Atomic layer deposition of ternary oxides of platinum group elements

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Atomic layer deposition (ALD) of multiple oxides containing noble metals (apart from Cu) has been little studied, although ALD processes are well developed for the platinum group elemental metals and many of their simple oxides. However, the multiple oxides have technologically very important properties, so that investigations into deposition processes for thin layers of these oxides and their characterizations are of great interest. The group of ternary noble metal oxides includes, among other things, the crystal groups of delafossite and pyrochlore iridate. In particular, the delafossites PdCoO2, PdCrO2, and PtCoO2 have received some attention in recent years because of their high conductivity in the form of single crystals. This is due to the high mobility of the electrons within the two-dimensional noble metal-containing layers, which also makes these materials candidates for the observation of hydrodynamic electron flow. Calculations have shown that PtCoO2 is a promising material for spintronic applications. Furthermore, it has recently been demonstrated that all three materials are excellent electrocatalysts for the hydrogen evolution reaction in acidic electrolytes, even surpassing platinum under certain conditions. Pyrochlorine iridates have received increased interest in recent years because of the combination of electron correlation and spin-orbit coupling leading to effects such as metal–semiconductor transitions and non-collinear antiferromagnetism. It is also worth mentioning here the prediction that Y2Ir2O7 should exhibit the properties of a Weyl semimetal in a certain temperature range. Weyl semimetals are currently an intensively studied material class in the field of topological materials. The scientific project pursues the goal of depositing and characterizing thin layers of ternary oxides, in which one of the metals belongs to the platinum group, from the gas phase using ALD. The focus is on two crystal groups, the delafossites (PdCoO2, PdCrO2 and PtCoO2) and the pyrochlore iridates (Y2Ir2O7). Amorphous layers are first deposited for the various materials. From these, crystalline layers are obtained by means of rapid thermal processing. The layers are then analyzed for their elemental composition and crystal structure. Finally, the physical properties such as the temperature-dependent electrical conductivity and the magnetic ordering of films for which the desired crystalline phase has been achieved are studied in detail. The aim is to determine the relationships between the process conditions and these physical properties.