JEOL JXA-8200 Electron Microprobe

An electron microprobe is an electron microscope designed for the non-destructive x-ray microanalysis and imaging of solid materials. It is capable of high spatial resolution and relatively high analytical sensitivity. The EPSC Microanalysis Facility has a JEOL JXA-8200 that can acquire digital secondary-electron and backscattered-electron images, digital x-ray maps, and digital cathodoluminescence images. It is equipped with 5 wavelength-dispersive spectrometers and a silicon-drift energy-dispersive spectrometer. Most of the periodic table can in principle be analyzed (Boron through Uranium), subject to several important considerations. The analytical sensitivity ranges from a low of a few parts per million for optimum cases, to a typical detection limit of several hundred ppm, but can be as high as several weight percent for problem elements. The volume sampled is typically a few cubic microns, corresponding to a weight of a few picograms. Samples should be prepared as flat, polished solid mounts up to 1.25 inch in diameter, and must be clean and stable in a 10^-5 torr vacuum environment. After preparation, samples are coated with a 22 nm layer of carbon using a high-vacuum carbon evaporator. The quality of analyses performed depends on the quality of sample preparation, character of the sample material, and availability of appropriate primary and secondary calibration standards for the desired elements. A precision approaching 0.X% relative and accuracy as good as 1-2% can be obtained with this instrument.

This laboratory is involved in the development and application of quantitative electron microprobe analysis to a wide array of problems and maintaines an active program in basic research in the development and refinement of microprobe analysis techniques. In particular, high precision and accuracy microanalysis of semiconductor materials is recieving a special emphasis.

Hardware Summary

The JEOL JXA-8200 electron microprobe is a fully-automated, customized instrument. This instrument has digital imaging capability and can acquire digital secondary-electron, backscattered-electron (in compositional and topographic modes), and cathodoluminescence images. Digital x-ray intensity maps can be obtained using either beam scanning or stage mapping modes. X-ray focus is maintained during automated runs by means of a Carnegie autofocus module.

The microprobe has 5 wavelength-dispersive spectrometers, of which one is a four-crystal spectrometer with light-element layered dispersive crystals, four are two-crystal spectrometers equipped with two analyzing crystals and have extended range capability, and the remaining spectrometer is a special H-type two-crystal spectrometer designed for the measurement of trace elements via low intensity x-rays. The crystal inventory and general list of elements that they can be used for is listed below:

Here is a list of the elements that each crystal can be used to detect. Note that in practice element analytical lists are set up in advance for most routine materials, and judgement based on experience is used to select a particular x-ray line and crystal for a given application.

Analyzing Crystal	Element Range
LDE1	K-alpha lines of C, N, O, and F
LDE2	K-alpha lines of B, C, and N
LDEB	K-alpha lines of Be and B
PETJ, PETH	K-alpha lines Si - Cr L-alpha lines Kr-Eu M-alpha lines Lu - Bi and Th - U PETJ is a high reflectivity crystal PETH is on H-type spectrometer
TAP	K-alpha lines O - Si L-alpha lines Cr - Zr M-alpha lines La - Pt
LIF, LIFH	K-alpha lines of Ca - Rb L-alpha lines of Sb - U LIFH is on H-type spectrometer

This analyzing crystal inventory nominally permits detection and analysis of elements B through Pu, at concentrations typically above a few hundred ppm but in selected cases as low as a few ppm. This instrument is equipped with oil-free vacuum pumps (a dry scroll roughing pump, a turbomolecular pump, and an ion pump on the electron gun). It routinely achieves ~10^-6 torr vacuum at the sample, and typically exhibits a low carbon contamination rate. These capabilities make the instrument desirable for light-element and/or low energy x-ray analysis. This instrument has very good electronic and analytical stability, vacuum cleanliness, and capability to perform analyses with high precision and accuracy as demonstrated by a history of applications.

The microprobe has a JEOL (e2v / Gresham) silicon-drift energy-dispersive spectrometer. This spectrometer is typically used for identification of samples during routine analysis, high-speed x-ray mapping, and monitoring of sample charging by inspection of the Duane-Hunt high voltage cutoff. It can also be used to analyze elements B - U either simultaneously or in conjunction with the wavelength spectrometers.

Software Summary

Our JEOL JXA-8200 has two software operating systems. The JEOL software system runs under Solaris on a Sun Ultra 45 and allows for completely integrated control of all spectrometers, imaging, and monitoring of system hardware. This instrument also runs Probe for Windows operating system, which was developed for this instrument by John Donovan, Brian Gaynor, and Paul Carpenter.

Probe for Windows and related programs are essentially advanced front-end programs that store their data in Microsoft Access database files. All standard compositions are maintained in a standard database and read in by Probe for Windows during correction. Probe for Windows performs all spectrometer and stage automation activities and handles all operations during an automated microprobe run. The Probe for Windows system enables sophisticated quantitative analysis that is not part of available turnkey systems.

Analytical Capabilities

Our microprobe is nominally capable of analyzing a wide range of elements, most of the periodic table, from B through U, at concentrations typically above 100 parts per million. The volume excited by the electron beam is nominally about 1 cubic micron, corresponding to a sample size of a few picograms. The primary advantage of microprobe analysis is that the analysis is non-destructive, although some material must be consumed in making a polished mount, and that a very small amount of material is sampled for a measurement. It is the ideal technique for analyzing crystals that are zoned, or samples that are made up of intimately-mixed phases where one needs to spatially resolve the phases being studied.

