powders results in formation of periodic arrangements of carbon nanoparticles.

The periodicity of these arrangement falls within the range of visible wavelength, hence contributing to the visually observable rainbow coloured rCB flakes. The patterned sample is also transferrable using PDMS stamps. This in turn broadens the application of this material in flexible electronic devices/displays.

Photocurrent measurements show most significant enhancement under yellow light illumination. Furthermore, in the presence of an applied potential, the fluorescence detected from the sample can easily be switched off. All in all, they present a simple process to add multiple functionalities to a material that is both inexpensive and sustainable.”

https://link.springer.com/article/10.1007/s12274-018-2239-x

Figure 1: (Left) The lattice mismatch between the monolayer graphene (black) on multilayer black phosphorous (blue) generates PMF on the graphene layer. (Right) The spatial distribution and intensity of the PMF can be tailored by changing the rotation angle between the graphene and black phosphorous. (Image: NUS)

NUS researchers have discovered a simple and effective method to produce a large area pseudo-magnetic field (PMF) on graphene, and demonstrated how it can be tuned with desired spatial distribution and intensity for data storage and logic applications (“Tailoring sample-wide pseudo-magnetic fields on a graphene-black phosphorus heterostructure“).

The field of electronics focuses on how to control and exploit the properties of electrons. To study or modify the properties of these electrons at the quantum regime, a magnetic field has to be applied. Continue Reading