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

Electrically driven host-dopant structure, such as single Ga-doped ZnO microwire, is promising for miniaturized light sources. However, the electroluminescence (EL) for a fixed concentration of Ga dopant barely vary for a single ZnO micro/nanostructure, limiting their applications in integrated optoelectronics. Here X-ray irradiation is reported as a simple and effective post-treatment to tailor the EL intensity and color coordinate of Ga-doped ZnO microwires. After irradiating the microwires under an X-ray dose of 180 Gy, the intensity of green EL light increases by ≈12 times, accompanied by a narrowed spectrum linewidth. Meanwhile, the EL color coordinate shifts from (0.309, 0.416) for pristine microwires to (0.319, 0.503) for X-ray irradiated ones, corresponding to more purified green emission. The EL intensity monotonically increases (>20 times) with further increments of irradiation doses, and intense X-ray irradiations shift the EL color center toward the green-yellow spectral region and a total average redshift of ≈30±6 nm is achieved. The density functional theory (DFT) simulations suggest that the EL variation may stem from the substitution of host Zn atoms by interstitial Ga dopant stimulated by high-energy X-ray. These presented results indicate X-ray irradiation is a potential post-treatment strategy for host-dopant light emitters toward practical applications.