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Effect of oxygen and nitrogen functionalization on the physical and electronic structure of graphene

Nano Research 2015年第8期8卷 2620-2635页

作者： Alexander J. Marsden Peter Brommer james J. mudd M. Adam Dyson Robert Cook Maria Asensio Jose Avila Ana Levy Jeremy Sloan David Quigley Gavin R. Bell Neil R. Wilson Department of Physics University of Warwick Coventry UK Centre for Scientific Computing University of Warwick Coventry UK Synchrotron SOLEIL L'Orme des Merisiers Saint Aubin-BP 48 91192 Gifsur Yvette Cedex France

Covalent functionalization of graphene offers opportunities for tailoring its properties and is an unavoidable consequence of some graphene synthesis techniques. However, the changes induced by the functionalization are not well understood. By using atomic sources to control the extent of the oxygen and nitrogen functionalization, we studied the evolution in the structure and properties at the atomic scale. Atomic oxygen reversibly introduces epoxide groups whilst, under similar conditions, atomic nitrogen irreversibly creates diverse functionalities including substitutional, pyridinic, and pyrrolic nitrogen. Atomic oxygen leaves the Fermi energy at the Dirac point （i.e., undoped）, whilst atomic nitrogen results in a net n-doping; however, the experimental results are consistent with the dominant electronic effect for both being a transition from delocalized to localized states, and hence the loss of the signature electronic structure of graphene.

关键词： graphene functionalization chemical vapor deposition density functional theory

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Weak mismatch epitaxy and structural feedback in graphene growth on copper foil

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Nano Research 2013年第2期6卷 99-112页

作者： Neil R. Wilson Alexander J. Marsden Mohammed Saghir Catherine J. Bromley Renald Schaub Giovanni Costantini Thomas W. White Cerianne Partridge Alexei Barinov Pavel Dudin Ana M. Sanchez james J. mudd Marc Walker Gavin R. Bell Department of Physics University of Warwick Coventry CV4 7AL UK EaStCHEM School of Chemistry University of St Andrews St Andrews KY16 9ST UK Department of Chemistry University of Warwick Coventry CV4 7AL UK Sincrotrone Trieste S.Cp.A. Area Science Park 1-34012 Basovizza Trieste Italy

Graphene growth by low-pressure chemical vapor deposition on low cost copper foils shows great promise for large scale applications. It is known that the local crystallography of the foil influences the graphene growth rate. Here we find an epitaxial relationship between graphene and copper foil. Interfacial restructuring between graphene and copper drives the formation of （nl0） facets on what is otherwise a mostly Cu（100） surface, and the facets in turn influence the graphene orientations from the onset of growth. Angle resolved photoemission shows that the electronic structure of the graphene is decoupled from the copper indicating a weak interaction between them. Despite this, two preferred orientations of graphene are found, ±8° from the Cu[010] direction, creating a non-uniform distribution of graphene grain boundary misorientation angles. Comparison with the model system of graphene growth on single crystal Cu（110） indicates that this orientational alignment is due to mismatch epitaxy. Despite the differences in symmetry the orientation of the graphene is defined by that of the copper. We expect these observations to not only have importance for controlling and understanding the growth process for graphene on copper, but also to have wider implications for the growth of two-dimensional materials on low cost metal substrates.

关键词： graphene chemical vapordeposition mismatch epitaxy structural feedback low energy electrondiffraction angle resolvedphoto-emissionspectroscopy (ARPES)

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Impact of Ventricular Assist Device Implantation on Clinical and Economic Outcomes of Heart Transplantation in the United States from 2003-2007

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World Journal of Cardiovascular Surgery 2013年第5期3卷 154-159页

作者： Julie W. Doberne Brian Diggs Frederick Tibayan Matthew Slater Christopher V. Chien Jill Gelow james mudd Howard K. Song Divisions of Cardiothoracic Surgery and Cardiovascular Medicine Oregon Health & Science University Portland USA

