Black phosphorus and its isoelectronic materials


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.

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Nobel Laureate Konstantin Novoselov joins CA2DM !

Prof Novoselov has been an international scientific advisor to the NUS Centre for Advanced 2D Materials since 2015. He will be the first Nobel Laureate to join a Singapore university.

The man behind graphene, the revolutionary supermaterial

Prof Novoselov and Professor Sir Andre Geim were awarded the Nobel Prize for Physics in 2010 for their ground-breaking achievements with the two-dimensional material graphene. Then 36, Prof Novoselov was the youngest Nobel Laureate in Physics since 1971 and the youngest overall since 1992. 

The joint discovery of graphene by Prof Novoselov and Prof Geim not only led to the discovery of a new material that is the world’s most conductive, stretchable and strongest, it also opened up an entirely new area of multidisciplinary research

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CA2DM researchers transformed recovered carbon black (rCB) into dazzling multicolour fluorescence and visual display

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.”

Tailoring a large area pseudo-magnetic field in graphene by placing it on a crystal with different symmetry

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

Scientists solve 65-year-old open theoretical problem on electron interactions

New discovery published in Science explains what happens during the phase transition in Dirac materials, paving the way for engineering advanced electronics that perform significantly faster

Shaffique Adam, who holds joint appointments in Centre for Advanced 2D Materials and the Department of Physics at the National University of Singapore, is the lead author for a recent work that describes a model for electron interaction in Dirac materials, a class of materials that includes graphene and topological insulators, solving a 65-year-old open theoretical problem in the process. The discovery will help scientists better understand electron interaction in new materials, paving the way for developing advanced electronics such as faster processors. The work was published in the peer-reviewed academic journal Science on 10 August 2018.

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Graphene enters the stratosphere

Graphene’s usefulness on Earth has already been established in the last decade. It is now an opportune time to expand its prospects for use in space applications – an area touted as being the most challenging to modern technology – and shift the paradigm of materials science. Space is the final frontier for graphene research, and I believe this is the first time that graphene has entered the stratosphere,”
– Professor Antonio Castro Neto

On 30 June 2018, the spacecraft was launched over the Mojave Desert in the United States. CA2DM has teamed up with US-based aerospace company Boreal Space to test the properties of graphene after it has been launched into the stratosphere. The results could provide insights into how graphene could be used for space and satellite technologies.

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CA2DM Director among world’s most impactful researchers 2017

Thirteen NUS researchers have been named among the world’s most highly cited, based on Clarivate Analytics’ 2017 Highly Cited Researchers report released on 15 November. This is also the fourth consecutive year NUS has fielded the most number of highly cited researchers among research institutions in Singapore.

Clarivate Analytics’ citation analysis has shown that these researchers consistently win peer approval from around the globe for their remarkable research in their respective fields, including chemistry, computer science, engineering, materials science, mathematics, physics, psychology and social sciences.  This was determined by the extent their papers have supported, influenced, inspired and challenged other researchers internationally.

Professor Ho Teck Hua, NUS Deputy President (Research & Technology) and Tan Chin Tuan Centennial Professor, said that the University is proud of the achievements of the 13 NUS researchers that have helped raise Singapore’s global standing in research excellence, adding that it is a strong recognition of the University’s broad base of research capabilities.

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Research team led by NUS scientists breaks new ground in memory technology

Novel organic thin film significantly outperforms existing flash memory devices

An international research team led by scientists from the National University of Singapore (NUS) pioneered the development of a novel thin, organic film that supports a million more times read-write cycles and consumes 1,000 times less power than commercial flash memories.

The novel organic film can store and process data for 1 trillion cycles and has the potential to be made even smaller than its current size of 60 square nanometers, with potential to be sub-25 square nanometres.

“The novel properties of our invention opens up a new field in the design and development of flexible and lightweight devices. Our work shifts the paradigm on how the industry has traditionally viewed organic electronics, and expands the application of such technologies into new territories,” said Professor T Venky Venkatesan, Director of NUS Nanoscience and Nanotechnology Institute (NUSNNI), the overall coordinator for this groundbreaking project.

The invention of this novel memory device was first reported online in the journal Nature Materials on 23 October 2017.
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Novel “converter” invented by NUS scientists heralds breakthrough in ultra-fast data processing at nanoscale

Invention bagged four patents and could potentially make microprocessor chips work 1,000 times faster

Advancement in nanoelectronics, which is the use of nanotechnology in electronic components, has been fueled by the ever-increasing need to shrink the size of electronic devices in a bid to produce smaller, faster and smarter gadgets such as computers, memory storage devices, displays and medical diagnostic tools.

While most advanced electronic devices are powered by photonics – which involves the use of photons to transmit information – photonic elements are usually large in size and this greatly limits their use in many advanced nanoelectronics systems.

Plasmons, which are waves of electrons that move along the surface of a metal after it is struck by photons, holds great promise for disruptive technologies in nanoelectronics. They are comparable to photons in terms of speed (they also travel with the speed of light), and they are much smaller. This unique property of plasmons makes them ideal for integration with nanoelectronics.

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Space, the final frontier for Graphene and 2D Materials

Several years ago Prof. Castro Neto predicted the importance of graphene and other 2D materials on space technology and exploration: “In the space business weight is a big issue from the financial and physical perspectives. The heavier the payload the higher the cost of launching rockets and accelerating them into higher speeds. Graphene and 2D materials are the lightest functional materials in the universe and hence are perfect in terms of mass density”, says Prof. Castro Neto, “and, moreover, in the absence of air and water, 2D materials never corrode and can last indefinitely.”  Prof. Castro Neto goes further “In deep space the temperatures are so low that some 2D materials superconduct reducing the energy cost of operation to a perfect zero.”

Prof Castro Neto’s dreams of making graphene a big player in the space race are becoming reality. In collaboration with Boreal Space, a US based satellite launcher, CA2DM is soon launching the first graphene devices into orbit opening a new chapter in space exploration for 2D materials.

Find out more of this exciting news here.