# Substrate-Driven Atomic Layer Deposition of High-\(\kappa\) Dielectrics on 2D Materials
## 2 Atomic Layer Deposition on 2D Materials
### Methods to Promote ALD Growth on 2D Materials  
To date, a wide variety of processes has been reported to promote ALD nucleation on 2D layered materials, which finally results in the deposition of uniform dielectric layers. Table 1 reports a selection of the literature results for different types of 2D materials, with the indication of the used surface activation for ALD, the deposited high-\(\kappa\) insulator, its thickness and uniformity, and eventual damage introduced in the 2D material by the ALD process. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Ref**} & \multirow{2}{*}{**2D Material**} & \multicolumn{4}{c}{**ALD Process**} \\ \cline{3-6}  & & **ALD Activation** & \(\mathbf{T_{\text{ALD}}}\) & \(\mathbf{F^{\text{C}}}\) & **High-\(\kappa\) Type** & **Uniformity** & **2D Damage** \\ \hline \hline \multicolumn{6}{c}{**Seed layer deposition**} \\ \hline \([34]\) & CVD-graphene on SiO\({}_{2}\) & 3,4,91-perylene tetracarboxylic acid & 100 \({}^{\circ}\)C & Al\({}_{2}\)O\({}_{3}\), -2 nm & High & Not \\ \([35]\) & CVD-graphene on SiO\({}_{2}\) & Poly(4-vinylened) (PVP) & Al\({}_{2}\)O\({}_{3}\) & 20 nm & High & Not \\ \([36]\) & CVD-MoF\({}_{2}\) and CVD-WS\({}_{2}\) & Perylene bisimide & 80 \({}^{\circ}\)C & Al\({}_{2}\)O\({}_{3}\) -3 nm & High & Not \\ \([37]\) & Efoldulated graphene & Evaporated Al & 250 \({}^{\circ}\)C & Al\({}_{2}\)O\({}_{3}\) -3 nm & Inger \(\times\)12 nm & Not \\ \([38,99]\) & CVD-MoF\({}_{2}\) & Al & 150 \({}^{\circ}\)C & Z\({}_{20}\) -15 nm & High & Not \\ \([40]\) & MoS\({}_{2}\) by sulfurization of Mo & SiO\({}_{2}\) nanoparticles & 300 \({}^{\circ}\)C & Al\({}_{2}\)O\({}_{3}\) -5.7 nm & High & Not \\ \([41]\) & Efoldiated graphene & Seed layer of H\({}_{2}\)O-assisted dielectric at low & 100 \({}^{\circ}\)C & Al\({}_{2}\)O\({}_{3}\), -11 nm & High & Not \\ \([42]\) & Transferred CVD-graphene on SiO\({}_{2}\) & Seed layer of H\({}_{2}\)O-assisted dielectric at low & 250 \({}^{\circ}\)C & Al\({}_{2}\)O\({}_{3}\), -22 nm & High & Not \\ \([43]\) & Efoldiated MoS\({}_{2}\) & Seed layer of H\({}_{2}\)O-assisted dielectric at low & 180\({}^{\circ}\)C & Al\({}_{2}\)O\({}_{3}\), +10 nm & High & Not \\ \([44]\) & Efoldiated WS\({}_{2}\) & Evaporated Al & 95 \({}^{\circ}\)C & H\({}_{2}\)O\({}_{3}\) -20 nm & High & Not \\ \hline \hline \end{tabular}
\end{table} 
Table 1: ALD deposition of high-\(\kappa\) dielectrics on 2D materials. Figure 1: (**a**) Schematic of a typical cycle in ALD growth. (**b**) Schematic diagram showing the adsorption and desorption processes of a TMA precursor during the ALD deposition of Al\({}_{2}\)O\({}_{3}\) on the 2D materials [32]. (**c**) AFM image of the ALD-Al\({}_{2}\)O\({}_{3}\) layer deposited on a pristine MoS\({}_{2}\) surface [33]. (**d**) APLO process. From the historical point of view, most of these approaches have been developed for graphene [35; 37; 55; 56], and many of them have been adapted to other layered materials, such as TMDs [36]. These processes can be grouped into two categories:  
1. [label=()]
2. Predeposition of a seed-layer;
3. Chemical pre-functionalization. The seed layers can be of both an organic nature, such as self-assembled monolayers (SAM) [34; 57] or spin-coated polymers layers [35; 36; 55], and an inorganic nature, such as sputtered or evaporated metal or metal oxide films [37; 38; 39; 56] or SiO\({}_{2}\) nanoparticles [40]. They can be pre-deposited \"ex situ\" (i.e., outside the ALD reactor chamber) and also \"in situ\" (i.e., within the reactor), like in the case of low temperature H\({}_{2}\)O-assisted dielectric seed layer growth on the surface of graphene [41; 42]. The seed layer approach proved to be an efficient and widely used method to promote the subsequent ALD growth process on graphene and TMDs. Typically, the spin-coating, self-assembling, and physical deposition methods (e.g., evaporation) used to deposit seed layers result in limited damage to the 2D membranes.