The pump-probe spectroscopy infrastructure @ FORTH provides in-situ probes of the excited state of the matter, i.e. in the time/frequency domain at the fs-ps scales.
Tabletop workstations, based on fs laser sources combining wavelengths from the UV to visible to NIR and THz, can follow in time the electronic and lattice evolution, gaining thus insight in the material dynamics. Carrier transport and recombination dynamics, as well as phase transition dynamics in nanosystems, can be monitored, via their optical and near-optical signature through absorption and photoluminescence changes that are induced by ultrafast laser excitation.
The NFFA-SPRINT facility @ CNR-IOM is designed to provide pump-probe photoelectron spectroscopy (ARPES and Spin Polarimetry) experiments. The High Harmonics Generation (HHG) beamline is based on a PHAROS laser, providing 20 W, 400 mJ pulses @ 50 kHz, with a tunable repetition rate from single shot to 1 MHz and a pulse duration around 290 fs. 90% of this radiation is used to generate high harmonics in gases (Ar and Ne), covering the energy range between 17 to 76 eV, with high photons flux, up to 1012 photons/seconds @ 27 eV, 50 kHz, and allowing very good generation also @ 200 kHz. The remaining 10% can be used to pump two Optical Parametric Amplifiers (OPA), in the range 630 nm -16000 nm, used for pump-probe measurements.
The facility is connected with two end station for Time resolved-ARPES (T-ReX group) and Spin polarimetry (SPRINT). The SPRINT end station is a stand-alone spectrometer for UV and soft X-ray time-resolved photoelectron spectroscopy, readily moveable to FEL sources, but routinely available for users at NFFA-SPRINT. A Scienta SES-2002 electron spectrometer devoted to PES and ARPES is presently equipped with a phosphor detector and CCD camera and will be soon upgraded with a crossed delay-line detector (developed by Elettra Detector group) to allow pump-probe experiments. A reference statistical VUV source, a resonant HeI-II lamp, provides 21.2 eV and 40.8 eV light for reference photoemission spectra and resolution tests. Cryogenic temperature control (down to 40 K) is implemented. The samples are prepared in an annex sample preparation module that can also receive samples via a UHV shuttle.
SPRINT (Spin Polarized Research Instrument in the Nanoscale and Time Domain) @ CNR-IOM
Photoelectron spectroscopy of complex materials, secondary electron spin-polarimetry, ARPES
Dynamics of magnetization and electronic structure
Generation of High Harmonics from a Solid State Laser: the driving laser wavelength is multiplied by highly non-linear multiphoton processes triggered by extremely high laser power densities in high-pressure jet of gas; the source delivers odd multiples of the driving laser photon energy (1.2 eV) in ultrashort (300-200 fs) pulses; the flux is 2x1012 ph/s (4x107 ph/pulse) in the energy range 10-30 eV and 5x108 ph/s (1x104 ph/pulse) in the range 40-75 eV; the natural linewidth is in the tens of meV
He discharge lamp: (21.22 eV), natural linewidth < 10 me
Solid state based:
Laser (1030 nm ) (1.2eV)
OPA (630-16000 nm)
OPA+crystals (630-200 nm) (2-6 eV)
Argon HHG (High flux):
VUV (125-40 nm) (10-30 eV) In odd harmonics separated by 4.8 eV steps
Neon HHG (High photon energy):
XUV (30-16.5 nm) (40-75 eV) In odd harmonics separated by 2.4 eV steps
Hemispherical electron analyzer Scienta SES 2002: main radius 200 mm, working distance 55 mm, aperture diameter 16 mm, variable slit width from 0.2 to 4.0 mm; angular acceptance ±3.5°; lens modes: transmission and angular; detection: Multi-Channel Plate with phosphorous screen and CCD camera
Mott detector for spin polarization of secondary electrons; vectorial analysis of the spin polarization vector; single electron counting and multi-hit detection electronics
Final overall energy resolution: 35 meV
Spot-size on the sample: 185 mm
Four degrees of freedom (x, y, z, θ)
x,y: ±10 mm, resolution 10 mm
z: ±300 mm, resolution 10 mm
θ: 360°, resolution 0.1°
Ferrovac sample-holder
Measurement temperature range: 40-900 K
Preparation temperature limits: 500 K during sputtering, 1000 K only annealing (in separated stage)
