Progress on PEEM3 - An Aberration Corrected X-Ray PhotoemissionElectron Microscope at the ALS Page: 1 of 4
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Progress on PEEM3 - An Aberration Corrected X-Ray
Photoemission Electron Microscope at the ALS
A.A.MacDowell', J.Feng', A.DeMello', A.Doran', R.Duarte', E.Forest2, N.Kelez',
M.A.Marcus', T.Miller', H.A.Padmore', S.Raoux3, D.Robin', A.Scholl',
R.Schlueter', P .Schmid', J.Stdhr4, W.Wan', D.H.Wei5 and Y.Wu6
'Advanced Light Source, Lawrence Berkeley National Lab. Berkeley, CA 94720, USA
2 High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki,305-0810, Japan
3IBM, Almaden Research Center, 650 Harry Road, San Jose, CA 95120, USA
4 Stanford Synchrotron Radiation Laboratory, PO Box 20450, Stanford, CA 94309, USA
5 NSRRC, 101 Hsin-Ann Road, Hsinchu 30077, Taiwan
6 Department of Physics, Duke University, Durham, NC 27708, USA
Abstract. A new ultrahigh-resolution photoemission electron microscope called PEEM3 is being developed and built at the
Advanced Light Source (ALS). An electron mirror combined with a much-simplified magnetic dipole separator is to be used to
provide simultaneous correction of spherical and chromatic aberrations. It is installed on an elliptically polarized undulator (EPU)
beamline, and will be operated with very high spatial resolution and high flux to study the composition, structure, electric and
magnetic properties of complex materials. The instrument has been designed and is described. The instrumental hardware is being
deployed in 2 phases. The first phase is the deployment of a standard PEEM type microscope consisting of the standard linear
array of electrostatic electron lenses. The second phase will be the installation of the aberration corrected upgrade to improve
resolution and throughput. This paper describes progress as the instrument enters the commissioning part of the first phase.
Keywords: Photoemission Electron Microscope, PEEM, Aberration Correction.
PACS: Replace this text with PACS numbers; choose from this list: 07.85.Qe, 07.78.+s
The photoemission electron microscope (PEEM) has been developed since 1930  to study the surface and thin
film properties of various materials. In a PEEM, photons impinging on the sample cause the emission of secondary
photoelectrons. These electrons are accelerated to typically 10-30keV and focused to produce a magnified
intermediate image by an immersion objective lens. A series of projection lenses are used to magnify this
intermediate image further and form a final image on a CCD or other imaging detector. When tunable X-rays from a
storage ring are used, different contrast mechanisms such as topographic, elemental, chemical, orientation and
magnetic are available. The lateral resolution limit of state-of-the-art PEEMs is about 20nm such as the second-
generation PEEM2 instrument  now operating on a bend magnet beamline at the Advanced Light Source (ALS).
This limit is due to the spherical and chromatic aberrations of the immersion objective lens. By incorporating an
electron mirror  with its own aberrations but of opposite sign, aberration cancellation can be effected with
consequent resolution and throughput improvement. The ALS has embarked on the building of such a PEEM3
instrument that will be stationed on a dedicated EPU insertion device at Beamline 11.0.1 .
DESCRIPTION OF THE PEEM3 INSTRUMENT
Figure 1 shows the schematic overview of the electron optics of PEEM3. Photoelectrons from the sample are
collected and accelerated by the immersion objective lens to the nominal energy of 20keV. The objective lens is an
electrostatic four-electrode lens, in which the sample is also part of the lens and located 2mm away from the second
grounded electrode. This distance is adjustable to accommodate different sample cases. This objective lens is
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MacDowell, Alastair A.; Feng, J.; DeMello, A.; Doran, A.; Duarte,R.; Forest, E. et al. Progress on PEEM3 - An Aberration Corrected X-Ray PhotoemissionElectron Microscope at the ALS, article, May 20, 2006; Berkeley, California. (https://digital.library.unt.edu/ark:/67531/metadc889767/m1/1/: accessed March 22, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.