1、 ISO 2012 Surface chemical analysis General procedures for quantitative compositional depth profiling by glow discharge optical emission spectrometry Analyse chimique des surfaces Modes opratoires gnraux pour le profilage en profondeur compositionnel quantitatif par spectromtrie dmission optique dch
2、arge luminescente INTERNATIONAL STANDARD ISO 11505 First edition 2012-12-15 Reference number ISO 11505:2012(E) ISO 11505:2012(E)ii ISO 2012 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2012 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or util
3、ized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISOs member body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax
4、+ 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ISO 11505:2012(E) ISO 2012 All rights reserved iii Contents Page Foreword iv 1 Scope . 1 2 Normative references 1 3 Principle 1 4 Apparatus . 1 4.1 Glow discharge optical emission spectrometer 1 5 Adjusting the glow d
5、ischarge spectrometer system settings . 3 5.1 General . 3 5.2 Setting the discharge parameters of a DC source . 4 5.3 Setting the discharge parameters of an RF source . 6 5.4 Minimum performance requirements 7 6 Sampling 9 7 Calibration 9 7.1 General . 9 7.2 Calibration specimens 9 7.3 Validation sp
6、ecimens 11 7.4 Determination of the sputtering rate of calibration and validation specimens .11 7.5 Emission intensity measurements of calibration specimens 12 7.6 Calculation of calibration equations 12 7.7 Validation of the calibration .12 7.8 Verification and drift correction .13 8 Analysis of te
7、st specimens .14 8.1 Adjusting discharge parameters .14 8.2 Setting of measuring time and data acquisition rate 14 8.3 Quantifying depth profiles of test specimens 14 9 Expression of results .15 9.1 Expression of quantitative depth profile .15 9.2 Determination of total coating mass per unit area .1
8、5 9.3 Determination of average mass fractions .16 10 Precision 16 11 Test report 16 Annex A (normative) Calculation of calibration constants and quantitative evaluation of depth profiles 17 Annex B (informative) Suggested spectral lines for determination of given elements 31 Bibliography .33 ISO 115
9、05:2012(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject fo
10、r which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on
11、all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees ar
12、e circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held r
13、esponsible for identifying any or all such patent rights. ISO 11505 was prepared by Technical Committee ISO/TC 201, Surface chemical analysis, Subcommittee SC 8, Glow discharge spectroscopy.iv ISO 2012 All rights reserved INTERNATIONAL ST ANDARD ISO 11505:2012(E) Surface chemical analysis General pr
14、ocedures for quantitative compositional depth profiling by glow discharge optical emission spectrometry 1 Scope This International Standard describes a glow discharge optical emission spectrometric (GD-OES) method for the determination of the thickness, mass per unit area and chemical composition of
15、 surface layer films. It is limited to a descript ion of general procedures of quant if icat ion of GD-OES and is not applicable direc t ly for the quantification of individual materials having various thicknesses and elements to be determined. NOTE Any individual standard for a test material will h
16、ave to specify a scope of a thickness of the surface layer as well as analyte elements, and include results of interlaboratory tests for validation of the methods. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable f
17、or its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 14707, Surface chemical analysis Glow discharge optical emission spectrometry (GD-OES) Introduction to use ISO 14284
18、, Steel and iron Sampling and preparation of samples for the determination of chemical composition 3 Principle The analytical method described here involves the following processes: a) cathodic sputtering of the surface layer in a direct current or radio frequency glow discharge device; b) excitatio
19、n of the analyte atoms and ions in the plasma formed in the glow discharge device; c) spectrometric measurement of the intensities of characteristic spectral emission lines of the analyte atoms and ions as a function of sputtering time (qualitative depth profile); d) conversion of the qualitative de
20、pth profile in units of intensity versus time to mass fraction versus depth by means of calibration functions (quantification). Calibration of the system is achieved by measurements on calibration specimens of known chemical composition and measured sputtering rate. 4 Apparatus 4.1 Glow discharge op
21、tical emission spectrometer 4.1.1 General The required instrumentation includes an optical emission spectrometer system consisting of a Grimm type 10or similar glow discharge source (direct current or radio frequency powered) and a simultaneous optical spectrometer as described in ISO 14707, capable
22、 of providing suitable spectral ISO 2012 All rights reserved 1 ISO 11505:2012(E) lines for the analyte elements. Sequential optical spectrometers (monochromators) are not suitable, since several analytical wavelengths must be measured simultaneously at high data acquisition speed. The inner diameter
23、 of the hollow anode of the glow discharge source should be in the range 1 mm to 8 mm. A cooling device for thin specimens, such as a metal block with circulating cooling liquid, is also recommended, but not strictly necessary for implementation of the method. Since the principle of determination is
24、 based on continuous sputtering of the surface layer, the spectrometer shall be equipped with a digital readout system for time-resolved measurement of the emission intensities. A system capable of a data acquisition speed of at least 500 measurements/second per spectral channel is recommended, but,
25、 for a large number of applications, speeds of 50 measurements/second per spectral channel are acceptable. 4.1.2 Selection of spectral lines For each analyte to be determined, there exist a number of spectral lines which can be used. Suitable lines shall be selected on the basis of several factors,
26、including the spectral range of the spectrometer used, the analyte mass fraction range, the sensitivity of the spectral lines and any spectral interference from other elements present in the test specimens. For applications where several of the analytes of interest are major elements in the specimen
27、s, special attention shall be paid to the occurrence of self- absorption of certain highly sensitive spectral lines (so-called resonance lines). Self-absorption causes nonlinear calibration curves at high analyte mass fraction levels, and strongly self-absorbed lines should therefore be avoided for
