| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2018) | |
| Thin Films | Wednesday Sessions |
| Session TF-WeE |
| Session: | Emerging Topics: Growth and Properties of Electronic Materials, 2D Layers, and Metallic-glass Thin Films |
| Presenter: | Paolo Branchini, INFN RomaTre, Italy |
| Authors: | P. Branchini, INFN RomaTre, Italy S. De Rosa, National Institute of Nuclear Physics Roma Tre, Italy L. Tortora, INFN RomaTre, Italy R. Yivlialin, Politecnico di Milano, Italy G. Bussetti, Politecnico di Milano, Italy |
| Correspondent: | Click to Email |
Among two-dimensional semiconductors, graphene is universally recognized as an emerging material having potentials for a wide range of applications including organic electronics and photonics. Graphene flakes can be produced following different preparation protocols,[1] such as: dry and liquid-phase exfoliation, growth on SiC and metal substrates, CVD, molecular beam epitaxy, atomic layer epitaxy, chemical synthesis etc.. Within the European Graphene flagship program, different analytical techniques [SEM/FIB, TEM, EDS, SPM, XPS, XRD, Raman] are routinely adopted to provide the structural and chemical characterization and to validate the production process.
Here, we propose ToF-SIMS combined with multivariate analysis as validation tool for monitoring the graphene production. In particular, we focused the research on most diffused production methods: (i) the mechanical exfoliation by adhesive tape and (ii) the dispersion of graphene flakes inside an electrochemical bath after the intercalation of ions inside a graphite (HOPG) sample.
The (i) preparation protocol foresees the deposition of graphene onto a silicon wafer, which is then cleaned with acetone, ethanol, and deionized water and dried on a hot plate maintained at 300°C for 1min. The (ii) procedure requires an acid media (e.g. sulphuric or perchloric solutions), purified by bubbling Ar gas inside a separator funnel for several hours. A three-electrode cell is then exploited for inducing ion intercalation in graphite, used as a working electrode, which expands the crystal helping the weakening of the layer-layer interaction.
The high sensitivity of ToF-SIMS technique (few ppm) reveals graphene contamination due to the presence of residual glue coming from the scotch-tape. Furthermore, PCA and K-means cluster analysis were successfully applied to ToF-SIMS high resolution images, showing three different contributions from silicon substrate, residual glue, and graphite/graphene layers. At the same way, results from the graphite mother-crystal, used in the electrochemical approach, also show residual compounds related to the production process such as SO2-, SO3-, ClO-, ClO2, ClO3-, ClO4-. Dual beam depth profiling experiments showed that these compounds are present not only onto the HOPG surface but also between graphite terraces and inside the nanoprotrusions produced during the intercalation process. These preliminary results contribute to shed light on the chemistry of the intercalation process.
References
G. Bussetti, R. Yivlialin, D. Alliata, A. Li Bassi, C. Castiglioni, M. Tommasini, C. Spartaco Casari, M. Passoni, P. Biagioni, F. Ciccacci, and L. Duo, J. Phys. Chem. C 2016, 120, 6088−6093