期刊
NATURE NANOTECHNOLOGY
卷 12, 期 9, 页码 871-+出版社
NATURE PUBLISHING GROUP
DOI: 10.1038/NNANO.2017.124
关键词
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资金
- National Science Foundation [DMR-0964886]
- Air Force Office of Scientific Research [FA9550-11-1-0055]
- Gordon and Betty Moore Centre for Physical Biology at the California Institute of Technology
- KNI Prize Postdoctoral Fellowship in Nanoscience at the Kavli Nanoscience Institute of the California Institute of Technology
Charge carrier dynamics in amorphous semiconductors has been a topic of intense research that has been propelled by modern applications in thin-film solar cells(1), transistors and optical sensors(2). Charge transport in these materials differs fundamentally from that in crystalline semiconductors(3,4) owing to the lack of long-range order and high defect density. Despite the existence of well-established experimental techniques such as photoconductivity time-of-flight(5-8) and ultrafast optical measurements(9-12), many aspects of the dynamics of photo-excited charge carriers in amorphous semiconductors remain poorly understood. Here, we demonstrate direct imaging of carrier dynamics in space and time after photo-excitation in hydrogenated amorphous silicon (a-Si: H) by scanning ultrafast electron microscopy (SUEM)(13,14). We observe an unexpected regime of fast diffusion immediately after photoexcitation, together with spontaneous electron-hole separation(15) and charge trapping(3) induced by the atomic disorder. Our findings demonstrate the rich dynamics of hot carrier transport in amorphous semiconductors that can be revealed by direct imaging based on SUEM.
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