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Representation of THz spectroscopy of a metamaterial with a Nanowire THz sensor

Representation of THz spectroscopy of a metamaterial with a Nanowire THz sensor

Credit: Rendering by Dimitars Jevtics

Prof Michael Johnston

Professor of Physics

Research theme

  • Photovoltaics and nanoscience

Sub department

  • Condensed Matter Physics

Research groups

  • Terahertz photonics
  • Advanced Device Concepts for Next-Generation Photovoltaics
michael.johnston@physics.ox.ac.uk
Johnston Group Website
  • About
  • Publications

Correction to “A Templating Approach to Controlling the Growth of Coevaporated Halide Perovskites”

ACS Energy Letters American Chemical Society (ACS) 8:11 (2023) 4714-4715

Authors:

Siyu Yan, Jay B Patel, Jae Eun Lee, Karim A Elmestekawy, Sinclair R Ratnasingham, Qimu Yuan, Laura M Herz, Nakita K Noel, Michael B Johnston
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Terahertz characterization of charge carrier dynamics in 3D Dirac semi-metal Cd3As2 nanowires

2023 48th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) IEEE (2023) 1-2

Authors:

Y Saboon, D Damry, CQ Xia, P Schoenherr, X Liu, Thorsten Hesjedal, Laura M Herz, Michael B Johnston, JL Boland

Abstract:

Optical Pump Terahertz Probe (OPTP) spectroscopy is a well-established measurement technique with which charge-carrier dynamics of semiconductor nanowires (NW) can be extracted in a noncontact manner. Here in this work, we employ OPTP spectroscopy for measuring temperature-dependent photoconductivity spectra of 3D Dirac Cd 3 As 2 semi-metal nanowires, revealing a high Extrinsic carrier concentration of ∼2.0x1017cm−3 and ultrahigh carrier mobility of up to ∼13x103cm2V−1s−1 at a temperature of 5 K.
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Topological materials for helicity-dependent THz emission

2023 48th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) IEEE (2023) 1-2

Authors:

A Mannan, Y Saboon, CQ Xia, DA Damry, P Schoenherr, Dharmalingam Prabhakaran, Laura M Herz, Thorsten Hesjedal, Michael B Johnston, Jl Boland

Abstract:

Topological insulator (TI) materials are emerging as novel materials for spintronic applications. Here, we demonstrate helicity-dependent THz emission from Dirac semi-metal Cd 3 As 2 nanowires and used scattering-type scanning optical microscopy (s-SNOM) to identify potential single nanowire candidates for device applications. The preliminary investigation data of a candidate nanowire shows a homogenous topography and constant dielectric function in the MIR range. Indicating high-quality crystalline growth ideal for topological characterization.
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Roadmap on Photovoltaic Absorber Materials for Sustainable Energy Conversion

(2023)

Authors:

James C Blakesley, Ruy S Bonilla, Marina Freitag, Alex M Ganose, Nicola Gasparini, Pascal Kaienburg, George Koutsourakis, Jonathan D Major, Jenny Nelson, Nakita K Noel, Bart Roose, Jae Sung Yun, Simon Aliwell, Pietro P Altermatt, Tayebeh Ameri, Virgil Andrei, Ardalan Armin, Diego Bagnis, Jenny Baker, Hamish Beath, Mathieu Bellanger, Philippe Berrouard, Jochen Blumberger, Stuart A Boden, Hugo Bronstein, Matthew J Carnie, Chris Case, Fernando A Castro, Yi-Ming Chang, Elmer Chao, Tracey M Clarke, Graeme Cooke, Pablo Docampo, Ken Durose, James R Durrant, Marina R Filip, Richard H Friend, Jarvist M Frost, Elizabeth A Gibson, Alexander J Gillett, Pooja Goddard, Severin N Habisreutinger, Martin Heeney, Arthur D Hendsbee, Louise C Hirst, M Saiful Islam, KDG Imalka Jayawardena, Michael B Johnston, Matthias Kauer, Jeff Kettle, Ji-Seon Kim, Dan Lamb, David Lidzey, Jihoo Lim, Roderick MacKenzie, Nigel Mason, Iain McCulloch, Keith P McKenna, Sebastian B Meier, Paul Meredith, Graham Morse, John D Murphy, Chris Nicklin, Paloma Ortega-Arriaga, Thomas Osterberg, Jay B Patel, Anthony Peaker, Moritz Riede, Martyn Rush, James W Ryan, David O Scanlon, Peter J Skabara, Franky So, Henry J Snaith, Ludmilla Steier, Jarla Thiesbrummel, Alessandro Troisi, Craig Underwood, Karsten Walzer, Trystan Watson, J Michael Walls, Aron Walsh, Lucy D Whalley, Benedict Winchester, Samuel D Stranks, Robert LZ Hoye
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Cation-disorder engineering promotes efficient charge-carrier transport in AgBiS2 nanocrystal films

Advanced Materials Wiley 35:48 (2023) 2305009

Authors:

Marcello Righetto, Yongjie Wang, Karim A Elmestekawy, Chelsea Q Xia, Michael B Johnston, Gerasimos Konstantatos, Laura M Herz

Abstract:

Efficient charge-carrier transport is critical to the success of emergent semiconductors in photovoltaic applications. So far, disorder has been considered detrimental for charge-carrier transport, lowering mobilities and causing fast recombination. This work demonstrates that, when properly engineered, cation disorder in a multinary chalcogenide semiconductor can considerably enhance the charge-carrier mobility and extend the charge-carrier lifetime. Here, the properties of AgBiS2 nanocrystals (NCs) are explored where Ag and Bi cation-ordering can be modified via thermal-annealing. Local Ag-rich and Bi-rich domains formed during hot-injection synthesis are transformed to induce homogeneous disorder (random Ag-Bi distribution). Such cation engineering results in a six-fold increase in the charge-carrier mobility, reaching ∼2.7 cm2V−1s−1 in AgBiS2 NC thin films. It is further demonstrated that homogeneous cation disorder reduces charge-carrier localisation, a hallmark of charge-carrier transport recently observed in silver-bismuth semiconductors. This work proposes that cation-disorder engineering flattens the disordered electronic landscape, removing tail states that would otherwise exacerbate Anderson localisation of small polaronic states. Together, these findings unravel how cation-disorder engineering in multinary semiconductors can enhance the efficiency of renewable energy applications.

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