## 4 ALD on EG With a Seeding-Layer
### Self-Assembled Organic Monolayer  
[PERSON] et al. [36] demonstrated an alternative ALD seeding layer based on organic monolayers of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA). EG on SiC(0001) grown by sublimation in UHV conditions at 1350 \({}^{\circ}\)C was used in this study. PTCDA was deposited on the EG surface via gas-phase sublimation in ultrahigh vacuum (UHV), resulting in a highly uniform and ordered self-assembled monolayer. Two typical AFM images of the bare EG and PTCDA/EG surfaces are presented in Figure 9a,c, respectively, showing nearly identical roughness. Figure 9b,d shows two representative AFM images of Al\({}_{2}\)O\({}_{3}\) deposited on the bare EG (b) and on PTCDA/EG (d) using  
Figure 8: (**a**) Raman spectra of as-grown EG, after physical vapor deposition (PVD) of 5 nm HfO\({}_{2}\) and after HfO\({}_{2}\)-seeded (or Al\({}_{2}\)O\({}_{3}\)-seeded) ALD of HfO\({}_{2}\) and Al\({}_{2}\)O\({}_{3}\). (**b**) Hall mobility \(\upmu_{\text{Hall}}\) vs. carrier density n\({}_{\text{s}}\) measured on as-grown EG, after electron beam physical vapor deposition (EBPVD) of oxide seed-layers and the complete oxide-seeded ALD (O-ALD) process. Images adapted with permission from Ref. [35], Copyright American Chemical Society 2010.  
25 cycles of TMA and H\({}_{2}\)O at a temperature of 100 \({}^{\circ}\)C. While a discontinuous Al\({}_{2}\)O\({}_{3}\) film was observed on the bare EG, the use of the PTCDA seeding layer resulted in a uniform Al\({}_{2}\)O\({}_{3}\) film, conformal with the underlying terraces of the EG surface. Figure 9e shows the evolution of the Al\({}_{2}\)O\({}_{3}\) film thickness as a function of ALD growth cycle evaluated by spectroscopic ellipsometry on the bare EG, on PTCDA/EG and on a reference SiO\({}_{2}\) surface. The Al\({}_{2}\)O\({}_{3}\) ALD on the bare EG surface was initially inhibited for 3-4 ALD cycles, indicating a lack of reactive sites for the ALD precursors, as compared to the case of the SiO\({}_{2}\) surface. On the other hand, nucleation on the PTCDA-seeded EG surface was more efficient with ALD growth showing a linear behavior after only 1-2 ALD cycles, similarly to the case of the SiO\({}_{2}\) surface with a high density of reactive sites.  
To probe the adhesion and the insulating properties of the deposited ALD films, C-AFM imaging was employed. The morphology and current maps in Figure 10a,b show that for a thin Al\({}_{2}\)O\({}_{3}\) film (25 ALD cycles) on bare EG, conductive defects were produced after only one C-AFM scan in contact mode (contact force 20 nN, tip/sample voltage V = 0.3 V), resulting in localized conduction spots in the current map. This defect density was further increased after multiple C-AFM scans. Figure 10c,d shows the C-AFM morphology and current maps acquired under the same measurement conditions on the Al\({}_{2}\)O\({}_{3}\) film grown using the same number of ALD cycles on PTCDA/EG. These maps demonstrate the excellent morphological and uniform insulating properties of Al\({}_{2}\)O\({}_{3}\) on PTCDA seeded EG, which are maintained even after multiple C-AFM scans.  
Figure 9: (**a**) Representative AFM image of an EG surface prepared by UHV graphitization. (**b**) AFM images of EG surface after ALD of 25 cycles of Al\({}_{2}\)O\({}_{3}\). (**c**) AFM images of EG surface immediately after PTCDA deposition and (**d**) following ALD of 25 cycles of Al\({}_{2}\)O\({}_{3}\). (**e**) Al\({}_{2}\)O\({}_{3}\) film thickness as a function of ALD growth cycle evaluated by spectroscopic ellipsometry on the bare EG, on PTCDA/EG and on a reference SiO\({}_{2}\) surface. Images adapted with permission from Ref. [36], Copyright American Chemical Society 2011.