The FOCUS PEEM Product  | © Scienta Omicron
FOCUS PEEM with integrated sample stage.
Similar to SEM: navigation along large structures.  | © Scienta Omicron
Similar to SEM: navigation along large structures. Platinum wire array on TiOx A) 590 µm FoV (white circles) B) 94 µm FoV.

PEEM

The Versatile High-Resolution Photoemission Electron Microscope

PEEMEF-PEEMTOF-PEEMμARPEStr-ARPESARPES

  • Surface Sensitive Microscopy
  • 20 nm Lateral Resolution
  • Local Spectroscopy
  • k-Space imaging
  • Easy to Operate
  • Compatible with MULTIPROBE UHV Systems

Photoemission Electron Microscopy (PEEM) is an extremely powerful imaging technique, whose versatility for topographical, chemical and magnetic contrast imaging at high resolution has been demonstrated in many laboratory and synchrotron applications.

Important contributions to the characterization of magnetic devices, Plasmon research, surface chemistry and high lateral resolution chemical analysis in combination with synchrotron radiation, investigation of time resolved processes and k-space imaging are only a few examples of active PEEM based research. In contrast to a Scanning Electron Microscope (SEM), PEEM directly images surface areas emitting photoelectrons in real-time, without scanning. 

Electron emission from surfaces can be caused in various ways - by photon irradiation excitation, thermally, via electron/ion bombardment or by field emission. Over the years the FOCUS-PEEM has been continually improved in performance and usability. The PEEM together with the dedicated high stability integrated sample stage (IS) and various available energy filters follow a modular concept easy to upgrade. In addition software assisted operation ensures time efficient and secure PEEM operation even on challenging samples. With more than 50 units in the market the FOCUS IS-PEEM is a powerful surface analysis tool.

More Information

The Modular Concept

Technical drawing of the PEEM module components  | © Scienta Omicron
PEEM modules.

The FOCUS PEEM BA is the basic version of the PEEM instrument series. It is a bolt-on instrument which can be easily integrated in vacuum chambers. It is the heart of all extended PEEM instruments. The modular design of the PEEM allows adapting the instrument to the individual needs of the planned applications. 

The integral sample stage of the IS-PEEM guarantees ultimate stability, various energy filters allow for optimum spectroscopy conditions, the position read out for the sample and aperture positioning offers e.g. fast re-allocation of small sample  features, a dedicated LHe cooled high precision 4 axis sample stage allows sample analysis at < 30 K together with eucentric sample rotation a k-space (transfer) lens allows for local ARUPS analysis with exceptional large angle acceptance of ± 1.8 Å-1.

Imaging Energy Filter (IEF)

Diagram of the IEF PEEM, comparing the two operational modes features | © Scienta Omicron
The IEF PEEM features two operational modes: the standard non-filtered PEEM mode and the filter mode. The IEF operates as a high pass filter. The potential difference between a micro-grid and the sample is tuned to select the cut off energy. For kinetic energies of incident electrons higher than the potential E0 electrons pass the grid and will be recorded by the data acquisition system (middle). In case the kinetic energy is lower than E0 the electrons will be repelled at the micro grid (bottom).

The retarding imaging energy filter (IEF) acts as a high pass filter for the full image. Setting the energy filter to a specific electron energy facilitates element mapping with increased contrast.

The IEF is a dedicated energy filter for all applications with good photoelectron yield. The IEF effectively reduces the chromatic aberration, i.e. the energy spread of the electrons contributing to the formation of the image. This is of particular importance for chemical and magnetic imaging in synchrotron applications, where the achievable resolution is reduced due to the “unfocused” contribution of high energy electrons. 

The IEF can also be used for micro spectroscopy analysis. XPS and AES spectra up to a kinetic energy of 1600 eV and with energy resolution well below 100 meV can be obtained in areas smaller than 1 μm.

Spectral Unmixing is an algorithm integrated in the PEEM imaging software  | © Scienta Omicron
Spectral Unmixing is an algorithm integrated in the PEEM imaging software that performs a least error fit of up to four prototype spectra (here two: green and red) to each pixel in the spectral image series (see below). It identifies the correlation of the image with the ‘finger print’ of the related spectra. The weights of each prototype spectrum are displayed in separate images. The right hand image represents the mixed weights of the two prototype spectra shown above colored in green and red within the image.

