期刊
ACS NANO
卷 4, 期 4, 页码 2466-2474出版社
AMER CHEMICAL SOC
DOI: 10.1021/nn100275z
关键词
silicon nanomembrane; quantum confinement; surface roughness; thermoelectric; valley splitting
类别
资金
- DOE [DE-FG02-03ER46028]
- NSF/MRSEC [DMR-0520527]
- AFOSR [FA9550-09-1-0230]
- NSF [DMR-0537588]
- Chinese Scholar Council (CSC)
- Thai government
We report direct measurements of changes in the conduction-band structure of ultrathin silicon nanomembranes with quantum confinement. Confinement lifts the 6-fold-degeneracy of the bulk-silicon conduction-band minimum (CBM), Delta, and two inequivalent sub-band ladders, Delta(2) and Delta(4), form. We show that even very small surface roughness smears the nominally steplike features in the density of states (DOS) due to these sub-bands. We obtain the energy splitting between Delta(2) and Delta(4) and their shift with respect to the bulk value directly from the 2p(3/2)->Delta transition in X-ray absorption. The measured dependence of the sub-band splitting and the shift of their weighted average on degree of confinement is in excellent agreement with theory, for both Si(001) and Si(110).
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