Page 33 - Academic Press Encyclopedia of Physical Science and Technology 3rd Analytical Chemistry

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Encyclopedia of Physical Science and Technology En001f25 May 7, 2001 13:58

572 Analytical Chemistry

sample. Here, lateral analysis can be performed by move- 5. Has high sensitivity
ment of the impacting electron beam, and depth studies 6. Has high spatial resolution
can be achieved by removing layers of sample by impinge- 7. Is applicable to a wide range of samples
ment of a sputtering ion beam. 8. Does not discriminate against any component
Not surprisingly, AES has found tremendous use in the 9. Has no influence on surface composition and structure
analysis of surfaces of samples in metallurgy and mate-
rials science. It has been used extensively in alloy analy- As expected, no single technique possesses all these
sis, metal oxidation, segregation, adsorption phenomena, requirements. The battery of methods that are available
catalysis, electrodeposition, corrosion, films and coatings, is outlined in Table XII. From these data it is clear that
tribology, adhesion, and the semiconductor industry. the overall strategy is the study of information carried by
emitted photons, ions, or electrons after perturbation of a
4. Surface Analysis
We now describe briefly the principles of a number
In view of the comments regarding the use of XPS and of important methods. In secondary-ion mass spectrome-
AES in surface analysis, it is appropriate to summarize try (SIMS), solids are bombarded by 1- to 30-keV ions,
this area concisely. An ideal method for surface analysis resulting in the ejection of substrate species as posi-
should possess the following features: tively and negatively charged atomic and molecular par-
ticles (and neutrals). The charged species are subjected
1. Is capable of monolayer examination to mass spectral analysis. The method is used in both
2. Detects elements dynamic and static modes; in the latter the target is
3. Identifies molecular species bombarded “gently,” resulting in a low sputtering rate
4. Elucidates surface topography and a relatively long average lifetime of the monolayer.

TABLE XII Example Methods of Surface Analysis
Exit species and information carrier
Excitation or probe Photons Electrons Ions (neutrals)
Photons Laser optical-emission spectroscopy X-ray photoelectron spectroscopy (XPS) Photodesorption (PD)
(LOES)
Light (Raman) scattering spectroscopy Ultraviolet photoelectron spectroscopy
(LS) (UPS)
Fourier transform infrared spectroscopy
(FTIR)
Ellipsometry (E)
Evanescent wave spectrofluorimetry
(EWS)
Electrons Electron microprobe (EMP) Auger electron spectroscopy (AES) Electron-stimulated desorption
Scanning electron microscopy X-ray Scanning electron microscopy (SEM) (ESD)
detection (XSEM) Low-energy electron diffraction (LEED)
Electron-impact energy loss spectroscopy
(EELS)
Ions Ion-induced X-ray spectroscopy (IIX) Ion-neutralization spectroscopy (INS) Secondary-ion mass spectrometry
(SIMS)
Proton-induced X-ray spectroscopy Ion-induced Auger electron spectroscopy Ion-scattering spectroscopy (ISS)
(PIX) (IAES)
Surface composition by analysis of Rutherford backscatter
neutral species and ion-impact spectroscopy (RBS)
radiation (SCANIIR)
Glow-discharge optical spectroscopy
(GDOS)
Electric field — Field electron microscopy (FEM) Atom probe field-ion microscopy
(APFIM)