Sputtering process, and

Because SIMS can measure only ions created in the sputtering process and not neutral atoms or clusters, the detection limit of a particular element is affected by how efficiently it ionizes. The ionization efficiency of an element is referred to as its ion yield. The ion yield of a particular element A is simply the ratio of the number of A ions to the total number of A atoms sputtered from the mixing zone. For example, if element A has a 1 100 probability of being ionized in the sputtering process—that is, if 1 ion is formed from every 100 atoms of A sputtered from the sample—the ion yield of A would be 1/100. The higher the ion yield for a given element, the lower (better) the detection limit. 

Both positive and negative ions are produced during the sputtering process, and either can be recorded by an appropriate choice of instrumental parameters. Positive ions are the result of protonation, [M + H]", or cationiz-ation, [M +cation], whereas negative ions are preponderantly [M-H], but can also be formed by the addition of an anion, that is, [M+anion]". The type of pseudomolecular ion produced is governed by the chemical nature of the sample and by the composition of the matrix from which it is ionized. 

The Mg isotopic measurements were performed with a modified AEI IM-20 ion microprobe [13,14]. Secondary ions were generated by bombarding the sample with a focussed ion beam to excavate a small volume of the sample. A fraction of the sputtered material is ionized during the sputtering process and is drawn off into the mass spectrometer. A duoplasmatron ion source produces a... 

All major functions of a plant, such as glass transport, control of the sputter processes and pump control, are carried out fully automatically. This is the only way to ensure high productivity along w/ith high product quality. 

Depth resolution in SIMS is limited to about Inm (14 15.) by the sputtering process and varies with the material being sputtered (14 lfi). The best depth resolution is obtained for heavier bombarding ions at lower energies (16 18 19). An example of good depth resolution for Ta20c on Ta is 3.5nm which was less than I.IX of the sputtered depth (15). 

Most commonly, aluminum layers between 0.5 pm and 2 pm thick are deposited by a sputtering process and then annealed at a temperature of about 400 °C to achieve the desired electrical properties. 

One of the more important practical applications of ESCA is in the study of surface phenomena. Such areas as the direct study of surface reactions, diffusion processes under preselected conditions, the study of dopants in solids, surface-catalysis phenomena, sputtering processes, and gas-surface interactions are open to investigation. 

Lower topography formation on the sample from the sputtering process and lower damage cross sections for depth profiling of molecules are additional advantages of the Cgo source compared to liquid metal ion sources [15]. These sources are most often used with TOE SIMS. 

As the compositions of only the first (and second) atomic layers are modified by the sputtering process and, since in AES and XPS signals come from a few atomic layers, the higher-energy peaks (i.e., those corresponding to greater IMFP) which select more of the bulk material will be less affected by this problem. 

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