Equipments

Tuesday, 16 June 2020

Malvern PANalytical X’pert Pro MPD

The MPD (Materials Powder Diffractometer) is suitable for the analysis of polycrystalline samples at room temperature. This diffractometer has a vertical theta-theta goniometer (240 mm radius), where the sample stage is fixed and does not rotate around omega axis as in omega-2theta diffractometers.

MPD allows different geometries configurations:

In the standard configuration (reflection Bragg-Brentano geometry), the sample is kept horizontal during the measurements, suitable for large/heavy samples. This equipment has an automatic sample changer with 15 position sample magazines to scan several samples in a programmable mode. The X-ray source is a ceramic X-ray tube with Cu Κα anode (λ=1.540 Å). The detector used is an X’Celerator which is an ultra-fast X-ray detector based on Real Time Multiple Strip (RTMS) technology.

Technical specifications

  • X-ray source: Cu Κα radiation (Κα = 1.54187 Å)
  • Goniometer radius: 240 mm
  • Geometry: Bragg-Brentano (θ-θ system, vertical goniometer)
  • Scan range of 2θ: 3°-150°
  • Minimum-Maximum step size: 0.001°-1.27°
  • Automatic Sample changer: 15 samples
  • Incident PreFIX Module: Fixed divergence slit holder
    Focusing X-ray Mirror for Cu Κα
  • Diffracted PreFIX Module: X’Celerator lineal Detector
  • Available Software: X’pert Data Collector, X’pert Data Viewer, X’pert Highscore, X’pert EasySAXS

 

Bragg-Brentano Geometry

The main powder analysis applications for the Bragg-Brentano Geometry are:

  • Identification of crystalline phases in organic and inorganic compounds.
  • Quantitative phase analysis in organic and inorganic compounds.
  • Particle size determination.
  • Crystal structure determination performing Rietveld refinements.
Bragg-Brentano Geometry
X’pert Pro MPD Theta-Theta system in reflection Bragg-Brentano geometry for powder measurements.
Transmission Geometry

Available capillaries in the facility are (Diameter): 0.3mm, 0.5mm, 0.7mm. Material: Borosilicate

Advantages of transmission-mode powder diffraction

Transmission geometry requires samples that are sufficiently transparent for the type of X-rays used. The incident X-ray beam fully penetrates, and is transmitted through, the sample with only moderate attenuation.

The advantages of transmission geometry in powder diffraction are detailed:

  • Generally, transmission mode is good for low density samples or weakly absorbing materials; i.e. pharmaceutical substances, proteins, synthetic polymers (foils and fibers) and other organic materials.
  • Small amounts of sample are sufficient. We can transfer the sample into a thin capillary or in horizontal sample holders in our setup.
  • Fluids; i.e. liquid dispersions can be measured.
  • Air-sensitive samples can be sealed in a capillary or between kapton foils.
  • Reduction of the preferred orientation effects in powder samples.
  • To obtain accurate Rietveld refinements. Using this geometry the data resolution is increased due to much quantity of sample is illuminated by X-rays and as a consequence it enhances statistics.
MPD Transmission GeometryMPD Transmission Geometry
(Top) X’pert Pro MPD Theta-Theta system in transmission (vertical) configuration and (bottom) the goniometer head for capillary measurements in horizontal configuration.
MPD Transmission Geometry
Rietveld refinement from laboratory X-ray diffraction measured with X’pert Pro MPD at room temperature for (a) BiVO4 and (b) GdBaCo2O5.5. Their respective crystal structures are also plotted.
SAXS Geometry

Advantages of SAXS measurements

This technique allows sensitive measurements of the X-rays that are just barely scattered by the sample (scattering angle < 6°) using a transmission geometry. The length scale of d(Å) is inversely proportional to the scattering angle, therefore, small angles represent larger features in the samples.

This angular range contains information about the shape and size of nanoparticles and porous materials, characteristic distances of partially ordered materials, and pore sizes distributions. SAXS is capable of delivering structural information of macromolecules between 5 and 25 nm, of repeated distances in partially ordered systems of up to 150 nm.

Applications

The most common applications for these measurements are:

  • Nanoparticle size distribution
  • Particle shape
  • Specific surface area
  • Pore size distribution

Tuesday, 16 June 2020

Malvern PANalytical X’pert Pro MRD

The MRD (Materials Research Diffractometer) is suitable for the structural characterization in thin-films materials at room and high temperature. This diffractometer has a horizontal ω-2θ goniometer (320 mm radius) in a four-circle geometry and it works with a ceramic X-ray tube with Κα anode (λ=1.540 Å). This diffractometer is equipped with different incident and diffracted optics which can be interchanged depending on the application required (i.e. a parabolic mirror, a hybrid monochromator, a Ge(440) four-crystal monochromator, a parallel plate collimator, and a polycapillary lens). The detector used is a PIXcel which is a fast X-ray detector based on Medipix2 technology with a 256x256 pixels array.

