Two dimensional III-VI semiconductors and graphene-hybrid heterostructures

Lead Research Organisation: University of Nottingham
Department Name: Sch of Physics & Astronomy

Abstract

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. A variety of two-dimensional (2D) crystals have been investigated, including large band gap insulators and semiconductors with smaller band gaps such as transition metal dichalcogenides. Interest in these systems is motivated partly by the need to combine them with graphene to create field effect transistors with high on-off switching ratios. More importantly, heterostructures made by stacking different 2D crystals on top of each other provide a platform for creating new artificial crystals with potential for discoveries and applications.
The possibility of making van der Waals heterostructures has been demonstrated experimentally only for a few 2D crystals. However, some of the currently available 2D layers are unstable under ambient conditions, and those that are stable offer only limited functionalities, i.e. low carrier mobility, weak optical emission/absorption, band gaps that cannot be tuned, etc. In a recent series of pilot experiments, we have demonstrated that nanoflakes of the III-VI layer compound, InSe, with thickness between 5 and 20 nanometers, have a "thickness-tuneable" direct energy gap and a sufficiently high chemical stability to allow us to combine them with graphene and related layer compounds to make heterostructures with novel electrical and optical properties. The main goal of this project is to develop graphene-hybrid heterostructures based on this novel class of two-dimensional (2D) III-VI van der Waals crystals. This group of semiconductors will enrich the current "library" of 2D crystals by overcoming limitations of currently available 2D layers and by offering a versatile range of electronic and optical properties. From the growth and fabrication of new systems to the demonstration of prototype devices, including vertical tunnel transistors and optical-enhanced-microcavity LEDs, our project will provide a platform for scientific investigations and will contribute to the technology push required to create new routes to device miniaturization, fast-electronics, sensing and photonics. There is great potential for further growth of all these sectors as the fabrication of 2D systems improves and as new properties are discovered and implemented in functional devices.

Planned Impact

From the fabrication and growth of new heterostructures to the demonstration of prototype devices, including transistors, and optical-microcavity-enhanced LEDs and photodetectors, our project will provide a platform for scientific investigations and will contribute to the technology required to create new routes to device miniaturization, fast-electronics, sensing, miniaturised LEDs/photodetectors, and graphene-based integrated optoelectronic circuits.
To maximize this impact, we will promote the adoption of our methods of fabrication, new 2D layers and graphene-hybrid systems to collaborators within the EU GRAPHENE Flagship and interested parties in academia and industry. This will be facilitated by our links to leading international research groups, facilities and industry. In particular, in 2011 Nottingham established a partnership with e2v Technologies ltd, a UK company with over 1500 employees and turnover exceeding £200M (http://www.e2v.com). e2v Technologies ltd. has established a centre within the School of Physics and Astronomy at Nottingham, which manufactures semiconductor devices. e2v Technologies ltd. will work with our team to assess the technical and economic feasibility of a commercial product and provide expertise in identifying routes to technology transfer. The vertical tunnel transistor based on 2D III-VI layers provides an innovative device architecture that will enable access to fast electron speeds at room temperature ; photonic applications of the 2D III-VI layers are also particularly attractive due to the potential to access a wide spectral range across the visible and near-infrared range, and will be explored in collaboration with Helia Photonics ltd, a company specializing in optical coatings for micro-optics and light emitting semiconductor devices. We have also links with the UK National Graphene Institute funded by the EPSRC and Bluestone Global Tech, which has established their European production plant in Manchester. Relationshipswith industry are central to the operation of the Institute and some of the world's biggest and most influential companies are already working with it on applications of graphene.
The proposed activities align with plans to establish at Nottingham the first Molecular Beam Epitaxy dual-chamber system in the UK for the synthesis of graphene/boron nitride heterostructures (operational in summer 2014). This is part of over £50M UK investment to establish the UK as a graphene research and technology 'hub'. Our work on new 2D van der Waals crystals will both benefit from this new national initiative and will contribute to its expansion by enabling the fabrication of new graphene-hybrid structures.
In addition to the impact arising from research outputs, we highlight the output of 2 post-doctoral researchers and 3 PhD students who will contribute to a new generation of talent and leaders in key scientific areas and whose training will be enhanced through their participation in this project.
In summary, our project will generate transformational impact on science and technology; maintain and enhance the UK leadership in key scientific areas and training; leverage impact through the alignment and collaboration with national and international programmes.

