TT 26.1 Tue 9:30 H17 Transport properties of high-quality reduced graphene oxide — ∙Michael Enzelberger1, Siegfried Eigler2, Philipp Hofmann1, Stefan Grimm2, Andreas Hirsch2, and Paul Müller1 — 1Department of Physics and Interdisciplinary Center for Molecular Materials, Universität Erlangen-Nürnberg — 2Department of Chemistry and Pharmacy, and Institute of Advanced Materials and Processes (ZMP), Universität Erlangen-Nürnberg

We present a fabrication process for freely suspended membranes consisting of bi- and trilayer graphene grown on silicon carbide. The procedure, involving photoelectrochemical etching, enables the simultaneous fabrication of hundreds of arbitrarily shaped membranes with an area up to 500 μm2 and a yield of around 90%. Micro-Raman and atomic force microscopy measurements confirm that the graphene layer withstands the electrochemical etching and show that the membranes are virtually unstrained. The process delivers membranes with a cleanliness suited for high-resolution transmission electron microscopy (HRTEM) at atomic scale. The membrane, and its frame, is very robust with respect to thermal cycling above 1000 °C as well as harsh acidic or alkaline treatment.

The formation, stability, and decomposition of CO, intercalated graphene oxide was analyzed by FTIR, TGA-MS, TGA-IR, AFM, and SEM for the first time. We found that the formation starts at 50 degrees C and develops up to 120 degrees C. The formation process can be best observed by FTIR spectroscopy, and the product is stable at ambient conditions. At higher temperatures, the decomposition of CO2 intercalated graphene oxide occurs due to the release of water, CO2, and CO that can be monitored by TGA-MS and TGA-IR analysis. AFM and SEM images can visualize the formation of blisters in GO films that become instable at 210 degrees C. We further prepared graphene oxide with a low water-content and found that the formation of CO2 was significantly suppressed and CO became the major species responsible for the weight loss. In addition we prepared (OH2)-O-18 treated graphene oxide to elucidate the formation process of CO2 and found (COO)-O-16-O-18 by TGA-MS analysis that proves the crucial role of water daring CO2 formation. From these experiments we propose that hydrate species are key-intermediates for the formation of CO2, Hence, it seems likely that rearrangement reactions that can proceed via hydrate intermediates, known from organic chemistry, are probably responsible for the formation of carboxylic acids at the edges of graphene oxide sheets after sonication of graphite oxide. Further, our investigations prove that graphene oxide is less stable than shown by TGA measurements. This has a high impact on the electronic properties of reduced graphene oxide, especially for all those using it for electronic applications.