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Our group and Black Phosphorus

Atomically thin black phosphorus, also known as phosphorene, is the new two-dimensional wonder material that could outperform graphene in transistor applications. In 2014 our group was among the first to fabricate phosphorene field effect transistors and study the electrical properties of this novel material. It was shown that phosphorene allows both relatively high charge carrier mobility and practical on-off ratio which is orders of magnitude higher than in graphene transistors. Since then, interest and research on phosphorene has been rapidly accelerating in labs around the world, but one major challenge remained the material's air-sensitivity in ambient atmosphere.


In two recent papers accepted by Nature Communications and ACS Nano our group demonstrated isolation, passivation, and encapsulation of phosphorene in inert atmosphere with a process which does not require any exposure of the material to air. Using a sophisticated dry transfer technique performed in a glove box, we demonstrated that stable two-dimensional crystals, such as graphene or boron nitride can protect phosphorene in ambient air, which then allowed us to study pristine phosphorene. The process was then further expanded to allow electrical contacting of atomically thin black phosphorus using graphene electrodes, which resulted in the first air-stable passivated phosphorene transistor.

  1. Air-Stable Transport in Graphene-Contacted, Fully Encapsulated Ultrathin Black Phosphorus-Based Field-Effect Transistors;
    Avsar, A., Vera-Marun, I. J., Tan, J. Y., Watanabe, K., Taniguchi, T., Castro Neto, A. H., and Özyilmaz, B.
    ACS Nano, Published online (Mar 2015)

  2. Transport properties of pristine few-layer black phosphorus by van der Waals passivation in inert atmosphere;
    Doganov, R. A., O’Farrell, E. C. T., Koenig, S. P., Yeo, Y., Ziletti, A., Carvalho, A., Campbell, D. K., Coker, D. F., Watanabe, K., Taniguchi, T., Castro Neto, A. H., and Özyilmaz, B.
    Nature Comms., 6: 6647 (Apr 2015)



In our lab, we focus on diverse research topics, pertaining to graphene and other promising 2D materials like metal dichalcogenides and black phosphorus, ranging from fundamental research including spintronics, chemical reactivity studies, etc. to applied research such as in the fields of flexible electronics (in conjunction with functional polymers), energy storage and conversion, nanoengines and transparent conducting electrodes.

We are currently looking for highly motivated PhD students and post doctoral fellows to join our efforts. Please see our openings.

Check out these useful links to learn more about Graphene.

The following YouTube Logo videos by our group shows how to make graphene and how to transfer CVD graphene:

Gen 1

Making Graphene

Gen 3

Flexible Touchpanel

Gen 2

Transfer of CVD Graphene

Graphene/Functional Polymer Laminates and Blends

Graphene has attracted a lot of interest from a wide range of industries. Graphene's high mechanical strength & flexibility, optical transparency and exceptional heat & charge transport properties make it appealing for a wide range of novel device concepts. These range from flexible smart phones, roll-able AM-OLED, anti-bacterial coatings, water filtration membranes, photovoltaics, energy storage, etc. While proof-of-concepts, for most of these ideas, has already been realized at the lab scale, many challenges still lie ahead in terms of large scale synthesis, transfer and incorporation in existing industrial production processes. Our group is working on overcoming some these challenges by combining graphene with functional polymers. This approach not only provides mechanical support to an atomically thin membrane but also enhances graphene's unique intrinsic properties.

One of the polymers which can potentially boost tremendously the robustness of graphene films and simultaneously offer chemical resistance is PVDF. In addition, the multi-functionality of PVDF (ferro-electric, pyro-electric, piezo-electric) adds new possibilities for graphene's use in novel applications including nanogenerators, temperature sensors, etc.

Some of the recent results from our lab are:

Energy Storage

A phone battery typically takes at least 30 min to 1 hour to charge completely. Imagine being able to charge the same within a few minutes. Supercapacitors are one of the key devices for energy-storage applications which possess much better power handling capabilities than batteries, i.e. they can be charged much faster than batteries, and can store much higher amounts of energy than conventional capacitors. To achieve a high performance supercapacitor, we need materials with high surface area, along with high material density and superior conductivity. But unfortunately, as surface area and material density are inversely proportional characteristics of a material. In particular, porous materials have high surface area, but lack a large material density and hence exhibit a poor electrical conductivity. We have recently been awarded S$ 10 million from the Singapore National Research Foundation (NRF) to produce self-standing supercapacitor electrodes, in the form of a highly dense porous graphene foams, which have excellent conductivity (comparable to graphene) combined with high surface area as part of this project. A new lab is under construction for this operation and is expected to become operational in October, 2014. (List of awarded NRF CRP projects)


Just six months ago, our group was among the first to explore, that this ultra-thin version of black phosphorus could provide complementary properties to graphene and could also surpass some unique properties of the latter. For example, in the short term, graphene might not be useful for semi-conducting transistor applications for computer circuits since it lacks a natural band gap. Phosphorene on the other hand has a direct band gap in a suitable energy range, making it a very promising material in areas such as transistor applications, photodetectors, heat-dessipating layers, etc.

One of the first papers in this area is:

2D van der Waals Heterostructures

There are a wide range of 2D crystals with distinct properties. For example, graphene is a semi-metal, boron nitride (BN) is an insulator, molybdenum disulfide (MoS2) is a semiconductor. By combining atomically thin layers of these materials in a layer-by-layer fashionn, one creates a new three dimensional crystal with completely new properties. These new crystals are generally referred to as van der Waals heterostructures. Our group is in particular interested in enhancing graphene's spin transport properties by combining it with metal dichalcogenides such as tungsten disulfide. We have recently demonstrated that the spin orbit coupling of graphene can be enhanced by a factor of thousand, utilizing the proximity effect. These efforts are the first steps towards spin-based electronics: