Tailoring Colour Centres of Host-Dopant Light Emitters by X-Ray Radiations

Area of Science:

• Materials Science
• Optoelectronics
• Solid State Physics

Background:

• Electrically driven host-dopant structures like gallium-doped zinc oxide (ZnO) microwires are key for miniaturized light sources.
• Current limitations include minimal variation in electroluminescence (EL) intensity with fixed dopant concentrations, hindering integrated optoelectronics.
• Tailoring EL properties of micro/nanostructures is crucial for advanced applications.

Purpose of the Study:

• To investigate X-ray irradiation as a post-treatment method for modifying the EL properties of Ga-doped ZnO microwires.
• To enhance the EL intensity and tune the color coordinates of these microwires.
• To explore the underlying mechanisms responsible for the observed EL variations.

Main Methods:

• Gallium-doped ZnO microwires were synthesized and characterized.
• Post-treatment involved controlled X-ray irradiation at various doses (e.g., 180 Gy).
• Electroluminescence spectra, intensity, and color coordinates were analyzed before and after irradiation. Density functional theory (DFT) simulations were employed to understand the mechanism.

Main Results:

• X-ray irradiation at 180 Gy increased green EL intensity by approximately 12 times and narrowed the spectrum.
• EL color coordinates shifted from (0.309, 0.416) to (0.319, 0.503), indicating purer green emission.
• Higher irradiation doses led to monotonic EL intensity increases (>20 times) and a redshift of ~30±6 nm, shifting emission towards green-yellow.

Conclusions:

• X-ray irradiation is a simple and effective post-treatment for tailoring the EL intensity and color of Ga-doped ZnO microwires.
• The observed EL variations are attributed to X-ray-stimulated substitution of host Zn atoms by interstitial Ga dopants, as suggested by DFT.
• This technique presents a viable strategy for optimizing host-dopant light emitters for practical optoelectronic applications.