Reflection electron energy loss spectroscopy during initial stages of Ge growth on Si by molecular beam epitaxy

Using a conventional reflection high-energy electron diffraction gun together with an electron energy loss spectrometer, we have combined in situ measurements of inelastic scattering intensities from Si L2,3 and Ge L2,3 core losses with reflection electron diffraction data in order to analyze the initial stages of Ge heteroepitaxy on Si(001). Diffraction data indicate an initial layer-by-layer growth mode followed by island formation for Ge thicknesses greater than 0.8–1.1 nm. The electron energy core loss data are consistent with a simple model of grazing incidence electron scattering from the growing Ge film. Reflection electron energy loss spectroscopy is found to be highly surface sensitive, and the energy resolution and data rate are also sufficiently high to suggest that reflection electron energy loss spectroscopy may be a useful real-time, in situ surface chemical probe during growth by molecular beam epitaxy

EELS at very high energy losses

Electron energy-loss spectroscopy (EELS) has been investigated in the range from 2 to >10 keV using an optimized optical coupling of the microscope to the spectrometer to improve the high loss performance in EELS. It is found that excellent quality data can now be acquired up until about 5 keV, suitable for both energy loss near edge structure (ELNES) studies of oxidation and local chemistry, and potentially useful for extended energy loss fine structure (EXELFS) studies of local atomic ordering. Examples studied included oxidation in Zr, Mo and Sn, and the ELNES and EXELFS of the Ti-K edge. It is also shown that good quality electron energy-loss spectroscopy can even be performed for losses above 9.2 keV, the energy loss at which the collection angle becomes ‘infinite’, and this is demonstrated using the tungsten L3 edge at about 10.2 keV

Detection of nanoparticles by means of reflection electron energy loss spectroscopy depth profiling

The various studies of nanoparticles are of great importance because of the wide application of nanotechnology. The shape and structure of the nanoparticles can be determined by transmission electron microscopy (TEM) and their chemistry by electron energy loss spectroscopy. TEM sample preparation is an expensive and difficult procedure, however. Surface sensitive, analytical techniques, such as Auger electron spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS) are well applicable to detect the atoms that make up the nanoparticles, but cannot determine whether particle formation occurred. On the other hand, reflection electron energy loss spectroscopy (REELS) probes the electronic structures of atoms, which are strongly different for the atoms being in solution or in precipitated form. If the particle size is in the nm range, plasmon resonance can be excited in it, which appears as a loss feature in REELS spectrum. Thus, by measuring AES (XPS) spectra parallel with those of REELS, besides the atomic concentrations the presence of the nanoparticles can also be identified. As an example, the appearance of nanoparticles during ion beam induced mixing of C/Si layer will be shown

Electron energy loss spectroscopy with parallel readout of energy and momentum

We introduce a high energy resolution electron source that matches the requirements for parallel readout of energy and momentum of modern hemispherical electron energy analyzers. The system is designed as an add-on device to typical photoemission chambers. Due to the multiplex gain, a complete phonon dispersion of a Cu(111) surface was measured in seven minutes with 4 meV energy resolution