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

The compositional, structural and morphological recovery of α-MoO 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 α-MoO and seems to be unable to recover the original oxygen content of the nanostructures. In contrast, conventional annealing in air at 450 °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.This work has been supported by MINECO through projects MAT2012-31959, MAT2015-65274-R and CSD2009-0013. KL thanks FCT Portugal for her grant as “Investigador FCT”. CM acknowledges the financial support by the “Ramón y Cajal” Program of MINECO (RYC-2014-16626)