Engineered resonant tunnelling nanostructures for the Terahertz realm

Lead Research Organisation: University of Liverpool
Department Name: Electrical Engineering and Electronics

Abstract

The engineering of the metal/insulator nanostructures capable of harnessing THz energy is the central aim of this project. The challenge lies in tuning the barrier heights at the metal/insulator interfaces for optimal terahertz energy conversion. Instrumental in achieving this ambitious goal is thorough understanding of interfacial barrier formation and correlation of physical and electrical properties of proposed nanostructures. The nanostructures will be fabricated using atomic layer deposition (ALD). The ALD deposition system enables a controlled microstructure, leading to better uniformity and control of the tunnelling barriers' composition and thickness, as well as interface integrity and stability. The target is addressed in three coupled work phases, which are strongly linked, and entail voluminous theoretical and experimental study with a wide range of characterization techniques.

The successful outcome of the project will facilitate an emerging technology and complement research efforts at Manchester University and Imperial College in the UK to bring about new efficient electronic devices for terahertz energy harvesting in infrared and visible domain.

Planned Impact

The aim of the proposed project is to provide terahertz metal/insulator-based nanodiodes of small geometry, ability to function without biasing, high speed, room temperature operation and frequency selectivity. Additional advantage is the CMOS compatibility of the metal/insulator technology, which means easy integration, scale-up and low cost for these devices. The successful completion of the project will point to feasibility of proposed nanostructures to perform beyond the current state-of-the-art approaches to contribute to compact, fast and affordable terahertz system architectures. The project outcome is expected to make a significant impact on a wide range of disciplines and the general public.

Terahertz radiation will, due to its long wavelength, penetrate many materials such as clothing, packing materials, and certain construction materials. Therefore, there is significant interest in the development of imaging methods that can combine this 'see-through' capability with the spectroscopic information that materials such as explosives, pharmaceutical, and narcotic materials contains in the terahertz range. Practical applications of terahertz systems are many: security applications (body scanners, concealed powders in postal mail), medical imaging (without hazard of X-rays), pharmaceutical industry (quality control of tablet coatings), food industry (detection of foreign bodies in eatables, quality control), plastics industry (in-line monitoring of polymeric compounding processes, the quality control of plastic weld joints, etc.), paper industry (to monitor the thickness and moisture content of the paper during the production process), art conservation (information on the thickness of the hidden paint layers) and others.

The ultimate aim is to integrate these high-frequency diodes directly into the nantennas. An array of the nantennas can be printed using conductive metals (like gold) onto a flexible sheet of polymer or a thin metal foil. It is inexpensive, non-toxic, light weight, and operates at room temperature and it has a wide angle of acceptance, so no need to change its angle with respect to the emitter to maintain its efficiency. The energy from infrared spectrum can be received to harvest industrial waste heat. A 1% increase in efficiency by converting some waste heat into electricity would save billions of pounds per year. As such, nantennas will be complementary to photovoltaics (PV), offering increased efficiencies through thermal harvesting when coupled to existing solar PV collection devices.

A further major outcome of the project is its excellent potential to generate wealth in the UK by the worldwide sale of precursors developed for atomic layer deposition. SAFC Hitech is a major supplier of precursors and support the project.
 
Description A number of ultra-thin double insulator nano rectifiers for THz energy harvesting, based on Al2O3, Ta2O5 and Nb2O5, have been successfully fabricated by atomic layer deposition and RF sputtering. The novelty refers to resonant tunnelling effect on these structures, which has been observed and studied in detail. The device based on Nb/Nb2O5/Al2O3/Ag shows state-of-the-art rectification parameters (asymmetry, nonlinearity) in low-voltage regime (up to 0.5 V). A design of a zero bias resonant tunnelling device has been envisaged and validated with a computer model. The work attracted interest for further collaboration with Southampton University, University of Colorado at Boulder (USA) and RedWave Energy Inc. (USA).
Exploitation Route The metal/multiple-insulator nanostructures capable of harnessing terahertz energy have inherent potential to be a disruptive and enabling technology. The study from this project can be taken further to fabricate nantenna (or rectifying antenna) for the applications in: (i) security and medical imaging; (ii) pharmaceutical and the performance of drugs; (iii) energy industry. The partners (academic and as Industrial Advisory Board) have been identified to take up work forward into fabricating nantenna device.
Sectors Electronics,Energy,Pharmaceuticals and Medical Biotechnology,Security and Diplomacy

