分光分析（EELS、EDS、电子构造） - 版本历史

Li.qun：/* 21. chemical shift */

2020-06-30T05:35:16Z

‎21. chemical shift

Li.qun：/* 21. chemical shift */

2020-06-30T05:34:12Z

‎21. chemical shift

Li.qun：/* 21. chemical shift */

2020-06-30T05:33:26Z

‎21. chemical shift

Li.qun：/* 21. chemical shift */

2020-06-30T05:31:54Z

‎21. chemical shift

Li.qun：/* 17. (L2, L3), (M4, M5)…spectra */

2020-03-23T06:40:03Z

‎17. (L2, L3), (M4, M5)…spectra

Li.qun：/* 17. (L2, L3), (M4, M5)…spectra */

2020-03-23T06:38:54Z

‎17. (L2, L3), (M4, M5)…spectra

Li.qun：/* 17. (L2, L3), (M4, M5)…spectra */

2020-03-23T06:37:51Z

‎17. (L2, L3), (M4, M5)…spectra

Li.qun：/* 17. (L2, L3), (M4, M5)…spectra */

2020-03-23T06:36:15Z

‎17. (L2, L3), (M4, M5)…spectra

Li.qun：/* 17. (L2, L3), (M4, M5)…spectra */

2020-03-23T06:35:06Z

‎17. (L2, L3), (M4, M5)…spectra

Li.qun：/* 98. Surface plasmon */

2019-06-10T04:44:44Z

‎98. Surface plasmon

←上一版本		2020年6月30日 (二) 05:35的版本
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	Fig. 1 Threshold energies of a core-loss spectrum obtained from metal at the ground state and from its oxide.		Fig. 1 Threshold energies of a core-loss spectrum obtained from metal at the ground state and from its oxide.
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		+	[[文件:Chemical shift 02.png]]

	Fig. 2 L2,3-shell excitation spectra of various manganese oxides. As the valence number of manganese is higher, an L2,3-absorption edge shifts to the high energy side.		Fig. 2 L2,3-shell excitation spectra of various manganese oxides. As the valence number of manganese is higher, an L2,3-absorption edge shifts to the high energy side.

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 For the insulating material, it is known that the core hole and the excited electrons often form a bound state (core exciton). The exciton level that appears in the band gap may become the final state for EELS. In such a case, the threshold energy decreases by the energy value of the binding energy of the exciton. The binding energy of the core exciton depends on materials, but ranging from about 100 meV to beyond 1 eV. When the binding energy of the core exciton is large, a spectral peak is observed as a separate peak just below the absorption edge. Since the chemical shift measured by EELS is affected also by the change in the final state, the interpretation of the EELS spectra is not easy. If the spectra of standard materials can be obtained in advance, it is possible to use the chemical shift to determine the valence number.
 It should be noted that X-ray Photoelectron Spectroscopy (XPS) provides also information on chemical shift arising at ionization of a core electron. The final state of XPS exists in vacuum outside the specimen. Thus, the final state always stays the same and does not contribute to the chemical shift in XPS, this situation being different from the case of the core-hole interaction in EELS. Therefore, the spectral interpretation of chemical shift by XPS is easier than that by EELS.
-(By Professor Hiroki Kurata, Kyoto University) Related term
+(By Professor Hiroki Kurata, Kyoto University)
 [[文件:Chemical shift 01.png]]
 Fig. 1  Threshold energies of a core-loss spectrum obtained from metal at the ground state and from its oxide.

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 It should be noted that X-ray Photoelectron Spectroscopy (XPS) provides also information on chemical shift arising at ionization of a core electron. The final state of XPS exists in vacuum outside the specimen. Thus, the final state always stays the same and does not contribute to the chemical shift in XPS, this situation being different from the case of the core-hole interaction in EELS. Therefore, the spectral interpretation of chemical shift by XPS is easier than that by EELS.
 (By Professor Hiroki Kurata, Kyoto University) Related term
+[[文件:Chemical shift 01.png]]
 Fig. 1  Threshold energies of a core-loss spectrum obtained from metal at the ground state and from its oxide.