Publications

10 25 50
 
Description We have demonstrated that two-dimensional metal chalcogenide materials have unprecedented physical properties, e.g. high electron mobility and strong photosensitivity. Furthermore, their properties are compatible with and complement the two most established vdW crystals, hexagonal boron nitride (hBN) and graphene, thus enabling us to fabricate a new class of functional devices "beyond graphene", including high mobility field effect transistors, sensitive photodetectors and photovoltaic junctions. Our prototype devices have optical and electrical properties that are already comparable or superior to those of conventional semiconductors (e.g. Si and III-Vs). To realise their full potential for a viable commercial technology, we are developing scalable and reliable fabrication methods, and techniques to probe and modify surface and heterostructure interfaces.
We have identified InSe as an optimal choice for device fabrication due to its optical stability and electronic properties. The InSe flakes are optically active at room temperature, in the technologically important near-infrared spectral range between 1 and 0.7 micron, and their near-band edge optical emission undergoes a strong blue-shift to higher photon energies with decreasing thickness. The quantum shift was observed in p- and n-type InSe, and for deposition of the layers on various substrates, including graphene. The direct-to-indirect band gap crossover and the quantum shift of the energy band gap were investigated by density functional theory (DFT) and magneto-optical studies.
We have exploited the broad-band transparency of graphene, the favourable energy band line-up of graphene with n-type InSe nanosheets, and the electronic properties of InSe to create graphene-InSe-graphene heterostructures with high photosensitivity at room temperature. In these devices an InSe nanosheet and two graphene layers are "laterally" or "vertically" stacked. For the device fabrication, we have used different methods that employ exfoliated graphene and CVD-graphene. The latter differs from those previously used to form vertical devices with exfoliated graphene; it could be extended to other material systems and device architectures, and offers a route to device scalability.
We have investigated and grown successfully different crystal phases of In-Se and demonstrated electronic, vibrational and optical properties distinct from those of other compounds. The successful growth of thin films with thicknesses down to a few layers, represent an important step-forward towards the development of van der Waals 2D crystals and scalable processes for 2D technologies.
We have reported on a "giant" quantum Hall effect plateau in a graphene-based field effect transistor where graphene is capped by a layer of the van der Waals crystal InSe. The "giant" quantum Hall effect plateau arises from the close alignment of the conduction band edge of InSe with the Dirac point of graphene. This feature enables the magnetic field and electric field effect-induced transfer of charge carriers between InSe and the degenerate Landau level states of the adjacent graphene layer, which is coupled by a van der Waals hetero-interface to the InSe.
Exploitation Route Our research results were shared with members of the research community through conference presentations and our involvement in the EU graphene flagship (2014-20).
Sectors Chemicals,Digital/Communication/Information Technologies (including Software),Education,Electronics,Energy

