Congratulations to group PhD Stefan Skalsky

A post-viva call

A huge congratulations to group PhD student Stefan Skalsky (co-supervised with Prof. Wendy Flavell) who passed his PhD viva with minor corrections. Even more impresively, he managed to deal with the challenges of a video-cal based viva.

His examiners were Prof. David Mowbray (Sheffield) and Prof. Mark Dickinson (Manchester).

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

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)

Talk at UK Semiconductors 2019

Group PhD student Stefan Skalsky gave a talk at the UK Semiconductors meeting in Sheffield. His talk, on “Nanosecond lasing and mm-scale optical coherence length in GaAsP/GaAs Quantum-Well Nanowire Lasers” descibed his recent work using interferometric time-resolved spectroscopy to reveal the end-facet reflectivity in nanowire lasers.

Photon 2018

Both Stefan and Arturo will present at Photon 2018 in Aston, UK (September 3rd-6th, 2018).

20180904_175257.jpgStefan presented a poster on “Time and Spectrally-Resolved Microscopy of GaAsP-GaAs core-shell Quantum Well Lasers“, describing some recent work with collaborators in the group of Prof. Huiyun Liu at University College London.





Arturo presented a talk on “Nanolaser optimization through statistical optoelectronic analysis“. This work, done in collaboration with the EME group at the Australian National University, describes his recent work on all optical high throughput techniques for nanolaser optimization.

The group goes to Oxford

Arturo, Xiaoyan, Stefan and Patrick visited Oxford for the UK III-V Nanowire workshop hosted at Corpus Christi College. While Arturo presented a poster and Patrick a talk, the whole group got to meet the ever increasing number of researchers working on III-V Nanowires in the UK.