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  • Zhang, Chao; Vehkamäki, Marko; Pietikäinen, Mika; Leskelä, Markku; Ritala, Mikko (2020)
    Novel area-selective molecular layer deposition (AS-MLD) of polyimide (PI) on Cu versus native SiO2 was studied. By use of 1,6-diaminohexane (DAH) and pyromellitic dianhydride (PMDA) as precursors, PI films can be selectively deposited on the Cu surface at 200-210 degrees C with a rate around 7.8 A/cycle while negligible growth takes place on SiO2. The selectivity was successfully demonstrated also on Cu/SiO2 patterns at 200 degrees C; after 180 MLD cycles, around 140 nm thick PI was deposited on Cu regions while
  • Hämäläinen, Jani; Mattinen, Miika; Mizohata, Kenichiro; Meinander, Kristoffer; Vehkamäki, Marko; Räisänen, Jyrki; Ritala, Mikko; Leskelä, Markku (2018)
    2D materials research is advancing rapidly as various new “beyond graphene” materials are fabricated, their properties studied, and materials tested in various applications. Rhenium disulfide is one of the 2D transition metal dichalcogenides that has recently shown to possess extraordinary properties such as that it is not limited by the strict monolayer thickness requirements. The unique inherent decoupling of monolayers in ReS2 combined with a direct bandgap and highly anisotropic properties makes ReS2 one of the most interesting 2D materials for a plethora of applications. Here, a highly controllable and precise atomic layer deposition (ALD) technique is applied to deposit ReS2 thin films. Film growth is demonstrated on large area (5 cm × 5 cm) substrates at moderate deposition temperatures between 120 and 500 °C, and the films are extensively characterized using field emission scanning electron microscopy/energy‐dispersive X‐ray spectroscopy, X‐ray diffractometry using grazing incidence, atomic force microscopy, focused ion beam/transmission electron microscopy, X‐ray photoelectron spectroscopy, and time‐of‐flight elastic recoil detection analysis techniques. The developed ReS2 ALD process highlights the potential of the material for applications beyond planar structure architectures. The ALD process also offers a route to an upgrade to an industrial scale.