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