Effects of thermal annealing on the structural and electronic properties of rare earth-implanted MoO3 nanoplates

The compositional, structural and morphological recovery of alpha-MoO3 nanoplates implanted with Eu and Er ions has been assessed as a function of post-implantation thermal treatments. Rapid thermal annealing induces the formation of phases different from alpha-MoO3 and seems to be unable to recover the original oxygen content of the nanostructures. In contrast, conventional annealing in air at 450 degrees C for 4 hours fully recovers the original molybdenum trioxide structure and leads to an effective optical activation of both Er and Eu ions. Synchrotron-based X-ray photoelectron spectroscopy and X-ray absorption studies confirm the incorporation of the rare earth ions into their trivalent charge state and reveal the modification of the original valence band structure of the nanoplates.