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

Abstract

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) while their chemistry by electron energy loss spectroscopy (EELS).TEM sample preparation is an expensive and difficult procedure, however. Surface sensitive, analytical techniques, like Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS) are well applicable to detect the atoms that make up the nanoparticles, but cannot tell whether particle-formation occurred. On the other hand, reflection electron 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 nano particles during ion beam induced mixing of C/Si layer will be shown.2

The chemical resistance of nano-sized SiC rich composite coating

“…The 2 nd C, 2 nd Si and 3 rd C layers are unaffected by the irradiation, which is expected since the penetration (projected range) of 30 keV Ga in this layer system is 24±7 nm. We have shown that the measure of intermixing increased with fluence [15] and that majority of SiC was amorphous nano particles [18]. The intermixed layer besides SiC always contained Ga and if the fluence was ≤ 20 x 10 15 Ga + /cm 2 free (non-reacted) C and Si as well.…”

“…These plasmon losses can be utilized for the identification of the particles. Reflection electron energy loss spectroscopy (REELS) was used to identify the appearance of SiC and Ga particles [18].…”

“…The intermixed layer besides SiC always contained Ga and if the fluence was ≤ 20 x 10 15 Ga + /cm 2 free (non-reacted) C and Si as well. Based on the REELS analysis, the Ga is in solution if the irradiation fluence less than 80x10 15 Ga + ions/ cm 2 , while it forms -at least in parts -small nanoparticles if the fluence larger than the above value [18].…”

Wafer-scale SiC rich nano-coating layer by Ar+ and Xe+ ion mixing

“…These regions will not be considered from the point of view of IBM induced SiC production. Low energy (1 keV) REELS measurements exhibited the bulk plasmon loss of SiC, showing that considerable amount of SiC is located in nanoparticles with sizes of larger than 1-2 nm [19]. 120 keV Xe + irradiation to a fluence of 1 × 10 16 Xe + cm −2 (Fig.…”

“…C and Si was visualized by EELS elemental mapping. Reflection electron energy loss spectroscopy (REELS) measurement at low, 1 keV, primary electron energy was used to measure the plasmon energy of the nano-particles produced [19] giving a limit of the particle size.…”