Thin film rf magnetron sputtering of gadolinium-doped yttrium aluminum garnet ultraviolet emitting materials

Y3Al5O12:Gd thin films were co-deposited by using a multi-source radio frequency reactive magnetron sputtering process. A statistical design of experiment (DOE) was conducted to analyze the effects that the substrate bias, substrate temperature, and O2 flow rate have on the composition, structure, and cathodoluminescence properties of the Y3Al5O12:Gd thin films. The structure and composition of the films were characterized by scanning electron microscopy (SEM) and energy dispersive X-ray spectra (EDS). The crystallinity of the films has been investigated by X-ray diffraction (XRD). The effect that each parameter has on the cathodoluminescent (CL) properties and XRD integrated intensity of the films has been correlated to the chemical and microstructural properties of the films. The DOE results showed that low O2 flow rate, high substrate temperature, and bias sputtering are the conditions that lead to the highest CL efficiency of YAG:Gd thin films. As O2 flow rate increases, both CL efficiency and XRD intensity decrease due to the effect of O2 flow rate on film stoichiometry. Increasing substrate temperature enhances the CL intensity and has a negligible effect on the XRD intensity due to higher temperature annealing. Substrate bias slightly decreases the XRD intensity, but improves the CL efficiency due to higher light scattering improved by enhanced surface roughness.