Unusual Red Light Emission from Nonmetallic Cu$_2$Te Microdisk for Laser and SERS Applications

TL;DR

This study reports the synthesis of hexagonal Cu₂Te microdisks that exhibit unusual red light emission, functioning as optical microcavities for lasing and as effective SERS substrates, with potential applications in photonics and biosensing.

Contribution

The paper introduces a novel method to prepare Cu₂Te microdisks with unique optical properties, including red lasing and high SERS enhancement, expanding their application scope.

Findings

Cu₂Te microdisks support whispering gallery modes for red lasing at 627.5 nm.

The microdisks exhibit a high quality factor of 1568 and a low lasing threshold.

They serve as efficient nonmetallic SERS substrates with an enhancement factor of ~1.95×10⁵.

Abstract

Physical characteristics of Cu$_2$Te are poorly investigated due to limited Te sources available and unclear atomic positions of crystal structure. Herein, hexagonal Cu$_2$Te microdisks are successfully prepared via chemical vapor deposition procedure using GaTe as Te source. The epitaxial growth mechanism of the Cu$_2$Te hexagonal structures with the orthorhombic phase are rationalized by proposed layer-over-layer growth model. The photoluminescence (PL) spectrum of Cu$_2$Te microdisks shows a new red emission band in addition to usual infrared light emission due to Cu deficiency. Single Cu$_2$Te microdisk operates as an optical microcavity supporting whispering gallery modes for red lasing around 627.5 nm. This Cu$_2$Te microdisk microcavity exhibits a high quality factor of 1568 and a low lasing threshold of 125 kW cm$^{-2}$ at room temperature. Meanwhile, Cu$_2$Te microdisks have been exhibited as an ideal platform for surface enhanced Raman scattering (SERS) eliminating drawbacks of noble metal substrates with detection limitation to nanomolar level and an enhancement factor of $\sim$1.95$\times$10$^5$. Hexagonal Cu$_2$Te microdisks turn out to be an efficient microcavity for red lasing and low-cost nonmetallic SERS substrates, opening potential applications in photonics and biological detection of aromatic molecules.