Congratulations to first group PhD student Juan (Arturo), who managed to graduate today. Having passed his viva in March 2020, it was a long wait to return to Manchester. He is now working with Synaptec in Glasgow.

PhD Viva: Arturo

Arturo Alanis (the first PhD student of the group) had a successful PhD viva today. His thesis examiners were Dr Hannah Joyce (Cambridge) and Dr Jessica Boland (Manchester).

Arturo has already secured a postdoctoral position to start in a few weeks; we’ll be sad to see him go, but wish him the best for his future beyond Manchester and the North West! Over the past four years Arturo has built much of the experimental tools and techniques for our work on nanowires and nanowire lasers – as well as dealing with lab moves and teaching.

All the best to Arturo on the next stage of his career!

New Paper: Characterisation, Selection and Micro-Assembly of Nanowire Laser Systems

Our collaborative work on the selection, transfer and testing of semiconductor nanowire lasers has now been published in Nano Letters.

In this work, growth colleagues at ANU prepared nanowire lasers which were characterised at Manchester. This characterisation was used to select bins of nanowires, which were transferred using a cutting edge pick-and-place tool at the University of Strathclyde. The transferred wires were re-tested in Manchester; while some wires showed identical behaviour, some showed a change in lasing mode.

This work will guide the heterointegration of nanowire lasers with photonic circuits, targetting high-yield and industrial applicability.

Reference: Characterisation, Selection and Micro-Assembly of Nanowire Laser Systems, Jevtics et al., Nano Letters (ASAP), DOI: 10.1021/acs.nanolett.9b05078

New Paper – Threshold reduction and yield improvement of semiconductor nanowire lasers via processing-related end-facet optimization

Arturo has had a paper accepted for publication in Nanoscale Advances, describing the impact of the transfer process on the morphology and threshold of semiconductor nanowire lasers.

While many studies have sought to improve the threshold for lasing in semiconductor nanowire lasers, the role of process has not been significantly considered. By applying a large-scale population study to this system, Arturo has used statistical tools to identify the optimal processing methods which is transferrable to a wide varity of nanowire laser structures.

(Left) Threshold as a function of processing conditions, showing the improvement arising from PDMS or ultrasound transfer. (Right) A typical laser, showing coherent emission and lasing onset.

Reference: “Threshold reduction and yield improvement of semiconductor nanowire lasers via processing-related end-facet optimization“, J. A. Alanis et al., Nanoscale Advances, 2019 (10.1039/C9NA00479C)

New Paper – Visible and infrared photocurrent enhancement in a graphene-silicon Schottky photodetector through surface-states and electric field engineering

Spatially mapped photocurrent response from an engineered graphene/Silicon Schottky photodiode at telecommunication wavelengths showing enhancement at trench edges.

Nawapong Unsuree has had a paper accepted for publication in 2D Materials. coming from a collaboration between the Echtermeyer group (Manchester) and the Parkinson group. The research was conducted in the National Graphene Institute and the Photon Science Institute.

This new research reports the application of infrared scanning photocurrent microscopy to new devices with structured electric field, to reveal a ten-fold enhancement in photocurrent responsivity close to lateral edges.

This research paves the way towards high-sensitivity infrared photodetectors based on the graphene-silicon architecture.

Reference: Visible and infrared photocurrent enhancement in a graphene-silicon Schottky photodetector through surface-states and electric field engineering, 2D Materials, 2019, DOI: 10.1088/2053-1583/ab32f5

New Paper – Emission Properties and Ultrafast Carrier Dynamics of CsPbCl3 Perovskite Nanocrystals

Visual abstract
Emission and absorption of perovskite nanocrystals, with associated electron microscopy

Congratulations to Ruben Ahumada-Lazo for his new paper on emission properties of perovskite nanocrystals. In his new paper, published in ACS Journal of Physical Chemistry C, he used ultrafast and high-fluence optical techniques based at the Photon Science Institute to reveal the radiative and non-radiative recombination pathways in CsPbCl3 perovskite nanocrystals.

In this collaboration between the Binks group (Manchester Physics), Parkinson group (Manchester Physics), the Ducati group (Cambridge Materials), and the Humphreys Group (Cambridge Materials), a combination of synthesis, electron microscopy, photoluminescence and transient absorption are combined to reveal exciton, biexciton and trion lifetimes.

The new work is available online:
“Emission Properties and Ultrafast Carrier Dynamics of CsPbCl3 Perovskite Nanocrystals”, J. Phys. Chem. C, Just Accepted Manuscript DOI: 10.1021/acs.jpcc.8b11906

Project Summary: Large-scale approaches for nanolaser optimization

The emission of light at the nanoscale is of great importance for information processing, medicine and fabrication for optical circuits. Optical circuits would improve processing speeds and decrease the energy consumption necessary to operate data centres. This is due to the manipulation of light which can carry more information at faster speeds more efficiently than electrical signals over copper.

An important element of optical circuits is the light source; in our case, we focus on semiconductor nanowires. These tiny crystals can emit signals in the form of light and due to their compact size (one tenth the thickness of a human hair) and electronic properties; they can be easily integrated with current silicon technology. However, nanowires cannot be fabricated individually; they require a process which “grows” very big quantities. So, when we want to integrate them with current technology, it is necessary to select the ones with the best light emission quality.

We have developed a technique that allows us to test thousands (from 1000 to 10,000) of these wires rapidly and gather a large amount of information from each one. This gives us the advantage of finding the top performing wires which can be isolated and retrieved for their implementation in optical circuits. Additionally, we can perform a large statistical study to find trends in nanowires performance as a function of particular characteristics. For example, one could find that longer wires tend to emit light more efficiently, or a change in its chemical composition makes them better candidates for lasers.

These findings are a good stepping stone towards the improvement of nanowire design and fabrication.


New Paper – Optical Study of p-Doping in GaAs Nanowires for Low-Threshold and High-Yield Lasing

Our new work on large-scale statistical spectroscopy to optimize nanowire lasers is published today in Nano Letters. In this work, PhD student Arturo studied thousands of nanowires to identify the lowest threshold nanowire, as well as to model emission to identify the primary sources of non-radiative emission.

By quickly sorting nanowires by doping and length, he was able to demostrate sub-sets with over 90% yield and class-leading thresholds, pointing the way towards electrically injected nanolasers.

Congratulations Arturo!

(Left) Far-field emission from a record breaking nanowire laser, emitting at room temperature and low exciation levels. (Right) Doping vs Quantum efficiency, showing two key limiting behaviours.

Reference: “Optical Study of p-Doping in GaAs Nanowires for Low-Threshold and High-Yield Lasing”, Juan Alanis et al., Nano Letters, ASAP 2018, DOI: 10.1021/acs.nanolett.8b04048