 
Description From the growth of new semiconductor materials to the demonstration of prototype devices, our project has provided a platform for scientific discoveries and new technologies with potential for innovation and wide benefits for society. We have operated a framework of activities (including discussion meetings, workshops, and outreach) to engage with all stakeholders, including academia, industry, and international organizations (e.g. NPL, Teledyne e2v, EMFL, National Graphene Institute, Chinese Academy of Sciences), with whom we have establied joint research. In particualr, we have engaged with businesses and industrial partners. - We highlight our links to the National Physical Laboratory, the UK's National Measurement Institute, a world-leading centre of excellence in developing and applying the most accurate measurement standards, science and technology available. Among its priorities is the development of primary quantum standards based on 2D materials . - We established a partnership with Teledyne e2v, a UK company with >1500 employees and annual turnover > £200M (http://www.e2v.com). Since 2011, Teledyne e2v has run an R&D and manufacturing centre within the School of Physics and Astronomy at the UoN, staffed by 2 of their engineers, to produce semiconductor devices. Our new materials and prototype devices have potential for a variety of innovative applications, such as low power transistors and high-frequency electro-acoustic devices for the "Internet of things". - Photonic applications are also attractive due to the potential of our materials for miniaturized phototransistors and diodes covering a wide VIS-IR spectral range. These applications have been explored in collaboration with the National Graphene Institute (NGI).
First Year Of Impact 2016
Sector Education,Electronics,Energy
Impact Types Cultural

 
Description EU graphene flagship (Horizon 2020)
Amount € 512,000 (EUR)
Organisation European Commission 
Sector Public
Country European Union (EU)
Start 04/2016 
End 03/2020
 
Description EU-ITN, Postgraduate Research on Dilute Metamorphic Nanostructures and Metamaterials in Semiconductor Photonics "PROMIS"
Amount € 262,000 (EUR)
Organisation European Commission 
Sector Public
Country European Union (EU)
Start 01/2015 
End 12/2019
 
Description Partnerships with members of the EU Graphene Flagship (Horizon 2020) 
Organisation National Physical Laboratory
Department Environmental Measurement Group
Country United Kingdom 
Sector Academic/University 
PI Contribution Our research on metal chalcogenide van der Waals crystals initiated new research activities and received funding within Horizon 2020. Collaborations include work on device fabrication and quantum transport in InSe, and magnetic force microscopy studies of magnetic InSe with the University of Manchester, ETH-Zurich and the National Physical Laboratory (UK). Nottingham provided materials to these partners and took part in all discussions/paper writing.
Collaborator Contribution The University of Manchester and ETH-Zurich provided device fabrication and experimental transport studies of InSe. The NPL assisted with the magnetic force microscopy studies of magnetic InSe.
Impact The collaboration has led to joint publications, as listed in the list of publications.
Start Year 2015
 
Description Partnerships with members of the EU Graphene Flagship (Horizon 2020) 
Organisation University of Manchester
Department Cancer Research UK Manchester Institute
Country United Kingdom 
Sector Academic/University 
PI Contribution Our research on metal chalcogenide van der Waals crystals initiated new research activities and received funding within Horizon 2020. Collaborations include work on device fabrication and quantum transport in InSe, and magnetic force microscopy studies of magnetic InSe with the University of Manchester, ETH-Zurich and the National Physical Laboratory (UK). Nottingham provided materials to these partners and took part in all discussions/paper writing.
Collaborator Contribution The University of Manchester and ETH-Zurich provided device fabrication and experimental transport studies of InSe. The NPL assisted with the magnetic force microscopy studies of magnetic InSe.
Impact The collaboration has led to joint publications, as listed in the list of publications.
Start Year 2015
 
Description Partnerships with members of the EU Graphene Flagship (Horizon 2020) 
Organisation University of Zurich
Department Neurology Department Zurich
Country Switzerland 
Sector Academic/University 
PI Contribution Our research on metal chalcogenide van der Waals crystals initiated new research activities and received funding within Horizon 2020. Collaborations include work on device fabrication and quantum transport in InSe, and magnetic force microscopy studies of magnetic InSe with the University of Manchester, ETH-Zurich and the National Physical Laboratory (UK). Nottingham provided materials to these partners and took part in all discussions/paper writing.
Collaborator Contribution The University of Manchester and ETH-Zurich provided device fabrication and experimental transport studies of InSe. The NPL assisted with the magnetic force microscopy studies of magnetic InSe.
Impact The collaboration has led to joint publications, as listed in the list of publications.
Start Year 2015
 
