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Layer‐Dependent Nonlinear Optical Properties and Stability of Non‐Centrosymmetric Modification in Few‐Layer GaSe Sheets
Author(s) -
Jie Wenjing,
Chen Xi,
Li Dian,
Xie Lu,
Hui Yeung Yu,
Lau Shu Ping,
Cui Xiaodong,
Hao Jianhua
Publication year - 2015
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201409837
Subject(s) - materials science , stacking , second harmonic generation , semiconductor , layer (electronics) , nonlinear optical , thin film , optoelectronics , bilayer , nonlinear optics , nonlinear system , condensed matter physics , optics , nanotechnology , chemistry , laser , physics , biochemistry , organic chemistry , quantum mechanics , membrane
Gallium selenide, an important second‐order nonlinear semiconductor, has received much scientific interest. However, the nonlinear properties in its two‐dimensional (2D) form are still unknown. A strong second harmonic generation (SHG) in bilayer and multilayer GaSe sheets is reported. This is also the first observation of SHG on 2D GaSe thin layers. The SHG of multilayer GaSe above five layers shows a quadratic dependence on the thickness; while that of a sheet thinner than five layers shows a cubic dependence. The discrepancy between the two SHG responses is attributed to the weakened stability of non‐centrosymmetric GaSe in the atomically thin flakes where a layer–layer stacking order tends to favor centrosymmetric modification. Importantly, two‐photon excited fluorescence has also been observed in the GaSe sheets. Our free‐energy calculations based on first‐principles methods support the observed nonlinear optical phenomena of the atomically thin layers.