Welcoming back returning MPhys students

The group welcomes back our returning MPhys students who will continue on their projects this semester. This includes:

Big-data for nano-electronics – development of machine-learning tools for analysis of imaging and spectroscopic data for nanotechnology
Rafe Whitehead, Thomas Blackmore, Jonathan Ryding
Earth’s-field NMR – design and construction of an NMR system to operate in the Earth’s magnetic field
Luis Pedro Martins Mestre, Alexander O’Sullivan, James Overend, Ewan Kilpatrick
i-TCSPC analytics – studying single photon sources with inteferometric single-photon counting
Jake Manning

2020.S7 – Group MPhys Students

The group welcomes a bumper set of new MPhys (Masters project) students on a range of projects. Welcome to all students!

Big-data for nano-electronics – development of machine-learning tools for analysis of imaging and spectroscopic data for nanotechnology
Rafe Whitehead, Thomas Blackmore, Omar Ahmed, Jonathan Ryding
Earth’s-field NMR – design and construction of an NMR system to operate in the Earth’s magnetic field
Luis Pedro Martins Mestre, Alexander O’Sullivan, James Overend, Ewan Kilpatrick
i-TCSPC analytics – studying single photon sources with inteferometric single-photon counting
Jake Manning

New Paper: Carrier dynamics and recombination mechanisms in InP twinning superlattice nanowires

(a) Twinning superlattice nanowire on substrate, (b) high-resolution SEM and (c) TEM image showing superlattice.

A new paper has been published in Optics Express, led by collaborator Xiaoming Yuan at Central South University (Changsha) and growth colleagues in the group of Prof. Jagadish at Australian National University.

In this work, novel “twinning-superlattice” nanowires are grown. Once passivated, this growth method produces extremely high quality nanowires, with carrier lifetimes of over 7ns. This work made use of the Manchester iTCSPC spectrometer, built by group PhD student Stefan Skalsky to study the low fluence dynamics at room temperture.

This growth method opens up a new facet in crystal-phase engineering for nanowire optoelectronics.

Reference: Carrier dynamics and recombination mechanisms in InP twinning superlattice nanowires, Xiaoming Yuan, Kunwu Liu, Stefan Skalsky, Patrick Parkinson, Long Fang, Jun He, Hark Hoe Tan, and Chennupati Jagadish, Optics Express 28, 16795 (2020) DOI: 10.1364/OE.388518

New Paper: Visualizing the role of photoinduced ion migration on photoluminescence in halide perovskite grains​

Group student Hoyeon has had a paper accepted in the RSC Journal of Materials Chemistry C, studying the photo-brightening effect in perovskite grains using correlated optical and chemical mapping. In collaboration with the Flavell group and the NanoSIMS group at Manchester, this study linked luminescence lifetime and emission energies to local changes in oxygen and iodine density close to the surface of methyammonium lead iodide grains; a prototypical next-generation photovoltaic material.

This new study unambiguously links the emission efficiency improvement under illumination – the so-called photo-brightening effect – to light-induced migration of iodine into the bulk of the crystal and an increase in oxygen levels close to the surface of the grains. By mapping the emission efficiency and chemical levels on the sub-micron scale, we find that grain size has a decreasing role with light-soaking.

Reference: “Visualizing the role of photoinduced ion migration on photoluminescence in halide perovskite grains​“, J. Mater. Chem. C (2020), DOI:10.1039/d0tc01441a

Conference Proceedings: Spatially and temporally resolved degradation in antisolvent treated perovskite films

Group PhD student Hoyeon Choi has had a conference proceedings accepted for SPIE Europe 2020. As this conference has been cancelled, his talk is available throught the SPIE Digital Form.

In his work, Hoyeon describes the application of confocal and time-resolved spectral mapping to study and understand photobrightening and degradation processes in a prototypical perovskite material fabricated with and without use of anti-solvent treatment.

The presentation and paper are available online now.

Reference: Spatially and temporally resolved degradation in antisolvent treated perovskite films, Hoyeon Choi, Chun-Ren Ke, Stefan Skalsky, Wendy Flavell, and Patrick Parkinson, Proc. SPIE 11365, Organic Electronics and Photonics: Fundamentals and Devices II, 113650Q

New Paper: Heterostructure and Q-factor engineering for low-threshold and persistent nanowire lasing

Group PhD student Stefan Skalsky’s paper on semiconductor nanowire lasing has just been published in Light: Science and Applications. In this new work, Stefan used his newly developed Interferometric Time-Correlated Single Photon Counting system (i-TCSPC) to measure the coherence length of laser emission from nanowires grown by the Liu group at UCL. These measurements allowed the direct calculation of the nanowire mirror reflectivity.

During this study, Stefan found that it was possible to use indirect bandgap materials as a holding state for carriers before they relax into the emissive wells; this finding both allows multi-nanosecond lasing after a sub-picosecond excitation, and record low lasing thresholds through resonant excitation.

This work was supported by TEM provided by the Sanchez group at Warwick.

Reference: Heterostructure and Q-factor engineering for low-threshold and persistent nanowire lasing, Skalsky et al., Light: Science and Applications, 9, 43 (2020) https://doi.org/10.1038/s41377-020-0279-y