News

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

 

 

 

Research Assistant Position: van der Waals heterostructures for advanced electronics and spintronics

Job Purpose

Professor Barbaros Özyilmaz group is opening a Research Assistant position to support advanced electronics and spintronics research based on 2D materials. Our group is at the forefront of 2D materials-based spintronics research and we are exploring exotic Majorana bound states in van der Waals heterostructures for topological quantum computation.

Your role will be to fabricate van der Waals heterostructures devices by exfoliation, characterisation and transfer of 2D materials. You will also have the opportunity to develop new processes for more reliable exfoliation and optical determination of 2D materials thickness. You will be able to participate in authoring scientific manuscripts.

For a better understanding of our group, please visit: http://graphene.nus.edu.sg/barbaros.

Duties & Responsibilities

  • Exfoliate various 2D crystals including graphene, boron nitride, black phosphorus, etc.
  • Transfer atomic layers of 2D crystals on top of another using motorised transfer stage
  • Characterise 2D materials using atomic force microscopy, Raman spectroscopy, fluorescence microscopy, etc..
  • Fabricate nano devices using electron beam lithography, thermal evaporator and UHV chamber.
  • Develop new processes for reliable exfoliation and optical determination of 2D materials thickness.
  • Procurement of equipment and consumables
  • Manage and maintain stock for key consumables and chemicals.
  • Perform routine equipment testing and maintenance.

Requirements 

  • Great hands-on working skills. 
  • B.E., B.Sc. or equivalent degree in Engineering / Science fields or higher. (Experienced in thin film fabrication and characterisation tools relevant to the field of interest is an advantage.)
  • High fluency in English with excellent written and verbal communication skills.
  • Able to work independently without direct supervision.
  • Strong drive and motivation to excel.
  • Strong sense of responsibility and works well with other lab members.

Please send your application, CV and contact details to barbaros@nus.edu.sg

Post-Doctoral Position: Majorana Bound States in van der Waals Heterostructure

Introduction

Prof Barbaros Özyilmaz’s group at the National University of Singapore (NUS) is looking for a Post-Doctoral researcher to explore Majorana Bound States (MBS) in van der Waals heterostructures consisting of 2D materials such as graphene, black phosphorus, boron nitride, 2D ferromagnetic insulators (Cr2Ge2Te6, CrI3, etc.) and 2D superconductors (NbSe2, BSCCO, etc.). Your role will be to investigate these building block materials, study the interfacial effects when these materials are brought into proximity and eventually assemble them together to realize MBS, the ingredient for topological qubits.

Motivation

The realization of MBS in semiconductor-superconductor nanowire heterostructure was a breakthrough in the experimental implementation of topological quantum computation. However, braiding operation of MBS, which is the basic operation of a topological quantum computer, requires a branched junction that is extremely challenging to realize in nanowire-based devices. Extension to 2D semiconductor heterostructure (2DEG) is a natural direction. However, 2DEG is buried between buffer layers and as a result, proximity effect is very weak. Here, van der Waals heterostructures offer unique advantages. The interface between 2D materials in a van der Waals heterostructure can be atomically clean, leading to much stronger proximity effects. The recent emergence of 2D ferromagnetic insulators open new doors to engineer MBS without external magnetic field. This greatly relaxes the design constraints and vastly expands the choices of allowed material combinations. Ultimately, the combination of superior properties of 2D materials and strong interactions may enable the demonstration of braiding operation and stable topological qubits with long decoherence time.

Our related works in this area:

  1. O’Farrell, E. C. T., J. Y. Tan, Y. Yeo, G. K. W. Koon, B. Özyilmaz, K. Watanabe, and T. Taniguchi. "Rashba Interaction and Local Magnetic Moments in a Graphene-BN Heterostructure Intercalated with Au." Physical Review Letters 117, no. 7 (2016): 076603.
  2. Avsar, Ahmet, Jong Hak Lee, Gavin Kok Wai Koon, and Barbaros Özyilmaz. "Enhanced spin–orbit coupling in dilute fluorinated graphene." 2D Materials 2, no. 4 (2015): 044009.
  3. Avsar, A., Tan, J. Y., Balakrishnan, J., Koon, G. K. W., Lahiri, J., Carvalho, A., Rodin, A. S., Taychatanapat, T., O'Farrell, E. C. T., Eda, G., Castro Neto, A. H., and Özyilmaz, B. "Spin-orbit proximity effect in graphene." Nature Communications, 5:4875
  4. Balakrishnan, J., Koon, G. K. W., Jaiswal, M., Castro Neto, A. H., Özyilmaz, B. "Colossal enhancement of spin-orbit coupling in weakly hydrogenated graphene." Nature Physics 9.5 (2013): 284-287.

