Our recent work on single-nanowire terahertz detectors has been published in a special issue of the Lithuanian Journal of Physics, celebrating the 70th birthday of Prof. Arunas Krotkus.
In this work, Dr Kun Peng used single-nanowire terahertz detectors with different capping to understand the relative contribution of the core and cap to the detected THz signal. By tuning the cap to be thicker, it is possible to engineer these detectors to have shorter carrier lifetimes and as a result, to exhibit direct THz field detection.
In research led by Hannah Joyce (University of Cambridge), and colleagues at the University of Oxford and the Australian National University we have reported an in-depth terahertz study of the influence of surfaces on carrier recombination in nanowires.
By performing power-dependant and diameter-dependant measurements, Hannah determined the surface recombination velocity in GaAs nanowires. Given the huge surface-area-to-volume ratio in nanowires, this is a key property and one which is essential to understanding the electronic performance in this nanomaterial.
Kun Peng has written a paper accepted in IOP Nanotechnology (http://iopscience.iop.org/article/10.1088/1361-6528/aa5d80).
The work, building on previous progress in single nanowire terahertz detectors, uses a combination of an axial doping profile and novel optical characterisation to improve the contact quality for these devices.
The new nanowire detectors show improved signal-to-noise ratio, now approaching that of conventional detectors.
Conor, a UoM 4th year undergraduate has spent the summer working in the lab (see here for details). He has been kind enough to describe working on a long summer project in the group:
This summer, I spent ten weeks designing, building, and testing a terahertz time domain spectroscopy system that utilised optical laser diodes rather than the standard technique involving femtosecond lasers. The aim of this system was that it would be significantly cheaper while still retaining the quality of previous systems.
These ten weeks was a huge opportunity to learn in depth about experimental physics and all the struggles and challenges behind the scenes of every journal paper. Dealing with limited resources, liaising with other members of the PSI, and deciding how to approach and deal with various obstacles to your progress were all vital experiences I went through that helped me develop an understanding of the processes involved in taking on real physical research.
In terms of the experiment itself, I handled the taking of measurements by using electronics and analysed data computationally, as well as designing a number of custom parts for use in the experiment. I was also able to use relatively low-tech skills I hadn’t expected would be necessary, such as soldering, to build parts, while simultaneously getting to grips with the electron beam lithography technique used to print antennas on semiconductor substrates.
If you are interested in this research or want to know more about research in the group, please contact Patrick.
Over the past 10 weeks, Conor Wilman (a UoM undergraduate) has been working with the group developing a low-cost and easy method of doing terahertz spectroscopy, known as terahertz quasi-time-domain-spectroscopy. His work, funded by the Rank Prize Funds Summer Studentship has been in trying to replicate this technique in the Manchester labs.
While the final spectrometer unfortunately did not work out, he produced a number of interesting findings and new designs along the way.
Thanks to Conor!