2D Materials

LATEST NEWS

June 2016:  Our paper ‘Electrically pumped single-defect light emitters in WSe2′ has been published in 2D Materials.

May 2016: The group has expanded into a new lab fully dedicated to magneto-optics and microcavity polaritons in 2D materials. Part of the lab is used to support our growing fabrication effort. See new photographs in the Resources section below.

April 2016: Two Marie Sklodowska-Curie researchers have started in the group: Luca Sortino and Alessandro Catanzaro. The positions are funded by the new Marie Sklodowska-Curie Innovative Training Network ‘Spin-NANO’ coordinated by Sheffield.

December 2015: The group has expanded into a new lab fully dedicated to optics of 2D materials providing ample space for development of micro-Raman and micro-absorption techniques.

November 2015:  Our paper ‘WSe2 Light-Emitting Tunneling Transistors with Enhanced Brightness at Room Temperature’ has been published in Nano Letters.

October 2015: Our paper ‘Exciton–polaritons in van der Waals heterostructures embedded in tunable microcavities’ has been published in Nature Communications: Nature Communications 6, Article number: 8579 doi:10.1038/ncomms9579. 

September 2015: Three Sheffield’s Masters students joined the group: Lokesh Gurung, Catherine Phillips and David Draper.

August 2015: The group acquired a so-called ‘2D film transfer system’ from Manchester’s spin-off Graphene Industries designed for layer-by-layer assembly of van der Waals  heterostructures. First Sheffield-made MoSe2/hBN heterostructures giving exceptionally bright photoluminescence were produced by Evgeny Alexeev.

July 2015: Our paper ‘Photoluminescence of two-dimensional gallium chalcogenide films’ has been published in the journal 2D Materials (IoP): 2D Materials, 2 (3), 035010 (2015).

See more in the news archive below.

Overview

Open cavity set-up

Stefan Schwarz aligning the open cavity set-up. Autumn 2014.

The isolation of single-atomic layer graphene has led to a surge of interest in other layered crystals with strong in-plane bonds and weak, van der Waals-like, interlayer coupling. Here we research new properties of two-dimensional chalcogenides (sulfides, selenides, and tellurides) such as MoS2, MoSe2, WSe2, WS2, NbSe2, gallium and indium chalcogenides and others from the huge family of these synthesized and natural materials. In their bulk form chalcogenides may vary from insulators to semiconductors, from metals to superconductors, and exhibit topological insulator properties. We obtain 2D films by mechanical exfoliation from layered van-der-Waals-bonded bulk crystals. The properties of 2D films may differ from the bulk quite dramatically. For example, some indirect band-gap semiconductors turn to direct band-gap ones and become optically active. Our recent effort is on development of hybrid photonic devices comprising these 2D films and artificially built van der Waals heterostructures consisting of atomically thin layers of various materials.

Mirror design and calculated electric field distribution in an open-access microcavity used for experiments with 2D films and heterostructures. The 2D structures are placed on the bottom dielectric mirror. The top mirror has a concave shape and can be positioned at a precise vertical displacement from the bottom mirror.

Mirror design and calculated electric field distribution in an open-access microcavity used for experiments with 2D films and heterostructures. The 2D structures are placed on the bottom dielectric mirror. The top mirror has a concave shape and can be positioned at a precise vertical displacement from the bottom mirror.

People

The group is led by Prof Sasha Tartakovskii. In 2016 the group reached its highest number so far of 5 PhD students, Robert Schofield, Oleksandr Skrypka, Thomas Lyons, Alessandro Catanzaro, and Luca Sortino, and 4 postdocs, Tillmann Godde, Scott Dufferwiel, Evgeny Alexeev, and Stefan Schwarz. We are very international and currently have people with origin in the UK, Italy, Russia, Ukraine, Germany and Austria.

