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Seminar PLUM: Thursday, 7th March 2024 at 11:15 am

Javier Garcia Fernandez (candidate for the Junior Professorship on Transmission Electron Microscopy)

Title: New insights in Complex Transparent Conducting Oxides and Polymorph Engineering in ß-Ga2O3

Zoom link: https://univ-grenoble-alpes-fr.zoom.us/j/3160667278

Institut Néel, Room E424 (Louis Weil)


Transparent conducting oxides (TCOs) represent a crucial category of functional materials that have
attracted considerable attention in recent years due to their promising applications in optoelectronics.
One of the main advantages that have attracted this interest is that they possess a broad bandgap (≥ 3
eV) and relatively high electrical conductivity. Some examples of oxides in this family are In2O3, SnO2,
Ga2O3 and ZnO. However, recent studies have highlighted concerns about the use of critical elements such
as In, Ga and Ge in TCOs due to economic considerations and supply chain risks. Consequently, efforts to
mitigate the dependence on these crucial elements, while preserving functionality, have led to explore
the synthesis of superstructures resulting from the intergrowth of different structural types.
My presentation will illustrate the main findings derived from the transmission electron microscopy
investigation of several systems belonging to the TCO family. In particular, the study will focus on systems
such as ZnkIn2Ok+3 (IZO) doped with Ga and Al and the NaxGan+xTin-4-xO2n-2 (NGTO) series with n= 5, 6 and 7
and x≈ 0.7. The structure of IZOs can be described as the ordered intergrowth of InO2- layers and InZnOk+1+
blocks with wurtzite structure, where the ordering of indium atoms inside the wurtzite blocks follow a zig-
zag pattern (Figure 1). NGTO terms are formed by the ordered intergrowth of β-Ga2O3 slabs and Ga/TiO6
octahedral. In the last part, I will present my results of the influence and effects of ionic implantation in
β-Ga2O3. Unlike many conventional semiconductors, ion implantation in β-Ga2O3 has been observed to
induce a phase transformation from β- to γ-polymorph (Figure 2). Details on the different ions used,
radiation tolerance, etc. will be presented and discussed. The presentation will focus on crystallographic
and structural characterization (polymorphic transformations, defects, modulations, changes in polarity
of wurtzite…) at the atomic level, chemical analysis (by means of EDS and EELS), low loss EELS, and in-situ