Latest revision as of 09:50, 3 February 2023

Feedback to this page: click here

Element analysis at Nanolab

The following techniques for elemental analysis are available at Nanolab.

EDX
SIMS (no longer available at Nanolab, SIMS service can be provided by this company: [1])
XPS (ESCA)

In the table below the three techniques are compared

Comparison of EDX, SIMS and XPS

	SEM with EDX	Atomika SIMS	XPS (or ESCA)
Full name	Energy Dispersive X-ray Analysis	Secondary Ion Mass Spectroscopy	X-ray Photoelectron Spectroscopy (or Electron Spectroscopy for Chemical Analysis)
Technique	The primary beam of high energy electrons used in the SEM for imaging impinges on the sample atoms and leaves them in an excited state. X-rays with a characteristic energy are generated in the relaxation process. The combination of the fine control of the primary beam offered by the SEM and the detection of the X-rays makes it possible to make point-like elemental analysis.	A beam of high energy ions (cesium or oxygen) is used for sputtering off surface atoms of the sample. The material coming off the sample in this process is analysed with a mass spectrometer.	In a process in which a monochromatic beam of X-rays irradiates the sample surface, electrons bound inside the sample are knocked free to become photoelectrons. Escaping the sample with characteristic energy, these electrons not only carry elemental information but also chemical information. Analysing them respect to energy and numbers and adding an ion gun for depth profiles provide a powerful analysis tool.
What elements are detected	Every element heavier than boron/carbon	In principle every element, however, the sensitivity	Every element except hydrogen and helium.
Chemical information	None	None	Chemical state information
Sample requirements	Vacuum compatible	UHV vacuum compatible The sample needs to be cut into small (app. 5*5 mm) pieces.	UHV vacuum compatible Sample size max 50x50 mm, thickness max 20 mm.
Spatial resolution	Very precise point-like analysis is possible with SEM electron beam.	A square with dimensions of a few hundred microns is selected for analyis with a camera	Using a magnified view from a camera, a point that covers an area down to an ellipse of 40 microns may be irradiated with photons (the default size is 400 microns)
Depth resolution	The size of the interaction volume depends on the high voltage in the SEM and the sample density: The higher the SEM high voltage the bigger and deeper the interaction volume. The more dense the material is the smaller is the interaction volume. See section 'Spatial resolution using EDX' below.	The sputtering of the surface makes it possible to perform detailed depth profiling with extremely good sensitivity and depth resolution.	Very surface sensitive technique. Only photoelectrons from the top layer (a few nanometers deep) escape unscattered. By using the ion beam etch, the composition of deeper lying layers can be probed.
Detection limit	Approximately 1 % atomic weight	Down to 1 ppb for certain elements	Approximately 1 % atomic weight
Speed of measurement	Very fast and easy	Time consuming	Quite fast and easy

