Photoluminescence of Few-Layer Indium Selenide Encapsulated with Hexagonal Boron Nitride

Naomi Paylaga^1,2*, Kenji Watanabe³, Takahashi Taniguchi³, Raman Sankar^4,5, Shao-Yu Chen⁴, Wei-Hua Wang¹

¹Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan
²Department of Physics, National Central University, Taoyuan, Taiwan
³Advanced Materials Laboratory, National Institute for Materials Science, Tsukuba, Japan
⁴Center of Condensed Matter Sciences, National Taiwan University, Taipei, Taiwan
⁵Institute of Physics, Academia Sinica, Taipei, Taiwan

* Presenter:Naomi Paylaga, email:naomitabudlong@gmail.com

Indium selenide is a layered two-dimensional material with promising electronic and optoelectronic applications. Previous studies have shown photoluminescence (PL) of transitions A and B occurring at the Γ point and the layer dependence of PL energy due to quantum confinement. However, a systematic study of the quantum confinement effect to the InSe band structure and the exciton binding energy for few-layer InSe have not been reported. Moreover, the detailed transition mechanism for few-layer InSe is still elusive. In this work, we report the photoluminescence of the atomically-thin InSe encapsulated in hexagonal boron nitride measured at 10 K. The hexagonal boron nitride encapsulation protects against oxygen exposure and sample damage due to prolonged laser exposure. We reveal the PL for transition A and B from 2L to bulk. Moreover, we show that the transition A can be deconvoluted to band-to-band recombination and exciton recombination. This peak assignment is consistent from 2L to bulk InSe. Lastly, we found that the exciton binding energy of InSe is layer dependent, with increasing exciton binding energy as the thickness decreases due to quantum confinement effect.

Keywords: two-dimensional materials, nanostructures, optical properties