The analytical sensitivity does depend on the matrix of other elements present, and the material properties of the compound to be analyzed.

Imaging Capabilities

Digital imaging (secondary-electron, backscattered-electron, cathodoluminescence, x-ray, and electron-channeling pattern) may be performed on the microprobe using the JEOL hardware and software. Both wavelength-dispersive and energy-dispersive digital x-ray maps as well as secondary-electron, backscattered-electron, or CL digital images can be simultaneously acquired. Two basic x-ray mapping modes are available. Beam scanning is used for x-ray maps typically obtained using the silicon-drift energy-dispersive spectrometer, which does not exhibit x-ray defocus problems, and has a relatively high x-ray throughput that rivals the WDS spectrometers. Stage scanning is used for x-ray maps using the both the silicon-drift detector and the wavelength-dispersive spectrometers, where the stage is scanned with a fixed electron beam. X-ray intensity maps can be acquired on elements down to low concentration, dependent only on the time available for measurement, and are usually run during overnight sessions. A guide-net mapping mode allows for the acquisition of mosaic-style maps and can be used to map materials that are topographically non-uniform.

Particle analysis capabilities have been added to the Probe for Windows software.

Digital images are acquired using the JEOL OS-9 computer and the automated mapping software, and can be saved in Jpeg or TIFF format. These images can be processed further using a number of image processing programs.

Precision and Accuracy

The precision of measurements on the electron microprobe is a function of x-ray counting statistics, which depend on the total number of x-ray counts collected on both the standard used for calibration, and also on the counts collected on the sample. The minimum precision attainable on the instrument is in the vicinity of 0.5% relative, as determined by replicate measurements on wafer standards involving extensive spectrometer movement. Spectrometer mechanical reproducibility is considered to be the limiting factor in precise measurements on our instrument. Therefore, at low total counts collected, counting statistics errors dominate, and at high total counts collected, instrumental reproducibility dominates. Precision also depends on the chemical homogeneity of both the standard used for calibration, and also that of the sample.

The accuracy of measurements on the electron microprobe depends on accurate knowledge of the composition of the primary calibration standard, and the "correctness" of the algorithm used to convert from x-ray intensity to concentration units (i.e. the ZAF or F(rz) procedure). A global accuracy statement cannot be made. However, the accuracy is typically better than 5%, but may be worse for elements subject to peak interferences, or where there is a large compositional difference between the standard and sample and a large correction factor is observed (i.e. x-ray absorption, for example).

Maintenance, Calibration and ISO 9000 Issues

The Microanalysis Facility JEOL JXA-8200 microprobe is continuously maintained under ongoing contract by JEOL engineers. High priority is given to WDS spectrometer alignment, spectrometer reproducability, detector counting system deadtime calibration and correction. Specific procedures are followed that exceed the specifications of the instrument manufacturer, in terms of spectrometer calibration and reporoducibility testing. Records have continuously been kept since acceptance of the instrument. From discussions with other operators of microprobes and field engineers, and through exchange of calibration data, it is clear that our instrument is maintained to a high standard not achieved at a number of other facilities.

Sample Requirements

Samples must be flat (planar on a micron scale), polished to 0.25 mm final polish, and made electrically conductive by evaporative coating with carbon (using our high-vacuum carbon evaporator).

Microprobe Use Policy

Time is available on a first-come, first serve basis. Calibration, repair, or other maintenance routines have highest priority, followed by EPSC users, followed by all other users.

Microprobe users need to be trained prior to instrument use. Please read the manuals before your checkout session (hard copy available for checkout). Please sit in with a fellow user for one session to familiarize yourself with procedures prior to checkout.

Your samples should be completely polished, coated, and mounted (if applicable and reasonable) before the beginning of your session.

If you need a checkout or you just need help from Paul Carpenter, please coordinate schedules before you sign up. Paul may not be available if working on another project or on travel.

Writeup Summary

Here is a summary of the instrument hardware, software, standards, and correction scheme used for typical analytical runs. Your run may entail the use of non-standard analytical protocols.

Analyses are performed on a JEOL JXA-8200 electron microprobe equipped with 5 wavelength-dispersive spectrometers, and a JEOL (e2v / Gresham) silicon-drift energy-dispersive spectrometer. Analyses are acquired using either the Probe for Windows or JEOL analysis software, and x-ray correction is performed using the CITZAF correction software (see references for a document reference). Typical operating conditions are 15 KV accelerating potential and 25 nA probe current, but conditions appropriate for analysis of special materials warrant other values. Standards used in the facility range from pure elements and oxides to simple or complex silicates and glasses recognized throughout the analytical community. A wide range of standards appropriate to specific analytical problems may also be used.

Download Manuals

You can download some of the manuals that you need from this web page. The other manuals are copyrighted.

JEOL JXA-8200 Manuals

Probe for Windows Manuals

The Probe for Windows manuals are in a password-protected zip archive. Paul Carpenter will give you the password to open them. The JEOL manuals are not password protected.

This is the manual you need in order to do microprobe analysis using the Probe for Windows operating system on the microprobe. It gives you a step by step procedure for setting up an analytical run. It is the first manual you should read before using the microprobe.

This manual covers advanced topics such as the use of sample setups, importing sample setups from other runs, etc.

This manual covers detailed aspects of the Probe for Windows program. In particular, the instrument parameter settings, and detailed description of the programs themselves are documented here. This is not the "Getting Started" manual that steps you through setting up a run, but rather is for more experienced microprobe users.