Abstract
We report the high-powered laser modification of the chemical, physical, and structural properties of the two-dimensional (2D) van der Waals material GaSe. Our results show that contrary to expectations and previous reports, GaSe at the periphery of a high-power laser beam does not entirely decompose into Se and Ga2O3. In contrast, we find unexpectedly that the Raman signal from GaSe gets amplified around regions where it was not expected to exist. Atomic force microscopy (AFM), dielectric force microscopy (DFM), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) results show that laser irradiation induces the formation of nanoparticles. Our analyses demonstrate that, except for a fraction of Ga2Se3, these nanoparticles still belong to the GaSe phase but possess different electrical and optical properties. These changes are evidenced in the increased Raman intensity attributed to the near-resonance conditions with the Raman excitation laser. The elemental analysis of nanoparticles shows that the relative selenium content increased to as much as 70% from a 50:50 value in stoichiometric GaSe. This elemental change is related to the formation of the Ga2Se3 phase identified by Raman spectroscopy at some locations near the edge. Further, we exploit the localized high-power laser processing of GaSe to induce the formation of Ag–GaSe nanostructures by exposure to a solution of AgNO3. The selective reaction of AgNO3 with laser-irradiated GaSe gives rise to composite nanostructures that display photocatalytic activity originally absent in the pristine 2D material. The photocatalytic activity was investigated by the transformation of 4-nitrobenzenethiol to its amino and dimer forms detected in situ by Raman spectroscopy. This work improves the understanding of light–matter interaction in layered systems, offering an approach to the formation of laser-induced composites with added functionality.
Highlights
Results obtained from Atomic force microscopy (AFM) topography analyses showed that a large number of nanoparticles were formed in several micrometer wide regions next to the laserhowever, this approach relies on gold nanoparticles as ablated trench
In contrast to those previous studies, our work aims at the material on the edge of the laser-irradiated line had investigating the effects of GaSe irradiation in the air by a different morphology from the original flat and smooth twosemiconductor laser with a wavelength near the UV spectrum (405 nm) and a laser excitation power in the range of 1 W
The appearance of NPs upon laser irradiation was reported for the case of MoS2 layers before laser power reached levels to induce layer thinning.[28,31] distribution reported to depend on layer thickness and GaSe was studied by Raman spectroscopy in the near-infrared power density.[28]
Summary
From graphene to other two-dimensional (2D) materials like metal dichalcogenides and graphene oxide,[1,2] research groups around the globe are continuing to create, investigate, and modify these materials as well as finding ways to apply them as photodetectors, transistors, and a range of sensors.[3−5]. Gallium selenide has been gaining interest since the last few years, especially in applications such as photodetectors[10] and solar cells.[11] there are large number of reports on the different characteristics of GaSe, from conductivity and nonlinear optical to photocatalytic properties.[12,13] Functionalization with plasmonic nanoparticles is a promising approach for the modification and control of 2D material properties.[14,15]. Height distributions (histograms) for nanoparticles shown in the Z-scale images and the roughness from different regions numbered from 1 to 5. These five images are rescaled regions from sections in (e).
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