Gas-Phase Formation of Highly Luminescent 2D GaSe Nanoparticle Ensembles in a Nonequilibrium Laser Ablation Process.

Salah Elafandi,Zabihollah Ahmadi,Nurul Azam,Masoud Mahjouri-Samani

doi:10.3390/nano10050908

Abstract

Interest in layered two-dimensional (2D) materials has been escalating rapidly over the past few decades due to their promising optoelectronic and photonic properties emerging from their atomically thin 2D structural confinements. When these 2D materials are further confined in lateral dimensions toward zero-dimensional (0D) structures, 2D nanoparticles and quantum dots with new properties can be formed. Here, we report a nonequilibrium gas-phase synthesis method for the stoichiometric formation of gallium selenide (GaSe) nanoparticles ensembles that can potentially serve as quantum dots. We show that the laser ablation of a target in an argon background gas condenses the laser-generated plume, resulting in the formation of metastable nanoparticles in the gas phase. The deposition of these nanoparticles onto the substrate results in the formation of nanoparticle ensembles, which are then post-processed to crystallize or sinter the nanoparticles. The effects of background gas pressures, in addition to crystallization/sintering temperatures, are systematically studied. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectroscopy, and time-correlated single-photon counting (TCSPC) measurements are used to study the correlations between growth parameters, morphology, and optical properties of the fabricated 2D nanoparticle ensembles.

Highlights

During the past decade, a large family of two-dimensional (2D) materials beyond graphene have been under intense investigation [1,2,3]
We report a nonequilibrium gas-phase synthesis method for the stoichiometric formation of gallium selenide (GaSe) nanoparticles ensembles that can potentially serve as quantum dots
We show that the laser ablation of a target in an argon background gas condenses the laser-generated plume, resulting in the formation of metastable nanoparticles in the gas phase

Summary

Introduction

A large family of two-dimensional (2D) materials beyond graphene have been under intense investigation [1,2,3]. Ultrasonication-based [38,39], especially the ones accompanied by solvothermal treatments [40,41], syntheses methods have been widely adopted to produce 2D nanoparticles due to their low toxicity and ability to maintain the intrinsic properties of 2D bulk crystals [42] These techniques are time-consuming with low quantum yield, production yield, and repeatability [42]. The pulsed laser ablation/deposition (PLA/PLD) method is used as a versatile method to ablate a bulk GaSe target and form a stoichiometric plume (see Supporting Information) Condensation of this plume in background argon gas pressure allows tuning the formation of aggregates and nanoparticles in the gas phase. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectroscopy, and time-correlated single-photon counting (TCSPC) spectroscopy were used to study the correlations between the growth parameters, morphology, and optical properties of fabricated structures

Materials and Methods

Results and Discussion

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