Description UK-Japan Collaboration 
Organisation Tohoku University
Country Japan 
Sector Academic/University 
PI Contribution This project will provide an opportunity for Japan to access methods for the fabrication of novel two dimensional materials and devices, and to collaborate with internationally leading experts in this field. This research will be very important for developing national and international research activities, including the Japanese five-year integrated Master's and Doctor's degree program, which promotes international student exchange (http://m-dimension.tohoku.ac.jp/eng/).
Collaborator Contribution The collaboration of the UK with internationally leading experts in Japan on scanning optical microscopy of electron spins will enable world-class research on advanced materials with the potential for new nanotechnologies. UK industry and academia will also benefit from supply of qualified staff as this project will provide a stimulating environment for training of students and early career researchers in condensed matter physics and in the use of state-of-the-art facilities.
Impact This collaboration has led to one publication.
Start Year 2016
 
Description "Indium Selenide: from nanosheets to heterostructures" Flagship-NSF Workshop '2D Materials, heterostructures and devices' Manchester, UK 10-12 October 2016 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Supporters
Results and Impact Flagship-NSF Workshop '2D Materials, heterostructures and devices' to engage the US community in research activities
Year(s) Of Engagement Activity 2016
 
Description "Novel routes to 2D Science and Technologies" CDT Summer Conference on the Science and Technology of Graphene and related Materials, Cheshire, UK 27-30 June 2016 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Postgraduate students
Results and Impact Centre of Doctoral Training: Summer Conference on the Science and Technology of Graphene and related Materials, Cheshire, UK 27-30 June 2016
Year(s) Of Engagement Activity 2016
 
Description Conference-Invited Talk-InSe rediscovered: a van der Waals crystal for electronics and optoelectronics, US-EU Graphene Flagship Symposium Arlington, US 23-25 October, 2017 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Policymakers/politicians
Results and Impact Plan for research application with other teams
Year(s) Of Engagement Activity 2017
 
Description Conference-invited talk- Hybrid quantum systems based on two-dimensional van der Waals crystals, International Symposium on Hybrid Quantum Systems (HQS2017) Miyagi-Zao, Japan, 10-13 Sept, 2017 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact scientific discussions
Year(s) Of Engagement Activity 2017
 
Description Conference-invited talk- Novel two-dimensional van der Waals crystals and heterostructures, The First International Semiconductor Conference for Global Challenges, Nanjing, China 16-19 July 2017 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact Plans for further research
Year(s) Of Engagement Activity 2017
 
Description InSe rediscovered: a van der Waals crystal for electronics and optoelectronics, EP2DS-22 / MSS-18 (22nd International Conference on Conference-Invited Talk-Electronic Properties of Two Dimensional Systems and 18th International Conference on Modulated Semiconductor Structures) Pennsylvania State University, US July 31- Aug4, 2017 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact Plans made for future related activity
Year(s) Of Engagement Activity 2017
 
Description Invited talk at EDISON2015, Salamanca, Spain 2015 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact Report on new research findings on InSe
at The 19th International Conference on Electron Dynamics in Semiconductor"
Salamanca, Spain 29 June-2 July 2015
Year(s) Of Engagement Activity 2015
 
Description Seminar - InSe rediscovered: a van der Waals crystal for electronics and optoelectronics, Lausanne, EPFL, Switzerland, 7 July 2017 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Plans made for future related activity
Year(s) Of Engagement Activity 2017
 
Description Seminar- InSe rediscovered: a van der Waals crystal for electronics and optoelectronics NPL, Teddington 4 April 2017 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact Joint research activity
Year(s) Of Engagement Activity 2017
 
Description Seminar-InSe rediscovered: a van der Waals crystal for electronics and optoelectronics, Dresden, HZDR, Germany, 30 June 2017 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Plans future related activity
Year(s) Of Engagement Activity 2017