Ultraflat Sub-10 Nanometer Gap Electrodes for Two-Dimensional Optoelectronic Devices

Abstract

Two-dimensional (2D) materials are promising candidates for building ultrashort-channel devices because their thickness can be reduced down to a single atomic layer. Here, we demonstrate an ultraflat nanogap platform based on atomic layer deposition (ALD) and utilize the structure to fabricate 2D material-based optical and electronic devices. In our method, ultraflat metal surfaces, template-stripped from a Si wafer mold, are separated by an Al2O3 ALD layer down to a gap width of 10 nm. Surfaces of both electrodes are vertically aligned without a height difference, and each electrode is ultraflat with a measured root-mean-square roughness as low as 0.315 nm, smaller than the thickness of monolayer graphene. Simply by placing 2D material flakes on top of the platform, short-channel field-effect transistors based on black phosphorus and MoS2 are fabricated, exhibiting their typical transistor characteristics. Furthermore, we use the same platform to demonstrate photodetectors with a nanoscale photosensitive channel, exhibiting higher photosensitivity compared to microscale gap channels. Our wafer-scale atomic layer lithography method can benefit a diverse range of 2D optical and electronic applications.

Hybrid System Combining Two-Dimensional Materials and Ferroelectrics and Its Application in Photodetection

“…Such a physical exfoliation method has been rapidly popularized in the fabrication of 2D materials ( e.g ., boron nitride, TMDs, etc .) due to the simple process and high properties of the nanoflakes. − However, the morphology of exfoliated 2D materials is random, and the sizes of most nanoflakes are as small as tens of micrometers, which restrained the application of these materials in integrated device applications that require a large area or even wafer-scale 2D materials. Alternative methods were therefore proposed, including the liquid-phase exfoliation (LPE), , pulse laser deposition (PLD), − physical vapor deposition (PVD), − molecular beam epitaxy (MBE), − atomic layer deposition (ALD), − sputtering, chemical vapor deposition (CVD), etc .…”

Two dimensional semiconducting materials for ultimately scaled transistors

“… (F) AFM image of MoS 2 flake on Au surface with a nanogap. Figures E and F are reproduced with permission from ( Namgung et al., 2021 ) Copyright© 2021, American Chemical Society. (G) Schematic illustration of graphene-contacted ultra-short channel MoS 2 transistors in top-gated geometry.…”

“… (F) AFM image of MoS 2 flake on Au surface with a nanogap. Figures E and F are reproduced with permission from ( Namgung et al., 2021 ) Copyright© 2021, American Chemical Society. …”

The Applications of Ultra-Thin Nanofilm for Aerospace Advanced Manufacturing Technology

“…Atomic layer deposition (ALD) is a unique chemical vapor deposition technology that demonstrates two properties: surface self-saturation and ordinal reaction [20]. It is generally applied in the preparation of functional nanomaterials, such as lithium batteries [21], nanostructures [22,23], optoelectronic devices [24], and nanocatalysis [25]. It is worth pointing out that the ALD nanofilm is compact and has a controllable sub-nanometer thickness.…”