On-Chip milliKelvin Electronic Refrigerator for Astronomical and Quantum Device Applications

Lead Research Organisation: Cardiff University
Department Name: Sch of Engineering


We intend to develop a new user-friendly technology that would enable small devices to be cooled to exceedingly low temperatures (<100mk). Such a capability will allow diverse and futuristic applications to flourish. These include the detection of black holes, cancer detection and quantum computing. We propose to do this by using an electronic cooling process where relatively energetic (hot) carriers (electrons or holes) quantum mechanically tunnel out of a medium, thereby causing the average electronic temperature in the medium to decrease. The application of this process to realise extremely low temperatures is very new, and we want to greatly improve its efficiency by introducing a new generation semiconductor SiGe into the design of the electronic cooler and, along with it, the well developed silicon processing techniques - so that, ultimately, such coolers can be produced economically and to industrial standards. Coolers will be fabricated around the periphery of a small silicon chip with thermal links to the active device ( payload ) mounted in the centre of the chip. This requires very good thermal design such that the electronic cooler efficiently cools the payload. However, in some cases, it is only necessary to cool the electrons / not the lattice atoms; here SiGe gives a lot of flexibility in controlling the thermal coupling between the electrons and the lattice. Such electronic coolers can operate from a starting temperature of 0.3K, which can be produced by a cryogenic fluid-free closed-cycle helium cryostat, so that a turn-switch technology can be envisaged enabling access to ~10mK working environments. This will be a huge technology step forward, as existing techniques require massive and complex cryogenic fluid-based equipment.During the first phase of the project we will examine several approaches to the realisation of effective electronic cooling, exploiting the wide range of fundamental electronic conditions that can be obtained at very low temperatures in SiGe with its associated metal silicides / thereby enhancing carrier transport and thermoelectric effects. The new coolers will then be tested in two areas of great topical interest, namely radiation detectors and quantum information devices. They could dramatically enhance our ability to detect, for example, the photons that emanate from the earliest black holes, with satellite-based detectors operating at <100mK. And, very significantly, such detectors could revolutionize the fluorescence light detection that is used extensively in biomedical research, enabling advances in our understanding of genetically-based diseases (e.g. cancer) and the workings of a single cell. Furthermore, the computational vista that is opened-up by the quantum computing era requiring qubit devices operating at 10-20mK, is truly awe inspiring. Warwick is co-ordinating the project and has assembled a tightly knit consortium of scientists and engineers with appropriate expertise from four UK universities -Warwick, Cardiff, Leicester and London(Royal Holloway) - and four leading-edge companies, concerned with the development of this technology and the demonstration of its applicability and advantages in two key areas. We are also working closely with Europe's leading centre on mK coolers (Helsinki University of Technology). The UK is exceedingly well positioned to derive benefit from this genuinely new and exciting technology, and this project will sow the seeds for its realisation.


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Description • Theoretical evaluation confirms that it is possible to improve the cooling performance of SINIS by replacing the normal metal with a heavy-fermion metal.
• FeSiGe and FeSi thin films can be fabricated using the "reactive deposition" technique that exhibits heavy fermion characteristics.
Exploitation Route Implementing at device level to fabricate prototype heavy-fermion coolers
Sectors Aerospace, Defence and Marine,Chemicals,Digital/Communication/Information Technologies (including Software),Electronics,Environment,Healthcare,Pharmaceuticals and Medical Biotechnology,Security and Diplomacy

Description The key findings of this work include:1) theoretical evaluation confirms that it is possible to improve the cooling performance of SINIS by replacing the normal metal with a heavy-fermion metal; 2) FeSiGe and FeSi thin films can be fabricated using the "reactive deposition" technique that exhibits heavy fermion characteristics. These results provide foundation toward developing this new type of electron tunneling devices.
First Year Of Impact 2012
Sector Aerospace, Defence and Marine,Agriculture, Food and Drink,Chemicals,Digital/Communication/Information Technologies (including Software),Electronics,Energy,Environment,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology
Impact Types Economic

Description Nanostructured thermoelectrics based on Mg2Si (ThermoMag)
Amount £244,759 (GBP)
Funding ID 263207 
Organisation European Commission 
Sector Public
Country European Union (EU)
Start 05/2011 
End 10/2014
Description To transfer the knowledge and skills of Cardiff Thermoelectric Group in helping a SME to establish thermoelectric module fabrication capability in the UK for creating a key energy device in supply chain of every harvesting systemCardiff University
Amount £129,345 (GBP)
Funding ID KTP008739 
Organisation TSB Bank plc 
Sector Private
Country United Kingdom
Start 02/2012 
End 01/2014
Title Principle of Superconducting Junction for Detection of Resonant States in Thermoelectric Materials 
Description A principle of a technique to measure the resonant density of states in thermoelectric materials has been established, which will enable the detection of existence of resonant states in thermoelectric materials, which are considered to be an important mechanism responsible for the improvement of thermoelectric ZT. 
Type Of Material Improvements to research infrastructure 
Provided To Others? No  
Impact It is believed that thermoelectric properties can be improved if resonant density of states exist near the Fermi level of a thermoelectric material. The technique which can detect the existence of the resonant states will lead to confirmation of this hypothesis. 
Description Collaboration between Prof J Luo (Bolton University) and Dr. Gao Min (Cardiff University) 
Organisation University of Bolton
Country United Kingdom 
Sector Academic/University 
PI Contribution Collaborative efforts to develop high quality and ultra thin ZnO insulating layer using ALD. The successful fabrication of the proposed devices requires a suitable insulating layer, which could not be prepared using the originally designed technique. Consequently, an attempt is made through collaborative effort.
Start Year 2011
Description Collaboration between Prof Y Terai (Osaka University) and Dr. Gao Min (Cardiff University) 
Organisation Osaka University
Country Japan 
Sector Academic/University 
PI Contribution FeSi and FeSiGe heavy fermion thin films were successfully fabricated through the collaboration between Osaka and Cardiff. Preparation of heavy fermion thin films is one of the key tasks of this EPSRC project. Difficulties had been encountered with the originally proposed techniques. Consequently, the collaboration was sought and resulted in successful fabrication of the required heavy fermion thin films.
Start Year 2010
Description "New concepts and prospects in search for high ZT thermoelectric materials" 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? Yes
Geographic Reach International
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact Invited lectures at Zhejiang University China, which sparked discussions particularly in the aspects of Cardiff-Zhejiang collaboration in thermometric research.

Established continued collaboration include sample exchange, and measurement activities
Year(s) Of Engagement Activity 2009
Description "Thermoelectric energy conversion" 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? Yes
Geographic Reach Regional
Primary Audience Professional Practitioners
Results and Impact Invited talk to scientists and engineers at EADS, Newport, UK.

Sparked discussion on possible novel applications of thermoelectric devices in defense and security industries
Year(s) Of Engagement Activity 2011