Atomic Layer Deposition of FeSe₂, CoSe₂, and NiSe₂

Atomic layer deposition (ALD) of the iron-group transition-metal diselenides FeSe2, CoSe2, and NiSe2 is reported for the first time. The ALD processes employ the associated metal amidinates as the metal precursors and diethyldiselenide (DEDSe) as the selenium precursor, together with Ar/H2 plasma for DEDSe activation. All of the ALD processes are able to grow highly pure, smooth, and crystalline MSe2 (M = Fe, Co, Ni) films with ideal layer-by-layer film growth behavior, which highlights good controllability over film quality and fabrication process as benefited from ALD. It is further demonstrated that all of the MSe2 films can be uniformly deposited into 10:1 high-aspect-ratio microtrenches with excellent conformality, which underscores the great promise of these processes for conformal MSe2 coatings on three-dimensional (3D) complex topologies in general. In situ ALD mechanism investigation further reveals that the efficient dissociation of DEDSe by plasma is key to the success of these ALD processes.