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X03DA - PEARL

Photoemission and Atomic Resolution Laboratory

PEARL is dedicated to the characterisation of local atomic and electronic structure at the surface of a variety of systems such as molecular networks, organic and inorganic semiconductors, nanostructures, thin films, and complex materials. Soft x-ray photoelectron spectroscopy (XPS, ARPES) and diffraction (XPD/PhD) as well as scanning tunnelling microscopy (STM) and spectroscopy (STS) give insight into fundamental phenomena in condensed matter physics that are intimately tied to atomic arrangement or structural transitions.


The laboratory integrates a soft x-ray beamline with an angle-resolved photoelectron spectrometer and a low-temperature scanning tunnelling microscope (STM) in the same ultra-high vacuum system. On-site surface preparation facilities include ion sputtering, high-temperature annealing and physical vapour deposition. A fast-entry load lock and ports for user-supplied equipment are also available.

Publications Website
Beamline Energy Resolution
60 [meV] @ 400 [eV]
Beamline Resolving Power
7000 [E/deltaE] @ 400 [eV]
Beamline Energy Range
60 - 2000 [eV]
Max Flux On Sample
2 * 1011 [ph/s] @ 1000 [eV]
Spot Size On Sample Hor
200 [um]
1 [mm]
Spot Size On Sample Vert
100 [um]
1 [mm]
Angle Of Incidence Light On Sample Value
0 - 60 [degrees]
Photon Sources

Bending Magnet

Type
Bending Magnet
Available Polarization
Linear horizontal, Elliptical
Additional Lightsources

He Discharge Lamp

Type
Focus HIS-13 gas discharge lamp, not monochromatized
Central Wavelength/Energy
21.22 [eV]
Beam shape
Gaussian
Polarisation
Unpolarized
Monochromators

PGM

Energy Range
60 - 2000 [eV]
Type
Jenoptik plane-grating plane-mirror monochromator
Resolving Power
7000 [deltaE/E] @ 400 [eV]
Number Of Gratings
2
Grating Type
600 lines/mm Au coated laminar
1200 lines/mm Au coated laminar
Pre-focusing Mirror Type
toroidal
Refocusing Mirror Type
toroidal
Endstations or Setup

Main

Description
Multi-purpose angle-resolved photoelectron spectroscopy and diffraction
Base Pressure
2 * 10-10 [mbar]
Detectors Available
Photoelectron Spectrometer
Partial electron yield
Total electron yield
Endstation Operative
Yes

Sample

Sample Type
Crystal, Amorphous, Powder, Other: surface, interface, nanostructure, thin film
Mounting Type
flag-style sample plate (Omicron)
Required Sample Size
X = 200 [um], Y = 100 [um], Z = 0.001 [um]

Techniques usage

Absorption / NEXAFS
photon energy scan at normal incidence, TEY or PEY detection using drain current, scintillator or electron analyser.
limited sample rotation (pure p-polarization not possible)
Absorption / XMCD
circular dichroism of resonant photoemission and Auger lines in the electron spectrum using off-axis elliptic light from bending magnet.
sample must be magnetized in remanence.
switch polarization and/or rotate sample to detect contrast.
Photoelectron emission / Angular Resolved PES
angle-resolved PES possible in the photon energy range above 60 eV.
limited angular resolution 0.5°.
Photoelectron emission / Photoelectron diffraction
angle scan (full hemisphere)
photon energy scan
Photoelectron emission / XPS
high-resolution XPS resolving chemical shifts and spin-orbit multiplets.
resonant excitation.