More information about the project, the lab and facilities can be found at the group website: https://graphene.nus.edu.sg/barbaros/

Job Description

  1. Nanofabrication of devices (thin film deposition, electron beam lithography, etching)
  2. Magnetotrasport measurements (high magnetic fields and low temperatures)
  3. Data analysis and physical understanding of the results

Eligibility

In this frame, we are looking for a highly motivated candidate holding (or about to hold) a PhD in Physics, Material Science, or related disciplines. The ideal candidate is expected to demonstrate:

  1. Proven track record of excellence in experimental research and list of publications in international journals.
  2. Experience in using low-temperature facilities, other techniques to characterize superconductors
  3. Experience in the following areas will be a bonus:
    1. Experience in Majorana experimental research based on nanowire or 2DEG.
    2. Experience in using Dilution fridge
    3. Experience in superconductor research
    4. Experience in a.c. Josephson effect measurement
    5. Experience in fabrication of heterostructures made of 2D materials and familiarity with preparation of samples in a glove box with inert atmosphere

How to apply

Please send your Cover Letter, CV (with publication list) and contact details to barbaros@nus.edu.sg

Prof Barbaros is featured in FoS Research

Prof Barbaros is featured in the latest newsletter of Faculty of Science, on "Two-dimensional materials for wearable electronics"! Click here for the pdf version.

High crystallinity combined with atomic thinness unlock some unique applications for two-dimensional (2D) materials in the field of human-machine interfaces and flexible electronics.

"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

Post-Doctoral Position: Spin Transport studies in Black Phosphorus heterostructures

One post-doctoral research fellow position in the group of Prof Özyilmaz is available at the Centre for Advanced 2D Materials at National University of Singapore to study the spin based devices in two dimensional materials. Our lab is the first in the world to achieve electrical spin injection, transport and detection in few-layer black phosphorus­ (BP), a two-dimensional semiconductor [1]. In our BP experiment, we demonstrated long spin lifetime of up to 4 ns and long spin diffusion length of a few microns, which is comparable to the best reported values in graphene spintronics devices. Non-local spin signal observed in our BP spin valves are > 100 Ω, significantly higher than graphene spin valves (~2.5 Ω), metallic spin valves (~20 mΩ), as well as bulk semiconductor spin valves (~ 20 mΩ). We also demonstrated electron doping of BP by few-layer boron nitride/Co tunnel contacts and by Cu adatoms [2]. Large spin signal, intrinsic bandgap, and ability to dope to both p-type and n-type in BP enables many novel semiconductor spintronics devices, including bipolar spin diodes, magnetic bipolar transistors, spin transfer torque devices. The ultimate goal of the spintronics in Özyilmaz group is to employee 2D semiconductor to achieve useful spin device that integrate information processing and data storage. The candidate is going to focus on:

1) Deep understanding of spin transport properties in BP, such as optical spin injection, anisotropy and proximity effect.

2) Demonstration of bipolar spin diodes and magnetic bipolar transistor based on BP.

Facilities

The project will mainly leverage on a UHV-MBE chamber specifically designed for the growth of MgO tunnel junctions and ferromagnetic contacts. This UHV system is integrated with a glove box and hence allowing a complete fabrication of BP-based spin valve without exposing the surface of crystal to air. The glove box is equipped with an auto-transfer stage for creating two dimensional heterostructures. The group has already extensive experience in the fabrication of BP-based heterostructure devices and their charge and spin transport characterization. Measurement systems in the group include one 16T VTI (2K-400K) and a dilution refrigerators (10mK-400K) with a 7-2-2 T vector magnet. Information about lab and facilities can be found at the group pages.

Application Instructions: 

Candidates must hold a PhD degree or provide evidence of its completion in the near future preferably in physics or a closely related field. The candidate should have a proven track record of excellence in experimental research, preferably experienced with low temperature physics and the measurement.  Experience in the fabrication of 2D heterostructures and their basic characterizations will be an added advantage. The position is available for 1 year with possible extension to 2 years, or longer, salaries are internationally competitive and depend on experience.

Application Procedure: 

Please send your resume and cover letter to Prof. Barbaros Özyilmaz (barbaros@nus.edu.sg).

Referencre:

[1] Avsar A, Tan J Y, Kurpas M, et al. Gate-tunable black phosphorus spin valve with nanosecond spin lifetimes, Nature Physics, 2017.

[2] Koenig S P, Doganov R A, Seixas L, et al. Electron doping of ultrathin black phosphorus with Cu adatoms, Nano letters, 2016, 16(4): 2145-2151.

Post-Doctoral Position: Superconducting 2D Heterostructures

A post-doctoral position is available in Prof. Barbaros Özyilmaz’s group at the National University of Singapore (NUS) to investigate the transport properties of heterostructures made of layered superconductors such as BSCCO, NbSe2, and other two-dimensional (2D) materials such as BN, graphene.

