LabAdviser/314/Microscopy 314-307/SEM/Nova

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

The FEI Nova nanoSEM 600

The Nova is, in it's normal configuration, a very versatile characterisation instrument. Capable of producing enlarged images of a variety of specimens and achieving magnifications of over 500.000 times with ultra high resolution imaging in both high and low vacuum. The Nova has become highly evolved in it’s life at DTU Nanolab and it is possible to carry out advanced processes including in-situ experiments using heat, gas injection and probing. At the time being this microscope is mainly designated for advanced microstructural characterisation and particle analysis techniques using electron backscatter diffraction (EBSD) ,Energy-dispersive X-ray spectroscopy (EDS) and forward scatter electron imaging by detectors recently bought from Bruker.

Who may operate the Nova

There are restrictions on who is given access to the Nova due to the development activities of the Bruker detectors fitted to the tool. Currently, Dr. Alice Bastos Fanta is co-ordinating the activities that take place on Nova. Alice is consulted about the planned activities beforehand in the bi-weekly meetings which are held at DTU Nanolab and coordinates the bookings in agreement with all the users. The rules of who may operate the Nova and to what extent they may operate it are:

• Only users who have been trained and approved by DTU Nanolab personnel may operate the instrument. Irregardless of their prior experience any new user without official DTU Nanolab training or approval may not operate the instrument, not even under close supervision by experienced users.

• Users may only use the instrument to the extent they have been trained. This means that one should not try to operate the following options/capabilities without explicit training:
  • Low vacuum
  • EBSD capability
  • EDX capability
  • Backscatter detectors
  • STEM

How to operate the Nova

To find the basic instructions for operating the instrument, the reader is referred to the labmanager manual.

Processing guidelines on the Nova

When one combines the 6 different detectors, 2 vacuum modes and 3 SEM modes with the traditional SEM parameters such as high voltage, working distance, spot sizes etc. it is clear that the FEI SEM has a huge number of different ways to be operated in. The number of ways that produce ultra high quality images is, however, limited. It is therefore crucial that the operators share their knowledge of how to obtain great images.

Steps to follow

There is no single general approach to taking good images on the FEI SEM. These points below are only guidelines.

What kind of images are needed

It is important to consider what kind of images are needed before you start. The different requirements/conditions could be some of the following:

High resolution at high magnification (above 10.000x) images are wanted

For conducting samples: Use TLD and mount the sample so that short WD's are possible.

For non-conducting samples: Mount the Helix detector and use short (app. 5 mm) WD.

Images of very thin (> 10 nm) metal films on low atom number materials

Use the backscatter detectors

Images with high resolution, large field of view and depth of focus are wanted

The TLD and Helix detectors do not provide large field of view and depth of focus when operated in SEM mode II.

Detectors on the Nova

The Nova has 8 electron detectors and 2 photon (X-ray) detectors.

Tag	Name	Vacuum mode	Signal	SEM modes
ETD	Everhardt Thornley Detector	HiVac	SE, BSE (detector bias adjustable)	1 and 3
TLD	Through Lens Detector	HiVac	SE, BSE (detector bias adjustable)	1, 2 and 3
BSED	BackScatter Electron Detector	HiVac	BSE	1, 2 and 3
EBSD/TKD	Electron Backscatter Diffraction	HiVac+LowVac	BSE	1 and 2
ARGUS	ARGUS(TM)	HiVac+LowVac	BSE,FSE and STEM (BF and DF)	1 and 2
LVD	Low Vacuum Detector	LowVac	SE + BSE	1 and 3
Helix	High resolution Low Vacuum detector	LowVac	SE	1, 2 and 3
GAD	Gaseous Analytical Detector	HiVac and Lowvac	BSE	1, 2 and 3
EDS	Energy Dispersive X-ray detector	HiVac and Lowvac	X-ray photons	1,2 and 3
EDS	Flat Quad X-ray detector	HiVac ONLY	X-ray photons	1,2 and 3

Equipment performance and process related parameters

Equipment		"Nova" FEI Nova nanoSEM 600
Purpose	Visualisation and Microanalysis	Visualisation of surfaces (topography and Z contrast) Visualisation of projected image (BF STEM image) Energy Dispersive X-ray analysis (EDS) Microstructural characterisation (EBSD/TKD/STEM)
Performance	Resolution	The resolution of Nova depends on the sample and is in Mode II
		High Vacuum operation in Mode II: 1.0 nm at 15 kV (TLD detector and optimum working distance) 1.8 nm at 1 kV (TLD detector and optimum working distance) Low Vacuum operation in Mode II: 1.5 nm at 10 kV (Helix detector and optimum working distance) 1.8 nm at 3 kV (Helix detector and optimum working distance)1 nm at 15keV for Au on C sample with the TLD 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	X, Y: 75 × 75 mm (piezo) Z 10mm (DC motor) T: 0 to 70o (DC motor) R: 360o (piezo)
	FlatQuad EDS	Bruker FlatQuad (High Vacuum ONLY)
	EBSD/TKD	Bruker eFlash
	EDS	Bruker 50 mm2 silicon drift detector, MnKα resolution at 124 eV
	Operating pressures	High vacuum (10-4 Pa), Low vacuum mode (up to 130Pa)
Samples	Sample sizes	No actual limit (limitted by stage movment and detector position).
	Allowed materials	Conductors, Semiconductors,Insulators,Wet Samples, Biological (not pathogents!)

Characterization Techniques

• Electron backscatter diffraction
• Transmission Kikuchi diffraction
• Micro 4-point probe
• File:In situ x-ray diffraction and electron microscopy investigations of noncatalytic metal oxide nanowire growth.pdf