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 UHV nanofabricacion

Two-dimensional (2D) materials, extracted from bulk layered crystals with covalent intra-layer bonding and weak van der Waals interlayer coupling, offer a new scenario for studying novel beautiful physics. Furthermore, these materials have the potential to be key players in the incoming nanoscale technological leap, offering applications in many different fields such as electronics, optoelectronics, medical devices, or hear management, among others.

The 2D materials family is formed by thousands of members, with famous representatives like the semi-metallic graphene, the wide band-gap insulating hBN, or the semi-conducting transition metal dichalcogenides (TMDs). However, they are not only interesting as isolated systems. Much of the excitement of 2D materials stems from our ability to combine them in any desired sequence layer-by-layer and with controlled twisting angles to produce 2D material heterostructures (2DMH) with atomically sharp and clean interfaces. Unlike conventional crystal growth, their fabrication is not restrained by lattice matching or interfacial chemistry and therefore offers a versatile platform for creating unique quantum and optoelectronic metamaterials with properties tailored for particular applications.

Despite the great academic interest and high application potential, the field has been held back by the extreme cleanliness necessary to reach the limit where 2DMH display quantum properties. All existing techniques, mostly relying on polymeric matrices to produce the stacks, cannot avoid the presence of airborne hydrocarbon molecules on the surface of the exfoliated crystals. When trapped between layers, these molecules coalesce into bubble and distort the properties of the 2DMH. Furthermore, many 2D materials are very sensitive to air, degrading fast when exposed to the atmosphere. Thus, they require special fabrication procedures performed in controlled environments such as Ar or vacuum, in order to preserve the intrinsic properties of the crystals. As a result, the intrinsic properties of these materials are negatively affected, making their fabrication and studies extremely unreliable.

Researchers at the University of Manchester have developed a unique ultra-high vacuum press (UHV-press) system, that allows stacking 2D materials flakes at pressures down to , comparable with the state-of-the-art of other fabrication techniques such as molecular beam epitaxy (MBE) (PAPER LINK HERE WHEN PUBLISHED). Together with this, a ground-breaking heterostructure fabrication procedure has been developed by the team substituting the ubiquitous polymeric matrices by SiN cantilevers (PAPER LINK HERE WHEN PUBLISHED). The combination of these two technologies ensures the complete removal of hydrocarbon contamination, and reduces the oxygen- and water-induced degradation of sensitive 2D materials to its minimum. These cutting-edge advancements will have an extraordinary impact on the community allowing the fabrication of novel heterostructures based on air sensitive materials, and the development of 2DMH with the purest intrinsic properties. Several fields such as electronics, opto-electronics, or twistronics, among others, will benefit from these advancements, which are key for the development of novel nanoscale applications based on 2D materials.

For more information, see the NGI Cleanroom facilities.

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