# Epitaxial Graphene on 4H-SiC (0001) as a Versatile Platform for Materials Growth: Mini-Review
## 6 Concluding Remarks  
We have summarized recent results on the deposition of metals and insulators on epitaxial graphene on 4H-SiC. Three different methods (dc magnetron sputtering, electrodeposition, and atomic layer deposition) were exploited to grow ultra-thin metal and dielectric layers to study early-stage nucleation of selected materials on epitaxial graphene. The comparison of growth morphologies of magnetron-sputtered gold and silver layers supported by DFT calculations and Raman data analysis enabled us to consider a difference in metal-substrate interaction strengths as a candidate explanation of the formation of separated silver islands and fractal-like gold nanostructures at the initial growth stages. We then presented a discussion related to the effect of the grown metal layers on the Raman spectra of epitaxial graphene. Except for gold deposition, the deposition of other metals (Li, Pb, and Ag) caused the generation of defects, which is evidenced by the observation of initially forbidden Raman peaks. The \(D/G\) ratio as an important indicator of structural disorder reached the maximal value after Li electrodeposition and hence must be due to the largest number of generated defects. We argued that this finding can be understood in terms of the difference in the adsorption energies of metals and magnitudes of charge transfer from metal to graphene. Three-dimensional diffusion-controlled instantaneous nucleation mechanism was identified as a dominating and probably common mechanism behind initial kinetics of metals during early-stage of the electrodeposition process.  
The atomic layer deposition technique recommended itself as a reliable route for seed-layer-free growth of uniform Al\({}_{2}\)O\({}_{3}\) layers on epitaxial graphene without defects generation. We highlighted the important role which water molecules probably play in providing reactive sites for Al\({}_{2}\)O\({}_{3}\) formation.  
The above-listed observations led to the proposal that the versatility of epitaxial graphene on SiC as a hosting substrate for other materials growth is due to its enhanced reactivity compared to chemically inert free-standing exfoliated graphene. Indeed, numerous experimental results by theoretical predictions indicate that by virtue of its physical and structural properties, epitaxial graphene may contain several different highly reactive regions (step edges, charge-unbalanced electron-hole puddles, strained regions, and edges of bilayer inclusions) that may serve as effective nucleation centres. The cumulative effect of the mentioned regions on the growth kinetics makes the epitaxial graphene on SiC a unique platform for both boosting the development of synthesis technologies of novel hybrid materials and designing high-performance electronic and sensing devices.  
Conceptualization, I.S., F.G. and R.Y.; methodology, I.S. and F.G.; software, I.S.; validation, I.S., F.G. and R.Y.; formal analysis, I.S.; investigation, I.S., F.G. and R.Y.; resources, F.G. and R.Y.; data curation, I.S. and F.G.; writing--Original draft preparation, I.S.; writing--Review and editing, F.G. and R.Y.; visualization, I.S.; supervision, R.Y.; project administration, R.Y. and F.G.; funding acquisition, R.Y. and F.G. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The data that support the findings of this study are available within the article.  
I.S. acknowledges the support from Angpanneforeningens Forskningsstiftelse (Grants 16-541 and 21-112). R.Y. acknowledges financial support from VR grant 2018-04962. Financial support by SSF via grant RMA 15-0024 is greatly acknowledged. F.G. acknowledges financial support from MIUR in the framework of the FlagERA project \"ETMOS\".  
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.