期刊
PHYSICAL REVIEW B
卷 91, 期 16, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevB.91.165308
关键词
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资金
- DOD through the National Defense Science & Engineering Graduate Fellowship Program
- Center for Solar and Thermal Energy Conversion
- DOE [DE-SC0000957, DE-AC02-05CH11231]
- EFRC
- NSF [DMR-1254314]
- Direct For Mathematical & Physical Scien
- Division Of Materials Research [1254314] Funding Source: National Science Foundation
- U.S. Department of Energy (DOE) [DE-SC0000957] Funding Source: U.S. Department of Energy (DOE)
Optical measurements and first-principles calculations of the band structure and exciton states in direct-gap bulk and few-layer PbI2 indicate that the n = 1 exciton is Frenkel-like in nature in that its energy exhibits a weak dependence on thickness down to atomic-length scales. Results reveal large increases in the gap and exciton binding energy with a decreasing number of layers and a transition of the fundamental gap, which becomes indirect for one and two monolayers. Calculated values are in reasonable agreement with a particle-in-a-box model relying on the Wannier-Mott theory of exciton formation. General arguments and existing data suggest that the Frenkel-like character of the lowest exciton is a universal feature of wide-gap layered semiconductors whose effective masses and dielectric constants give bulk Bohr radii that are on the order of the layer spacing.
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