What is the EELS ? The process of historical development How does it work ? Components and properties Why is it used ? Advantages and Disadvantages Compare with EDX Applications Summary References
Analytical technique Quantitative analysis Analysis of the inelastic scattering suffered by the transmitted electron beam with measurement of the electron energy distribution Capable of giving structural and chemical information Electron spectrometer
High-resolution electron energy loss spectroscopy (EELS) is a high- sensitivity, non-destructive technique for the study of surface and adsorbate vibrations and low-energy electronic excitations. Figure 1
James Hillier RF Baker in the mid 1940s Research 1990s due to advance in microscope instrumentations and vacuum technology
Can be obtained experimentally In elastic scattering of X-ray photons or optical measurements Change in momentum and direction of propaganation Change in internal degrees of freedom
A typical EELS spectrum from an thin film Figure 2
Magnetic field is between two parallel plates. Objective aperture Specimen Lens Collector aperture
Figure 3 Photograph of the first electron microanalyzer (Hiller and Baker 1944)
The measurements of a) Local properties b) Including specimen thickness c) Mechanical and electronical d) Chemical composition
Higher core-loss signal Higher ultimate spatial resolution Absolute, standardless quantification Structural information available
Higher spectral background Very thin specimen needed Possible inaccuracy in crystals More operator intensive
Table 1.Comprasion between EELS and EDX.
Table 2. X-ray fluorescence yield for K-,L- and M- shells as a function of atomic number, from Krause (1979)
Thickness measurements Pressure measurements Analytical electron microscopy (AEM)
Electron energy-loss spectroscopy (EELS) is an analytical technique that measures the change in kinetic energy of electrons after they have interacted with a specimen.
1) Journal de Physique IV, Colloque C7, supplément au journal de physique III,Volume 3 2) R.F. EGERTON Electron Energy Loss Spectroscopy in The Electron Microscope 3. Edition 3) Yüksek Lisans Tezi NANO ÖLÇEKLİ VANANYUM OKSİT İNCE FİLMLERİN YAPISAL VE ELEKTRİKSEL KARAKTERİZASYONU Ogeday ÇAPAR