Conformal Growth of Nanometer-Thick Transition Metal Dichalcogenide TiSx‑NbSx Heterostructures over 3D Substrates by Atomic Layer Deposition: Implications for Device Fabrication

The scalable and conformal synthesis of two-dimensional (2D) transition metal dichalcogenide (TMDC) heterostructures is apersisting challenge for their implementation in next-generation devices.In this work, we report the synthesis of nanometer-thick 2D TMDC heterostructures consisting of TiSx-NbSx on both planar and 3D structures using atomic layer deposition (ALD) at low temperatures (200−300 °C).To this end, a process was developed for the growth of 2D NbSx by thermal ALD using (tert-butylimido)-tris-(diethylamino)-niobium (TBTDEN) and H2S gas. This process complemented the TiSx thermal ALD process for the growth of 2D TiSx-NbSx heterostructures. Precise thickness control of the individual TMDC material layers was demonstrated by fabricatingmultilayer (5-layer) TiSx-NbSx heterostructures with independently variedlayer thicknesses. The heterostructures were successfully deposited on large-areaplanar substrates as well as over a 3D nanowire array for demonstrating the scalability and conformality of the heterostructure growth process. The current study demonstrates the advantages of ALD for the scalable synthesis of 2D heterostructures conformally over a 3D substrate with precise thickness control of the individual material layers at low temperatures. This makes the application of 2D TMDC heterostructures for nanoelectronics promising in both BEOLand FEOL containing high-aspect-ratio 3D structures.