MAC
ResourcesGlossary of Terms
Accelerating Voltage
The amount of voltage being sent to the electron gun from the power supply in an electron microscope.
Allotrope
Different forms of the same chemical element. E.g. Carbon: Diamond, Amorphous, Graphite and nanotubes.
Amorphous
Without real of apparent crystalline form: "an amorphous mineral"
Angstrom
A metric unit of length equal to one ten billionth of a meter (or 0.0001 micron, (1 nanometer = 1000 angstroms)): used to specify wavelengths of electromagnetic radiation.
Auger
Type of standard used in Auger spectroscopy, standards are embedded into a conductive matrix and not carbon coated, not all elements are able to be used as they still present charging. Standards are embedded into a stainless steel block.
Block
Term used for the Brass/Aluminium/Steel or carbon mount the standards are mounted into.
BSD/ Backscattered Electron Detector
Backscattered electrons (BSE) consist of high-energy electrons originating in the electron beam, that are reflected or back-scattered out of the specimen interaction volume by elastic scattering interactions with specimen atoms. Since heavy elements (high atomic number) backscatter electrons more strongly than light elements (low atomic number), and thus appear brighter in the image, BSE are used to detect contrast between areas with different chemical compositions
BSD Reference Standard
The BSD reference standards are used for checking the contrast efficiency of Backscattered Detectors. Each of the reference specimens consists of two high purity elements that have an atomic number difference of 1.
Carbon Coat
A carbon coating applied to the surface of samples to reduce any charge build up that could be detrimental to analysis. It also prevents charging
Charging
A fundamental property of the elementary particles of which matter is made that gives rise to attractive and repulsive forces. There are two kinds of charge: colour charge and electric charge. This is an effect which is caused by a lack of coating. Charging causes a 'glow' effect and blackening of the image in the SEM. Charging can also affect analysis results.
Composition
The act of combining parts or elements to form a whole.
Duplex Brass
The Duplex Brass standard allows for checking the resolution and performance of the Backscattered Electron Detector. The resolution of a detector is usually quoted as 0.1 (Z) where the atomic number (Z)=30. This is obtained in our standard by the mean atomic number between phases of α/β Brass, being 0.1Z
EDS / EDX
Energy Dispersive Spectrometry/ x-ray, Method of analysis.
Electron
An electron is a negatively charged subatomic particle. It can be either free (not attached to any atom), or bound to the nucleus of an atom. Electrons in atoms exist in spherical shells of various radii, representing energy levels. The larger the spherical shell, the higher the energy contained in the electron.
Electron Microprobe
Technique for the analysis of a very small amount of material by bombarding it with a narrow beam of electrons and examining the resulting X-ray emission spectrum
Form of analysis using crystal spectrometers.
Form of analysis using crystal spectrometers.
Eutectic
Mixture of two or more components in such proportion that their combined melting point is the lowest attainable in some cases as low as 60°C (140°F). Eutectic alloys are fusible: upon cooling they convert from liquids to intimately mixed solids.
Faraday Cup
A Faraday Cup is used for measuring the beam current at the specimen plane. The beam of electrons is focused inside the hole by increasing magnification so that when the hole fills the screen all the electrons are trapped and a true measure of current is achieved. The hole size of the Faraday Cup is 150μm
Filament
Source of electrons in the electron gun in electron microscopes. Heated Filament–The filament consists of a piece of wire, commonly made of a refractory material such as tungsten, which is heated by an electric current
Homogenous
When a sample is consistent across its surface and does not contain phases or inclusions of other materials or compositions of the same material. This is ideal for x-ray microanalysis.
Igneous
Rock type, being produced from the solidification and cooling of magma/lava. There are more than 700 different igneous rocks.
Inclusion
An area in some materials (minerals) that is a different composition to the main sample.
Interaction Area
In analysis, the area from which the x-rays for the spectrum are gathered.
ISO
International Organization for Standardization.
Lapping/Polishing
A process in which the standards are made flat and polished to 0.25 um.
LN2
Liquid nitrogen, used to cool older EDX detectors, very cold liquid at -196 °C.
