Mr Gerald Troppenz,
The growth of macroscopic single-layer graphene and its implementation in large-area electronic devices is of major interest. Large area graphene is grown by an optimized chemical vapor deposition (CVD)-process on polycrystalline copper foil and transferred to suitable substrates. Large internal biaxial compressive strain is introduced in graphene due to the thermal expansion mismatch between graphene and copper. Here, we reveal the mechanism of the stepwise strain relaxation by the use of AFM and Raman measurement techniques. The remaining strain in the material is thoroughly quantified.1 Hall effect measurements of an 8 x 8 mm2 graphene layer on corning eagle borosilicate glass exhibit a charge carrier mobility of 2070 cm2 V-1 s-1 at hole concentrations of 3.6 x 1012 cm-2. After deposition of Si cover layers, the structure of graphene is preserved. It is found that the crystallization of the Si has a significant influence on the field effect doping of buried graphene layers. Hall and Raman experiments show that the crystallization process of amorphous silicon leads to a change in the type of majority charge carriers in graphene. The n-type behavior originally displayed in the conductivity of the studied graphene layer changes to a p-type behavior.2 Expectations for further applications in solid phase crystallized superstrate thin film solar cells are raised by the retention of the structure of graphene after burial under polycrystalline Si.
1 Troppenz, G. V.; Gluba, M. A.; Kraft, M.; Rappich, J.; Nickel, N. H. Strain Relaxation in Graphene Grown by Chemical Vapor Deposition. Journal of Applied Physics 2013, 114, 214312.
2 Gluba, M. A.; Amkreutz, D.; Troppenz, G. V.; Rappich, J.; Nickel, N. H. Embedded Graphene for Large-Area Silicon-Based Devices. Applied Physics Letters 2013, 103, 073102.
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Helmholtz-Zentrum Berlin (HZB) is a research centre for energy materials research, thus contributing to knowledge-based solutions, and it provides large-scale research infrastructure for the national as well as international scientific community and industry. HZB employs about 1200 people and has got an annual budget of about 146 million Euros. HZB is a member of the Helmholtz Association - Germany's largest scientific organisation. In order to stimulate technology transfer the Helmholtz Association has recently established seven Innovation Labs. HZB runs one of them - namely the Helmholtz Innovation Lab HySPRINT.