Excitonic luminescence of iodine-intercalated HfS$_2$

TL;DR

This study reports on the photoluminescence properties of bulk HfS$_2$ intercalated with iodine, revealing excitonic emissions linked to iodine molecules and their phonon interactions, confirmed by spectroscopic analysis.

Contribution

It demonstrates the excitonic luminescence in iodine-intercalated HfS$_2$ and identifies the role of iodine molecules in the emission process, a novel insight into intercalated layered materials.

Findings

Observation of excitonic emission lines at 1.4-1.5 eV

Identification of phonon-assisted excitonic transitions

Confirmation of iodine intercalation via spectroscopy

Abstract

Photoluminescence from bulk HfS$_2$ grown by the chemical vapor transport method is reported. A series of emission lines is apparent at low temperature in the energy range of 1.4 - 1.5 eV. Two groups of the observed excitonic transitions followed by their replicas involving acoustic and optical phonons are distinguished using classical intensity correlation analysis. The emission is attributed to the recombination of excitons bound to iodine (I$_2$) molecules intercalated between layers of HfS$_2$. The I$_2$ molecules are introduced to the crystal during the growth as halogen transport agents in the growth process. Their presence in the crystal is confirmed by secondary ion mass spectroscopy.