LabAdviser/314/Microscopy 314-307/SEM/QFEG

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This section is written by DTU Nanolab internal if nothing else is stated.

QFEG 200 Cryo ESEM (FEI Quanta FEG 200)

DTU Nanolabs QFEG positioned in building 314 room no. 010

The QFEG 200 Cryo is an FEI Quanta FEG (Field Emission Gun) scanning electron microscope with a spatial resolution of 2 nm for the ETD detector in high vacuum at 30 keV. The microscope can operate in several modes, such as high vacuum, low vacuum, environmental mode, room temperature, low temperature and cryo. Our QFEG is fitted with an EDS detector, which allows for analytical measurements in all the operation modes. With the cryo transfer system available, it is especially suited for cryo experiments.

Process information

  • Electron source

Field emission gun

  • Accelerating voltage

500 V- 30 kV

  • Resolution

2 nm at 30 kV (SE)

  • Imaging detectors

Everhart-Thornley (SE/BSE), Solid State BSE, Large Field, Gaseous SE, Gaseous BSE, Gaseous Analytical, STEM, vCD and CCD Camera

  • Imaging modes

High, low vacuum and environmental

  • Analytical capabilities

Energy dispersive X-rays (Oxford Instruments 80 mm2 X-Max silicon drift detector, MnKα resolution at 124 eV)

  • Attachments

Quorum PP2000 Cryo System, FEI Peltier stage (-10°C to 22°C).

Equipment performance and process related parameters

Equipment QFEG Cryo SEM FEI Quanta FEG 200
Purpose Vizualization and Microanalysis
  • Vizualization of surfaces (topography and Z contrast)
  • Vizualization of projected image (BF STEM image)
  • Energy Dispersive X-ray analysis (EDS)
Performance Resolution The resolution of QFEG dependends on the sample and the operation mode!
  • 2 nm at 30 keV for Au on C sample with the ETD detector
Instrument specifics Detectors
  • ETD- Everhart-Thornley for secondary electrons
  • BSD- Solid state Back Scattered Detector
  • LFD- Large Field Detector for secondary electrons
  • GSED- Gaseous Secondary Electron Detector
  • GBSD- Gaseous Backscattered Electron Detector
  • GAD- Gaseous Analystical Detector
  • STEM- right field Scanning Tramission Electron detector
  • vCD- low voltage BSED
  • CCD camera
Electron source
  • Field Emission - Tungsten filament
Stage (room temperature)
  • X, Y: 25 × 25 mm
  • T: 0 to 60o (Full tilt require removment of cryo cold trap.)
  • R: 360o
Peltier stage
  • FEI Peltier stage -10o to 22o
Cryo stage
  • Quorum PP2000 Cryo System
EDS
  • Oxford Instruments 80 mm2 X-Max silicon drift detector, MnKα resolution at 124 eV
Operating pressures
  • High vacuum (10-4 Pa), Low vacuum and Enviromental mode (up to 2700Pa)
Samples Sample sizes
  • No actual limit (limitted by stage movement and detector position).
Allowed materials
  • Conductors, Semiconductors,Insulators,Wet Samples, Biological (not pathogens!)


Examples of the QFEG's capabilities

All images are taken by Marie Karen Tracy Hong Lin @DTU Nanolab

SEM (Scanning Electron Microscopy)

The SEM is a remarkable technique which can offer information such as the surface morphology of a sample and also a 3D appearance of the specimen. It can offer the best resolution (2 nm at 30kV) at high magnification and also topographical details because of its great depth of field.

SEM imaging of Microalgae with gold nanoparticles


SEM imaging of Bacteria


SEM imaging of Spider


SEM imaging of Spider web


BSD (Backscattered Electron Detector)

BSD imaging of Microalgae with gold nanoparticles



STEM (Scanning Transmission Electron Microscopy)

STEM combines the principles of transmission electron microscopy and scanning electron microscopy and can be performed on either type of instrument. In the STEM setting, the sample requires to have a thickness of less than 200 nm for visualization. Sample preparation prior to STEM microscopy involve samples being embedded in epoxy resin and then ultra sectioning using the Ultramicrotome. For more sensitive samples that need to be sectionned at cryogenic temperatures (below −180 °C), the Cryo-Ultramicrotome can be used for that purpose.

STEM imaging of a cross section of Microalgae, 100 nm thick section


STEM imaging of a cross section of Yeast, 100 nm thick section


ESEM (Environmental Scanning Electron Microscopy)

In the ESEM setting, sample temperature and specimen chamber vapour pressure can both be controlled thus allowing visualiztion of the specimen when heated, cooled, wetted or dried.


Cryo-SEM

In the cryo-SEM setting, the sample is visualized in a frozen state (down to -190 °C). This setting is very useful when the specimen being observed needs visualiztion in its hydrated form. It can be imaged by using either the secondary electrons (SE) or backscattered electrons (BSE) detector.

Cryo-SEM imaging of Blue cheese


Cryo-SEM imaging of Mucus in rat intestine


Cryo-SEM imaging of Moulded and expired jam



EDS (Energy Dispersive X-ray Spectroscopy)

The EDS is an analytical technique which can provide elemental or chemical characteristics of a sample.

EDS mapping of bacteria and gold nanoparticle


SEM analysis and EDS mapping of microalgae with iron nanoparticles


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