Berlin 2018 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 30: Heterostructures, interfaces, and surfaces

HL 30.8: Talk

Wednesday, March 14, 2018, 17:00–17:15, EW 202

Exceptional Carrier Diffusion on CdTe Surfaces Revealed by 4D Electron Microscopy — •Ahmed M. El-Zohry, Basamat S. Shaheen, Jun Yin, Boon Ooi, Osman M. Bakr, and Omar F. Mohammed — King Abdullah University of Science and Technology

To further develop any real-world-energy devices, light light-triggered charge carrier dynamics near the surface of the absorber layers need to be visualized in space and time. Such spatial and dynamical information can only be accessed using the one of-a-kind technique of scanning ultrafast electron microscopy. Here, we clearly demonstrate not only that charge transport on material surfaces behaves very differently from that of the bulk, but also the surface orientation can control the overall charge carrier dynamics. More specifically, in CdTe single crystal with orientation of (110), we found that shows a the diffusion coefficient at surfaces of 3-4 order of magnitude higher than in bulk. The detected charges for the first time can move up to ~ 60 nm within 6 nanosecond time scale. Moreover, the X-ray photoelectron spectroscopy experiments and Density functional theory (DFT) calculations show that the surface diffusion process relay mostly on the crystal orientation and termination, in which other crystal with (211) orientation, highly tends to form ultrathin-oxidative layers that in turn suppress the charge transport through formation of mid surface-trap states