Dr Naresh Gunasekar

Research Associate

Physics

Publications

High figure-of-merit gallium oxide UV photodetector on silicon by MBE : a path toward monolithic integration
Mukhopadhyay Partha, Hatipoglu Isa, Sakthivel Tamil Selvan, Hunter Daniel A, Gunasekar Naresh Kumar, Edwards Paul R, Martin Robert W, Seal Sudipta, Schoenfeld Winston Vaughan
Advanced Photonics Research Vol 2 (2021)
https://doi.org/10.1002/adpr.202000067
Origin of red emission in β-Ga2O3 analysed by cathodoluminescence and photoluminescence spectroscopy
Naresh-Kumar Gunasekar, Macintyre Hazel, Shanthi Shanthi, Edwards Paul R, Martin Robert W, Daivasigamani Krishnamurthy, Sasaki Kohei, Kuramata Akito
Physica Status Solidi B Vol 258 (2021)
https://doi.org/10.1002/pssb.202000465
Advances in electron channelling contrast imaging and electron backscatter diffraction for imaging and analysis of structural defects in the scanning electron microscope
Trager-Cowan C, Alasmari A, Avis W, Bruckbauer J, Edwards P R, Hourahine B, Kraeusel S, Kusch G, Jablon B M, Johnston R, Martin R W, McDermott R, Naresh-Kumar G, Nouf-Allehiani M, Pascal E, Thomson D, Vespucci S, Mingard K, Parbrook P J, Smith M D, Enslin J, Mehnke F, Kneissl M, Kuhn C, Wernicke T, Knauer A, Hagedorn S, Walde S, Weyers M, Coulon P-M, Shields P A, Zhang Y, Jiu L, Gong Y, Smith R M, Wang T, Winkelmann A
IOP Conference Series: Materials Science and Engineering Vol 891 (2020)
https://doi.org/10.1088/1757-899X/891/1/012023
Metrology of crystal defects through intensity variations in secondary electrons from the diffraction of primary electrons in a scanning electron microscope
Naresh-Kumar G, Alasamari A, Kusch G, Edwards P R, Martin R W, Mingard K P, Trager-Cowan C
Ultramicroscopy Vol 213 (2020)
https://doi.org/10.1016/j.ultramic.2020.112977
Structural and luminescence imaging and characterisation of semiconductors in the scanning electron microscope
Trager-Cowan Carol, Alasmari Aeshah, Avis William, Bruckbauer Jochen, Edwards Paul R, Ferenczi Gergely, Hourahine Benjamin, Kotzai Almpes, Kraeusel Simon, Kusch Gunnar, Martin Robert W, McDermott Ryan, Gunasekar Naresh, Nouf-Allehiani M, Pascal Elena, Thomson David, Vespucci Stefano, Smith Matthew David, Parbrook Peter J, Enslin Johannes, Mehnke Frank, Kuhn Christian, Wernicke Tim, Kneissl Michael, Hagedorn Sylvia, Knauer Arne, Walde Sebastian, Weyers Markus, Coulon Pierre-Marie, Shields Philip, Bai J, Gong Y, Jiu Ling, Zhang Y, Smith Richard, Wang Tao, Winkelmann Aimo
Semiconductor Science and Technology Vol 35 (2020)
https://doi.org/10.1088/1361-6641/ab75a5
Subgrain structure and dislocations in WC-Co hard metals revealed by electron channelling contrast imaging
Jablon BM, Mingard K, Winkelmann A, Naresh-Kumar G, Hourahine B, Trager-Cowan C
International Journal of Refractory Metals and Hard Materials Vol 87 (2020)
https://doi.org/10.1016/j.ijrmhm.2019.105159

More publications

Projects

Quantitative non-destructive nanoscale characterisation of advanced materials
Hourahine, Ben (Principal Investigator) Edwards, Paul (Co-investigator) Roper, Marc (Co-investigator) Trager-Cowan, Carol (Co-investigator) Gunasekar, Naresh (Research Co-investigator)
"To satisfy the performance requirements for near term developments in electronic and optoelectronic devices will require pioneering materials growth, device fabrication and advances in characterisation techniques. The imminent arrival of devices a few atoms thick that are based on lighter materials such as graphene or boron nitride and also advanced silicon and diamond nano-structures. These devices pose new challenges to the currently available techniques for producing and understanding the resulting devices and how they fail. Optimising the performance of such devices will require a detailed understanding of extended structural defects and their influence on the properties of technologically relevant materials. These defects include threading dislocations and grain boundaries, and are often electrically active and so are strongly detrimental to the efficiency and lifetimes of nano-scale devices (a single badly-behaved defect can cause catastrophic device failure). These defects are especially problematic for devices such as silicon solar cells, advanced ultraviolet light emitting diodes, and advanced silicon carbide and gallium nitride based high power devices (used for efficient switching of large electrical currents or for high power microwave telecoms). For graphene and similar modern 2D materials, grain boundaries have significant impact on their properties as they easily span the whole size of devices.

Resolving all of these problems requires new characterisation techniques for imaging of extended defects which are simultaneously rapid to use, are non-destructive and are structurally definitive on the nanoscale. Electron channelling contrast imaging (ECCI) is an effective structural characterisation tool which allows rapid non-destructive visualisation of extended crystal defects in the scanning electron microscope. However ECCI is usually applied as a qualitative method of investigating nano-scale materials, has limitations on the smallest size features that it can resolve, and suffers from difficulties in interpreting the resulting images. This limits this technique's ability to work out the nature of defects in these advanced materials.

We will make use of new developments in energy resolving electron detectors, new advances in the modelling of electron beams with solids and the knowledge and experience of our research team and partners, to obtain a 6 fold improvement in the spatial resolution of the ECCI technique. This new energy-filtered way of making ECCI measurements will radically improve the quality of the information that can be obtained with this technique. We will couple our new capabilities to accurately measure and interpret images of defects to other advanced characterisation techniques. This will enable ECCI to be adopted as the technique of choice for non-destructive quantitative structural characterisation of defects in a wide range of important materials and provide a new technique to analyse the role of extended defects in electronic device failure."
01-Jan-2017 - 30-Jan-2021

More projects