Synthesis and optical properties of MoS2 and isomorphous nanoclusters in the quantum confinement regime

被引:244
作者
Wilcoxon, JP
Newcomer, PP
Samara, GA
机构
[1] Sandia National Laboratories, Albuquerque
关键词
D O I
10.1063/1.365367
中图分类号
O59 [应用物理学];
学科分类号
摘要
Highly crystalline nanoclusters of hexagonal (2H polytype) MoS2 and several of its isomorphous Mo and W chalcogenides have been synthesized with excellent control over cluster size down to similar to 2 nm. These clusters exhibit highly structured, bandlike optical absorption and photoluminescence spectra which can be understood in terms of the band-structures for the bulk crystals. Key results of this work include: (1) strong quantum confinement effects with blue shifts in some of the absorption features relative to bulk crystals as large as 4 eV for clusters similar to 2.5 nm in size, thereby allowing great tailorability of the optical properties; (2) the quasiparticle (or excitonic) nature of the optical response is preserved down to clusters less than or similar to 2.5 nm in size which are only two unit cells thick; (3) the demonstration of the strong influence of dimensionality on the magnitude of the quantum confinement. Specifically, three-dimensional confinement of the carriers produces energy shifts which are over an order of magnitude larger than those due to one-dimensional (perpendicular to the layer planes) confinement emphasizing the two-dimensional nature of the structure and bonding; (4) the observation of large increases in the spin-orbit splittings at the top of the valence band at the K and M points of the Brillouin zone with decreasing cluster size, a feature that reflects quantum confinement as well as possible changes in the degree of hybridization of the electronic orbitals which make up the states at these points; and (5) the observation of photoluminescence due to both direct and surface recombination. Several of these features bode well for the potential of these materials for solar photocatalysis. (C) 1997 American Institute of Physics.
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页码:7934 / 7944
页数:11
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