The relatively small size of thin （one or few layers） graphene flakes makes it extremely difficult to study the behavior of suspended graphene by characterization techniques other than the electron microscopies. Her...The relatively small size of thin （one or few layers） graphene flakes makes it extremely difficult to study the behavior of suspended graphene by characterization techniques other than the electron microscopies. Herein, we exploited the capability of spatially resolved photoemission in combination with high resolution transmission electron microscopy to investigate the interaction of thermally evaporated Pt atoms on suspended and supported graphene. Spectroscopic and microscopic analyses reveal that the nucleation of nanometer- sized Pt particles in these two regions exhibit different trends. While only small nanometer-sized islands are present on the supported graphene, relatively larger clusters of islands were also found on the suspended flakes. The X-ray photoemission C ls core levels acquired after the Pt deposition show an increase in the number of vacancies in the graphene sheets.展开更多
Contactless monitoring with photoelectron microspectroscopy of the surface potential along individual nano-structures,created by the X-ray nanoprobe,opens exciting possibilities to examine quantitatively size-and surf...Contactless monitoring with photoelectron microspectroscopy of the surface potential along individual nano-structures,created by the X-ray nanoprobe,opens exciting possibilities to examine quantitatively size-and surface-chemistry-effects on the electrical transport of semiconductor nanowires(NWs).Implementing this novel approach-which combines surface chemical microanalysis with conductivity measurements-we explored the dependence of the electrical properties of undoped GaAs NWs on the NW width,temperature and surface chemistry.By following the evolution of the Ga 3d and As 3d core level spectra,we measured the position-dependent surface potential along the GaAs NWs as a function of NW diameter,decreasing from 120 to~20 nm,and correlated the observed decrease of the conductivity with the monotonic reduction in the NW diameter from 120 to~20 nm.Exposure of the GaAs NWs to oxygen ambient leads to a decrease in their conductivity by up to a factor of 10,attributed to the significant decrease in the carrier density associated with the formation of an oxide shell.展开更多
文摘The relatively small size of thin （one or few layers） graphene flakes makes it extremely difficult to study the behavior of suspended graphene by characterization techniques other than the electron microscopies. Herein, we exploited the capability of spatially resolved photoemission in combination with high resolution transmission electron microscopy to investigate the interaction of thermally evaporated Pt atoms on suspended and supported graphene. Spectroscopic and microscopic analyses reveal that the nucleation of nanometer- sized Pt particles in these two regions exhibit different trends. While only small nanometer-sized islands are present on the supported graphene, relatively larger clusters of islands were also found on the suspended flakes. The X-ray photoemission C ls core levels acquired after the Pt deposition show an increase in the number of vacancies in the graphene sheets.
基金This project was funded by Friuli Venezia Giulia L.R.47/78-1953 Ambient and Biological SensorsPartici-pation of AK was supported through National Science Foundation(NSF)No.ECCS-0925837 grant.
文摘Contactless monitoring with photoelectron microspectroscopy of the surface potential along individual nano-structures,created by the X-ray nanoprobe,opens exciting possibilities to examine quantitatively size-and surface-chemistry-effects on the electrical transport of semiconductor nanowires(NWs).Implementing this novel approach-which combines surface chemical microanalysis with conductivity measurements-we explored the dependence of the electrical properties of undoped GaAs NWs on the NW width,temperature and surface chemistry.By following the evolution of the Ga 3d and As 3d core level spectra,we measured the position-dependent surface potential along the GaAs NWs as a function of NW diameter,decreasing from 120 to~20 nm,and correlated the observed decrease of the conductivity with the monotonic reduction in the NW diameter from 120 to~20 nm.Exposure of the GaAs NWs to oxygen ambient leads to a decrease in their conductivity by up to a factor of 10,attributed to the significant decrease in the carrier density associated with the formation of an oxide shell.
