Identification of point defects using high-resolution electron energy loss spectroscopy

Abstract

Although there are many techniques that can detect bandgap states associated with point defects in the lattice, it is not routinely possible to determine the type of defect at submicron spatial resolution. Here we show that high-resolution electron energy loss spectroscopy (EELS) in a scanning transmission electron microscope can locate and identify point defects with a resolution of about 10nm in a wide-bandgap BAlN semiconductor. B interstitials, N vacancies, as well as other point defects have been experimentally detected using EELS and have been identified using density functional theory.

Visualizing quantum phenomena at complex oxide interfaces: An atomic view from scanning transmission electron microscopy

“…We note that monochromated EELS with high energy resolution may be a possible choice to overcome the above issue. Recently, monochromated EELS in STEM with resolution below 20 meV has been achieved [145], which can locate and identify the point defects and its associated bandgap with a resolution of about 10nm in BAlGaN semiconductor [146]. In complex oxides, the high resolution monochromated EELS is also particularly important as it can detect subtle changes in the oxygen electronic configurations [147,148].…”

Nanoscale observation of subgap excitations in β-Si3N4 with a high refractive index using low-voltage monochromated STEM: a new approach to analyze the physical properties of defects in dielectric materials

“…39) Corresponding to the EELS spectra at positions P2 and P1, the onset energies were observed to decrease, with the bandgaps estimated to be 6.1 and 5.2 eV, respectively. Notably, additional continuous intensities were clearly observed in the spectra at positions P1 and P2 below the bandgap of the single crystal, even though no peak structures 29) were observed. We focused on the additional intensities, which were attributed to the formation of the subgap states.…”

“…The first is the Cerenkov loss, [23][24][25][26][27] which is due to the high refractive index of SiN. By reducing the accelerating voltage to 80 kV or 60 kV in addition to using a monochromator, 19) the subgap excitations can be measured without Cerenkov loss in α-Al 2 O 3 28) and BAlN 29) with a relatively low refractive index of 1.7 30) and one lower than 2.2, 31) respectively. Assuming a refractive index of 2 to 2.5 for SiN, 32) the accelerating voltage should be further reduced to 30 kV (supplementary Fig.…”

Probing Correlation of Optical Emission and Defect Sites in Hexagonal Boron Nitride by High-Resolution STEM-EELS

“…For instance, core-level spectroscopy techniques where the inner-shell electrons are excited, provide information about the underlying electronic structure, composition, and bonding properties. 40,41 Among these, electron energy-loss spectroscopy (EELS) can be particularly useful for atomic-scale elemental analysis. 42−44 In scanning transmission electron microscopy EELS (STEM-EELS), a focused electron beam is directed toward the sample (Figure 1a) and scanned over each atom.…”

“…Relying on some sort of elemental-specific spectroscopic signal could result in a more accurate assessment of the local chemical environment near the emission sites. For instance, core-level spectroscopy techniques where the inner-shell electrons are excited, provide information about the underlying electronic structure, composition, and bonding properties. , Among these, electron energy-loss spectroscopy (EELS) can be particularly useful for atomic-scale elemental analysis. − In scanning transmission electron microscopy EELS (STEM-EELS), a focused electron beam is directed toward the sample (Figure a) and scanned over each atom. As the high-energy electrons interact with it, they lose energy mostly through inelastic scattering and ionization processes.…”