New X-ray insight into oxygen intercalation in epitaxial graphene grown on 4H-SiC(0001)

Abstract

Efficient control of intercalation of epitaxial graphene by specific elements is a way to change properties of the graphene. Results of several experimental techniques, such as X-ray photoelectron spectroscopy, micro-Raman mapping, reflectivity, attenuated total reflection, X-ray diffraction, and X-ray reflectometry, gave a new insight into the intercalation of oxygen in the epitaxial graphene grown on 4H-SiC(0001). These results confirmed that oxygen intercalation decouples the graphene buffer layer from the 4H-SiC surface and converts it into the graphene layer. However, in contrast to the hydrogen intercalation, oxygen does not intercalate between carbon planes (in the case of few layer graphene) and the interlayer spacing stays constant at the level of 3.35–3.32 Å. Moreover, X-ray reflectometry showed the presence of an oxide layer having the thickness of about 0.8 Å underneath the graphene layers. Apart from the formation of the nonuniform thin oxide layer, generation of defects in graphene caused by oxygen was also evidenced. Last but not least, water islands underneath defected graphene regions in both intercalated and non-intercalated samples were most probably revealed. These water islands are formed in the case of all the samples stored under ambient laboratory conditions. Water islands can be removed from underneath the few layer graphene stacks by relevant thermal treatment or by UV illumination.

Role of the Potential Barrier in the Electrical Performance of the Graphene/SiC Interface

“…Then, the buffer layer can be converted into a new graphene layer with graphene symmetry and typical electronic structure. As was confirmed by experimental studies, H [9,35], Na [36], O [37,38], Li [39], Si [40], Au [12], F [11] and Ge [41] intercalation can transform the buffer layer into a graphene layer with enhanced electrical performance in comparison with untreated monolayer graphene, which exists on the buffer layer. Intercalant species can penetrate into the interface between the buffer layer and the Si-face SiC substrate and create the chemical bonds with topmost Si atoms, thereby causing the transformation of the buffer layer to quasi-free-standing graphene.…”

Twistronics: a turning point in 2D quantum materials

“…58 Second: When O2 intercalates between a 2D material and their substrate, the 2D material decouples from the substrate and behaves more "free standing". [213][214][215][216][217][218][219] Third: Lithium forms itself into a superdense crystal when intercalated between bilayer graphene, disrupting the tBLG properties. 64 Optical image of a laser-written pattern on a Bi2Se3/MoS2 2D heterostructure.…”

The effect of graphene-nanoplatelets on gelation and structural integrity of a polyvinyltrimethoxysilane-based aerogel

“…65,66 The rst peak was attributed to the silicon bond with hydroxyl-based oxygen atoms (that is, the silanol groups: Si-O-H). [67][68][69] Meanwhile, the second, weaker peak was attributed to the Si-O for the silicon bonded to multiple oxygen atoms in the bridging Si-O-Si species. 68,70,71 Fig.…”