#phosphorene

Scientists confirm one-dimensional electron behavior in phosphorus chains

Atom-thin phosphorus chains have been shown to host true 1D electrons—and squeezing them tighter could turn them metallic.

Researchers at BESSY II have, for the first time, experimentally confirmed that a material can exhibit truly one-dimensional electronic properties. The team studied short chains of phosphorus atoms that naturally arrange themselves at specific angles on a silver surface. By applying advanced measurement and analysis techniques, they separated the signals coming from chains aligned in different directions. This careful work showed that each individual chain behaves as a genuine one-dimensional electronic system. The findings also point to a dramatic shift in behavior depending on how closely the chains are spaced. When the chains are farther apart, the material acts as a semiconductor. If packed tightly together, however, calculations predict it would behave like a metal.

Phosphorene nanoribbons shown to exhibit magnetic and semiconductor properties at room temperature

Scientists have long suspected that phosphorene nanoribbons (PNRs)—thin pieces of black phosphorus, only a few nanometers wide—might exhibit unique magnetic and semiconducting properties, but proving this has been difficult. In a recent study published in Nature, researchers focused on exploring the potential for magnetic and semiconducting characteristics of these nanoribbons. Using techniques such as ultrafast magneto-optical spectroscopy and electron paramagnetic resonance they were able to demonstrate the magnetic behavior of PNRs at room temperature, and show how these magnetic properties can interact with light. The study, carried out at the Cavendish Laboratory in collaboration with other institutes, including the University of Warwick, University College London, Freie Universität Berlin and the European High Magnetic Field lab in Nijmegen, revealed several key findings about phosphorene nanoribbons.

Phosphorene nanoribbons live up to hype in first demonstration

Researchers have incorporated phosphorene nanoribbons into new types of solar cells, dramatically improving their efficiency.

Phosphorene nanoribbons (PNRs) are ribbon-like strands of the 2D material phosphorous, which, similar to graphene, are made of single-atom-thick layers of atoms. PNRs were first produced in 2019, and hundreds of theoretical studies have predicted how their properties could enhance all kinds of devices, including batteries, biomedical sensors, and quantum computers.

However, none of these predicted exciting properties have so far been demonstrated in actual devices. Now, for the first time, a team led by Imperial College London and University College London researchers has used PNRs to significantly improve the efficiency of a device—a new kind of solar cell—demonstrating that the 'wonder material' may indeed live up to its hype.

The details are published today in the Journal of the American Chemical Society.

Shifting dimensions: Exciting excitons in phosphorene

Since its discovery in 2014, phosphorene—a sheet of phosphorus atoms only a single atom thick—has intrigued scientists due to its unique optoelectronic anisotropy. In other words, electrons interact with light and move in one direction only. This anisotropy means that despite being two dimensional (2-D), phosphorene shows a mix of properties found in both one-dimensional (1-D) and 2-D materials. Scientists believe that the distinct quasi-1-D nature of phosphorene could be exploited to develop new, innovative optoelectronic devices, from LEDs to solar cells.

Now, scientists from the Femtosecond Spectroscopy Unit at the Okinawa Institute of Science and Technology Graduate University (OIST) have shed light on how excitons—an excited state of matter at the core of optoelectronics—move and interact within phosphorene.

"Because of the anisotropy, excitons behave in a really unique way in phosphorene compared to other 2-D materials, which we are only just beginning to understand," said Vivek Pareek, Ph.D. student and first author of the study, published in Physical Review Letters.

Wonder material: Individual 2D phosphorene nanoribbons made for the first time

Tiny, individual, flexible ribbons of crystalline phosphorus have been made by UCL researchers in a world first, and they could revolutionise electronics and fast-charging battery technology.

Since the isolation of 2-dimensional phosphorene, which is the phosphorus equivalent of graphene, in 2014, more than 100 theoretical studies have predicted that new and exciting properties could emerge by producing narrow 'ribbons' of this material. These properties could be extremely valuable to a range of industries.