The use of ventricular assist devices (VADs) as a bridge to transplantation (BTT) has evolved considerably as clinical experience has grown and newer generation devices have become available. This study investigated the impact of VAD implantation on the clinical and economic outcomes of patients undergoing heart transplantation in the United States(US) from 2003-2007. A retrospective study was carried out using the Nationwide Inpatient Sample, to track the characteristics and outcomes of an estimated 7859 patients undergoing heart transplantation in the United States from 2003-2007. Patients were divided based on whether they were bridged to transplant with a VAD and whether they were outpatient (VAD Outpt) or inpatient (VAD Inpt). Multivariate analysis was performed to identify risk factors for inhospital mortality following heart transplantation. Hospital costs were also measured. A VAD was used as a BTT in 20.8% of patients undergoing heart transplantation during the study period. Early in the series the frequency of VAD Outpts and Inpts was similar but in later years patients were more commonly bridged as outpatients. Hospital mortality for the entire population was 6.2%. Multivariate analysis identified several risk factors for mortality, including advanced age, history of congenital heart disease, and VAD Inpt status. VAD Inpt status was the strongest predictor of mortality. The hospital cost of patients bridged as inpatients was more than double the cost of outpatients. Median hospital cost declined by 11% over the study period, from $115,868 to $103,578. Much of this cost reduction was related to the shift in VAD status from Inpt to Outpt. Heart transplant recipients are increasingly bridged to transplantation with VADs as outpatients. Those bridged as inpatients have substantially higher hospital mortality and cost. These findings have important clinical implications and should inform policy development, resource utilization and donor allocation.

关键词： Ventricular Assist Device Heart Transplantation Cost Effectiveness

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Electrically focus-tuneable ultrathin lens for high-resolution square subpixels

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Light(Science & Applications) 2020年第1期9卷 1066-1078页

作者： Sehong Park Gilho Lee Byeongho Park Youngho Seo Chae bin Park Young Tea Chun Chulmin Joo Junsuk Rho Jong Min Kim james Hone Seong Chan Jun School of Mechanical Engineering Yonsei University50 Yonsei-roSeodaemun-guSeoul 03722Republic of Korea Electrical Engineering Division Engineering DepartmentUniversity of Cambridge9 JJ Thomson AvenueCambridge CB3 OFAUK Department of Electronic Material Engineering Korea Maritime and Ocean UniversityBusan 49112Republic of Korea Department of Mechanical Engineering Pohang University of Science and Technology(POSTECH)77 Cheongam-roNam-guPohang 37673Republic of Korea Department of Chemical Engineering Pohang University of Science and Technology(POSTECH)77 Cheongam-roNam-guPohang 37673Republic of Korea Institute for Convergence Research and Education in Advanced Technology Yonsei University50 Yonsei-roSeodaemun-guSeoul 03722Republic of Korea Department of Mechanical Engineering Columbia University500 West 120th StreetMudd 220New YorkNY 10027USA

Owing to the tremendous demands for high-resolution pixel-scale thin lenses in displays,we developed a graphenebased ultrathin square subpixel lens(USSL)capable of electrically tuneable focusing(ETF)with a performance competitive with that of a typical mechanical refractive *** fringe field due to a voltage bias in the graphene proves that our ETF-USSL can focus light onto a single point regardless of the wavelength of the visible light—by controlling the carriers at the Dirac point using radially patterned graphene layers,the focal length of the planar structure can be adjusted without changing the curvature or position of the lens.A high focusing efficiency of over 60% at a visible wavelength of 405 nm was achieved with a lens thickness of <13 nm,and a change of 19.42% in the focal length with a 9% increase in transmission was exhibited under a driving *** design is first presented as an ETF-USSL that can be controlled in pixel units of flat panel displays for visible *** can be easily applied as an add-on to high resolution,slim displays and provides a new direction for the application of multifunctional autostereoscopic displays.

关键词： visible driving competitive

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