We describe highly accurate (02-1%) intensity measurements for the inelastic scattering of 75-keV electrons in \ensuremath{\sim} 1000-\AA{}-thick polycrystalline aluminum films in the region of (00-31)-${\mathrm{\AA{}}}^{\ensuremath{-}1}$ transferred wave vector and (0-100)-eV energy loss The work was performed on the Cornell University electron spectrometer-microscope-computer system These measurements clarify some experimental problems associated with multiple scattering which obscure the single scattering distribution We present a new method for eliminating the distribution of intensity attributable to multiple scattering involving quasielastic events This subtraction method is accurate to \ensuremath{\sim}001% of the single-bulk-plasmon intensity Next, we extend an earlier correction method to obtain the single scattering energy-loss function $\mathrm{Im}(\ensuremath{-}\frac{1}{\ensuremath{\epsilon}})$ from the residue of the first process, which consists of multiple plasmons and quasiparticle transitions Details of the specific procedures are included We point out several features in the result---the bulk-plasmon intensity, dispersion, and width, the quasi-particle continuum, and a simultaneous two-plasmon scattering The latter is, for the first time, characterized completely as to intensity, dispersion, and energy width Finally, we present a comparison of the measured bulk-plasmon dispersion with some recent model calculations

Experimental energy-loss function, Im [ − 1 ε ( q , ω ) ] , for aluminum

SUMMARY

The physical basis of microanalysis using measurements of electron energy losses associated with atom ionization or plasmon excitation in thin electron microscope specimens is explained in a simple manner. In addition the equipment used to resolve both the high and low energy regions of the loss electron spectrum is described. It is shown that ionization loss analysis is still in its infancy, but plasmon loss analysis has now been providing quantitative microanalytical data on light metal alloys for 8 years. The results obtained from both techniques and their application to specific metallurgical problems are reviewed. Conclusions are drawn concerning the future use of these techniques in high resolution microanalysis.

High resolution microanalysis in materials science using electron energy loss measurements

SUMMARY

This paper describes the electron microscope and gives details of its performance at an operating voltage of 3 MV.



Some initial results are reported concerning: penetrating power; resolving power; studies of radiation damage, and other interactions between electrons and crystalline materials. Several observations are also described concerning biological materials (bacteria, frog skeletal muscle, filaments from mushroom spores …).



Because at high voltage, radiation damage is considerably reduced, the results obtained indicate a new range of applications of high voltage electron microscopy in biological ultrastructure research.

Performance and applications of the Toulouse 3 million volt electron microscope.

Calculation of the angular and energy distribution of multiple scattered electrons using fourier transforms

The main point of spectrometry performed point-by-point using an electron probe of nanometre dimensions is to acquire chemical and electronic information about the defects and interfaces which control structural, electronic and optical properties of materials According to some, our civilisation now depends upon electrical current sheets travelling along the interfaces between silicon and its oxide; others claim that it depends upon load transfer across the interfaces between weak, ductile metals bonded to strong but brittle fibres Every polycrystalline material depends upon its grain boundaries, whether for strength or for optical transparency Analytical electron microscopy, particularly EELS acquired using STEM, is the unique experimental method available to probe the interfacial density of states as well as the chemistry and the structure of such interfaces Although it is a relatively new technique still improving, it has already solved a number of problems which could not otherwise be tackled However, its main fundamental limitation is the damage caused to the material by the intense focused probe of electrons in the time required to extract the desired information

Electron Energy Loss Spectrometry in the Electron Microscope

It is shown that the electron energy loss distributions observed in electron transmission (energy 23–70 kev) through Al films 435 A–1950 A thick may be fitted in the energy ranges from 5 to 55–100 ev within a deviation of a few per cent. The fitting is made in terms of assumed electron energy loss distributions for the principal volume and surface losses which are centred, respectively, at about 15 ev and 7 ev. Consistent values of λi, the mean free path for single (volume) inelastic electron scattering into all angles, are evaluated for six electron energies in the given range. An attempt has been made to evaluate in detail the effects on the observed energy loss spectra of the energy loss distributions arising from surface and surface-volume electron interactions. The determined values of λi are in good agreement with the plasma oscillation theory.

R. E. Burge

Papers

Electron Energy Loss Spectra for Aluminium