Technical specifications

  • X-ray source: Cu Κα radiation (Κα = 1.54187 Å)
  • Goniometer radius: 320 mm
  • Geometry: Four-circle geometry (ω-2θ system, horizontal goniometer)
  • Scan range of 2θ: 3°-150°
  • Minimum-Maximum step size: 0.001°-1.27°
  • Incident PreFIX Module: Parabolic Mirror for Cu Kα radiation
    Hybrid Monochromator
    Ge(440) four-crystal monochromator
    Polycapillary lens
  • Diffracted PreFIX Module: Rocking curve
    Parallel Collimator
  • Detector: PIXcel Detector
  • Temperature chamber: Anton Paar DHS 1100 Dome hot stage
  • Available Software: X’pert Data Collector, X’pert Data Viewer, X’pert Epitaxy, X’pert Reflectivity, X’pert Texture, X’pert Highscore

 

High-resolution XRD routine applications
  • Crystal structure analysis: phase identification, determination of cell parameters, domain orientation and stress on thin films.
  • θ-2θ measurements (normal and high resolution) in epitaxial and polycrystalline thin-films.
  • X-ray Reflectivity measurements for estimation of thickness and roughness.
  • Rocking curves measurements.
  • Reciprocal Space Mappings.
  • Texture analysis (Phi and pole figures measurements).
  • Grazing incidence measurements.
Comparison of a ω-2θ scan in normal (top) and high-resolution (bottom) of SrRuO3 films on SrTiO3 (001) substrate measured in an X’pert Pro MRD system at room temperature.
Example of a Reciprocal Space Map for a BiFeO3 thin film on LaAlO3 (001) substrate measured in the X’pert Pro MRD diffractometer at RT.
Non ambient XRD at MRD

Apart from the routine measurements at Room Temperature, there is the possibility to carry out XRD measurements in non-ambient conditions. Two different kind of chambers are available in the XRD Facility (under request):

High-resolution XRD unconventional applications

  • In-plane reciprocal space mappings (grazing incidence and grazing exit).
  • Temperature-dependent reciprocal space mappings (at standard Bragg-Brentano and in-plane configuration).
  • In-situ thin films characterization applying:
    • Gas exchanges at elevated temperatures (redox kinetics, oxide ionic materials).
    • Applied voltage bias (piezoelectric, ferroelectric, electrostriction, resistive switching).
    • Exchange between wet and dry atmosphere (water uptake, protonic conducting materials).
    • Simultaneous atmosphere exchange and electrical conductivity.
    • LED illumination at RT and applying temperature (photo-activated phase transitions, photostriction or ageint studies…)
Non-ambient chamber Anton Paar DHS 1100

The Anton Paar DHS 1100 Dome hot stage can be mounted for temperature-induced phase transitions investigations, texture measurements, and stress analysis at high temperatures. The dome-shaped X-ray window made of graphite allows analysing samples under atmosphere control (air, vacuum, and inert gas) to avoid oxidation or other chemical reactions of thin films at up 1100°C.

Technical specifications Anton Paar DHS 1100

  • Operating temperature range: 25°C-1100°C
  • Heating rate: Max. 500°C/min
  • Atmospheres: Air, inert gases, N2, 2% O2, vacuum (10-2 mbar)
  • Max. operating pressure: 0.3 bar above atmospheric pressure
  • X-ray geometry: Reflection
  • Sample-holder material: Aluminium nitride
  • X-ray material window (DOME): Graphite
  • Sample fixing springs: Inconel
  • Heater: Kanthal
  • Thermocouple: Pt-Pt10Rh
DHS 1100 Domed Hot Stage mounted into the MRD Cradle.
Non-ambient chamber LED + Temperature

MRD is also equipped with a new LED sample stage which can be easily mounted in the MRD Cradle platform to perform in-situ XRD experiments under constant illumination, temperature and different atmospheres (N2, air, inert gases). Two different LED’s are available in the system. One is for UV light (380 nm) and the other one a High Visible LED. This chamber is also designed to perform electrical measurements simultaneously with XRD.

Technical specifications LED + temperature chamber

  • Operating temperature range: 25°C-150°C
  • Heating rate: Max. 1°C/min
  • Atmospheres: Air, inert gases, N2, 2% O2
  • X-ray geometry: Reflection
  • UV High power LED: λ= 380nm, radiation = 200-300mW
  • High Visible power LED: λ= 150-170nm, radiation = 3W
  • X-ray material window (DOME): Graphite
Non-ambient Chamber LED + Temperature stage mounted into the MRD Cradle.

Wednesday, 07 March 2018

Direct Write Laser Lithography

In maskless lithography, the radiation that is used to expose a photosensitive emulsion (or photoresist) is not projected from, or transmitted through, a photomask. Instead, most commonly, the radiation is focused to a narrow beam. The beam is then used to directly write the image into the photoresist, one or more pixels at a time.

Wednesday, 07 March 2018

UV Photolithography (Mask aligner)

Photolithography, also termed optical lithography or UV lithography, is a process used in microfabrication to pattern parts of a thin film or the bulk of a substrate. It uses light to transfer a geometric pattern from a photomask to a light-sensitive chemical "photoresist", or simply "resist," on the substrate.

Wednesday, 07 March 2018

ICP-RIE

Inductively Coupled Plasma etching is an anisotropic dry-etching process where material is removed with the use of chemically reactive plasma under a low pressure (~1-100 mTorr). Typically the material removed is a thin film previously deposited on a wafer.