Base pressure: 1x10-10 mbar
Max magnetic field strength: 16 kA/m
Max voltage: 2 kV
Max pumping field intensity: 1 mJ per pulse (1.4 mJ/ cm2)
LEED-AUGER
Quartz microbalance
Sputter gun (Ar+ ion bombardment)
Annealing stage (e-beam heating)
Fe and Au e-beam UHV evaporators (one pumped flange for additional evaporators)
Cesium evaporator
Laser based pump-probe setup with exchangeable technique (Transient Grating currently installed)
Uni-NG
Slovenia
CITIUS
time resolved photoemission
High order harmonics generation (HHG) form TiSa laser (fundamental wavelength 800 nm)
rep. rate 5 kHz, 3 mJ energy/pulse, time duration 35 femtoseconds
HHG in gas: from 13 eV to 70 eV
Harmonics in non linear crystals: 3 eV, 4.5 eV and 6 eV
Scienta R3000 electrons energy spectrometer
to be replaced in June 2022 with a Phoibos 150 with CMOS detector
150 meV
150 micron spot size
Max sample size 8x8 mm, thickness 2 mm mounted on flag style sample plates (Mo or Cu).
Cryogenic manipulator 5 degrees of freedom (x,y,z, polar angle and tilt), down to 20 K
Ultra high vacuum
Pump wavelength range:
- 800 nm up to 1 mJ/pulse
- (260-2600) nm OPA emission, with variable energy on the spectral range
time duration 35 fs
- pump at 800 nm with 10 femtosec time duration
Sample heating stage up to 1000 degrees by electronic bombardment
Ar ion sputtering
In vacuum cleaver
(0-1500) eV
CNR-ISM
Italy
Transient Absorption Spectrometer
Transient Absorption Spectroscopy in the UV-Vis-NIR pump-probe wavelength range to study ultrafast processes in materials (nanostructured, plasmonic, and photovoltaic materials), as well as in molecules.
Transient Absorption Spectroscopy involves the excitation of the sample using tunable light from the optical parametric amplifier (240 – 2500 nm) and probing with a time delayed white light supercontinuum (240 – 1600 nm). Both the transient absorbance and reflectance can be recorded as a function of temporal delay (maximum delay time 1 ns) of the arrival of the probe with an overall resolution of 50 fs.
The source of the optical parameter amplifier is a regenerative amplifier seeded by a mode-locked Ti:Sa oscillator: pulse duration 35 fs, repetition rate 1 kHz, power 4 W@800 nm.
Pump wavelength range: 240-2500 nm.
Probe energy range: 240-1600 nm.
Pump spot size 150 um , probe spot size 100 um
The sample can be mounted in air and in a high vacuum cryostat at LN temperature.
The samples can be measured at atmospheric pressure or at a pressure of 10E-4 mbar.
SAXS is a non-destructive and versatile method to study the nanoscale structure of any type of material (solid, liquid, aerosols) ranging from new nanocomposites to biological macromolecules. Averaged particle sizes, shapes and distributions, porosity, degree of crystallinity and electron density maps with nanometer precision can be obtained.
In SEM a beam is scanned over a sample surface while a signal from secondary or back-scattered electrons is recorded. SEM is used to image an area of the sample with nanometric resolution, and also to measure its composition, crystallographic phase distribution and local texture.
AFM is a surface sensitive technique permitting to obtain a microscopic image of the topography of a material surface and certain properties (like friction force, magnetization properties…). Typical lateral image sizes are within a range of only a few Nanometers to several Micrometers, and height changes of less than a Nanometer.
In TEM/Scanning TEM (STEM) high energy electrons incident on ultra-thin samples, allow imaging, diffraction, electron energy loss spectroscopy and chemical analysis of solid materials with a spatial resolution on the order of 1-2 Å. Samples must have a thickness of a few tens of nanometres and are prepared in sample preparation laboratory.
XRD provides non-destructive information on the structural order of a material. At large scattering angles XRD permits to identify different crystal phases and to quantify lattice distances and crystalline volume fractions. At low angles of incidence the surface roughness of a single crystal and the thickness of a deposition layer can be obtained.
