Latest News

Our probes specifically designed for spin transport measurements is featured in MagNews magazine.

Graphene exhibits weak intrinsic spin-orbit coupling (SOC; hence, it is suitable for use in spintronics applications that require a long spin mean-free path of charge carriers. Due to the weak SOC, the control over the spin is also poor. However, the proximity effect can be leveraged for overcoming this limitation. By depositing graphene on a tungsten disulphide substrate, the strong SOC properties of the substrate are taken up by graphene. Using graphene with both weak and strong SOC, developing a graphene-based spin field effect transistor at room temperature is expected to get closer.

For exploring the non-local magneto-resistance in graphene  deposited on a tungsten disulphide (WS2), a high magnetic field with two orientations with reference to the graphene plane is used. Based on these measurements, the orbital and the spin effects are distinguished. A rotational probe (Figure 1) is used to safeguard the sample from ambient conditions in all the experiments. This probes are designed specifically for  spin transport measurements in TeslatronTMPT Cryofree® system  (Figure2).

Figure 1. Rotating probe with chip holder

Figure 2. TeslatronTMPT Cryofree® system at Barbaros Ozyilmaz lab

You can find more information here: https://www.azonano.com/article.aspx?ArticleID=4156

Deputy Prime Minister, Mr. Teo, visit CA2DM

Deputy Prime Minister and Chairman of National Research Foundation (NRF), Mr. Teo Chee Hean, accompanied by NUS President, Prof. Tan Chorh Chuan, the Permanent Secretary of NRF and Public Service Division, Ms. Yong Ying-I, and the CEO of NRF, Prof. Low Teck Seng, visited our Centre on 26 September 2017.

During the visit, Prof Antonio Castro Neto, Director of CA2DM and Prof Barbaros Oezyilmaz, Deputy Director (Translation) of CA2DM’s Office for Industry and Innovation (OII), shared with DPM Teo on the achievements of the Centre and how we translate scientific research to industry applications by supporting researchers to validate and benchmark their technologies and working closely with industry partners to identify graphene’s unique properties relevant for their needs.

There was also a presentation and demonstration on CA2DM’s 2D materials-based magnetic sensor, which is developed and fabricated entirely within CA2DM’s Micro and Nano Fabrication Facility, using latest state-of-art tools such as Electron Beam Lithography. It is possibly the thinnest ever magnetic field sensor which allows it to be integrated effectively and customised into any industrial applications such as bio-medical fields, petroleum pipe-lines inspection gauges etc.

DPM shared the visit to CA2DM on his facebook page: https://www.facebook.com/MrTeoCheeHean/posts/1389607417784097

 

 

 

 

 

 

 

 

 

 

 

Graphene Experiment provided by Barbaros group and Wayfinder II for space applications

This is a 3U CubeSat Structure with experimental housing — The Centre for Advanced Two-Dimensional Materials (CA2DM) of the National University of Singapore (NUS) has partnered with US-based Boreal Space to test the properties of graphene material after it has been launched into the stratosphere.

During this launch, the graphene material will be subjected to rapid acceleration, vibration, acoustic shock, strong pressure, and a wide range in temperature fluctuations. The research team will retrieve the graphene material and will be testing its properties to see if it was able to resist the various challenges imposed by the launch environment. Technologies that push the limits in graphene research by demonstrating electro-magnetic shielding; efficient solar power generation; and excellent thermal protection.

http://www.satmagazine.com/story.php?number=1600200139

 

 

 

"Gate-tunable black phosphorus spin valve with nanosecond spin lifetimes" Published in Nature Physics

Although graphene is very promising for spin communication due to its extraordinary electron mobility, the lack of a bandgap restricts its prospects for semiconducting spin devices such as spin diodes and bipolar spin transistors. The recent emergence of black phosphorus, a high-mobility two-dimensional semiconductor, could help overcome this basic challenge. In this letter we report an important step towards making two-dimensional semiconductor spin devices. We have fabricated a spin valve based on ultrathin (~5 nm) semiconducting black phosphorus (bP), and established fundamental spin properties of this spin channel material, which supports all electrical spin injection, transport, precession and detection up to room temperature. In the non-local spin valve geometry we measure Hanle spin precession and observe spin relaxation times as high as 4 ns, with spin relaxation lengths exceeding 6 μm. Our experimental results are in a very good agreement with first-principles calculations and demonstrate that the Elliott–Yafet spin relaxation mechanism is dominant. We also show that spin transport in ultrathin bP depends strongly on the charge carrier concentration, and can be manipulated by the electric field effect.

We're hiring!

Want to work on high-impact research with a team of dedicated and passionate scientists? Our group is currently looking for new Post-Doctoral Researchers and Research Assistant to join our team. The detailed descriptions are in the links below and if you think you are a good fit for the job, please send your CV to Prof. Barbaros at phyob@nus.edu.sg.

  1. Post-Doctoral Position: Majorana Bound States In Van Der Waals Heterostructure
  2. Post-Doctoral Position: Black Phosphorus Spintronics
  3. Post-Doctoral Position: Towards Commercialization Of Graphene And Other 2D Materials
  4. Post-Doctoral Position: Energy Storage
  5. Research Assistant Position: Van Der Waals Heterostructures For Advanced Electronics And Spintronics
  6. Research Assistant Position: Towards Commercialization Of Graphene And Other 2D Materials

RESEARCH IN THE GRAPHENE LAB


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:

Making Graphene

Transfer of CVD Graphene

Fabrication of vdW Heterostructure

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, 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.

In our lab, we have developed a bottom-up approach to synthesise novel nano-structures, leading us to a unique, controlled spatial arrangement of nano-particles, which in turn has provided us the key to achieving the highest volumetric surface area reported so far for carbon. This approach enabled us to create carbon foams to target very specific applications and tailor material properties accordingly. For example, these carbon foams as ultra-thick electrodes for supercapacitor applications resulted in very high energy density and high power devices, thanks to the hierarchical structure of the pores made by nano-particles of specific aspect-ratios. Also, in the electrode developed for Si-based battery anodes, by introducing a novel elastic material, we have obtained excellent structural stability under high lithiation rate.

We have been awarded S$ 10 million from the Singapore National Research Foundation (NRF) for the above projects (List of awarded NRF CRP projects). A new lab is under operation for this at S12-01-08, Department of Physics, National University of Singapore. Simultaneously, we are in collaboration with a key industry player in supercapacitors, muRata Manufacturing Co. Ltd.

Phosphorene


In 2014, our group was among the first to explore, that this ultra-thin version of black phosphorus could provide complementary properties to graphene and MoS2 and could also surpass some unique properties of the latter. For example, in the short term, graphene might not be useful for semiconducting transistor applications for computer circuits since it lacks a natural band gap. MoS2 has a sizable bandgap but the carrier mobility is very low, limiting its applications in electronics. Phosphorene on the other hand has a direct band gap in a suitable energy range and high carrier mobility, making it a very promising material in areas such as transistor applications, photodetectors, heat-dessipating layers, etc.

Our recent publications in this area are:

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: