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Vibrational electron energy loss spectroscopy in truncated dielectric slabs
摘要： Specially designed instrumentation for electron energy loss spectroscopy (EELS) in a scanning transmission electron microscope makes it possible to probe very low-loss excitations in matter with a focused electron beam. Here we study the nanoscale interaction of fast electrons with optical phonon modes in silica. In particular, we analyze the spatial dependence of EEL spectra in two geometrical arrangements: a free-standing truncated slab of silica and a slab with a junction between silica and silicon. In both cases, we identify different loss channels, involving polaritonic and nonpolaritonic contributions to the total electron energy loss, and we obtain the corresponding energy-filtered maps. Furthermore, we present a comparison of the theoretical simulations for a silica-silicon junction with experimental results, and we discuss the spatial resolution attainable from the energy-filtered map considering optical phonon excitations in a conventional experimental arrangement.
关键词： optical phonon modes,nonpolaritonic,polaritonic,silica,electron energy loss spectroscopy,EELS,silicon
更新于2025-09-23 15:21:21
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Transmission Electron Microscopy and Electron Energy-Loss Spectroscopy Studies of Hole-Selective Molybdenum Oxide Contacts in Silicon Solar Cells
摘要： In this study, sub-stochiometric hole-selective molybdenum oxide (MoOx) contacts in crystalline silicon (c-Si) solar cells were investigated by a combination of transmission electron microscopy (TEM) and spatially-resolved electron energy-loss spectroscopy (SR-EELS). It was observed that a ≈ 4 nm SiOx interlayer grows at the MoOx/c-Si interface during the evaporation of MoOx over c-Si substrate. SR-EELS analyses revealed the presence of 1.5 nm diffused MoOx/ITO (indium tin oxide) interface in both as-deposited and annealed samples. Moreover, the presence of a 1 nm thin layer with a lower oxidation state of Mo was detected at SiOx/MoOx interface in as-deposited state which disappears upon annealing. Overall, it was evident that no hole-blocking interlayer is formed at MoOx/ITO interface during annealing and homogenization of the MoOx layer takes place during the annealing process. Furthermore, device simulations revealed that efficient hole collection is dependent on MoOx work function and that reduction in work function of MoOx results in loss of band bending and negatively impacts hole-selectivity.
关键词： silicon,electron energy-loss spectroscopy (EELS),hole-selective,transmission electron microscopy (TEM),molybdenum oxide (MoOx)
更新于2025-09-12 10:27:22
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Size-dependent dielectric function for electron-energy-loss spectra of plasmonic nanoparticles
摘要： A size-dependent complex dielectric function is proposed to describe the impact that size effects have on the dielectric response for electron energy loss spectroscopy (EELS) of plasmonic nanoparticles. Our implementation is based on experimental bulk complex refractive index and the modification of the Lorentz-Drude model. Our theoretical framework is verified and analysed by performing numerical simulation comparisons of EELS for Au spherical nanoparticles of different sizes. The results show that finite-size effects cannot be neglected for a broader size range of up to at least 200 nm for Au spherical nanoparticles. Moreover, the EELS regions in which contributions of surface or bulk energy loss are dominant are confirmed by the optical extinction spectra of Au spherical nanoparticles of different sizes, which takes into account the size-dependent dielectric function. The results provided here provide a suitable and versatile framework for the design of plasmonic elements on the nanometre scale.
关键词： metallic nanoparticles,Plasmonics,size-dependent dielectric function,surface plasmon,electron energy loss spectroscopy (EELS)
更新于2025-09-12 10:27:22