Heterometallic Rings for Future Electronics

Project Information

Herifuel

Grant agreement ID: 786734

DOI

10.3030/786734

Project closed

EC signature date 24 April 2018

Start date 1 September 2018

End date 31 May 2024

Funded under

• EXCELLENT SCIENCE - European Research Council (ERC)

Total cost

€ 2 477 003,00

EU contribution

€ 2 477 003,00

Coordinated by

THE UNIVERSITY OF MANCHESTER
United Kingdom

Periodic Reporting for period 4 - Herifuel (Heterometallic Rings for Future Electronics)

Reporting period: 2023-03-01 to 2024-05-31

Summary of the context and overall objectives of the project

1. The problem being addressed is the continuing miniaturisation of electronic devices, and the overall objective of the project is to develop novel chemistry that allows this miniaturisation to continue. There are two major strands:
(a) developing molecules based on heterometallic rings (HRs) that can be used as molecular electron spin qubits; the project seeks to like them into scaleable and addressable devices
(b) use similar chemistry to develop HRs that can be used as advanced resist materials in nano fabrication by lithography

2. The two strands have different timescales for value to society:
(a) There is now no doubt that quantum information processing will become used over the next decade or so, allowing calculations that are impossibly slow by conventional computing or allowing better simulations of quantum systems. There have been claims that "quantum supremacy" has been achieved, but still there are major issue about most routes to implementation. Our route is to use molecules which has some advantages - ease of linking into multiple qubit structures - and disadvantages - chiefly linking into conventional electronic architectures.

(b) Approximately 13 sextillion transistors have been made. For example, in each smart phone there are 8.5 billion transistors. All are made by lithography where structures are written using light (typically 193 or 365 nm) or electron-beams. The structures are written into resist materials. Our project will develop new resists that will allow better transistor device architectures to be written. The global resist market was worth around $4 billion in 2020.

3. The overall objectives are:
1) To design and build supramolecular assemblies with complete control of structure.
2) To characterise these supramolecular assemblies using a range of technique.
3) To examine the use of these assemblies in prototype qubit gates, targeting applications in QIP.
4) To study and improve the performance of these assemblies as resist materials for lithography.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

We have published around 30 publications based on results achieved during the ERC grant. Our granted patents are being examined by a major chemical company.

We have shown multiple controlled routes to new supramolecular assemblies featuring potential qubits, and some of these molecular assemblies are unprecedented. For example, the [13]rotaxane is one of the largest rotaxanes made, and certainly the largest hybrid inorganic-organic rotaxane. The structural characterisation makes it one of the largest non-protein structures studied. The solution studies by small angle X-ray scattering (SAXS) and molecular dynamics simulations show a way of characterising large paramagnetic assemblies in solution. We have then shown how this can be used to study equilibria and conformational flexibility. We have made supramolecules that can be regarded as molecular quantum memories with embedded error corrections or which could be used to study decoherence in strongly entangled quantum states. We have made the world's largest rotaxane (which gained some media attention). We have extended the use of multiple techniques to studying metallosupramolecular assemblies including SAXS, paramagnetic NMR and advanced mass spectrometry. The combination of NMR and mass spectrometry has been used to measure energetics of binding of organic molecules to the heterometallic rings, which is a first. We have also performed a pulsed EPSR spectroscopy experiment to study the use of this technique to perform two-qubit gates.

For lithography, we have resists that out perform industry standard resists in one or more parameters. We have shown that our resists are useful for multiple writing tools including electron beam lithography, helium ion beam lithography and EUV lithography. We have remarkable etch selectivity even for sub-10 nm structures. We are conducting studies with a major chemical company in the semiconductor supply chain to examine whether our indium based resists can be used for extreme-UV lithography at the 7 nm node and beyond. We expect the results of those tests during 2025.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The molecular assemblies we are reporting are unprecedented. For example, the [13]rotaxane is one of the largest rotaxanes made, and certainly the largest hybrid inorganic-organic rotaxane. The structural characterisation makes it one of the largest non-protein structures studied. The solution studies by SAXS and molecular dynamics simulations show a way of characterising large paramagnetic assemblies in solution. We have then shown how this can be used to study equilibria and conformational flexibility.

This work has been extended to produce multiple interesting molecules that contain distinct s = 1/2 centres, which can be regarded as individually addressable qubits. This includes:
(i) A supramolecule which can be regarded as a molecular quantum memory with an embedded route to error correction.
(ii) Synthesis of the world's largest rotaxane - which involves decorating a micrometer polystrene bead with [2]rotaxanes. This work gained some media attention.
(iii) Study of a five-spin supramolecule, involving both Cu(II) and Cr7Ni qubits, which could be used to simulate quantum decoherence of Bell states.
(iv) We have developed the use of advanced mass spectrometry techniques to measure stability of the heterometallic qubits. This has led to a series of high profile publications. More generally, this is a new method for measuring energetics in coordination cages.
(v) We carried out a careful study of the potential use of pulsed EPR spectroscopy to perform a two-qubit gate. The results illustrate the challenges that need to be overcome if this technique is to be used for quantum information processing. These challenges are very significant but could be met by better orientation of the two-qubit gates, probably in a single crystal.
(vi) We showed that paramagnetic NMR spectroscopy could be used to study the host-guest chemistry of the heterometallic qubits; this is vital for future development of complex supramolecular assemblies. The studies show that the heterometallic rings have binding constants that lie in the range of those found for conventional organic crown ethers, but with some significant differences, e.g. the heterometallic rings bind more strongly to secondary than primary ammonium cations, which is the opposite of organic crown ethers.

For lithography, we have resists that out perform industry standard resists in one or more parameters. We have remarkable etch selectivity even for sub-10 nm structures. We are conducting studies with a major chemical company in the semiconductor supply chain to examine whether our indium based resists can be used for extreme-UV lithography at the 7 nm node and beyond. We expect the results of those tests during 2025.

Overall the project has produced multiple supramolecules containing multiple qubits and proposed applications of such assemblies. We have performed a two qubit gate by pulsed EPR and studied the limitations of the technique. We have developed two new techniques for studying these paramagnetic materials - tandem mass spectrometry, with our collaborator Prof Perdita Barran, and paramagnetic NMR spectroscopy. The lithographic studies are at the stage of being studied for potential commercialisation.

A [13]rotaxane crystal structure

A five spin supramolecule for simulating decoherence in Bell states

Writing and etching sub 10 nm structures