Dr. F. Paparoni (1st year PhD student) will give a seminar in room E, physics bulding, 1st June 15pm, entitled: Phase dynamics of the amorphous MoO3 and WO3-metal heterostructures by Raman and XAS spectroscopy.

Abstract:

MoO 3 and WO 3 are high-k dielectric insulator, but their electronic structures can be tailored by
changing the oxygen sub-stoichiometry (WO 3-x and MoO 3−x ), introducing electronic gap states and
tuning, so, the electrical conductivity [1,2]. Recent studies [3,4] reported how MoO 3 films in contact
with a metallic substrate tends to become conductive in the first nm from the interface, while the
bulk work function remains high. This may be the result of the reduction of stoichiometric Mo 6+ at
the metal/oxide interface, a mechanism that is a function of the oxide thickness and the metal
reactivity. We propose that a similar behavior should be observed also with other transition metal
oxides with high work functions, such as WO 3 .
From our work [5,6], we will show how the metallic contact alters the concentration of oxygen
vacancies and how the use of a different metallic substrate can lead also to the diffusion of metallic
ions into the MoO 3 lattice, forming a ternary alloy. The effects of different atmospheric condition on
the film properties, as well as the heating treatments, will be discussed. Preliminary results on WO 3
will be shown and compared to the MoO 3 case.
These results points out to the important role played by the metallic substrate at the metal-metal
oxide interface and can lead to technological advancement in several applications, such as
protective coatings for RF cavities [7], contact material for CdTe solar cell [8] as well as in organic
electronics for the formation of ohmic contacts.

[1] O de Melo et al (2019), J. Phys.: Condens. Matter 31 295703.
[2] W. Wang et al (2016) J. Mater. Chem. C,4, 6641-6648.
[3] M.T. Greiner et al (2013), Adv. Funct. Mater. 23 215-226.
[4] M. T. Granier et al (2012), Adv. Funct. Mater. 22 4557-4568.
[5] F. Paparoni (2021), “Synthesis and Characterization of Transition Metal Films on Metal Substrates”,
Tesi di Laurea in Physics.
[6] F. Paparoni, S.J. Rezvani et al (2022), “Metallic interface induced ionic redistribution within amorphous
MoO 3 films”, (submitted and currently under review at Advanced Materials Interfaces).
[7] S. Macis et al (2019), Journal of Vacuum Science & Technology, A37, 021513.
[8] L. Qiu et al (2021), Mat. Science in Semic. Processing.