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Seminar Speakers (2018/19)

Seminar 5: Engineering at the Nanoscale – gaining insight through advanced characterisation

Barbara Shollock
1:30pm - 2:30pm, Wednesday 5th December
Materials & Analytical Sciences (MAS 2.06)

From the gas turbines that power the Airbus to the steels used for cars and food cans, engineering alloys form an important class of materials, but can appear less exciting than headline-grabbing nanomaterials and biomaterials.

Despite their unglamorous press, these alloys require understanding at the nanoscale to develop new alloys and to mitigate failure in service. This talk will review a range of alloys, the challenges they face in service and characterisation approaches to determine their nanoscale chemical, structural and physical behaviour.

Fancy Colored Diamonds: Towards an Understanding of their Color Origin

Ulrika D'Haenens-Johansson
GIA Research & Development
1pm - 2pm, Monday 3rd December
Materials & Analytical Sciences (MAS 2.06)

Traditionally, when people think of diamonds as a gemstone they visualize the classic colorless round brilliant. However, through the incorporation of point or extended defects in the crystal lattice, the full rainbow of colors can be found in natural diamonds. These rare diamonds, termed “Fancy Colored” in the gem trade, often command higher per carat* prices (up to $3.3 million per carat) compared to their colorless counterparts, generating great excitement at auctions and in the news. These colors can also be produced artificially through treatment of selected natural or laboratory-grown diamonds. By studying the structure, formation and destruction of color producing defects in diamond through a range of spectroscopic techniques it is possible to separate natural, treated and synthetic diamonds, maintaining transparency in the trade. In this seminar we will review some of the key color-producing defects in both natural and synthetic diamonds and see examples of how careful defect engineering can be used to produce attractive fancy colored materials.
*1 carat = 200 mg

Previous Seminars in the Series

Seminar 1: Qubits in diamond: towards new technologies and new physics

Gavin Morley
University of Warwick
11am - 12pm, Wednesday 10th October
Materials & Analytical Sciences (MAS 2.06)

Abstract: Nitrogen vacancy centres (NVC) in diamond are excellent quantum bits which has led to research into quantum technology (particularly magnetometry [1] and quantum computing [2]) as well as new insights into quantum physics such as a loophole-free violation of Bell’s inequalities [3]. We have proposed [4-7] and begun building [8-10] an experiment that would use a single NVC in a nanodiamond to try and make the most macroscopic superposition ever: we want to create Schrödinger’s kittens. Probing this quantum-to-classical boundary could solve the measurement problem in quantum mechanics: why does the Schrödinger equation sometimes stop working to be replaced by a measurement? Our experiments for this use nanodiamonds levitated in vacuum using optical tweezers, which were pioneered by 2018 Nobel Prize winner Arthur Ashkin.

In other experiments, with single NVC, we have shown that laser-written NVC can have spin coherence times that are as long as naturally occurring NVC [11-13] and deep enough for solid immersion lenses to be made around them. We hope to eventually use these for quantum computing [2].

Finally, we have developed a sensitive fibre-coupled magnetometer from an ensemble of NVC which we will use to search for the magnetic signals given off by our hearts [14] as it is known that magnetocardiography can be useful for medical diagnosis [15].

[1] L. Rondin et al., Rep. Prog. Phys. 77, 056503 (2014).
[2] S.D. Barrett and P. Kok, Phys. Rev. A 71, 060310 (2005).
[3] B. Hensen et al., Nature 526, 682 (2015).
[4] M. Scala et al., Phys. Rev. Lett. 111, 180403 (2013).
[5] C. Wan et al., Phys. Rev. A 93, 043852 (2016).
[6] C. Wan et al., Phys. Rev. Lett. 117, 143003 (2016).
[7] S. Bose et al., Phys. Rev. Lett. 119, 240401 (2017).
[8] A.T.M.A. Rahman et al., Sci. Rep. 6, 21633 (2016).
[9] A.T.M.A. Rahman, A.C. Frangeskou, P.F. Barker and G.W. Morley, Rev. Sci. Instrum. 89, 023109 (2018).
[10] A.C. Frangeskou et al., New J. Phys. 20, 043016 (2018).
[11] Y.-C. Chen et al., Nat. Photon. 11, 77 (2017).
[12] Y.-C. Chen et al., arXiv:1807.04028 (2018).
[13] C.J. Stephen et al., arXiv:1807.03643 (2018).
[14] M.W. Dale and G.W. Morley, arXiv:1705.01994 (2017).
[15] R. Fenici, D. Brisinda and A.M. Meloni, Expert Rev. Mol. Diagn. 5, 291 (2005).

Seminar 2: CVD Diamond for Optical Applications

Ian Friel
Element Six
2pm - 3pm, Wednesday 7th November
Materials & Analytical Sciences (MAS 2.06)

Chemical vapour deposition (CVD) is a well-established and robust method of diamond synthesis. The versatility of CVD enables a high degree of control over the formation of point and extended defects in diamond. This allows a range of single crystal and polycrystalline diamond grades to be engineered for specific applications. As an optical material, CVD diamond can provide solutions for extremely demanding applications. In this talk we review the key optical properties of CVD diamond and how these can be influenced by synthesis conditions. A range of optical applications will be presented, which harness diamond’s properties to enable performance beyond the capability of conventional optical materials.

Seminar 3: Nitrogen aggregation in diamond

Matthew Dale
De Beers Technologies
1pm - 2pm, Monday 26th November
Materials & Analytical Sciences (MAS 2.06)

Nitrogen is the most commonly identified impurity in diamond. When diamond is annealed with sufficient temperature, various species become mobile and single nitrogen substitutional atoms aggregate into larger complexes. Understanding and controlling this process is significant to engineering defects into diamond, such as the nitrogen-vacancy centre, as well as understanding the differences between natural and synthetic diamond. Irradiation prior to annealing increases the aggregation rate; this is caused by both vacancies and interstitials mediating the mobility of nitrogen. In this presentation I will talk about the migration of vacancies and interstitials and their role in enhancing the aggregation process. I will highlight differences between aggregation in natural, HPHT and CVD grown diamond. Finally, I will explain how these differences can be used to effectively distinguish natural from synthetic diamond and their use in De Beers’ screening instruments.

Seminar 4: Story of a Puzzle: Another Facet of Diamond

Gwenaelle Lefeuvre
Micronsemiconductor Ltd
2pm - 3pm, Wednesday 21st November
Materials & Analytical Sciences (MAS 2.06)

Although its optical properties are those most often cited and even revered, diamond also possesses characteristics that extend its field of application well beyond luxury jewellery.

This presentation focuses in particular on the electronic properties of diamonds, thanks to which Micron Semiconductor manufactures radiation sensors for applications as diverse as particle physics, space exploration, energy or medical diagnostics.

After an introduction on artificial diamond and its various uses, we will explore the steps involved in manufacturing a sensor and examine current and future applications in this sector.