  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.