28、the determination of major elements. Suggestions concerning suitable spectral lines are given in Annex B. Spectral lines other than those listed may be used, as long as they have favourable characteristics. 4.1.3 Selection of glow discharge source type 4.1.3.1 Anode size Most GD-OES instruments on t
29、he market are delivered with options to use various anode diameters, with 2 mm, 4 mm and 8 mm being the most common. Some older instruments have one anode only, usually 8 mm, while the most commonly used anode in modern instruments is 4 mm. A larger anode requires larger specimens and higher power d
30、uring analysis; therefore the specimen is heated to a greater extent. On the other hand, a larger anode gives rise to a plasma of larger volume that emits more light, resulting in lower detection limits (i.e. higher analytical sensitivity). Furthermore, a larger anode helps to mask inhomogeneity wit
31、hin a surface layer. This may or may not be an advantage, depending on the application. In a large number of applications, the 4 mm anode is a good compromise. However, in surface analysis applications it is rather common to encounter problems of overheating of the specimens due to, e.g. surface lay
32、ers of poor heat conductivity and/or very thin specimens. In such cases, the smaller 2 mm anode is preferable, even if there is some loss of analytical sensitivity. 4.1.3.2 Type of power supply The glow discharge source can be either a type powered by a direct current (DC) power supply or a radio fr
33、equency (RF) type. The most important difference is that the RF type can sputter both conductive and non-conductive specimens; hence this is the only type that can be used for, e.g. polymer coatings and insulating oxide layers. On the other hand, it is technically simpler to measure and control the
34、electrical source parameters (voltage, current, power) of a DC type. Several commercially available GD-OES systems can be delivered with the option to switch between DC and RF operation, but RF-only systems also exist. In short, there are a very large number of applications where DC or RF sources ca
35、n be used and several where only an RF source can be used.2 ISO 2012 All rights reserved ISO 11505:2012(E) 4.1.3.3 Mode of operation Both DC and RF sources can be operated in several different modes with respect to the control of the electrical parameters (current, voltage, power) and the pressure.
36、There are several reasons for this: “historical” reasons (older instruments have simpler but functional power supplies, while the technology has evolved so that newer models have more precise and easier-to-operate source control); different manufacturers have chosen different solutions for source co
37、ntrol; there are some application-related issues where a particular mode of operation is to be preferred. This International Standard gives instructions for optimizing the source parameters based on several available modes of operation. The most important reason for this is to make these instruction
38、s comprehensive so as to include several types of instrument. In most applications, there is no major difference between these modes in terms of analytical performance, but there are other differences in terms of practicality and ease of operation. For instance, a system equipped with active pressur
39、e regulation will automatically be adjusted to the same electrical source parameters every time a particular analytical method is used. Without this technology, some manual adjustment of the pressure to achieve the desired electrical source parameters is normally required. NOTE It should be noted in
40、 this context that what is known as the emission yield 1112forms the basis for calibration and quantification as described in this International Standard. The emission yield has been found to vary with the current, the voltage and, to a lesser extent, the pressure 17 . It is impossible in practice t
41、o maintain all three parameters constant for all test specimens, due to variations in the electrical characteristics of different materials. In several instrument types, the electrical source parameters (the plasma impedance) can therefore be maintained constant by means of automatic systems that va
42、ry the pressure during analysis. Alternatively, there exist methods to correct for impedance variations by means of empirically derived functions 17 , and this type of correction is implemented in the software of commercially available GD-OES systems. 5 Adjusting the glow discharge spectrometer syst
43、em settings 5.1 General Follow the manufacturers instructions or locally documented procedures for preparing the instrument for use. RF s o ur c e s d i ff e r fr o m D C s o u r c e s i n th e r e s p e ct th a t f o r s e v e r al i nstrum e n t m o d e l s , o nl y th e a p p l i e d (forward) RF
44、 power can be measured, not the actual power developed in the glow discharge plasma. The applied RF po wer is normally in the range 1 0 1 00 W , but it m ust be noted that the RF power losses in connectors, cables, etc. vary considerably between different instrument models. Typical power losses are
45、in the range 1050 % of the applied power. Furthermore, the possibilities to measure the additional electrical parameters voltage and current in the plasma are more or less restricted due to technical difficulties with RF systems, and several existing instrument models can only measure the applied RF
46、 power. There is no difference between DC and RF concerning the possibilities to measure the pressure. However, there are large pressures differentials in a Grimm type source, and pressure readings obtained depend on the location of the pressure gauge. Some instrument models have a pressure gauge at
47、tached to measure the actual pressure in the plasma, while others have a pressure gauge located on a “low pressure” side of the source closer to the pump. Therefore, the pressure readings can, for several instruments, just be used to adjust the source parameters of that particular instrument, not as
48、 a measure of the actual operating pressure in the plasma. For the optical system, the most important preparation step is to check that the entrance slit to the spectrometer is correctly adjusted, following the procedure given by the instrument manufacturer. This ensures that the emission intensitie
49、s are measured on the peaks of the spectral lines for optimum signal-to-background ratio. For further information, see ISO 14707. ISO 2012 All rights reserved 3 ISO 11505:2012(E) The most important step in developing a method for a particular application is to optimize the parameters of the glow discharge source. The source parameters shall be chosen to achieve three aims: a) adequate sputtering of the test specimen, to reduce the analysis time without overheating the specimen; b) good crater shape, for good depth resolution;