@@ Line 1: / Line 1: @@
-[[image:EDX-scheme.jpg|300x300px|right|thumb|X-rays, with an energy that is characteristic of the atom they are emitted from, are created when the high energy electrons impinge on the sample. ]]
+'''Feedback to this page''': '''[mailto:characterization@nanolab.dtu.dk?Subject=Feed%20back%20from%20page%20http://labadviser.nanolab.dtu.dk/index.php?title=Specific_Process_Knowledge/Characterization/Element_analysis&action=edit click here]'''
+<!--Checked for updates on 24/8-2021. ok/ jmli-->
-You can make detailed analysis on the elemental composition and distribution in a sample with 3 instruments at Danchip. The [[Specific Process Knowledge/Characterization/SEM: Scanning Electron Microscopy/Leo|Leo SEM]] and [[Specific Process Knowledge/Characterization/SEM: Scanning Electron Microscopy/FEI|FEI SEM]] are both equipped with an X-ray detector that allows you to make elemental analysis by using the technique Energy Dispersive Analysis or EDX. The [[Specific Process Knowledge/Characterization/SIMS: Secondary Ion Mass Spectrometry|Atomika SIMS]] uses a technique called Secondary Ion Mass Spectrometry or SIMS.
-== Energy Dispersive X-ray analysis ==
+= Element analysis at Nanolab =
-The technique of extracting information from the X-rays generated in a sample that is irradiated with electrons is called energy dispersive X-ray analysis or EDX. (Other acronyms are Energy Dispersive x-ray Spectroscopy, EDS, or Electron Probe Microanalysis, EPMA). The energetic electrons in the incident beam create core level vacancies as they collide with sample atoms electrons in a multiple scattering process. To decay from this excited state photons may be emitted. The energy of these photons is determined by the difference in energy of the shells involved. Since atomic shells are unique for every element so will be the transitions between them. Thus, every element has its own characteristic X-ray spectrum that can be used to determine the elemental composition.
+The following techniques for elemental analysis are available at Nanolab.
+* EDX
+* SIMS (no longer available at Nanolab, SIMS service can be provided by this company: [http://www.eag.com/secondary-ion-mass-spectrometry-sims/])
+* XPS (ESCA)
+In the table below the three techniques are compared
-== Secondary Ion Mass Spectrometry ==
+== Comparison of EDX, SIMS and XPS ==
-[[image:SIMScascade.gif|200x200px|right|thumb|Atoms that used to make up the surface are sputtered off by the high energy ions; some are emitted as secondary ions. ]]
+{| border="2" cellspacing="0" cellpadding="2" align="left"
+!width="100" style="background:silver; color:black" |
-When a solid sample is sputtered by primary ions of few keV energy, a fraction of the particles emitted from the target is ionized. Secondary Ion Mass Spectrometry consists of analyzing these secondary ions with a mass spectrometer. Secondary ion emission by a solid surface under ion bombardment supplies information about the elemental, isotopic and molecular composition of its uppermost atomic layers.
+!width="250" style="background:silver; color:black" | SEM with [[Specific Process Knowledge/Characterization/EDX|EDX]]
+!width="250" style="background:silver; color:black" | [[Specific Process Knowledge/Characterization/SIMS: Secondary Ion Mass Spectrometry#Atomika_SIMS|Atomika SIMS]]
-{| border="1" cellspacing="0" cellpadding="4" align="center"
+!width="250" style="background:silver; color:black" | [[Specific Process Knowledge/Characterization/XPS|XPS]] (or ESCA)
-!
+|- valign="top"
-!width="50" | Energy Dispersive X-ray Analysis
+! style="background:WhiteSmoke; color:black" width="60" | Full name
-!width="250" |Secondary Ion Mass Spectroscopy
+! style="background:WhiteSmoke; color:black" | Energy Dispersive X-ray Analysis
+! style="background:WhiteSmoke; color:black" | Secondary Ion Mass Spectroscopy
+! style="background:WhiteSmoke; color:black" | X-ray Photoelectron Spectroscopy (or Electron Spectroscopy for Chemical Analysis)
 |-
-| Technique
+! style="background:lightgrey; color:black" | Technique
-| Non destructive excitation of X-rays in the sample. The elemental analysis is possible because the energy of these photons is characteristic of the element they emitted from.
+| style="background:lightgrey; color:black" | The primary beam of high energy electrons used in the SEM for imaging impinges on the sample atoms and leaves them in an excited state. X-rays with a characteristic energy are generated in the relaxation process. The combination of the fine control of the primary beam offered by the SEM and the detection of the X-rays makes it possible to make point-like elemental analysis.
-| Destructive method that sputters off surface atoms with heavy ions.
+| style="background:lightgrey; color:black" | A beam of high energy ions (cesium or oxygen) is used for sputtering off surface atoms of the sample. The material coming off the sample in this process is analysed with a mass spectrometer.
