Growth, Integration, and Characterization of Atomic Layer Deposited Metal Oxides for Non-Ideal Surfaces

Abstract

This thesis aims to explore the nuances of atomic layer deposition (ALD) as a thin film growth process for various “non-ideal” surfaces that require careful consideration of deposition conditions, substrate surface preparation, and characterization of the final films. First, amorphous alumina films are considered for protecting limestone cultural heritage objects against aqueous acid attack. Specifically, deposition and characterization considerations are systematically explored for the chemically heterogenous, morphologically rough, and electrically insulating surfaces of geological limestone. The efficacy of the films as diffusion barriers is evaluated and the interaction between the films and the aqueous acidic environment is explored in both qualitative and quantitative manners. Of the most important results reported in this thesis is that ALD alumina films can slow the acid attack of limestone drastically. We show films corresponding to ~100 nm average thickness, delay the initial and total average rate of acid attack of limestone up to two orders of magnitude. In addition, these films produce only minor changes in the perceived appearance of the substrates, at levels generally considered insignificant in the cultural heritage conservation community. The second application of ALD for “non-ideal” surfaces considered is the growth of dielectric metal oxides on sacrificial substrates which aid in the transfer of films to target surfaces. The motivation for this technique is the unfavorable growth surface of 2D semiconductors which lack the dangling bonds necessary for ALD-film integration in next generation Metal Oxide Semiconductor Field Effect Transistor (MOSFET) devices. An exfoliation and transfer approach utilizing sacrificial polymer substrates and mica substrates is explored with particular attention given to the nuances of the growth process, characterization of the final films, and discussion of future research directions.