期刊
NANO LETTERS
卷 15, 期 12, 页码 8204-8210出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.5b03708
关键词
2D Materials; ultrafast dynamics; carrier recombination; quantum well; Auger scattering swface recombination
类别
资金
- CCMR under NSF [DMR-1120296]
- AFOSR-MURI [FA9550-09-1-0705]
- ONR [N00014-12-1-0072]
- Cornell Center for Nanoscale Systems - NSF
We present results on photoexcited carrier lifetimes in few-layer transition metal dichalcogenide MoS, using nondegenerate ultrafast optical pump-probe technique. Our results show a sharp increase of the carrier lifetimes with the number of layers in the sample. Carrier lifetimes increase from few tens of picoseconds in monolayer samples to more than a nanosecond in 10-layer samples. The inverse carrier lifetime was found to scale according to the probability of the carriers being present at the surface layers, as given by the carrier wave function in few layer samples, which can be treated as quantum wells. The carrier lifetimes were found to be largely independent of the temperature, and the inverse carrier lifetimes scaled linearly with the photo excited carrier density. These observations are consistent with defect-assisted carrier recombination, in which the capture of electrons and holes by defects occurs via Auger scatterings. Our results suggest that carrier lifetimes in few-layer samples are surface recombination limited due to the much larger defect densities at surface layers compared with the inner layers.
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