A Novel Technique for Determining Local Dielectric Function During Ferroelectric to Paraelectric Phase Transformation in Barium Titanate with a Transmission Eels

1995 ◽  
Vol 404 ◽  
Author(s):  
Kalpana S Katti ◽  
Maoxu Qian ◽  
Mehmet Sarikaya
Keyword(s):  
Phase Transformation ◽  
Barium Titanate ◽  
Energy Loss ◽  
Electron Energy ◽  
Dielectric Function ◽  
Optical Parameters ◽  
Edge Structure ◽  
Transmission Electron ◽  
Electron Energy Loss

AbstractIn this work a transmission electron microscopy (TEM) technique was used in obtaining local dielectric properties calculated from optical parameters for dynamic investigation of the effect of cubic to tetragonal phase transformation in barium titanate. In order to obtain in situ local dielectric during phase transformation, Kramers-Kronig relations were applied using the transmission electron energy loss (EELS) measurements. The optical excitations in the EELS spectra were consistent with the band structure results. The Re (1/ε) (real part of the dielectric function) obtained from the energy loss data indicated a change at the phase transformation. A broadening of the valence plasmon excitation suggested an order-disorder nature to the cubic to tetragonal transformation. In situ electron energy loss near edge structure (ELNES) studies from 500–700 eV energy range near the O-K edge exhibited a pre-edge feature that is associated with the Ti-L1, edge which further indicates an order-disorder nature to the phase transformation. The significance of the results is discussed.

Determination of local high-frequency dielectric function during the cubic-to-tetragonal phase transformation in barium titanate

1997 ◽  
Vol 12 (6) ◽  
pp. 1582-1588 ◽  
Author(s):  
Kalpana S. Katti ◽  
Maoxu Qian ◽  
Mehmet Sarikaya ◽  
Masuru Miyayama
Keyword(s):  
Phase Transformation ◽  
Barium Titanate ◽  
Energy Loss ◽  
Dielectric Function ◽  
High Frequency ◽  
Physical Property ◽  
Large Contribution ◽  
Transmission Electron ◽  
Electron Energy Loss

Transmission electron energy loss spectroscopy was used to obtain local dielectric properties in barium titanate. The high frequency dielectric function of the material was studied dynamically during the cubic-to-tetragonal (c → t) phase transformation in conjunction with the effect of a small amount (0.9%) of donor dopant (niobium). In order to obtain the local dielectric function during the phase transformation, Kramers–Kronig relations were applied to the energy loss measurements. The optical excitations in the energy loss spectra were consistent with band structure results from the literature. The Re (1/∈), real part of the inverse dielectric function, obtained from the energy loss data indicated a change at the phase transformation. Specifically, a broadening of the valence plasmon excitation is observed which is attributed to the order-disorder nature of the t → c transformation. A 0.4 eV shift in the volume plasmon was observed in the Nb-doped sample in all regions (within grains as well as at grain boundaries), indicating a uniform incorporation of the dopant in the lattice. In this paper, the changes in the dielectric function, such as shifts in collective excitations, are attributed to a large contribution from loosely bound Nb electrons. Furthermore, it is demonstrated that it is possible to obtain local (≈10 nm) physical property of a complex material dynamically at relatively high temperature.

Investigation of Switching Mechanism in HfO2-Based Oxide Resistive Memories by In-Situ Transmission Electron Microscopy and Electron Energy Loss Spectroscopy

2017 ◽  
Author(s):  
T. Dewolf ◽  
D. Cooper ◽  
N. Bernier ◽  
V. Delaye ◽  
A. Grenier ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Energy Loss ◽  
Electron Energy ◽  
Electron Energy Loss Spectroscopy ◽  
Hafnium Dioxide ◽  
Switching Mechanism ◽  
Transmission Electron ◽  
Electron Energy Loss

Abstract Forming and breaking a nanometer-sized conductive area are commonly accepted as the physical phenomenon involved in the switching mechanism of oxide resistive random access memories (OxRRAM). This study investigates a state-of-the-art OxRRAM device by in-situ transmission electron microscopy (TEM). Combining high spatial resolution obtained with a very small probe scanned over the area of interest of the sample and chemical analyses with electron energy loss spectroscopy, the local chemical state of the device can be compared before and after applying an electrical bias. This in-situ approach allows simultaneous TEM observation and memory cell operation. After the in-situ forming, a filamentary migration of titanium within the dielectric hafnium dioxide layer has been evidenced. This migration may be at the origin of the conductive path responsible for the low and high resistive states of the memory.

