A USER DESIGNED SOFTWARE SYSTEM FOR ELECTRON MICROPROBES - QUALITATIVE AND QUANTITATIVE TECHNIQUES+

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A USER DESIGNED SOFTWARE SYSTEM FOR ELECTRON MICROPROBES - QUALITATIVE AND

QUANTITATIVE TECHNIQUES+

J. Doyle, W. Chambers

To cite this version:

J. Doyle, W. Chambers. A USER DESIGNED SOFTWARE SYSTEM FOR ELECTRON MICRO-

PROBES - QUALITATIVE AND QUANTITATIVE TECHNIQUES+. Journal de Physique Collo-

ques, 1984, 45 (C2), pp.C2-227-C2-230. �10.1051/jphyscol:1984250�. �jpa-00223963�

JOURNAL DE PHYSIQUE

Colloque C2, supplément au n°2, Tome 45, février 1984 page C2-227

A USER DESIGNED SOFTWARE SYSTEM FOR ELECTRON MICROPROBES - QUALITATIVE AND QUANTITATIVE TECHNIQUES*

J.H. Doyle and W.F. Chambers*

Rockwell International, P.O. Box 464, Golden, CO 80402, U.S.A.

*Sandia National Laboratories, Albuquerque, NM 87185, U.S.A.

Résume - Des fonctions d'analyse qualitative et quantitative ont été inté- grées dans un programme de commande de microsonde de façon à offrir une grande diversité de techniques analytiques tout en laissant en même temps à l'opérateur la possibilité de commander toutes les fonctions de l'instru- ment.

Abstract - Qualitative and quantitative analysis functions have been in- tegrated in a microprobe control program in a way that provides a large variety of analytical techniques while simultaneously permitting the opera- tor to maintain control of all instrument functions.

Automated microprobe systems require several different types of programs for good qualitative and quantitative analysis. Traditionally, these programs have been un- related and individually run. By using a true systems approach, some 16 programs performing these functions have been integrated in the control program, Sandia-TASK /1,2/. They are called by and run inside Sandia-TASK in a manner that retains full availability of the microprobe control functions. The programs have been written by and for microprobe operators who deal with a large variety of geologic, elec- tronic, and metallurgical problems; they are versatile and user friendly. Most of the programs can also be called by a control program designed for scanning electron microscopes /3/. As such, they have a wide utility base.

Three levels of analysis are discussed. Qualitative techniques use both energy dis- persive (EDS) and wavelength dispersive (WDS) spectra to determine what elements are present. Semi-quantitative methods determine approximate concentration levels by WDS X-ray measurements of the ratio of the count-rate from the unknown to that from a 100% standard (K-ratio), elemental maps, and standardless EDS calculations. Full quantitative methods include atomic-number, absorption, fluorescence (ZAF) for general materials / 4 / , Bence-Albee (BA) for geologic materials /5/ and thin film on substrates (TFS) for electronic components /6/.

I - QUALITATIVE TECHNIQUES

The initial portion of a microprobe analysis normally starts with a qualitative survey to determine which elements are present in the areas of interest on the sample. Major elements above atomic number 10 are most easily surveyed with EDS.

It is convenient to use the EDS peak identification routine /7/ to give hard copy printout and label the elements in a spectrum. Two WDS methods are available for detecting trace elements (100 - 500 ppm), elements which overlap on an EDS spectrum (AE < 150eV), and elements from atomic number 5 through 10. If the analytical conditions for a specific element have been loaded into an element table, then the MEASURE command can quickly determine the presence or absence of a specific element.

Otherwise, a wavelength dispersive spectrum can be obtained with one of the crystal

spectrometers and the multi-channel analyzer. In this WDS mode, all of the EDS

spectral analysis capabilities are available (e.g. moving, smoothing, scale expansion

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1984250

C2-228 JOURNAL DE _PHYSIQUE

and contraction). Fitting and stripping techniques can be used in the analysis of samples containing overlapping lines (Fig. 1). These spectra can be plotted and/or saved on disk for future use.

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2000.

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0 . eS00 0.3626 0.3780 0.4376 0 . ~ 0 0 0

SPEC 3 (SINE)

Fig. 1 - The deconvolution of N-KA and Ti-L lines from Ti(C,N).

All of the Sandia-TASK /I/ commands are available during this qualitative analysis mode. Thus, the coordinates of areas of interest on a sample can be saved for more study, EDS spectra from standards compared, the WDS spectrometers calibrated, or the beam current set or measured.

11 - SEMI-QUANTITATIVE TECHNIQUES

The next stage of microanalysis is usually to determine approximate concentrations with semi-quantitative techniques. With this quality of data, one can decide if the analysis is adequate. If a full quantitative analysis is necessary, the microprobe operating parameters are usually determined from the semi-quantitative data.

An experienced operator can most easily make initial concentration judgements by observing the EDS spectra. A more thorough analysis can be quickly and easily obtained from an EDS spectrum through the standardless semi-quantitative ZAF analy- sis routine /8/.

The crystal spectrometers are also powerful tools for semi-quantitative analysis.

Once the electron beam current has been measured and the elements of interest have been entered into the element table /1/ and calibrated, the MEASURE command can be used to determine the K-ratio for specific points on the sample. Although this measurement does not correct for any interactions from other elements, it is very quick and valuable. Elemental mapping /I/ capabilities provide distribution infor- mation which may be self sufficient or may be used to determine where quantitative analyses are required.

