Characterization of plasma and gas-phase chemistry during boron-nitride nanomaterial synthesis by laser-ablation of boron-rich targets

TL;DR

This study investigates the plasma and gas-phase chemistry during laser ablation of boron and boron nitride targets, revealing the formation of BN and B2N molecules and analyzing plasma parameters to understand nanomaterial synthesis processes.

Contribution

It provides detailed insights into the chemical species and plasma conditions during laser ablation of boron-rich targets, highlighting the formation of complex molecules relevant for BN nanomaterial production.

Findings

BN molecules observed in nitrogen and helium environments

B2N molecules emitted regardless of conditions

Plasma electron temperature peaks at 1.3 eV

Abstract

In this work, solid targets made from boron and boron nitride (BN) materials are ablated by a nanosecond pulsed laser at sub-atmospheric pressures of nitrogen and helium gases. Excited species in the ablation plume from the target are probed with spatiotemporally resolved optical emission spectroscopy (OES). Evaluation of chemical composition in the plasma plume revealed that for both boron-rich targets, emission from BN molecules is always observed in nitrogen-rich environments. In addition, BN molecules also present when ablating a boron nitride target in helium gas -- an indication that BN molecules in the plume may originate from the solid target. Furthermore, the ablation of BN target features emission of B2N molecules, regardless of the pressure and surrounding gas. These results suggest that the ablation of the BN target is more favorable for the generation of complex molecules containing boron and nitrogen species and possibly hint that BN is also more favorable feedstock for high-yield BN nanomaterial synthesis. Plasma parameters such as electron temperature (peak value of 1.3 eV) and density (peak value of 2x10^18 cm^-3) were also investigated in this work in order to discuss the chemical dynamics in the plume.