Outside the lab on a sunny day: Sasha, Hakan, Osvaldo, Tillmann, Robert, Le, Stefan (picture by Freddie Withers, Manchester)

Outside the lab,  summer 2014: Sasha, Hakan, Osvaldo, Tillmann, Robert, Le, Stefan

Resources

Our expertise is in photonics and magneto-optics of nano-structured semiconductors. The group occupies dedicated high-spec optical laboratories (including a state-of-the-art magneto-optics set-up), and shares access to several other state-of-the-art optics laboratories of Prof M Skolnick’s group. Sample and device fabrication is usually carried out at the National III-V Semiconductor Facility in Sheffield, where we have a dedicated set-up to produce atomically thin flakes and heterostructures. Additionally, we have installed an optical microscopy set-up in one of our labs, where more sample fabrication can be done.

New lab

Equipment has just been moved in the new lab. End of May 2016.

Scott in the new lab

Scott is working on a set-up combining a vector magnet and a scanning microcavity in our new lab. June 2016.

Microscope in the new lab

Microscope for flake search installed in the new lab. June 2016

 

Collaborations

Our main collaborators in this field are Prof K Novoselov’s group in Manchester (joint work on optics of van der Waals heterostructures). We also continue our close collaboration with a leading theorist in the field of 2D materials Prof V Falko (the Director of the National Graphene Institute in Manchester from October 2015). Other important collaborations include: leading polariton physics theory group led by Dr G Malpuech (Clermont-Ferrand); leading ultra-fast optical spectroscopy group of Prof M Bayer/Dr I Akimov (Dortmund); specialist in tunable optical microcavities Dr J Smith (Oxford); dielectric coating specialist Helia Photonics (Livingston); low-temperature positioning specialist Attocube Systems (Munich). New collaborations are developing with Prof X Marie/Prof B Urbaszek (Toulouse), Prof N Grobert (Oxford), Prof P Beton (Nottingham) and Dr M Glazov (St Petersburg). Our collaborations with crystal growth groups include Dr N Kolesnikov (Chernogolovka) and Dr A Dmitriev (Kiev).

News-archive

June 2015: Our paper on stability of gallium and indium chalcogenides films has appeared on arxiv: http://arxiv.org/abs/1506.05619.

May 2015: Our paper on ‘Exciton-polaritons in van der Waals heterostructures embedded in tunable microcavities’ has appeared on arxiv: http://arxiv.org/abs/1505.04438.

May 2015: Proposal for a new Marie Sklodowska-Curie Innovative Training Network ‘Spin-NANO’ led by A. Tartakovskii has been successful.

April 2015: a new postdoctoral fellow Dr Evgeny Alexeev has been appointed to boost our micro-fabrication efforts. He will start in June 2015.

February 2015: Our paper on 2D LEDs (in collaboration with F Withers and K Novoselov, Manchester) has just been published: http://www.nature.com/nmat/…/nmat4205.html.

See also:
News and Views article
Sheffield’s press release
Manchester’s press release

January 2015: Our new paper entitled ‘Optical properties of two-dimensional gallium chalcogenide films’ has appeared on arxiv: http://arxiv.org/abs/1501.02214.

January 2015: Scott Dufferwiel joined the group as a postdoctoral researcher on our Graphene Flagship project.

December 2014: We have been awarded an EPSRC grant (collaboration with Prof A Patane, Nottingham) to investigate optical properties of layered III-VI materials.  We will be recruiting 2 postdocs, one with a focus on fabrication, and the other to do advanced optics experiments.

December 2014: Our joint paper with Prof K Novoselov’s group (Manchester) entitled ‘Light-emitting diodes by bandstructure engineering in van der Waals heterostructures’ has appeared on arxiv: http://arxiv.org/abs/1412.7621.

November 2014: Our paper on 2D semiconductors in tunable cavities has just been published online in Nano Letters  http://pubs.acs.org/doi/abs/10.1021/nl503312x. See a ‘Tech Update’ piece on this work at nanotechweb.org.

November 2014: Three master students have joined our group.

October 2014: A new PhD student Oleksandr Skrypka joined the group. He has arrived from Ukraine. He will work on 2D photonics including the latest microcavity projects.

June 2014: Sheffield’s group is joining the Graphene Flagship

Recent publications

2016

2015

2014

2013

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