111 - QUANTITATIVE TECHNIQUES

The contortions previously required to perform reasonable quantitative analyses pro-

vided the original impetus for the bulk of the work reported in this paper. Ac-

cordingly, special efforts have been made to make the quantitative analysis rou-

tines versatile yet user friendly. A single subroutine is used for initializing

the three different quantitative analysis programs / 9 / . The three quantitative

techniques can be used to analyze preselected points, perform line scans, or ana-

lyze individual user selected points. Analytical results are computed and printed

while the X-rays are being counted on the next analysis point. The results are

stored on magnetic disk and can be recalled for the production of summaries and/or

plots /lo/.

References for quantitative analysks are maintained in element tables /I/. Once an appropriate element table is in memory, any type of quantitative analysis is ini- tiated by giving the command QUANT. The system then requests the type of analysis and automatically loads the appropriate code. The first time a particular analysis is performed, the user is led through a series of questions which creates a file of the elements to be analyzed, the X-ray lines, and the standard references to be used for the analysis. As soon as the file is created, it is summarized and can be edited. It is then automatically saved on disk and a similar file describing the desired operating characteristics of the instrument is created and saved. These files are then available for future use. Up to 200 files of each type can be saved on each system device. Any time a file is called from disk, it is summarized and it can be edited before being used.

Data collection for a quantitative analysis proceeds on a statistical basis. Each spectrometer is run asynchronously. Three levels of priority are available to per- mit minimization of data loss with such mobile ions as Na. Within a given priority, the spectrometers are scheduled in a manner that minimizes their movement. As soon as the data set for one point is complete, the sample is moved to the next analysis point and the first data set is reduced while the second is collected. Detect- ability limits for the operating conditions associated with each element are calcu- lated and printed along with the quantitative results. All results are automatical- ly buffered to disk storage for later plotting and/or detailed statistical analyses.

The basic summary program is designed to produce both printed reports (Fig. 2) and plots (Fig. 3) of the data in a form that is ready to be given to the end user.

Each summary includes a full description of the operating conditions and both counting and sample statistics.

SAMPLE i/ 165014 BRAZE MATL 7/12/83 4:35 FILE // 121 SYSTEM RUN CONDITIONS

25 KEV 30 NA BEAM CURRENT WDS MAX TIME= 20 SEC. OR 1.0 % STANDARD DEVIATION WITH 1.0

MIN PEAK~BACKGROUND NECESSARY FOR MAX. TIME ZAF DEFINITIONS FILE # 1 SETUP FILE i/ 1 BEAM SIZE

1

MIN. DETECTION LIMITS

MG-K 0.006 WT % P -K 0.010 WT % FE-K 0.020 WT % CO-K 0.023 WT % NI-K 0.024 WT % CU-K 0.038 WT % AG-L 0.035 WT %

RUN /I ^{WEIGHT% ZAF82}

MG-K P -K FE-K CO-K NI-K CU-K AG-L BE-K TOTAL

M 25 0.16 0.20 0.02 0.03 0.10 6.06 93.98 0.00 100.55 48.0 26 0.12 0.23 0.02 0.03 0.07 6.53 93.20 0.00 100.20 50.0 27 0.U 0.17 0.04 0.03 0.08 5.44 93.94 0.18 100.01 52.0 28 0.19 0.21 0.03 0.04 0.U 6.00 93.04 0.36 100.00 54.0 RANGE 25- 28

MG-K P - K FE-K CO-K NI-K CU-R AG-L BE-K AVG 0.14 0.20 0.02 0.03 0.09 6.00 93.53 0.U 100.18

t 0.03 0.02 0.00 0.00 0.02 0.44 0.48 0.17 1-SIG t 0.02 0.01 0.01 0.01 0.02 0.05 0.50 0.10 COUNT

0.14 0.20 0.02 0.03 0.09 5.99 93.36 O . U N O R M W T % 0.63 0.65 0.04 0.05 0.16 9.47 87.44 1.51AIO

Fig. 2 - Abbreviated Summary of a Braze Analysis

JOURNAL DE PHYSIQUE

F i g . 3 - P l o t t e d Results of t h e Braze Analysis

7/12/83 B E / C U

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As an indication of the power of this system, one three-spectrometer microprobe equipped with this software has made over 79000 quantitative analyses in one year with an average of ten elements per point in addition to over 3000 element maps and normal qualitative survey work.

D I F F U S I O N

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I I I I

IV - SUMMARY

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With a systems approach, the operations involved in automated microprobe analysis have been made easy to learn yet powerful. Built in statistical routines verify the quality of data. Easy access to both EDS and WDS techniques has been maintained throughout any type of analysis so the microprobe operator can quickly perform a sequence of qualitative and/or quantitative microanalyses.

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References:

[l] CHAMBERS (W. F.) and DOYLE (J. H.), ICXOM 10, 1983.

[2] CHAMBERS (W. F.), Sandia National Laboratories report SAND82-1081, 1983.

[3] WODKE (N. F.) and SCHAMBER

H.), "Super ML," Tracor Northern report, 1979.

[4] DOYLE (J. H.) and CHAMBERS (W. F.), Rockwell Rocky Flats report RFP-3215, 1981.

[5] CHAMBERS (W. F.), Sandia National Laboratories report SAND78-1835, 1978.

[6] McCARTHY (3. J.) and WODKE (N. F.), "Thin Film on Substrate Program," Tracor Northern report, 1977.

[7] WODKE (N. F.), "X-ray Identification Program," Tracor Northern report, 1979.

181 McCARTHY (J. J.), "Standardless Semi-quantitative Analysis Program," Tracor Northern report, 1980.

[9] CHAMBERS (W. F.) and DOYLE (J. H.), Sandia National Laboratories report SAND78-1836, 1979.

[lo] DOYLE (J. H.), Rockwell Rocky Flats report RFP-3216, 1980.

his work was supported by the U. S. Department of Energy under Contracts

DE-AC04-76DP03533 and DE-AC04-76DP00789.