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Environmental Scanning Electron Environmental Scanning Electron Microscopy: Probing Ultrafast Microscopy: Probing Ultrafast
Solvation Dynamics at InterfacesSolvation Dynamics at Interfaces
Ding-Shyue (Jerry) Yang
FEIS 2013, Key WestDec. 12th, 2013
AcknowledgementAcknowledgement
Prof. Ahmed Zewail
Dr. Omar MohammedProf. Samir PalDr. Brett Barwick
Dr. Xing HeNapat PunpongjareornKarjini Rajagopal
Ultrafast Transmission Electron Ultrafast Transmission Electron Microscopy:Microscopy:
TEM with an ultrashort temporal TEM with an ultrashort temporal resolutionresolution
Flannigan and Zewail, Acc. Chem. Res. 45, 1828 (2012)
Pulsed-electron source:Pulsed-electron source:currently, front-illuminated thermionic emitters with a smallactive surface
Pulsed-electron source:Pulsed-electron source:currently, front-illuminated thermionic emitters with a smallactive surface
generation of single-electronpulses to reduce Boersch effect, orpulses that contain many electronsfor single-shot experiments
Pulsed-electron source:Pulsed-electron source:currently, typically front-illuminated thermionic emitters with a smallactive surface
generation of single-electronpulses to reduce Boersch effect, orpulses that contain many electronsfor single-shot experiments
Clocking by fs/ns excitation Clocking by fs/ns excitation pulse:pulse:stroboscopic or single-shotmeasurements
Detection of primary electronsDetection of primary electrons
Why SUEM?
obtaining 3D-like images for materials
surfaces
Scanning Ultrafast Electron Microscopy:Scanning Ultrafast Electron Microscopy:SEM with an ultrashort temporal SEM with an ultrashort temporal
resolutionresolution
Reimer, Scanning Electron Microscopy, 2nd ed., Springer, Berlin (1998)
Why SUEM?
obtaining 3D-like images for materials
surfaces
detected signals exhibiting surface sensitivity
easier sample preparation and handling
existence of the bulk for better energy
dissipation
environmental microscopy
Scanning Ultrafast Electron Microscopy:Scanning Ultrafast Electron Microscopy:SEM with an ultrashort temporal SEM with an ultrashort temporal
resolutionresolution
Reimer, Scanning Electron Microscopy, 2nd ed., Springer, Berlin (1998)
Environmental Scanning Electron Environmental Scanning Electron MicroscopyMicroscopy
Elimination of charging Elimination of charging artifacts:artifacts:ionization of gas molecules neutralizing surface charges;minimal sample preparation
Imaging specimens at native Imaging specimens at native states:states:imaging of hydrated samplesstudy of solid-gas interactions
Instrumentation of ScanningInstrumentation of ScanningUltrafast Electron MicroscopyUltrafast Electron Microscopy
Mohammed, Yang, Pal and Zewail, J. Am. Chem. Soc. 133, 7708 (2011)
Instrumentation of ScanningInstrumentation of ScanningUltrafast Electron MicroscopyUltrafast Electron Microscopy
Yang, Mohammed and Zewail, Proc. Natl. Acad. Sci. USA 107, 14993 (2010)
Schottkyemitter:
ZrO coatedW(100) tip
electrostaticfield
strength:~107 V/cm
Time-Resolved Imaging by SUEMTime-Resolved Imaging by SUEM
Silicon single crystal
Silicon single crystal
Time-Resolved Imaging by SUEMTime-Resolved Imaging by SUEM
Apparent laser fluence: ~0.5 mJ/cm2
Time (ps)(Publication in preparation)
Apparent laser fluence:55 J/cm2
Time-Resolved Imaging by SUEMTime-Resolved Imaging by SUEM
Mechanism for bright contrast at Mechanism for bright contrast at positive timespositive times