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Tunability of MoO3 Thin-Film Properties Due to Annealing in Situ Monitored by Hard X‑ray Photoemission
journal contribution
posted on 2019-06-24, 17:33 authored by Xiaxia Liao, Ah Reum Jeong, Regan G. Wilks, Sven Wiesner, Marin Rusu, Roberto Félix, Ting Xiao, Claudia Hartmann, Marcus BärThe
chemical and electronic structure of MoO3 thin films
is monitored by synchrotron-based hard X-ray photoelectron spectroscopy
while annealing from room temperature to 310 °C. Color-coded
2D intensity maps of the Mo 3d and O 1s and valence band maximum (VBM)
spectra show the evolution of the annealing-induced changes. Broadening
of the Mo 3d and O 1s spectra indicate the reduction of MoO3. At moderate temperatures (120–200 °C), we find spectral
evidence for the formation of Mo5+ and at higher temperatures
(>165 °C) also of Mo4+ states. These states can
be
related to the spectral intensity above the VBM attributed to O vacancy
induced gap states caused by partial filling of initially unoccupied
Mo 4d-derived states. A clear relation between annealing temperature
and the induced changes in the chemical and electronic structure suggests
this approach as a route for deliberate tuning of MoO3 thin-film
properties.