Micrometer: um
A micrometre (or micrometer) is by definition 1×10−6 of a metre (SI Standard prefix "micro" = 10−6); that is, one-millionth of a metre (or one-thousandth of a millimetre, 0.001 mm, or about 0.000039 inches; often referred to as micron. 1 millimetre = 1000 microns). Its unit symbol in the International System of Units (SI) is µm. The latter may be rendered as um if Greek fonts are not available or not admissible. "Micron" comes from Ancient Greek: μικρόν mikrón, which means "small".
Millibars
Millibar is a metric unit of pressure mainly used in European countries and is derived directly from the Bar pressure unit which equals 1,000 mbar. Pressure at sea level is 1013.25 Millibars.
Mineral
A mineral is a naturally occurring substance that is solid and stable at room temperature, representable by a chemical formula, usually abiogenic, and has an ordered atomic structure. Minerals can be described by a number of variable physical properties, which relate to its chemical structure and composition. Minerals are classified by key chemical constituents; the two dominant systems are the Dana classification and the Strunz classification.
Nanometer: nm
A nanometer (symbol nm) is a unit of length in the metric system, equal to one billionth of a metre (1 millimetre = 1,000,000 nanometres). The nanometer is often used to express dimensions on the atomic scales: the diameter of a helium atom, for example, is about 0.1 nm, and that of a ribosome is about 20 nm. The nanometer is commonly used to specify the wavelength of electromagnetic radiation near the visible part of the spectrum: visible light, in particular, ranges from 400 to 1000 nm. In these uses, the nanometer appears to be supplanting the other common unit for atomic scale dimensions, the angstrom, which is equal to; 0.1 nanometer. This unit is often associated with the field of nanotechnology.
Particle Feature
13mm Cambridge pin stub containing Cobalt, Carbon, Gold and Rhodium. Used with particle analysis software and backscattered electron detectors.
Phases
Different composition of the same compound within the same material, with BSD you can see different greyscale levels.
Probe Current
Probe current means an electron beam focused on a specimen. Working with the specimen, probe current emits electrons containing information on the specimen such as secondary electrons and backscattered electrons. The size of probe current determines the number of secondary electrons and backscattered electrons emitted. Probe current is determined by the size of the probe, which is directly related with the number and size of apertures and the control current of the condenser lens. In case of SEM that acquires images using secondary electrons, if the size of probe current is large, the brightness of images is high but their resolution is low. On the contrary, if the size of probe current is small, the resolution of images is high but their brightness is low. A faraday cup is used to measure this.
QCT
Quality Control Test blocks, MAC manufacture these blocks for calibration of SEM systems.
Silicon Test Specimen
The Silicon Test Specimen is made of single crystal silicon of overall dimension 5mm x 5mm. It is marked with clearly visible squares of periodicity 10μm. The dividing lines are about 1.9μm in width and are formed by electron beam lithography. A broader marking line is written every 500μm, which is a very useful additional feature for light microscopy.
Refurbishment
The Refurbishment service which is offered at MAC, allows you to have your set of standards restored to a "like new" condition at a fraction of the cost of a replacement. The standard block is re-diamond polished, carbon coated and the certificates of analysis checked.
Resolution Standard
Resolution standards are used for testing the resolved gaps and the number of grey levels in an image. This is to ensure that the resolution has not been distorted by using contrast to maximise the visibility of edges. These are available as either gold crystals or tin spheres on a carbon substrate. Gold on carbon is available in different particle size ranges, enabling it to cover the full resolution range.
Spectrum
A visual representation of the x-ray counts in x-ray microanalysis.
Standard Hole
Standard hole, allows for the insertion of a block of standards 25mm or 32mm diameter x 5mm thick brass block which allows calibration and test standards to be kept together
Thin Film
Type of standard used in a TEM. The material is suspended on a holey carbon film on a copper grid.
Thin Foil
Type of standard used in STEM. They are 0.1mm thick and 3mm diameter to fit into a TEM grid holder.
Torr
The torr (symbol: Torr) is a non-SI unit of pressure with the ratio of 760 to 1 standard atmosphere, chosen to be roughly equal to the fluid pressure exerted by a millimeter of mercury, i.e., a pressure of 1 torr is approximately equal to one millimeter of mercury. 760 Torr is the standard pressure at sea level.
Transporter
Custom made Perspex holder especially designed to keep your standard secure in transit.
WDX
Wavelength dispersive x-ray, method of analysis.
Working Distance
The distance between the surface of the sample and the bottom of the lens plate in the SEM.
