# Retrieval of B1 phase from high-pressure B2 phase for CdO nanoparticles by electronic excitations in CdxZn1−xO composite thin films

## TL;DR

This study shows how ion irradiation can recover a high-pressure phase in CdO nanoparticles within a composite thin film.

## Contribution

The novel use of oxygen ion irradiation to recover the B1 phase from the B2 phase in CdO nanoparticles is demonstrated.

## Key findings

- 80 MeV oxygen ion irradiation facilitates the recovery of the B1 phase in CdO nanoparticles.
- Silver ion irradiation causes complete amorphization of the B2 phase in CdO nanoparticles.
- XANES and XPS confirm the structural changes in Zn2SiO4 under different irradiation conditions.

## Abstract

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 CdxZn1−xO (x = 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 L3,2 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.