Microstructural Analysis and Optical Property Control of GeTe Chalcogenide-Zirconia Nanoparticle Nanocomposite Films for Device Application

Phase-change chalcogenide materials are extensively employed in various fields, particularly for electronic and optical applications. In this study, we demonstrated the optical property tuning of germanium telluride (GeTe) chalcogenide-ZrO2 nanocomposite films through microstructural modification using nanoparticle spin-coating and thin film reflow. Pile-up features were observed in the case of spin-coated ZrO2 nanoparticle nanocolloids, which optimized the higher spin speeds to enable the deposition of uniform and high-transmittance ZrO2 nanoparticle layers. Additionally, the capillary-driven mass transport at elevated temperatures resulted in the agglomeration and reflow of GeTe films, particularly in the near-eutectic composition of GeTe(1:4) with reduced thickness. The morphological evolution of the GeTe films was used to fabricate nanocomposite films by sputter depositing the films on spin-coated ZrO2 nanoparticle layers, followed by thermal annealing. The postannealing temperature was crucial for controlling the transmittance, which primarily determined the color of the nanocomposite films. Different colored nanocomposite films were obtained by adjusting the spin speed, GeTe thickness, and postannealing temperature. The results indicated that the application of the developed nanocomposite films to semitransparent photovoltaic devices increased the conversion efficiency owing to the light scattering property of the films, in addition to improving the aesthetic appearance.