Scalable production of single 2D van der Waals layers through atomic layer deposition: Bilayer silica on metal foils and films

TL;DR

This study demonstrates a scalable method for producing single-layer 2D van der Waals silica using atomic layer deposition on metal substrates, with post-deposition annealing inducing structural transformation to achieve the desired 2D form.

Contribution

It introduces a novel ALD-based approach for growing 2D-VDW silica, including a post-deposition annealing process to induce structural rearrangement, enabling scalable production.

Findings

ALD can produce 2D-VDW silica on metal foils and films.

Annealing above 950 K induces 2D structural rearrangement.

Choice of Si source influences phase control of the 2D silica.

Abstract

The self-limiting nature of atomic layer deposition (ALD) makes it an appealing option for growing single layers of two-dimensional van der Waals (2D-VDW) materials. In this paper it is demonstrated that a single layer of a 2D-VDW form of SiO2 can be grown by ALD on Au and Pd polycrystalline foils and epitaxial films. The silica was deposited by two cycles of bis (diethylamino) silane and oxygen plasma exposure at 525 K. Initial deposition produced a three-dimensionally disordered silica layer; however, subsequent annealing above 950 K drove a structural rearrangement resulting in 2D-VDW; this annealing could be performed at ambient pressure. Surface spectra recorded after annealing indicated that the two ALD cycles yielded close to the silica coverage obtained for 2D-VDW silica prepared by precision SiO deposition in ultra-high vacuum. Analysis of ALD-grown 2D-VDW silica on a Pd(111) film revealed the co-existence of amorphous and incommensurate crystalline 2D phases. In contrast, ALD growth on Au(111) films produced predominantly the amorphous phase while SiO deposition in UHV led to only the crystalline phase, suggesting that the choice of Si source can enable phase control.