Time Of Flight Energy Filter

The TOF PEEM features fast switching from standard (straight through) PEEM Mode to TOF PEEM operation by using a linear retraction mechanism | © Scienta Omicron
Operational modes: The TOF PEEM features fast switching from standard (straight through) PEEM Mode to TOF PEEM operation by using a linear retraction mechanism: (A) non filtered Standard PEEM operation, (B) TOF operation. While the electrons are separated in energy by passing a dedicated low energy drift tube, a time sensitive detector records the time structure of the incident electrons with respect to a trigger signal generated by the photon excitation source (e.g. laser, synchrotron etc.).

The Time Of Flight (TOF) imaging energy filter is ideally suited for energy filtered low intensity applications with electrons in the low kinetic energy range. Together with a time sensitive imaging Delay Line Detector (2D DLD), a dedicated drift tube and a pulsed light source, the TOF PEEM offers a unique detection system. 

The detector allows true single electron counting with massive parallel detection and excellent signal to noise ratio. In addition to standard energy filtered TOF PEEM experiments the detector also allows for time dependent studies with an overall time resolution of < 250 ps. 

Lower drift energies inside the drift tube allow higher energy resolution. The special design of the FOCUS PEEM allows for operation at extremely low drift energies (10 eV) while maintaining the lateral resolution of the instrument. The TOF PEEM has achieved an energy resolution of down to 50 meV. A prerequisite for any kind of TOF experiment is a pulsed light source such as pulsed lasers or synchrotrons. 

The TOF detector may be retrofitted to existing FOCUS (IS-)PEEMs.

Diagram of the two wire array, the 2D delay line detector (DLD) records the time-of-flight t0 (C) | © Scienta Omicron
A two wire array, the 2D delay line detector (DLD) records the time-of-flight t0 (C). In addition the travel time of the signal through the wire in x (tx1, tx2) and y directions is recorded to locate the position of the incident electron on the detector (D).

Specifications

Extraction voltage [V]

50 .. 16000

Contrast aperture [µm]

30, 70, 150, 500, 1750

Iris aperture

optionally

Real space Field of View [µm]

3 .. 800

Achievable lateral resolution [nm]

< 40

Energy filter

optional, see below

Detector system

MCP + CCD camera

MCP

single or double

CCD camera standard

up to 60 sec/ frame, 25 frames/sec

Slow scan CCD camera (optional)

up to 900 sec/frame, 50 frames/sec

S-CMOS camera (optional)

up to 10 sec/frame, 140 frames/sec

Event counting

optional, double MCP needed

Measurement Software

ProNanoESCA

Normal incidence mirror

optional

Optional 
PEEM with IEF energy filter (IEF option)

Energy filter: retarding field

Energy range [eV]: 0 .. 1595

Achievable energy resolution [meV]: < 50

PEEM with TOF energy filter (TOF option)

Energy filter: drift tube with DLD detector

Energy range [eV]: 0 .. 1595

Achievable energy resolution [meV]: < 30

PEEM with angular detection (AD option)

Extended Real space field of view [µm]: 2.5 .. 1700

k-space Field of View [Å-1]: > 6

Achievable k-space resolution [Å-1]: 0.018

Reference systems

MP Compact PEEM  at the School of Materials Science and Engineering, Gwangju Institute of Science and Technology | © Scienta Omicron
151807

TOF PEEM with k-space Lens

This PEEM uses a drift tube for time-of-flight energy filtering.

more
PEEM Probe | © Scienta Omicron
182309

PEEM Lab with Time-of-Flight Extension

This PEEM uses a drift tube for time-of-flight energy filtering.

more

Downloads

FOCUS PEEM: Photo Emission Electron Microscope

11.51 MB

The Photo Emission Electron Microscope has: 20 nm lateral resolution, real-time imaging, surface sensitivity microscopy, chemical mapping and local spectroscopy capabilities. It is also easy to operate and compatible with MULTIPROBE UHV Systems.