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PUBLISHED ONLINE: 19 SEPTEMBER 2016 | http://dx.doi.org/10.1038/nnano.2016.171
Web End =DOI: 10.1038/NNANO.2016.171
Likai Li1,2, Jonghwan Kim3, Chenhao Jin3, Guo Jun Ye2,4,5, Diana Y. Qiu3,6, Felipe H. da Jornada3,6, Zhiwen Shi3, Long Chen7, Zuocheng Zhang1,2, Fangyuan Yang1,2, Kenji Watanabe8, Takashi Taniguchi8, Wencai Ren7, Steven G. Louie3,6*, Xian Hui Chen2,4,5*, Yuanbo Zhang1,2* and Feng Wang3,6,9*
Phosphorene, a single atomic layer of black phosphorus, has recently emerged as a new two-dimensional (2D) material that holds promise for electronic and photonic technologies15.
Here we experimentally demonstrate that the electronic structure of few-layer phosphorene varies signicantly with the number of layers, in good agreement with theoretical predictions. The interband optical transitions cover a wide, technologically important spectral range from the visible to the mid-infrared. In addition, we observe strong photoluminescence in few-layer phosphorene at energies that closely match the absorption edge, indicating that they are direct bandgap semiconductors. The strongly layer-dependent electronic structure of phosphorene, in combination with its high electrical mobility, gives it distinct advantages over other 2D materials in electronic and opto-electronic applications.
Atomically thin 2D crystals have been recognized as a new class of materials with unique material properties that are potentially important for electronic and photonic technologies1,2,613. Various
2D crystals have been uncovered, ranging from metallic (and super-conducting) NbSe2 and semimetallic graphene to semiconducting
MoS2 and insulating hexagonal boron nitride (hBN). The energy bandgap, a dening characteristic of electronic materials, varies from 0 (in metals and graphene) to 5.8 eV (in hBN) in these 2D crystals. Despite the rich variety that is currently available, 2D materials with a bandgap in the range from 0.3 to 1.5 eV are notably absent14. Such a bandgap corresponds to the spectral range from mid-infrared to near-infrared, which is important for optoelectronic technologies such as telecommunications and solar energy harvesting. It is therefore desirable to obtain 2D materials with a bandgap that falls within this range and also matches that of the technologically important silicon (bandgap = 1.1 eV) andIIIV semiconductors such as InGaAs, without compromising sample mobility15.
Monolayer and few-layer phosphorene are predicted1620 to
bridge the much-needed bandgap range from 0.3 to 2 eV. Inside monolayer phosphorene, each phosphorus atom is covalently bonded with three adjacent phosphorus atoms to form a puckered honeycomb structure21. The three near sp3 bonds together...