期刊
NANO LETTERS
卷 18, 期 5, 页码 2870-2878出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.7b05484
关键词
Nanocrystal; depletion; dopant distribution; conduction; tin-doped indium oxide; band profile
类别
资金
- National Science Foundation (NSF)
- NASCENT
- NSF ERC [EEC-1160494, CHE-1609656]
- University of Texas at Austin MRSEC [DMR-1720595]
- University of Minnesota MRSEC [DMR-1420013]
- Welch Foundation [F-1848]
- Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy (DOE) [DE-AC02-05CH11231]
- DOE Early Career Research Program grant
- [DGE-1610403]
Electron conduction through bare metal oxide nanocrystal (NC) films is hindered by surface depletion regions resulting from the presence of surface states. We control the radial dopant distribution in tin-doped indium oxide (ITO) NCs as a means to manipulate the NC depletion width. We find in films of ITO NCs of equal overall dopant concentration that those with dopant-enriched surfaces show decreased depletion width and increased conductivity. Variable temperature conductivity data show electron localization length increases and associated depletion width decreases monotonically with increased density of dopants near the NC surface. We calculate band profiles for NCs of differing radial dopant distributions and in agreement with variable temperature conductivity fits find NCs with dopant-enriched surfaces have narrower depletion widths and longer localization lengths than those with dopant-enriched cores. Following amelioration of NC surface depletion by atomic layer deposition of alumina, all films of equal overall dopant concentration have similar conductivity. Variable temperature conductivity measurements on alumina-capped films indicate all films behave as granular metals. Herein, we conclude that dopant-enriched surfaces decrease the near-surface depletion region, which directly increases the electron localization length and conductivity of NC films.
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