+| style="background:lightgrey; color:black" | In a process in which a monochromatic beam of X-rays irradiates the sample surface, electrons bound inside the sample are knocked free to become photoelectrons. Escaping the sample with characteristic energy, these electrons not only carry elemental information but also chemical information. Analysing them respect to energy and numbers and adding an ion gun for depth profiles provide a powerful analysis tool.
 |-
-| What elements are detected
+! style="background:WhiteSmoke; color:black" | What elements are detected
-| Any element heavier than boron/carbon
+| style="background:WhiteSmoke; color:black" | Every element heavier than boron/carbon
-| Any element
+| style="background:WhiteSmoke; color:black" | In principle every element, however, the sensitivity
+| style="background:WhiteSmoke; color:black" | Every element except hydrogen and helium.
 |-
-| Chemical information
+! style="background:lightgrey; color:black" | Chemical information
-| None: Only transistions involving inner shell electrons are detected
+|style="background:lightgrey; color:black"| None
-| None
+|style="background:lightgrey; color:black"| None
+|style="background:lightgrey; color:black"| Chemical state information
 |-
-| Sample limitations
+! style="background:WhiteSmoke; color:black" | Sample requirements
-| Vacuum compatible
+| style="background:WhiteSmoke; color:black" | Vacuum compatible
-| Vacuum compatible
+| style="background:WhiteSmoke; color:black" align="left"|
+* UHV vacuum compatible
+* The sample needs to be cut into small (app. 5*5 mm) pieces.
+| style="background:WhiteSmoke; color:black" align="left"|
+* UHV vacuum compatible
+* Sample size max 50x50 mm, thickness max 20 mm.
 |-
-| Spatial resolution
+! style="background:lightgrey; color:black" | Spatial resolution
-| Very precise point-like analysis is possible with SEM electron beam.
+|style="background:lightgrey; color:black"| Very precise point-like analysis is possible with SEM electron beam.
-| Limited to what is visible in a camera
+|style="background:lightgrey; color:black"| A square with dimensions of a few hundred microns is selected for analyis with a camera
+|style="background:lightgrey; color:black"| Using a magnified view from a camera, a point that covers an area down to an ellipse of 40 microns may be irradiated with photons (the default size is 400 microns)
 |-
-| Depth resolution
+! style="background:WhiteSmoke; color:black" | Depth resolution
-| The size interaction volume depends on the SEM high voltage and sample density:
+| style="background:WhiteSmoke; color:black" | The size of the interaction volume depends on the high voltage in the SEM and the sample density: The higher the SEM high voltage the bigger and deeper the interaction volume. The more dense the material is the smaller is the interaction volume. See section 'Spatial resolution using EDX' below.
-  * The higher the SEM high voltage the bigger and deeper the interaction volume
+| style="background:WhiteSmoke; color:black" | The sputtering of the surface makes it possible to perform detailed depth profiling with extremely good sensitivity and depth resolution.
-  * The more dense the material is the smaller is the interaction volume
+| style="background:WhiteSmoke; color:black" | Very surface sensitive technique. Only photoelectrons from the top layer (a few nanometers deep) escape unscattered. By using the ion beam etch, the composition of deeper lying layers can be probed.
-| Depth profiling is
 |-
-| Detection limit
+! style="background:lightgrey; color:black" | Detection limit
-| Approximately 1 % atomic
+|style="background:lightgrey; color:black"| Approximately 1 % atomic weight
-| Down to 1 ppb for many elements
+|style="background:lightgrey; color:black"| Down to 1 ppb for certain elements
+|style="background:lightgrey; color:black"| Approximately 1 % atomic weight
+|-
+! style="background:WhiteSmoke; color:black" | Speed of measurement
+| style="background:WhiteSmoke; color:black" | Very fast and easy
+| style="background:WhiteSmoke; color:black" | Time consuming
+| style="background:WhiteSmoke; color:black" | Quite fast and easy
 |}
-SIMS is the most sensitive elemental and isotopic surface analysis technique.
-The secondary ion yields will vary greatly according to the chemical environment and the sputtering conditions (ion, energy, angle). This can add complexity to the quantitative aspect of the technique.
-(detection limit down to ppb level for many elements), high lateral resolution imaging (down to 40 nm), and a very low background that allows high dynamic range (more than 5 decades). This technique is "destructive" by its nature (sputtering of material). It can be applied to any type of material (insulators, semiconductors, metals) that can stay under vacuum.
-It allows molecular as well as elemental characterization of the first top monolayer in the static SIMS mode. It allows also the investigation of bulk composition or depth distribution of trace elements in the dynamic SIMS mode, with a depth resolution ranging from one to 20-30 nanometers.
-This is why SIMS is one of the most widespread surface analysis techniques for advanced material research.