Layer-dependent nonlinear optical properties and stability of non-centrosymmetric modification in few-layer GaSe sheets

Wenjing Jie, Xi Chen, Dian Li, Lu Xie, Yeung Yu Hui, Shu Ping Lau, Xiaodong Cui, Jianhua Hao*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

165 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)1185-1189
Number of pages5
JournalAngewandte Chemie - International Edition
Issue number4
Publication statusPublished - 19 Jan 2015
Externally publishedYes


  • Fluorescence
  • Gallium selenide
  • Photoluminescence
  • Second harmonic generation
  • Two-dimensional materials

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