Dr Maruf Sarkar

My research examines porous gallium nitride (GaN), a nanostructured semiconductor fabricated by electrochemical etching. I study this material through porous GaN distributed Bragg reflectors (DBRs) — high-reflectivity mirrors — for integration into next-generation displays. Elucidating their morphology requires electron microscopy to understand how etching proceeds through the material, study pore shape and distribution, and quantify porosity. 

I am proficient in FIB-SEM tomography via our Zeiss Crossbeam 540 for microscale volume and nanoscale spatial resolution 3D datasets. Zeiss Atlas 3D Tomography software is essential to this approach, enabling slice thickness tracking, auto-focus, and image registration. Furthermore, I have experience with Dragonfly, which is used to reconstruct, and segment registered serial sections. Through this approach, the most beautiful nanopores, akin to the branches or roots of a plant, can be reconstructed and rendered in 3D.

I have published a technique in Microscopy and Microanalysis using backscattered electron scanning electron microscopy (BSE-SEM), which offers a non-invasive, plan-view sub-surface imaging modality. Sub-surface BSE-SEM “sees through" the non-porous GaN cap to reveal sub-surface porous morphology. This approach provides access to changes in the pore morphology arising from variations in electrochemical etching, chemical composition, and crystallographic defects. I worked with experts across industry and academia in electrochemistry, metal-organic vapour phase epitaxy, atomic force microscopy, scanning transmission electron microscopy, and focused ion beam (FIB) slice-and-view tomography for a correlative microscopy approach to understand the associated spatial resolution, image contrast, and information depth.