 
Description The key findings of the project have been communicated and discussed with the representatives of the following industrial companies in the UK: Polysolar, BAE systems, Expro, Selex EX, McLaren Applied Technologies Ltd; and in the USA: RedWave Inc. They all expressed interest in taking the work on rectifier level (from this project) to the next stage of design and development of nantenna technology. The discussions above were conducted during 2015 and 2016.
First Year Of Impact 2015
Sector Education,Electronics,Energy
 
Description Dielectric engineering on GaN for sustainable energy applications
Amount £41,600 (GBP)
Organisation British Council 
Sector Charity/Non Profit
Country United Kingdom
Start 04/2018 
End 03/2020
 
Description Erasmus+
Amount £1,000 (GBP)
Organisation EU-T0 
Sector Public
Country European Union (EU)
Start 05/2018 
End 06/2018
 
Description Impact Acceleration Account (IAA), Nanorectifiers for solar energy harvesting
Amount £20,000 (GBP)
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom
Start 08/2014 
End 12/2014
 
Description Santander Travel Award, AVS-62, San Jose, CA, USA October 2015
Amount £1,000 (GBP)
Organisation Santander UK Ltd. 
Sector Private
Country United Kingdom
Start 06/2015 
End 12/2015
 
Description UKRI GCRF IAA Award: Nanolaminate scandium-based stack for GaN power devices
Amount £25,000 (GBP)
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom
Start 11/2018 
End 03/2019
 
Description Zepler Institute Research Collaboration Stimulus Fund, THz Nano-Rectifier for Infrared Energy Harvesting
Amount £12,610 (GBP)
Organisation University of Southampton 
Sector Academic/University
Country United Kingdom
Start 01/2015 
End 07/2015
 
Description eFUTURES: Portable and low-cost Mass Based Sensing of Hydrocarbons
Amount £14,400 (GBP)
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom
Start 02/2018 
End 09/2018
 
Title A computer model for design and optimisation of 2 and 3 level MIM nanodiodes 
Description The computer model is built to quantify, detail and understand effect of resonant tunnelling in metal/multiple insulator nanostructures. The model is based on calculating the bound states by solving numerically the time-independent Schrödinger equation in the dielectric layers; furthermore the modified multi-barrier Tsu-Esaki method was implemented in the model to calculate the current whereby the dielectric stack is assumed to consist of multiple slices of the oxide with different barrier heights. 
Type Of Material Computer model/algorithm 
Provided To Others? No  
Impact The immediate impact of the model is on devising a design for novel zero bias resonant tunnelling device, which offers a significant contribution in THz energy harvesting. 
 
Description Southampton University 
Organisation University of Southampton
Country United Kingdom 
Sector Academic/University 
PI Contribution Introduced work on high frequency rectifiers for IR energy harvesting.
Collaborator Contribution They provided access to nanofabrication facility.
Impact 1 joint paper presentation at the AVS 2015 conference, San Jose, CA, USA + invited talk at the ECS 2016, San Diego, CA, USA, May 2016. 1 journal paper in ECS Transactions 2016.
Start Year 2015
 
Description University of Colorado at Boulder and RedWave Energy Inc. USA 
Organisation University of Colorado Boulder
Country United States 
Sector Academic/University 
PI Contribution Discussions on MIIM rectifier experimental results achieved by ALD at Liverpool and how to push towards more efficient THz energy harvesting. The discussion were held at the American Vacuum Science 62nd Symposium and Exhibition (AVS-62), 18-23 October 2015, San Jose, CA, USA and later tele-call with representatives from RedWave Energy Inc., USA.
Collaborator Contribution Professor Moddel from the University of Colorado at Boulder invited Dr Mitrovic in 2017 to serve as Co-Vice Chair for a Gordon Research Conference on optical rectennas and high speed rectifiers, to be held January - March 2019, USA which is currently under approval.
Impact Dr Weerakkody who was Dr Mitrovic's PhD student is currently working a spost-doctoral reseracher in Professor Moddel's group. There has been one recent publication: I.Z. Mitrovic, A.D. Weerakkody, N. Sedghi, J.F. Ralph, S. Hall, V.R. Dhanak, Z. Luo, S. Beeby, "Controlled modification of resonant tunneling in metal-insulator-insulator-metal structures", Applied Physics Letters, vol. 112, 012902 - 1-5 (2018) (DOI: 10.1063/1.4999258)
Start Year 2015
 
