tailieunhanh - ENCYCLOPEDIA OF MATERIALS CHARACTERIZATIONC phần 8

dựa trên mối tương quan quan sát thấy trong các cụm cơ kim nhưng điều này đã không được nghiên cứu đầy đủ. Hình 5 cho thấy các tiện ích của giày cao gót trong việc thiết lập sự hiện diện của cả hai cầu ngoại quan và trên đỉnh CO chemisorbed trên Pt (111) và hai bề mặt hợp kim SnPt, | are performed by dissolving the surface or thin film into solution and analyzing the solution. This kind of methodology is often selected when the average composition of a surface or film over a large area must be measured or when a thin film exceeds the thickness of the analytical depth of other analytical techniques. ICP-OES is similar to ICPMS but uses an optical detection system rather than a mass spectrometer. Atoms and ions are excited in the plasma and emit light at characteristic wavelengths in the ultraviolet or visible region of the spectrum. A grating spectrometer is used for simultaneous measurement of preselected emission lines. Measurement of all elements is possible with the exception of a few blocked by spectral interferences. The intensity of each line is proportional to the concentration of the element from which it was emitted. Elemental sensitivities in the sub-ppb 100 ppb range are possible for solutions dilutions of 1000 times yield detection limits in the ppm range. Direct sampling of solids is performed using spark arc or laser ablation yielding similar detection limits. By sampling a solid directly the risk of introducing contamination into the sample is minimized. Like ICPMS ICP-OES is quantified by comparison to standards. Quantitative analyses are performed with accuracies between and 15 using standards typically better than 5 . ICP-OES is less sensitive than ICPMS poorer detection limits but is selected in certain applications because of its quantitative accuracy and accessibility. There are thousands of ICP-OES systems in use worldwide and the cost of a new ICP-OES is half that of an ICPMS. 531 Dynamic SIMS Dynamic Secondary Ion Mass Spectrometry PAUL K. CHU Contents Inưoduction Basic Principles Common Modes of Analysis and Examples Sample Requirements Artifacts Quantification Instrumentation Conclusions Introduction Dynamic SIMS normally referred to as SIMS is one of the most sensitive analytical techniques with elemental .