In a study published today in Nature, researchers from UCL, the University of Bristol, Virginia Commonwealth and University and École Polytechnique Fédérale de Lausanne, describe how they formed quantities of high-quality ribbons of phosphorene from crystals of black phosphorus and lithium ions.

"It's the first time that individual phosphorene nanoribbons have been made. Exciting properties have been predicted and applications where phosphorene nanoribbons could play a transformative role are very wide-reaching," said study author, Dr Chris Howard (UCL Physics & Astronomy).

2D Materials: Phosphorene

Often simply known as black phosphorus, phosphorene is the two-dimensional form of the single element phosphorus, in much the same way that graphene is the 2D equivalent for carbon, and stanene is the 2D equivalent for tin. The term black phosphorus refers to a particular allotropic form of phosphorus, known for it’s layered structure, and an analogy to carbon can be drawn again, because phosphorene is a single layer of black phosphorus the same way graphene is a single layer of graphite.

Unlike graphene, however - a strong conductor of electricity - phosphorene has a band gap, making it a semiconductor material and allowing it to (potentially) be used in applications that graphene is not well suited for. This relatively new 2D material was first created in 2014, though the bulk material and its properties have been known about for some time. 

The band gap of phosphorene is dependant upon the thickness of the material - a single layer has a direct band gap of just under 2eV, while the bulk material black phosphorus has one of 0.3eV. Bilayer or few-layer phosphorene lie between the two. Phosphorene is also compatible with silicon, whereas graphene is not. However, phosphorene is not very stable in air at ambient conditions. It reacts with water vapor and oxygen in the presence of visible light, and degrades rapidly.

Potential applications of this material include transistors, solar power, or flexible circuits, among other electronic and optoelectronic devices. Currently, synthesis of phosphorene is difficult, limiting any future applications, but research into the material is relatively new and ongoing. 

Chemically stabilizing atomically flat materials improves their potential for commercial application

Two-dimensional materials could underpin a novel family of flexible, low-power electronic devices, but their success depends on ensuring the layers are chemically stable. A*STAR researchers now show that one 2-D material, phosphorene, can be stabilized with the right choice of substrate and an electric field.

Graphene, a single layer of carbon atoms, deserves its reputation as a supermaterial; it's strong, hard, light, has excellent electronic and thermal properties. It is the archetypal 2-D material. More recently scientists have created single layers of other materials—tin, germanium, boron, silicon and phosphorus—with their own signature properties. For example, while graphene is a semi-metal without a band gap, phosphorene is a semiconductor like silicon, which makes it useful for electronic devices. However, phosphorene has a notorious drawback: the material oxidizes in air and its quality is rapidly degraded.

In search of a viable approach to overcome this, Junfeng Gao and colleagues from the A*STAR Institute of High Performance Computing use first-principles calculations to demonstrate that placing phosphorene on a molybdenum diselenide substrate and applying a vertical electric field can drastically increase its resistance to oxidation.

Phosphorene reveals its superconductivity

A new atomically thin material similar to graphene has been proven to be a promising new superconductive material.

Black phosphorous - a layered material, somewhat similar to graphite – has generated much excitement among scientists and engineers because of its many interesting and useful electronic and optical properties.

Just as graphite is made up of millions of layers of graphene, black phosphorus consists of layers of phosphorene that can be isolated. New research now reveals phosphorene to possess properties as intriguing as graphene.

Combining graphene and other new 2-D materials such as phosphorene, which individually have excellent characteristics complementary to the extraordinary properties of graphene, has resulted in exciting scientific developments and could produce applications as yet beyond our imagination.

Now phosphorene is helping scientists to answer the question of whether materials consisting of just one layer of atoms can be superconducting. Superconductors conduct electricity with zero resistance and are always sought after due to their potential applications in sensors, energy-efficient power lines and magnets capable of generating large magnetic fields, such as those used in MRI scanners and levitating trains.