Retrieval of B1 phase from high-pressure B2 phase for CdO nanoparticles by electronic excitations in Cd<i>_x</i>Zn₁₋<i>_x</i>O composite thin films

This study investigates the recovery of the B1 phase from the high-pressure B2 phase, at atmospheric pressure, in cadmium oxide (CdO) nanoparticles incorporated within sol-gel synthesized Cd <i>_x</i> Zn_1- <i>_x</i> O (<i>x</i> = 0.40) composite thin films. The recovery process is investigated using electronic excitations as an effective tool. Exposure to 120 MeV silver ion irradiation results in the complete amorphization of the B2 phase in CdO nanoparticles, while the crystalline hexagonal wurtzite phase of zinc oxide (ZnO) remains intact. In contrast, 80 MeV oxygen ion irradiation preserves the B2 phase and facilitates the reemergence of the B1 phase. The partial damage caused by electronic energy loss during oxygen ion irradiation in the willemite Zn₂SiO₄ phase is identified as a trigger for the B1 to B2 phase transformation in CdO nanoparticles, enabling the recovery of the B1 phase. The diminishing local pressure exerted by the Zn₂SiO₄ phase on CdO nanoparticles during oxygen ion irradiation leads to the coexistence of both B1 and B2 phases. X-ray absorption near-edge spectra (XANES) reveal minimal changes in the intensity of the spike-like Zn <i>L</i> _3,2 pre-edge feature associated with the Zn₂SiO₄ phase under oxygen ion irradiation, while it entirely disappears with silver ion irradiation, confirming the amorphization of the Zn₂SiO₄ phase. Complementary observations from X-ray photoelectron spectroscopy (XPS), specifically O 1s and Si 2p peaks in XPS spectra, support these findings. Additionally, the track diameter in CdO subjected to 120 MeV silver ion irradiation is calculated to be approximately 8 nm using an inelastic thermal spike simulation code. This study elucidates the intriguing reappearance of the B1 phase under oxygen ion irradiation and highlights the radiation stability of the B2 phase through diverse characterization techniques, demonstrating the potential reversibility of the B1 to B2 phase transformation induced by ion irradiation.