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Linear image transfer down to a few tens of pm can be attained by a modern Cs-corrected transmission electron microscope. However, it is difficult to accurately evaluate such a high-performance microscope. We examine three-dimensional (3D) Fourier transform (FT) analysis in comparison with diffractogram (2D FT) analysis to evaluate aberration-corrected electron microscopes. The 3D FT can analyze information transfer on the Ewald sphere up to high-angles using a thick sample or a sample containing strong scattering elements. Therefore, the 3D FT analysis is necessary to evaluate Cs-corrected microscopes, especially those equipped with a Cc-corrector, or a monochromator, or microscopes operated at lower voltages.
The resolution of high-resolution transmission electron microscopes (TEM) has been improved down to subangstrom levels by correcting the spherical aberration (Cs) of the objective lens, and the information limit is thus determined mainly by partial temporal coherence. As a traditional Young’s fringe test does not reveal the true information limit for an ultra-high-resolution electron microscope, new methods to evaluate temporal coherence have been proposed based on a tilted-beam diffractogram. However, the diffractogram analysis cannot be applied when the nonlinear contribution becomes significant. Therefore, we have proposed a method based on the three-dimensional (3D) Fourier transform (FT) of through-focus TEM images, and evaluated the performance of some Cs-corrected TEMs at lower voltages. In this report, we generalize the 3D FT analysis and derive the 3D transmission cross-coefficient. The profound difference of the 3D FT analysis from the diffractogram analysis is its capability to extract linear image information from the image intensity, and further to evaluate two linear image contributions separately on the Ewald sphere envelopes. Therefore, contrary to the diffractogram analysis the 3D FT analysis can work with a strong scattering object. This is the necessary condition if we want to directly observe the linear image transfer down to a few tens of picometer.
The crystal structure of SiAl5O2N5 was characterized by laboratory X-ray powder diffraction (CuKα1). The title compound is hexagonal with space group P63/mmc (Z = 2). The unit-cell dimensions are a = 0.303153(3) nm, c = 3.28153(3) nm, and V = 0.261178(5) nm3. The initial structural model was successfully derived by the direct methods and further refined by the Rietveld method. The final structural model showed the positional disordering of two of the four (Si,Al) sites. The maximum-entropy method-based pattern fitting (MPF) method was used to confirm the validity of the split-atom model, in which conventional structure bias caused by assuming intensity partitioning was minimized. The reliability indices calculated from the MPF were Rwp = 5.00%, S (=Rwp/Re) = 1.25, Rp = 3.76%, RB = 1.26%, and RF = 0.90%. The disordered crystal structure was successfully described by overlapping four types of domains with ordered atom arrangements. The distribution of atomic positions in each of the domains can be achieved in the space group P63mc. Two of the four types of domains are related by a pseudo-symmetry inversion, and the two remaining domains also have each other the inversion pseudo-symmetry.
We have investigated the influence of nitrogen incorporation into the HfAlOx film prepared by LL-D&A process with NH3 annealing step on structural change and electrical properties. Also, we have evaluated the effects of PDA treatment on electrical properties. Nitrogen concentration in HfAlOx(N) film was enhanced with increasing the NH3 annealing temperature. The shift of Hf 4f average binding energy towards lower side was observed in proportion to nitrogen concentration in HfAlOx(N) film. This result indicates the partial change of the local coordination from O-Hf-O to O-Hf-N. The increase of O-Hf-N component drastically degraded the gate leakage current in HfAlOx(N) film. Nitrogen atoms still maintained in HfAlOx(N) film even after PDA at 850°C in O2 ambient. PDA treatment at higher temperature after D&A(NH3) process improved the flat-band voltage shift and the electron mobility.
Nanocrystalline diamonds with several hundred nm in diameter have been prepared in a 13.56 MHz low pressure inductively coupled CH4/H2 or CH4/CO/H2 plasma. The bonding structures were investigated by Raman spectroscopy and electron energy loss spectroscopy (EELS). Visible (514 nm) and UV (325, 244 nm) excited Raman spectra with CO additive exhibit peaks at ∼1150 cm-1 assigned to sp3 bonding and at 1332 cm-1 due to zone center optical phonon mode of diamond, respectively. It indicates that the UV excitations are possibly sufficient to excite the σ state of both sp2- and sp3-bonded carbon. The high resolution EELS (HREELS) spectra with CO additive show peaks at ∼1100 cm-1 assigned to C-C stretching vibration of sp3 bonding and at ∼700 cm corresponding to the bending vibration of sp3 bonding. It is qualitatively agreement with the Raman spectra. Furthermore the EELS spectrum without CO additive exhibits two peaks at 284 eV and at 292 eV corresponding to π* states and σ* states, respectively, and is similar to that of graphite rather than that of sp2-rich amorphous carbon. The EELS spectrum with CO additive, on the other hand, shows a peak at 292 eV due to σ * states and is similar to that of diamond. A slight peak appears at ∼285 eV corresponding to π* states. It consequently implies that the particles almost consist of sp3 bondings and that the small amount of sp2 bondings are considered to exist in grain boundaries. The EESL spectra are consistent with the results of Raman scattering and HREELS.
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