Extraordinary Carrier Diffusion on CdTe Surfaces Uncovered by 4D Electron Microscopy

by Ahmed M.El-Zohry, Basamat S.Shaheen, Victor M.Burlakov, Jun Yin, Mohamed N.Hedhili, Semen Shikin, Boon Ooi, Osman M.Bakr, Omar F.Mohammed
Year: 2019 DOI: 10.1016/j.chempr.2018.12.020 / Chem, Volume 5, Issue 3, 14 March 2019, Pages 497-499

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Chem, Volume 5, Issue 3, 14 March 2019, Pages 497-499

Abstract

​Herein, we describe the selective mapping of surface charge carriers, achievedusing scanning ultrafast electron microscopy, for visualization of light-triggeredcarrierdynamicsonthenanometerscale,diffusingonthesurfaceofCdTe,alead-ing semiconductor in commercial photovoltaics. We reveal a novel diffusionmodel of charge carriers onsurfaces.The nature of charge diffusion varies signif-icantly, from superior diffusion to virtually trapped, depending on the crystalorientation. For instance, carriers on the(110) crystal orientation displayed adiffusion coefficient of40,000 cm2$s1(i.e.,104times larger than measuredin the bulk). In contrast, the (211) polar facets formed oxidative layers that, inturn, formed mid-surface-trap states that nearly arrested the charge diffusioncompletely. Complementary techniques and theoretical modeling explain theacute sensitivity of charge carriers to surface orientation and termination. Ourfindings reveal the enormous untapped potential for improved CdTe-baseddevices and optoelectronic materialsin general through facet management.

DOI: 10.1016/j.chempr.2018.12.020

https://doi.org/10.1016/j.chempr.2018.12.020

Keywords

Ultrafast electron imaging Crystal orientation Surface dynamics Renewable energy materials Oxidation layers Neat-surfaces DFT calculations Real-space imaging Surface termination