Description IEEE PRIME 2015 Awards Committee 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Dr Mitrovic was invited to Awards Committee at the 11th Conference on PhD Research in Microelectronics and Electronics, IEEE PRIME 2015, which was held on 29 June - 2 July 2015, at the University of Glasgow, UK. A range of awards covering several fields of electronics was delivered benefiting the postgraduates and their future prospect of securing jobs in industry and academia.
Year(s) Of Engagement Activity 2015
URL http://web.eng.gla.ac.uk/prime2015/
 
Description LivWiSE video promoting science and engineering 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Schools
Results and Impact Promote science and engineering career in the UK.
Year(s) Of Engagement Activity 2015
 
Description NANOENERGY 2016, Local Organising Committee 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact Dr Mitrovic was invited to the Local Organising Committee of the 3rd International Conference on Nanotechnology, Nanomaterials & Thin Films for Energy Applications, NANOENERGY'2016 held on 27-29 July 2016 at the University of Liverpool. The conference attracted around 200 participants from 25 countries worldwide, and provided a forum on the latest findings in nanomaterials and nanotechnologies. Dr Mitrovic invited Prof. Conley from Oregon State University, USA as an invited speaker to discuss future work on nano devices related to THz energy harvesting.
Year(s) Of Engagement Activity 2016
URL http://www.nanoenergy.co.uk/uploads/NANOENERGY%202016%20Programme%20(PDF)(1).pdf
 
Description Talk at IEEE Electron Device Society Italy Chapter 2018 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Dr Mitrovic gave talk titled "Tapping into solar energy by rectenna technology", under IEEE Electron Device Society Italy Chapter, at the University of Rome 'La Sapienza' on 28 May 2018. The audience had up to 20 postgraduate and undergraduate electrical engineering and physics students and colleagues from Department of Basic and Applied Sciences for Engineering at the University of Rome. This was part of Erasmus 2018 funding on establishing collaborative links with 'La Sapienza' and Liverpool universities.
Year(s) Of Engagement Activity 2018
 
Description eFUTURES EPSRC Evaluation Focus Group 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Other audiences
Results and Impact The focus group held 2 meetings in London and organised survey in the period from January-June 2017, with the purpose of identifying the impacts of the activities of eFutures in supporting electronics research in the UK.
Year(s) Of Engagement Activity 2017
 
Description eFUTUREs Steering Committee, ECR event 2014 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Other audiences
Results and Impact Dr Mitrovic was invited to eFUTURES Steering Group to organize the event "Electronics Forum: The next steps for Early Career Researchers", held on 25-26 November 2014 in Northumberland, UK. The event benefited early career researchers (ECRs) and gathered a number of successful and highly established professionals from academia and industry who engaged with the ECRs over two days of intense talks and round-table discussions.
Year(s) Of Engagement Activity 2014
URL http://efutures.ac.uk/event/electronics-forum-next-steps-early-career-researchers-25th-26th-november...
 
Description eFutures Steering Committee ECR event 2017 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Other audiences
Results and Impact Dr Mitrovic was invited to eFUTURES Steering Group to organize the event "Electronics Forum: The next steps for Early Career Researchers", held on 31 August - 1 September 2017 Cambridge, UK. The event benefited early career researchers (ECRs) and gathered a number of successful and highly established professionals from academia and industry who engaged with the ECRs over two days of intense talks and round-table discussions.
Year(s) Of Engagement Activity 2017
URL https://efutures.ac.uk/early-career-researcher%E2%80%99s-workshop