Manipulator or Sample stage

Description
high-precision variable-temperature CARVING manipulator with 3 translations and 3 rotation axes
Degrees Of Freedom
6
Translator Stages
3
Cradles
1
Positioning Precision
X = 5 [um], Y = 5 [um], Z = 20 [um]
Range Of Movement
X = 10 [mm], Y = 10 [mm], Z = 10 [mm]

Sample Environment

Description
Mu-metal ultra-high vacuum chamber
Pressure (min)
5 * 10-11 [mbar]
Pressure (Max)
5 * 10-8 [mbar]
Temperature
35 - 700 [K]

Sample Holders

Type
Small layered crystals for cleaving
Description
The sample holder consists of Cu block where thin crystals of about 0.2 mm thickness are attached by epoxy or carbon tape. The crystal is cleaved by attaching scotch tape or a top post, preferably in the load lock.
Type
Single crystal metal samples with top-hat shape for radiative heating
Description
The sample is mounted on a molybdenum support with a through-hole for radiative or e-beam heating through the bottom.
Type
Omicron flag-style sample holder
Description
There are obstructions in the chamber which restrict the size of samples and supports. Please ask for maximum dimensions and ideal sample position. For angle scans, it is essential that the sample is placed in the center of rotation of the manipulator.
Type
Semiconductor wafer pieces for direct-current heating
Description
The wafer piece must have a specific thickness (ideally 0.25 or 0.50 mm) and be cut into specific shape (9 mm x 5 mm)
Type
Semiconductor wafer for radiative heating (up to 1100 K)
Description
For wafer pieces up to 9 mm x 10 mm and arbitrary thickness from 0.2 to 2.0 mm, ideal thickness 1 mm.

STM

Description
low-temperature scanning tunnelling microscope (STM)
Microscopes
Omicron LT-STM
Base Pressure
5 * 10-11 [mbar]
Endstation Operative
Yes

Sample

Sample Type
Crystal
Mounting Type
Omicron flag-style sample plate
Required Sample Size
X = 200 [um], Y = 200 [um], Z = 200 [um]

Sample Environment

Description
The low temperature STM operates at 4 K or 77 K.
Pressure (min)
5 * 10-11 [mbar]
Pressure (Max)
5 * 10-10 [mbar]
Temperature
4 - 300 [K]
Detectors

Partial electron yield

Type
Everhart-Thornley
Description
scintillator-based partial electron yield (PEY) detector with photomultiplier tube readout
Array Size
X = 1 [pixel], Y = 1 [pixel]
Passive or Active (Electronics)
Active
Output Readout Software
EPICS

Detection

Detected Particle
Electron

Photoelectron Spectrometer

Type
Scienta EW4000
Description
two-dimensional, hemispherical photoelectron analyzer (angle, energy) with a nominal acceptance angle of 60°.
angular resolution 0.5°, energy resolution up to pass energy / 1700.
Array Size
X = 900 [pixel], Y = 900 [pixel]
Passive or Active (Electronics)
Active
Output Readout Software
EPICS array detector

Detection

Detected Particle
Electron

Total electron yield

Type
Keithley 6517 electrometer for total electron yield (TEY) measurement
Array Size
X = 1 [pixel], Y = 1 [pixel]
Passive or Active (Electronics)
Active
Output Readout Software
EPICS

Detection

Detected Particle
Electron
Support Laboratories

Surface preparation

Description

Ultrahigh-vacuum chamber with standard surface preparation facilities (ion sputtering, annealing), built-in evaporator for organic materials (up to 700 K), and ports for user-supplied evaporators.

contacts
Matthias Muntwiler
Techniques
Absorption
  • NEXAFS
  • XMCD
Photoelectron emission
  • Angular Resolved PES
  • Photoelectron diffraction
  • XPS
Disciplines
Chemistry
  • Physical Chemistry
Engineering & Technology
  • Nanotechnology & production processes
Material Sciences
  • Knowledge based multifunctional materials
Physics
  • Atomic & molecular physics
  • Hard condensed matter - electronic properties
  • Hard condensed matter - structures
  • Nanophysics & physics of confined matter
  • Quantum electronics & optics
  • Surfaces, interfaces and thin films
control/Data analysis
Control Software Type
  • EPICS, PShell
Data Output Type
  • spectra, angle scans, energy scans, angle distribution maps
Data Output Format
  • HDF5
Softwares For Data Analysis
  • Igor Pro
Equipment That Can Be Brought By The User
material evaporators, small growth chamber

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