Energy-filtering Transmission Electron Microscopy in materials and life science

1994 ◽  
Vol 52 ◽  
pp. 936-937
Author(s):  
L. Reimer
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Energy Loss ◽  
Electron Energy ◽  
Analytical Electron Microscopy ◽  
Edge Structure ◽  
Energy Filtering ◽  
Transmission Electron ◽  
Plasmon Loss ◽  
Electron Energy Loss

Energy-filtering transmission electron microscopy can be realized by an imaging filter lens in thecolumn of a TEM, a post-column electron energy-loss spectrometer or a dedicated STEM. This offers new possibilities in analytical electron microscopy by combining the operation modes of electron-spectroscopic imaging (ESI), electron-spectroscopic diffraction (ESD) and the record of an electron energy-loss spectrum (EELS).ESI can be used in the zero-loss mode to remove all inelastically scattered electrons. Thicker amorphous and crystalline specimens can be observed without chromatic aberration and with a transmissionof 10−3 up to 80(110) and 150(200) μg/cm2 at 80(120) keV, respectively. This results in a condiserable increase of scattering, phase and Bragg contrast, especially for low Z material because the ratio of inelastic-to-elastic cross section increases as 20/Z with decreasing atomic number. In future energy-filtered high-resolution crystal-lattice images will offer us a better comparison with dynamical simulations. Plasmon loss filtering can be applied for a better separation of phases (e.g. precipitates in a matrix), which differ in their plasmon loss by about 1 eV. Owing to intersections of the energy loss spectra, different parts of a specimen can change their contrast when tuning the selected energy window. Structures containing non carbon atoms will beconsiderably increased in a bright field like contrast relative to the carboneous matrix just below the carbon K edge (structure—sensitive imaging).

Structural Properties and ELNES of Polycrystalline and Nanoporous Mg3N2

2020 ◽  
Vol 26 (1) ◽  
pp. 102-111
Author(s):  
Olivia Wenzel ◽  
Viktor Rein ◽  
Radian Popescu ◽  
Claus Feldmann ◽  
Dagmar Gerthsen
Keyword(s):  
Energy Loss ◽  
Electron Energy ◽  
Crystal Size ◽  
Bulk Material ◽  
Structural Features ◽  
Edge Structure ◽  
Transmission Electron ◽  
Potential Applications ◽  
Magnesium Nitride ◽  
Electron Energy Loss

AbstractNanoporous, high-purity magnesium nitride (Mg3N2) was synthesized with a liquid ammonia-based process, for potential applications in optoelectronics, gas separation and catalysis, since these applications require high material purity and crystallinity, which has seldom been demonstrated in the past. One way to evaluate the degree of crystalline near-range order and atomic environment is electron energy-loss spectroscopy (EELS) in a transmission electron microscope. However, there are hardly any data on Mg3N2, which makes identification of electron energy-loss near-edge structure (ELNES) features difficult. Therefore, we have studied nanoporous Mg3N2 with EELS in detail in comparison to EELS spectra of bulk Mg3N2, which was analyzed as a reference material. The N-K and Mg-K edges of both materials are similar. Despite having the same crystal structure, however, there are differences in fine-structural features, such as shifts and absences of peaks in the N-K and Mg-K edges of nanoporous Mg3N2. These differences in ELNES are attributed to coordination changes in nanoporous Mg3N2 caused by the significantly smaller crystallite size of 2–6 nm compared to the larger (25–125 nm) crystal size in a bulk material.

scholarly journals Electron Energy Loss Spectroscopy for Aqueous in Situ Scanning Transmission Electron Microscopy

2011 ◽  
Vol 17 (S2) ◽  
pp. 778-779 ◽  
Author(s):  
K Jungjohann ◽  
J Evans ◽  
I Arslan ◽  
N Browning
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Energy Loss ◽  
Electron Energy ◽  
Electron Energy Loss Spectroscopy ◽  
Scanning Transmission Electron Microscopy ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Electron Energy Loss

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

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