Contact Details
- Dr Yongchang Fan
- Tel: (01382) 386 516
- Fax: (01382) 388 313
- y.fan@dundee.ac.uk
Analytical Services for Industry
Do you want access to materials and surface analysis facilities like:
- Detection of all elements in the uppermost surface layer to parts per million level?
- To analyse corrosion and surface contamination?
- Analysis of small areas, of the order of 10 nm?
- Bulk analysis of your materials?
- A composition map of your material?
- To analyse the composition of your materials below the surface by depth profiling?
- Microstructure of thin films?
- Composition of thin films?
- Facilities to examine defective circuit elements at high magnification in IC's in the powered up state?
The Analytical Electron Microscopy and Surface Analysis Unit in the Department of Electronic Engineering and Physics at Dundee University can help you to obtain the above and similar information about your materials or products:
- Materials Analysis for Industrial Problems
- Dundee University's Analytical Service
- What is Surface Analysis?
- What is Bulk Analysis?
- What is Thin Film Analysis?
- Who are these services for?
- Equipment at Dundee
- What type of results does this equipment produce?
- Details of the service
Materials Analysis for Industrial Problems
The analytical techniques available in the unit at Dundee are surface analytical techniques such as secondary ion mass spectrometry (SIMS), Auger electron spectrometry (AES) and x-ray photoelectron spectroscopy (XPS) and bulk analytical techniques such as energy dispersive x-ray microanalysis (EDX). Compositional analyses from thin films can be obtained from EDX and electron energy loss spectroscopy (EELS).
In addition to these analytical techniques a variety of electron imaging techniques are available that can be used to display the distribution of atomic species in a material, the surface topography and surface microstructure of a material or the internal defect structure of the material. These high resolution imaging techniques also include atomic force microscopy and scanning tunneling microscopy.
A wide range of problems can be tackled with this analytical equipment. This can be gauged by the wide variety of materials that can be analysed. These materials include metals, insulators, powders, fibres, ceramics, foils, inorganic and bio-organic chemicals.
Most of the analytical equipment at Dundee is highly specialised. Our expertise in using this equipment and analysing results has been built up over many years. Despite the capital cost of the equipment, customers can have their problems solved for a modest fee in many cases saving them the thousands of pounds that may be lost unless the problem is solved.
Dundee University's Analytical Service
The Electron Microscopy and Surface Physics group in the Department Applied Physics and Electronic & Mechanical Engineering at Dundee University utilises a number of analytical electron optical and surface physics techniques in its basic research. The research group is unique in Scotland in the variety of analytical techniques that are available within a single laboratory. The research group has a wide range of expertise in these techniques. These techniques have many applications in solving industrial problems.
These analytical techniques include energy dispersive x-ray microanalysis (EDX), electron energy loss spectroscopy (EELS), Auger electron spectroscopy (AES), x-ray photoelectron spectroscopy (XPS).
What is Surface Analysis?
When a surface is bombarded with atomic and subatomic particles, ions, electrons and atoms are emitted. Bombardment with x-ray photons leads to the emission of electrons, these are called photoelectrons. These particles typically are emitted from a l0 nm surface layer.
These emitted particles form the raw data for surface analysis and through a variety of spectrometric techniques can provide a vast range of detail on the composition and chemical state of surface layers. The analysis of ions emitted from a surface is called secondary ion mass spectrometry (SIMS) and enables analysis of the elements in the surface layers. The analysis of electrons emitted on bombardment of a surface with an electron beam is called Auger electron spectroscopy (AES). Auger electrons can be used to obtain information about the chemical state of a surface. The chemical state of a surface can also be monitored by analysing the photoelectrons emitted from a surface on bombardment with x-rays. This technique is called x-ray photoelectron spectroscopy (XPS).
The power of these techniques to detect surface conditions will enable manufacturers to monitor these conditions and experiment at controlling surface properties and behaviour. This ability could be crucial to the success of a product or process.
The Auger electron spectroscopy system is situated in a unique high-resolution scanning electron microscope. This arrangement allows high resolution, high magnification images to be obtained from analysed areas of a sample surface.
These analytical techniques can help a manufacturer in developing new products, for example, lubricants, adhesives or insulators. These techniques can also help a manufacturer to discover why corrosion is occurring in a fermentation plant, to determine the source of contamination on the phosphor of a television screen, to find out why a catalyst is not effective or to develop protective coatings or paints for use in hostile chemical environments.
What is Bulk Analysis?
When a material is bombarded by electrons, x-rays, characteristic of the material bombarded, are produced. These x-rays are emitted from within a layer of depth l μm from the surface. This layer is deep enough to be representative of the bulk composition of the sample. Analysis of these x-rays enables atomic concentrations to be determined to better than 1 % accuracy. This analytical technique has a wide variety of applications, for example, in identifying segregated impurities in materials, segregated second phase in alloys or any deviation from the required chemical composition of a fabricated material. The strength of this technique is that the area analysed can be related to the secondary electron image obtained in the scanning electron microscope. Composition mapping is also possible using the emitted characteristic x-rays.
What is Thin Film Analysis?
Many materials, especially in the microelectronics industry are fabricated as thin films and require special techniques for analysis. Transmission electron microscopy and electron diffraction with x-ray microanalysis and electron energy loss spectroscopy can give information about the microstructure and composition of thin films. Special techniques have been developed to prepare thin films for these analyses.
When an electron beam is transmitted through a thin film, a series of electromagnetic lenses can be used to deflect and focus electrons to obtain a high-resolution electron image. Some of these electrons in passing through the film lose energy in ionising atoms in the film resulting in the emission of characteristic x-rays. These x-rays can be used to determine thin film composition. The electrons which have lost energy can also be analysed to obtain thin film composition.