Moivation

van der Waals heterostructures made from the assembly of individual layers of 2D materials opens up a number of opportunities to control band structure of new artificial materials and provides an unprecedented control of their electronic properties. 2D heterostructures are sensitive to an applied electric field, which is an alternative way, besides chemical doping, to drive the electronic system throw superconducting phase transition. The effect of high temperature superconductivity (HTS) is still lacking an explanation creating a major challenge for this field. In the strong two dimensional limit quantum fluctuations are strongly enhanced giving rise to unconventional phases, such as superconductivity with spatially fluctuating order parameter [1]. Additionally heterostructures of superconducting materials can be fabricated to enable proximity interactions and the breaking of spatial inversion symmetries.

A number of specific projects are available in this area:

  • Electric field effects and thermal transport in high temperature cuprate superconductors;
  • Spin transport in superconductors;
  • Proximity induced superconductivity in transition metal dichalcogenides.

The candidate will work at the Centre for Advanced 2D Materials in the National University of Singapore. The Centre is equipped with state-of-the-art clean room facilities and specially designed for the fabrication and characterization of 2D materials. Information about lab and facilities can be found at the group pages.

  1. L. J. Li, E. C. T. O’Farrell, K. P. Loh, G. Eda, B. Özyilmaz & A. H. Castro Neto Controlling many-body states by the electric-field effect in a two-dimensional material. Nature 529, 185–189 (2015).

Eligibility

In this frame, we are looking for a highly motivated candidate holding (or about to hold) a PhD in Physics, Material Science, or related disciplines. The ideal candidate is expected to demonstrate:

  1. Proven track record of excellence in experimental research and list of publications in international journals.
  2. Experience in using low-temperature facilities, other techniques to characterize superconductors and other 2D materials like Raman, AFM.
  3. Experience in fabrication of heterostructures made of 2D materials and familiarity with preparation of samples in a glove box with inert atmosphere would be an advantage.

Application Procedure

Please send your resume and cover letter to Prof. Barbaros Özyilmaz (phyob@nus.edu.sg).

The call will remain open until suitable candidates are identified. http://staff.science.nus.edu.sg/~barbaros/open.html

Post-doctoral Position: Energy Storage

One (1) post-doctoral position is available in Prof. Barbaros Özyilmaz’s group at the National University of Singapore (NUS) to advance on the project that focuses on synthesis of novel foam structures, suitable for many different applications. Our research team’s principal goal is to specifically target the scientific and technological bottlenecks which are preventing most.

Motivation

Despite having several applications, a fully accessible pore structure with high surface area and material density has been very difficult to achieve. There is always a tug of war between material density and accessible surface area, which has been so far the biggest obstacle in obtaining high volumetric surface area. Volume/size matters the most, as that defines the compactness. This has remained as a challenge, because of lack of control in spatial arrangements of nano particles. Porous materials mainly end up either with the following combinations; either high surface area with poor density or dense material with poor accessibility.

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. Simultaneously, we are in collaboration with a key industry player in supercapacitors, muRata Manufacturing Co. Ltd.

We are now using this unique technique with other 2D materials, and we’re now synthesising unique porous materials out of them, which would open up potential new applications. such as solar steam generation, hydrogen evolution, hybrid-supercapacitors, Li-air batteries, carbon capture and storage (CCS), water disinfection and desalination applications.

In this frame, we are looking for a highly motivated and creative researcher with experience in energy storage applications (supercapacitors/batteries), characterization nano-porous structures, nanocarbon material synthesis.

Eligibility

In this frame, we are now seeking for candidates holding (or about to hold) a PhD in Physics, Material Science, Nanoscience and Nanotechnology or related disciplines. The ideal candidate will demonstrate:

  1. Proven track record of excellence in experimental research, preferably experienced with supercapacitors/batteries characterizations and related material development/synthesis and characterizations.
  2. Experience in using multiple techniques to characterize porous structures including BET surface area measurements.

Application procedure

Informal enquiries may be directed to Prof. Barbaros Özyilmaz barbaros@nus.edu.sg.

Formal submissions should include: Cover letter, Curriculum Vitae, the contact details of three potential references. (Potential candidates will be contacted by phone and invited for an interview.)

The position is available for 1 year and can be extended based on performance. Selected candidate will receive a salary package and globally competitive benefits (health insurance, housing, travel, and relocation allowance). Salary will be decided depending on previous experience.

The call will remain open until suitable candidates are identified. We also welcome qualified candidates to conduct 4 year PhD degree research program (http://staff.science.nus.edu.sg/~barbaros/open.html)

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