Abstract
The need for improved UV emitting luminescent materials underscored by applications in optical communications, sterilization and medical technologies is often addressed by wide bandgap semiconducting oxides. Among these, the Mg-doped ZnO system is of particular interest as it offers the opportunity to tune the UV emission by engineering its bandgap via doping control. However, both the doped system and its pristine congener, ZnO, suffer from being highly prone to parasitic defect level emissions, compromising their efficiency as light emitters in the ultraviolet region. Here, employing the process of femtosecond pulsed laser ablation in a liquid (fs-PLAL), we demonstrate the systematic control of enhanced UV-only emission in Mg-doped ZnO nanoparticles using both photoluminescence and cathodoluminescence spectroscopies. The ratio of luminescence intensities corresponding to near band edge emission to defect level emission was found to be six-times higher in Mg-doped ZnO nanoparticles as compared to pristine ZnO. Insights from UV-visible absorption and Raman analysis also reaffirm this defect suppression. This work provides a simple and effective single-step methodology to achieve UV-emission and mitigation of defect emissions in the Mg-doped ZnO system. This is a significant step forward in its deployment for UV emitting optoelectronic devices.
Highlights
Wide bandgap semiconductors have an immense potential for application in UV optoelectronics
We report, for the first time, facile control of this important optoelectronic characteristic in a single-step femtosecond pulsed laser ablation in a liquid (fs-pulsed laser ablation in liquid (PLAL)) process using the energy of ablating pulses as the knob to tune the ratio of near band edge emission (NBE) to deep level emission (DLE) emission
The doping of Mg in the ZnO matrix and the formation of Mg-doped ZnO (Mg-ZnO) nanoparticles has been confirmed by performing X-ray diffraction (XRD) measurements
Summary
Wide bandgap semiconductors have an immense potential for application in UV optoelectronics. ZnO owes this popularity to its large bandgap, ease of doping [4] and its relatively large exciton binding energy, 60 meV, evident even at room temperature. While these features make the ZnO system an attractive choice for optoelectronics [5,6,7,8], they render it an important candidate in photocatalytic, antibacterial and biomedical technologies [9,10,11]. Doping is one of the most convenient techniques to systematically tune the emission properties of a semiconductor nanoparticle [17]
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