Phase Identification and Strong Second Harmonic Generation in Pure ϵ-InSe and Its Alloys

Qiaoyan Hao, Huan Yi, Huimin Su, Bin Wei, Zhuo Wang, Zhezhu Lao, Yang Chai, Zhongchang Wang, Chuanhong Jin, Junfeng Dai, Wenjing Zhang

Research output: Journal article publicationJournal articleAcademic researchpeer-review

58 Citations (Scopus)


Two-dimensional material indium selenide (InSe) has offered a new platform for fundamental research in virtue of its emerging fascinating properties. Unlike 2H-phase transition-metal dichalcogenides (TMDs), ϵ phase InSe with a hexagonal unit cell possesses broken inversion symmetry in all the layer numbers, and predicted to have a strong second harmonic generation (SHG) effect. In this work, we find that the as-prepared pure InSe, alloyed InSe 1-x Te x and InSe 1-x S x (x = 0.1 and 0.2) are ϵ phase structures and exhibit excellent SHG performance from few-layer to bulk-like dimension. This high SHG efficiency is attributed to the noncentrosymmetric crystal structure of the ϵ-InSe system, which has been clearly verified by aberration-corrected scanning transmission electron microscopy (STEM) images. The experimental results show that the SHG intensities from multilayer pure ϵ-InSe and alloyed InSe 0.9 Te 0.1 and InSe 1-x S x (x = 0.1 and 0.2) are around 1-2 orders of magnitude higher than that of the monolayer TMD systems and even superior to that of GaSe with the same thickness. The estimated nonlinear susceptibility χ (2) of ϵ-InSe is larger than that of ϵ-GaSe and monolayer TMDs. Our study provides first-hand information about the phase identification of ϵ-InSe and indicates an excellent candidate for nonlinear optical (NLO) applications as well as the possibility of engineering SHG response by alloying.

Original languageEnglish
Pages (from-to)2634-2640
Number of pages7
JournalNano Letters
Issue number4
Publication statusPublished - 10 Apr 2019


  • alloy
  • indium selenide
  • nonlinear
  • Phase
  • second harmonic generation

ASJC Scopus subject areas

  • Bioengineering
  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanical Engineering


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