ε-InSe single crystals grown by a horizontal gradient freeze method

• Published in: CrystEngComm 2020-12, Vol.22 (45), p.7864-7869
• Main Authors: Sun, Maojun, Wang, Wei, Zhao, Qinghua, Gan, Xuetao, Sun, Yuanhui, Jie, Wanqi, Wang, Tao
• Format: Article
• Language: English
• Subjects: Chemical activity; Crystal growth; Free energy; Heat of formation; Indium selenides; Infrared absorption; Nonlinear optics; Optoelectronic devices; Phase diagrams; Photoluminescence; Raman spectroscopy; Second harmonic generation; Single crystals
• ISSN: 1466-8033; 1466-8033
• DOI: 10.1039/D0CE01271H

Indium selenide (InSe) single crystals have been considered as promising candidates for future optical, electrical, and optoelectronic device applications. In particular, due to its 2H stacking and non-centrosymmetric feature, ε-InSe is highly desirable for second harmonic generation. However, due to its complex phase diagram, the high chemical activity of the elements, and the large formation energy, single-phase crystal growth of ε-InSe still remains a challenge. In this work, we present our efforts using a horizontal gradient freeze (HGF) method to fabricate InSe single crystals for the first time, whose high-quality crystallinity has been confirmed by both X-ray diffraction (XRD) and transmission electron microscopy (TEM). Moreover, we further combine the photoluminescence, Raman spectroscopy and infrared absorption data to identify this single crystal to be ε-InSe. Finally, thickness-dependent second harmonic generation (SHG) measurements were carried out on our few-layer InSe samples, and the results demonstrate its promising application for non-linear optics.