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Electronic properties of embedded graphene: doped amorphous silicon/CVD graphene heterostructures
Arezki, Hakim,Boutchich, Mohamed,Alamarguy, David,Madouri, Ali,Alvarez, José,Cabarrocas, Pere Roca i,Kleider, Jean-Paul,Yao, Fei,Hee Lee, Young IOP 2016 Journal of Physics, Condensed Matter Vol.28 No.40
<P>Large-area graphene film is of great interest for a wide spectrum of electronic applications, such as field effect devices, displays, and solar cells, among many others. Here, we fabricated heterostructures composed of graphene (Gr) grown by chemical vapor deposition (CVD) on copper substrate and transferred to SiO<SUB>2</SUB>/Si substrates, capped by n‑ or p-type doped amorphous silicon (a-Si:H) deposited by plasma-enhanced chemical vapor deposition. Using Raman scattering we show that despite the mechanical strain induced by the a-Si:H deposition, the structural integrity of the graphene is preserved. Moreover, Hall effect measurements directly on the embedded graphene show that the electronic properties of CVD graphene can be modulated according to the doping type of the a-Si:H as well as its phase i.e. amorphous or nanocrystalline. The sheet resistance varies from 360 Ω sq<SUP>−1</SUP> to 1260 Ω sq<SUP>−1</SUP> for the (p)-a-Si:H/Gr (n)-a-Si:H/Gr, respectively. We observed a temperature independent hole mobility of up to 1400 cm<SUP>2</SUP> V<SUP>−1</SUP> s<SUP>−1</SUP> indicating that charge impurity is the principal mechanism limiting the transport in this heterostructure. We have demonstrated that embedding CVD graphene under a-Si:H is a viable route for large scale graphene based solar cells or display applications.</P>
Large local lattice expansion in graphene adlayers grown on copper
Chen, Chaoyu,Avila, José,Arezki, Hakim,Nguyen, Van Luan,Shen, Jiahong,Mucha-Kruczyń,ski, Marcin,Yao, Fei,Boutchich, Mohamed,Chen, Yue,Lee, Young Hee,Asensio, Maria C. Nature Publishing Group UK 2018 NATURE MATERIALS Vol.17 No.5
<P>Variations of the lattice parameter can significantly change the properties of a material, and, in particular, its electronic behaviour. In the case of graphene, however, variations of the lattice constant with respect to graphite have been limited to less than 2.5% due to its well-established high in-plane stiffness. Here, through systematic electronic and lattice structure studies, we report regions where the lattice constant of graphene monolayers grown on copper by chemical vapour deposition increases up to similar to 7.5% of its relaxed value. Density functional theory calculations confirm that this expanded phase is energetically metastable and driven by the enhanced interaction between the substrate and the graphene adlayer. We also prove that this phase possesses distinctive chemical and electronic properties. The inherent phase complexity of graphene grown on copper foils revealed in this study may inspire the investigation of possible metastable phases in other seemingly simple heterostructure systems.</P>
Retraction Note: Large local lattice expansion in graphene adlayers grown on copper
Chen, Chaoyu,Avila, José,Arezki, Hakim,Nguyen, Van Luan,Shen, Jiahong,Mucha-Kruczyń,ski, Marcin,Yao, Fei,Boutchich, Mohamed,Chen, Yue,Lee, Young Hee,Asensio, Maria C. Springer Science and Business Media LLC 2018 NATURE MATERIALS Vol.17 No.11