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PEEM-3 at the ALS:
X-ray Photoemission Electron Microscopy

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Lawrence Berkeley National Laboratory

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Rajesh Chopdekar

RVChopdekar@lbl.gov
last update: 03/30/2020

Beamline 11.0.1

PEEM3 is installed at BL11.0.1, a soft x-ray beamline equipped with a Sasaki-type Elliptically Polarizing Undulator

  • The EPU provides full polarization control with high brightness beams of circularly, elliptically, and variable linearly polarized x-rays
  •  The beamline has an energy range of 160 eV – 1800 eV, covering a wide range of elements including carbon, oxygen, transition metals, rare earths, silicon, and sulfur. This wide energy range allows for the study of materials in a wide range of fields, from polymer science to magnetic materials.
  • Adjustable bendable mirrors are used to tailor the x-ray spot size to the microscopy field of view, providing for the optimum illumination conditions.
Source
5.0-cm-period elliptical polarization undulator (EPU5)
Monochromator VLS-PGM
Energy range with useful flux
250–1700 eV
Energy resolution E/DE
4,000 at 800 eV
Polarization
Polarization is user selectable; linear polarization continuously variable from horizontal to vertical; left and right elliptical (or circular) polarization

Endstation 1: PEEM-3

Type Photoemission Electron Microscope
Contrast mechanism Elemental and chemical contrast using NEXAFS, magnetic and structural contrast via linear and circular dichroism.
Spatial resolution
Better than 50 nm depending on sample
Field of view
5 - 100 µm.
Time resolution
~1s preview.
80 ps in pump-probe mode.
Manipulator
xyz and sample tilt, up to 10x10mm xy travel on sample.
Sample size from 3 to 18 mm diameter
heating, magnetic field, cooling, pulses may require different sample sizes
Sample properties Flat, conductive surfaces, insulators can be metal coated
Sample environment

UHV (below 10-8 mbar).
In-plane pulsed magnetic fields up to 200 Gauss.
Sample cooling/heating from 32 K to 390 K or from 295 K to 1000 K (different sample holders may be needed)
Short pulse experiments using 20 ns electrical waveforms and pulses.
Bias voltages up to 400 V and currents up to 2 A on sample holder.
See sample holders page for details on what sample environments are available.

Sample preparation HV Ar ion Sputter clean
PEEM-3

The main experiment chamber houses an advanced sample manipulator which positions the sample with micron accuracy and nanometer stability. A unique cooling system allows users to cool samples down to 30 K using liquid He and 105 K using liquid N2 cooling.

The x-ray produced photoelectrons are imaged using a precision electron optics system mounted on a uhv optical table. This design provides for very stable operation, as well as enabling future upgrades.