BL3.2b: PEEM

At BL3.2b (PEEM), a sample is irradiated with monochromatic light from varied line-spacing plane-grating monochromator. Electrons which are created by photoemission and photoabsorption processes are projected by a set of magnetic lenses onto a micro-channelplate intensifier and a phosphor screen where the final image forms. By scanning incident photon energy and capturing PEEM image at each energy step, a series of images which contains photoabsorption spectra from nanometer-sized areas of the sample can be obtained. Alternatively, photon energy is fixed and an electron energy analyzer is used to determine the photoemission spectra of photoelectrons emitted from certain areas of the sample.

Sample Preparation

Samples need to be clean and ultra-high vacuum compatible (dry, containing no high vapor-pressure substance). They should be flat, smooth, and electrically conductive. Non-conductive samples may be coated with thin Pt films before imaging to prevent charging effect. The sample size compatible to the current sample holder is 1cm x 1cm

PEEM sample holder is equipped with an electron bombardment heater. Sample can be heated from room temperature up to 1500 C.

It can also be imaged in real-time during the temperature change. Various deposition and cleaning methods can be used to prepare

PEEM samples. An ion sputter gun can be installed to the high vacuum section, while a mini electron-beam evaporator and a sputter

deposition system are equipped in the ultra-high vacuum section. PEEM can observe in-situ thin-film deposition by mini electron-beam

evaporator or by gas feeding through a leak valve attached to the experimental chamber.

Applications

PEEM is an effective tool to study surface and interface phenomena.

Examples of researches that benefit from PEEM’s capbility include:

• Thin-fim deposition

• Structural analyses of composite materials

• Novel electronic substrate engineering

• Applied physics involving surface phenomena

Technical information
Technique:	Photoemission Electron Microscopy (PEEM)
Applications:	Electron microscopy for surface, interface and thin-film researches.
Source and beamline
Radiation source :	U-60 undulator
Photon flux at sample:	1e12 phs/s at 100 eV
Photon energy range:	40-160eV and 220-1040 eV
Monochromator type:	Varied-line-spacing plane-grating monochromator
Energy bandwidth:	0.01% minimum
Experimental Station
Model:	Elmitec PEEM III
Image resolution:	30 nm
Sources:	Synchrotron, Hg UV lamp, electron gun for low-energy electron microscopy (LEEM)
Samples:	Must be flat and smooth, ultra-high vacuum compatible, and electrically conductive. Sample holder for flat and thin samples can heat up to > 1500°C. Non-conductive samples can be coated with metal films before imaging.
Detectors:	Micro-channel plate, Sensicam QE CCD camera
Analyzer:	Hemispherical electron energy analyzer
Sample environment:	Ultra-high vacuum. Base pressure at 10e-10 torr.
Beamline status:	Commissioning

Beamline layout

Photon flux from BL-3 at PEEM’s sample position

Schematics of PEEM system

Mechanical design of PEEM/LEEM system

Computer software that controls PEEM mechanical support for alignment with synchrotron beam

Thin-film deposition system can be installed at PEEM’s experimental chamber for in-situ observation of thin-film growths

PEEM image of tungsten. Field of view is 75 microns.

PEEM system

PEEM sample can be heated up to > 1500°C. The temperature can be measured using an infrared pyrometer. PEEM can observe the sample during temperature change in real-time.

The loadlock of PEEM can store more than 4 samples in vacuum. Samples can be annealed or deposited with thin films by various methods.

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