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Direct Experimental Evidence of Metal-Mediated Etching of Suspended Graphene
Ramasse, Quentin M.,Zan, Recep,Bangert, Ursel,Boukhvalov, Danil W.,Son, Young-Woo,Novoselov, Konstantin S. American Chemical Society 2012 ACS NANO Vol.6 No.5
<P>Atomic resolution high angle annular dark field imaging of suspended, single-layer graphene, onto which the metals Cr, Ti, Pd, Ni, Al, and Au atoms had been deposited, was carried out in an aberration-corrected scanning transmission electron microscope. In combination with electron energy loss spectroscopy, employed to identify individual impurity atoms, it was shown that nanoscale holes were etched into graphene, initiated at sites where single atoms of all the metal species except for gold come into close contact with the graphene. The e-beam scanning process is instrumental in promoting metal atoms from clusters formed during the original metal deposition process onto the clean graphene surface, where they initiate the hole-forming process. Our observations are discussed in the light of calculations in the literature, predicting a much lowered vacancy formation in graphene when metal ad-atoms are present. The requirement and importance of oxygen atoms in this process, although not predicted by such previous calculations, is also discussed, following our observations of hole formation in pristine graphene in the presence of Si-impurity atoms, supported by new calculations which predict a dramatic decrease of the vacancy formation energy, when SiO<SUB><I>x</I></SUB> molecules are present.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2012/ancac3.2012.6.issue-5/nn300452y/production/images/medium/nn-2012-00452y_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn300452y'>ACS Electronic Supporting Info</A></P>
Alloyeau, Damien,Ding, Baoquan,Ramasse, Quentin,Kisielowski, Christian,Lee, Zonghoon,Jeon, Ki-Joon Royal Society of Chemistry 2011 Chemical communications Vol.47 No.33
<P>Here, we report a simple and rapid characterisation technique combining physical and chemical analysis for DNA origami with conventional TEM.</P> <P>Graphic Abstract</P><P>Here, we report a simple and rapid characterisation technique combining physical and chemical analysis for DNA origami with conventional TEM. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c1cc13654b'> </P>
Interface control of bulk ferroelectric polarization.
Yu, P,Luo, W,Yi, D,Zhang, J X,Rossell, M D,Yang, C-H,You, L,Singh-Bhalla, G,Yang, S Y,He, Q,Ramasse, Q M,Erni, R,Martin, L W,Chu, Y H,Pantelides, S T,Pennycook, S J,Ramesh, R National Academy of Sciences 2012 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.109 No.25
<P>The control of material interfaces at the atomic level has led to novel interfacial properties and functionalities. In particular, the study of polar discontinuities at interfaces between complex oxides lies at the frontier of modern condensed matter research. Here we employ a combination of experimental measurements and theoretical calculations to demonstrate the control of a bulk property, namely ferroelectric polarization, of a heteroepitaxial bilayer by precise atomic-scale interface engineering. More specifically, the control is achieved by exploiting the interfacial valence mismatch to influence the electrostatic potential step across the interface, which manifests itself as the biased-voltage in ferroelectric hysteresis loops and determines the ferroelectric state. A broad study of diverse systems comprising different ferroelectrics and conducting perovskite underlayers extends the generality of this phenomenon.</P>