Electrical identification of single dopant atoms

Lead Research Organisation: University of Cambridge
Department Name: Physics


Is it possible to design a solid-state electronic device with functionality based on the electronic occupancy, orbital-state or spin-state of a single atom? A positive answer could enable the ultimate miniaturisation of semiconductor devices. With this question in mind we will identify individual dopant atoms (intentionally added impurities) in silicon nanostructures and then determine the lifetime of their quantum mechanical spin states.Our main experimental technique to detect dopant atoms is ultra-sensitive charge detection using the single electron transistor. This will enable us to determine whether an electron resides on a randomly positioned dopant, or if the dopant is in its ionised state. Using radio-frequency techniques we will be able to measure this occupancy in a millionth of a second. On its own, this would only tell us that a dopant atom (or charge trap) is present but nothing of its identity. The key is to combine our charge detection technique with a means of spectroscopy. Electron spin resonance is a suitable technique, capable of identifying the unique spin environment of each species of impurity atom. To aid us we will collaborate with an expert in electron spin resonance, Prof. Martin Brandt at Walter Schottky Institute.Once we have identified a dopant atom we will use electron spin resonance not as a spectroscopy technique but to control its electron spin state. A similar technique has already been used in the case of electrons bound in quantum dots - devices often known as 'artificial atoms'. In this way we will be able to measure the quantum mechanical spin lifetimes of a single electron in silicon. Electron spins in silicon are known, from ensemble measurements, to be long-lived when compared to most other materials. Due to this longevity they are excellent candidates to be qubits - the building blocks of a quantum mechanical computer.


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Fernando Gonzalez-Zalba M (2012) A hybrid double-dot in silicon in New Journal of Physics

Description We have shown a new way to read-out the state of a single dopant by coupling it in series to a silicon quantum dot. Previous measurements have demonstrated electrical transport through single dopants but our experiment adds an artifical atom (a quantum dot) in series. So far, we read-out the charge state of the dopant and study the coupling between the dopant and the quantum dot. In the future our architecture will provide a useful way to extract the spin information from a single dopant via spin-blockade.
Exploitation Route I continue my collaboration with Hitachi Cambridge Laboratory who have provided resources (liquid helium) for the project. I am in discussion about possible joint projects in the future. We have published scientific papers and given talks at numerous international workshops. In addition the PI organised a UK workshop for silicon quantum computing attended by 40 delegates including a representitive from EPSRC.
Sectors Education,Electronics,Other

Description Consolidator grant
Amount € 2,400,000 (EUR)
Organisation European Research Council (ERC) 
Sector Public
Country Belgium
Start 05/2015 
End 05/2020
Description Programme grant
Amount £2,715,071 (GBP)
Funding ID EP/N017242/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 01/2016 
End 12/2020
Description Hitachi Cambridge Laboratory 
Organisation Hitachi Cambridge Laboratory
Country United Kingdom 
Sector Private 
PI Contribution I provided the use of equipment and staff time.
Collaborator Contribution They provided the use of complementary equipment and staff time and material.
Impact All papers reported are written jointly with members of HCL.
Start Year 2007
Description General audience lecture in Cambridge 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Professional Practitioners
Results and Impact As part of the Clare College 'Great books series', I presented a general audience talk about 'The Feynman Lectures in Physics'. This explained the background and strengths of these books and why they have had a big impact on physics. I believe that this lecture was successful in explaining what makes physicists tick to academics in other disciplines, predominantly in the humanities.
Year(s) Of Engagement Activity 2016
Description Stall at Maker Faire Rome 2015 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Together with colleagues at Hitachi Cambridge Laboratory I developed and ran a stall titled 'Microcontrollers in an adventure with science!' at Maker Faire Rome. This involved preparing a set of experiments and performing them with members of the public over three days. The event was attended by over 100,000 people and we estimate that we interacted directly with more than 1000. We aimed to spark interest in science and believe that we were highly successful in accomplishing this.
Year(s) Of Engagement Activity 2015
URL http://www.makerfairerome.eu/en/