Atomic Layer Deposition Route to Scalable, Electronic-Grade van der Waals Te Thin Films

Abstract

Scalable production and integration techniques for vander Waals(vdW) layered materials are vital for their implementation in next-generationnanoelectronics. Among available approaches, perhaps the most well-receivedis atomic layer deposition (ALD) due to its self-limiting layer-by-layergrowth mode. However, ALD-grown vdW materials generally require highprocessing temperatures and/or additional postdeposition annealingsteps for crystallization. Also, the collection of ALD-produciblevdW materials is rather limited by the lack of a material-specifictailored process design. Here, we report the annealing-free wafer-scalegrowth of monoelemental vdW tellurium (Te) thin films using a rationallydesigned ALD process at temperatures as low as 50 & DEG;C. They exhibitexceptional homogeneity/crystallinity, precise layer controllability,and 100% step coverage, all of which are enabled by introducing adual-function co-reactant and adopting a so-called repeating dosingtechnique. Electronically, vdW-coupled and mixed-dimensional verticalp-n heterojunctions with MoS2 and n-Si, respectively, aredemonstrated with well-defined current rectification as well as spatialuniformity. Additionally, we showcase an ALD-Te-based threshold switchingselector with fast switching time (& SIM;40 ns), selectivity (& SIM;10(4)), and low V (th) (& SIM;1.3 V).This synthetic strategy allows the low-thermal-budget production ofvdW semiconducting materials in a scalable fashion, thereby providinga promising approach for monolithic integration into arbitrary 3Ddevice architectures.