Paper TF-TuM1
Atomic Layer Deposition of the Metal Pyrites FeS₂, CoS₂, and NiS₂

Tuesday, October 23, 2018, 8:00 am, Room 101A

The pyrite-type transition-metal disulfides (MS₂, M = Fe, Co, Ni) form a series of compounds that are highly interesting in many aspects. These compounds share the same cubic pyrite crystal structure but differ in the progressive increase of an anti-bonding d electron in the conduction band, and as a result, the metal pyrites exhibit very diverse and intriguing electrical magnetic properties from diamagnetic semiconductive to itinerant-electron ferromagnetic and to antiferromagnetic semiconductive. This diversity of the material properties has not only offered a model system platform for fundamental science studies but also enabled tremendous engineering possibilities for practical applications, such as solar cells, lithium/sodium-ion batteries, and electrocatalytic hydrogen evolution, oxygen evolution, and oxygen reduction.

In this presentation, we will show our latest progress on the development of atomic layer deposition processes for the metal pyrites of FeS₂, CoS₂, and NiS₂ (Angew. Chem.Int. Ed. 2018, doi:10.1002/anie.201803092). We use the metal amidinate compounds as the precursors for the metals and H₂S plasma as the sulfur source, and we will show that the deposition processes for FeS₂, CoS₂, and NiS₂ all follow ideal layer-by-layer ALD growth behavior over a wide temperature range to produce fairly pure, smooth, pyrite-structure metal disulfide films. We will further show that the ALD FeS₂, CoS₂, and NiS₂ films can be conformally deposited into deep narrow trenches with aspect ratios as high as 10:1, which thereby highlights the broad and promising applicability of these ALD processes for conformal film coatings on complex high-aspect-ratio 3D architectures in general.