Final Report Summary - TAQUS (Tailored Quantum Structures)
Semiconductor nanostructures, consisting of just a few thousand atoms, are the subject of world-wide interest because of their potential use in quantum information technologies and nanoscale optoelectronics. The goal is to create designer quantum structures such as dots, double-dots, rings, multi-rings or molecules where electronic and optical properties are controlled by their size, shape, strain and composition. The ability to tune or ‘tailor’ these parameters during fabrication is of immense technological and scientific value and essential for the realisation of quantum nanostructure-based devices. The most promising quantum structures are based on elements from groups III and V of the periodic table (e.g. GaAs and InAs). A major achievement of this IIF project has been to establish a Low Energy Electron Microscope (LEEM) system in Europe (Fig. 1) which provides the unique capability to image III-V quantum structure formation in real-time. This significantly extends Europe’s capacity to understand quantum structure formation and fabricate new components which will underpin quantum technology.
Movies of GaAs quantum structure formation have been obtained using the droplet epitaxy method where liquid Ga droplets are transformed into quantum rings under a molecular flux of arsenic. The key observation was that a ring forms outside of the droplet periphery due to the reaction of incoming As with Ga diffusing away from the droplet. A second ring structure was seen to form at the droplet contact line. These two experimental observations were central to formulating a theory of droplet epitaxy which was published in the highest impact factor physics journal (PRL 111 (2013) 036102). This work successfully explains how all of the quantum ring morphologies present in the literature arise and the theory is now being utilised by leading groups to design and fabricate new structures. This work has resulted in five invited presentations at international conferences during the course of the project (please see dissemination of results).
Important collaborations have been established with leading European research groups based around the III-V LEEM and our recent research on droplet epitaxy. This has greatly complemented the IIF project, introducing the exciting areas of nano-hole formation by droplet etching which has been studied in collaboration with Professors Heyn (University of Hamburg) and Sanguinetti (Universita' di Milano Bicocca). Two papers on this topic have already been published (see section 2) and a third is in preparation. The successful nature of the project work has resulted in invited membership of International Advisory Committees for the EMN Meeting on Droplets 2015 (Chengdu, China) and the International conference of Molecular Beam Epitaxy 2016 (Montpellier, France).
Strong interactions and relationships have been established with the two leading manufacturers of LEEM, Elmitec and SPECS, both based in Germany. This has involved the design of novel specimen stages and molecular beam flux measurement capabilities. Discussions have also been held regarding the development of a new scanning LEEM system which would form a major new European initiative.
The establishment of the III-V LEEM group has important implications for quantum technology in Europe. For example, in the UK there is a significant investment in establishing quantum technology hubs. III-V LEEM can image how site selected quantum dots form, providing unique information on how to fabricate essential components for quantum information processing such as single photon sources. Success in this area will impact virtually all areas of life including pattern recognition algorithms which might yield almost real-time national surveillance. The ability to manipulate extremely large data sets has important implications for fundamental studies in physics, astronomy and the life-sciences while using quantum computation to simulate complex systems has relevance to pharmaceutical design, metrology and energy production.
Movies of GaAs quantum structure formation have been obtained using the droplet epitaxy method where liquid Ga droplets are transformed into quantum rings under a molecular flux of arsenic. The key observation was that a ring forms outside of the droplet periphery due to the reaction of incoming As with Ga diffusing away from the droplet. A second ring structure was seen to form at the droplet contact line. These two experimental observations were central to formulating a theory of droplet epitaxy which was published in the highest impact factor physics journal (PRL 111 (2013) 036102). This work successfully explains how all of the quantum ring morphologies present in the literature arise and the theory is now being utilised by leading groups to design and fabricate new structures. This work has resulted in five invited presentations at international conferences during the course of the project (please see dissemination of results).
Important collaborations have been established with leading European research groups based around the III-V LEEM and our recent research on droplet epitaxy. This has greatly complemented the IIF project, introducing the exciting areas of nano-hole formation by droplet etching which has been studied in collaboration with Professors Heyn (University of Hamburg) and Sanguinetti (Universita' di Milano Bicocca). Two papers on this topic have already been published (see section 2) and a third is in preparation. The successful nature of the project work has resulted in invited membership of International Advisory Committees for the EMN Meeting on Droplets 2015 (Chengdu, China) and the International conference of Molecular Beam Epitaxy 2016 (Montpellier, France).
Strong interactions and relationships have been established with the two leading manufacturers of LEEM, Elmitec and SPECS, both based in Germany. This has involved the design of novel specimen stages and molecular beam flux measurement capabilities. Discussions have also been held regarding the development of a new scanning LEEM system which would form a major new European initiative.
The establishment of the III-V LEEM group has important implications for quantum technology in Europe. For example, in the UK there is a significant investment in establishing quantum technology hubs. III-V LEEM can image how site selected quantum dots form, providing unique information on how to fabricate essential components for quantum information processing such as single photon sources. Success in this area will impact virtually all areas of life including pattern recognition algorithms which might yield almost real-time national surveillance. The ability to manipulate extremely large data sets has important implications for fundamental studies in physics, astronomy and the life-sciences while using quantum computation to simulate complex systems has relevance to pharmaceutical design, metrology and energy production.