The ultimate resolution for imaging in the transmission electron microscope is of the order of the interatomic spacing of the materials. With this resolution crystalline defects in thin films can be observed as well as defects at the substrate-thin film boundary.
Who are these services for?
The Dundee group have used surface, bulk and thin film techniques to solve problems involving corrosion, paper manufacture, ceramics, microelectronics, phosphors, printing, plastics and polymers.
The industrial work we are usually involved in arises when a problem occurs with a product or process. For example, a particular process may result in a high proportion of rejects for a given product. Analytical techniques can be used to study the reject material and pinpoint the cause of the problem.
Equipment at Dundee
Four electron optical systems are available for these investigations. The measurements obtained from each system are complementary and help to build up a complete analytical description.
Vacuum Generators HB100 Scanning Electron Microscope
This electron microscope is used for surface studies. It is fitted with a CLAM 100 electron spectrometer. The instrument is operated at ultra-high-vacuum and has a high intensity field emission electron source. High-resolution secondary images can be obtained in this instrument. The area scanned by the electron beam gives rise to electrons emitted from within 5 nm the surface. These are called Auger electrons and they are emitted with kinetic energies that depend on the particular atomic species on the surface. The composition of the first few atomic layers can therefore be determined by this technique. The area analysed can be as small as l0 nm.
Another surface analytical technique available on this instrument is x-ray photoelectron spectroscopy. In contrast to Auger electron spectroscopy, this is a large area technique and analyses are obtained from areas of about 1 cm x 1 cm. The kinetic energy of photoelectrons emitted when soft x-rays are incident over areas of this size is also characteristic of the surface atomic species.
Secondary Ion Mass Spectrometry (SIMS) System
This instrument can be operated by bombarding the sample with a fast atom beam or by a beam of energetic ions. Acquisition of the secondary ion spectra emitted enable atomic species in some cases at the ten parts per million levels to be detected. This equipment has potential applications in many areas including the semiconductor industry in detecting low levels of impurities and dopants.
JEOL T300 and JSM6310 Scanning Electron Microscopes
In these electron microscopes as well as the ability to form high-resolution secondary electron images a number of attachments are available that can be used to examine materials.
Bulk composition analysis can be made by energy dispersive x-ray microanalysis (EDX). The characteristic x-rays emitted when the imaging beam is incident on the specimen can be analysed to give the weight percent of each atomic species in the specimen.
The distribution of different atomic species in the specimen can also be obtained by mapping the x-ray signal from the specimen. Complementary information can also be obtained in the backscattered electronic image.
Both instruments are unusual in that wide variety of sizes of specimen can be examined, up to maximum size of 13cm. It is therefore possible to examine a complete silicon wafer.
A variety of images based on the electrical state of a material can be examined in these instruments for example; thin film devices such as integrated circuits can be examined in the active state. Voltage contrast images can be obtained for example, from areas of an active device at different potentials. Images produced by electron beam induced conductivity in thin film devices can also be obtained and give information about local changes in electric field, carrier mobilities and minority carrier lifetimes. Two types of problem can be tackled with this mode. In the first, the variation in charge collection current is used to probe structural features of the specimen. In the second, the behaviour of semiconductor devices such as diodes and field effect transistors can be examined under various working conditions.
transmition electron micrscope
JEOL 200CX and JEOL 100C Scanning Transmission Electron Microscopes (STEM)
These instruments are used to study materials in thin film form and are usually operated in the transmission mode. In this mode specimens generally have to be less than about 200 nm in thickness and a resolution of the order of 0.2 nm can be attained and observation of atomic lattice planes is possible. In conjunction with techniques available for obtaining thin sections of a bulk material such as electropolishing or ion beam thinning, transmission electron microscopy can be used to study crystal defects in for example, semiconductors or metals.
Secondary electron images, backscatter electron images and x-ray mapped images can also be obtained in this instrument and the topographic images and compositional images obtained can be correlated with the high resolution transmission image to give added information about the area studied.
In the STEM the composition of thin sections of materials can be obtained by energy dispersive x-ray microanalysis (EDX) and by electron energy loss spectroscopy (EELS). The EELS technique is particularly sensitive in detecting low atomic number elements, the region where detection by EDX is less efficient.
Crystal structure details can also be obtained in the STEM by electron diffraction. The crystal structure of areas as small as 50 nm can be obtained complementing information about composition obtained using EDX or EELS.
Digital Instruments Atomic Force Microscope, and the Molecular Imaging Scanning Tunneling Microscope
These are very powerful instruments for obtaining high resolution images and other information about specimens, and offer capabilities that are especially applicable to many industrial problems.
What type of results does this equipment produce?
Experimental results from our equipment usually come in two forms. As an image in the form of a chemical map showing the composition in bulk, in thin film or from the surface layers. Alternatively results can be presented as a data record of the spectrum obtained by one of the spectroscopy techniques. A verbal report or a full analytical report can be prepared.
Details of the service
Many companies are unaware of the time and money they can save by using analytical techniques.
If you have a problem we will be happy to discuss it with you by telephone. If, as is likely, we can help it is probably best to have a meeting to discuss the problem and assess which analytical techniques will contribute to its solution. We will advise on the types of samples required and the amount of instrument time that is likely to be required. Up to this point the customer has no cost obligations.
Once an agreement has been reached on the type of investigation to be made, samples can be brought for analysis.
Contact:
Dr Yongchan Fan
JEOL Analytical Electron Microscopy and Surface Analysis Centre
Department of Electronic Engineering, Physics & Renewable Energy
University of Dundee
Dundee DD1 4HN
Tel: 01382 386 516
Fax: 01382 388 313
E-mail: y.fan@dundee.ac.uk
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