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 electron energy-loss spectroscopy, EELS</pre>
 ==21. chemical shift ==
-"Chemical shift" in solid state physics means that the energy level of an inner-shell electron changes when the valence number (chemical state) changes. For example, if one valence electron is removed from an atom, inner-shell electrons are further attracted to the nucleus of the atom and the energy level of the inner-shell electrons shifts to a lower level. Thus, the energy difference between the inner-shell level and the bottom of the conduction band becomes larger. As a result, the onset energy of the EELS core-loss spectrum shifts to a higher energy. The removal of one valence electron can cause an energy shift of about 2.5 eV.
+Chemical shift means the change of the onset energy (threshold energy) of a core-loss spectrum obtained by Electron Energy-Loss Spectroscopy (EELS), which depends on the bonding states and the valence number of an excited atom (chemical environment).
 <pre>Related term
 core-loss spectrum</pre>
 ==22. cathodoluminescence ==
 Electrons in a solid are excited by electron-beam irradiation leaving holes. The electrons recombine with the holes to emit light (ultraviolet to infrared). This phenomenon is called "Cathodoluminescence". Cathodoluminescence is utilized as a method to analyze the electronic structure of solids in an electron microscope. The method can measure local electronic states (energy levels) of impurities and defects, the electronic states being formed between the valence band and the conduction band (in the forbidden band). Thus, the method enables the evaluation of inorganic materials containing the structural defects with a high spatial resolution (better than 1 μm) by the combined use with structural information obtained from SEM / STEM / TEM images. Applications to biological specimens, such as detection of specific proteins, have also been studied.

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 The L2 and L3 absorption edges of barium are reported to be 5247 eV and 5624 eV. Usually, as EELS measurements are performed up to about 1000 eV, it is difficult to observe the L2 and L3 spectra of barium.
-[[文件:L2L3M4M5spectra 03.JPG]]
+[[文件:L2L3M4M5spectra 03.JPG]]    [[文件:L2L3M4M5spectra 04.JPG]]
 Fig. 2 (a) M4 and M5 (absorption edge) spectra of Ba in barium titanate (BaTiO3). The M5 transition peak appears at 780 eV, and the M4 peak at 795 eV. The intensity ratio of the M4 and M5 spectra is approximately 2:3, indicating that the experimentally obtained ratio is close to the expected ratio. (b) Schematic of the electronic energy state of BaTiO3 and the process of M4 and M5 transitions. The pink part shows Ba-4f orbital component. Since 14 seats of Ba-4f orbitals are unoccupied, the M4 and M5 peaks are observed extremely strong. The Ba-6s and Ba-6p orbitals form a relatively broad conduction band and the density of states is small. The transition to the 6s orbital is forbidden. The transition spectra to the 6p orbitals form broad background. The background is very weak comparing with the M4 and M5 peaks.
 For the third periodic elements (Al, Si, etc.), L2 and L3 spectra are created by the transitions from the inner-shell 2p levels to 3s components in the conduction band. Since the energy difference between the L2 and L3 levels is less than 1 eV, L2 and L3 spectra are observed as one absorption edge spectrum without splitting. Then, L2 and L3 spectra in such a case are written as L2,3.

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 The intensity ratio of the L2 and L3 spectra is expected to be 1:2 from the occupation ratio of the inner-shell L2 and L3 levels. However, the ratio experimentally observed is different from the expected ratio because the density of states of 3d electron in the conduction band is modified and the selection rule for electron transitions becomes different due to the core-hole interaction, the spin orbit coupling at the final state and the Coulomb repulsion of 3d electrons. Utilizing the phenomenon in which the intensity ratio deviates from 1:2, information on the valence of the 3d transition metal can be obtained.
 Fig. 1(a) shows L2 and L3 (absorption edge) spectra of copper oxide (CuO). Two peaks of L2 and L3 spectra are separated by about 20 eV. The intensity ratio of L2 and L3 deviates from 1:2. Fig. 1(b) illustrates the electronic energy state of CuO. The L2 and L3 levels have an energy difference of approximately 20 eV due to spin orbit coupling. The observed spectra are interpreted as those from the inner-shell L2 and L3 levels to 3d unoccupied narrow states which is formed at the bottom of the conduction band. The electron configuration of Cu2+ in CuO is [3d9, 4s0] and one hole exists at 3d5/2. The transition selection rule in this case is not determined by the orbital angular momentum change  but by the total angular momentum change  due to the spin-orbit coupling. Thus, the transition from 2p3/2(L3) to 3d5/2 is allowed, but the transition from 2p1/2(L2) to 3d5/2 is forbidden. This indicates that the L3 peak should be observed, but the L2 peak should not be observed. However, a weak L2 peak is observed in the experiment as shown in Fig. 1(a). This is because there exist holes at the 3d3/2 orbital component, which are caused by a weak covalent bonding between Cu and O.
-[[文件:L2L3M4M5spectra 01.JPG]]
 Fig. 1 (a) L2 and L3 (absorption edge) spectra of copper oxide (CuO). The L3 transition peak appears at 932 eV and the L2 transition peak appears at 952 eV. The intensity ratio between the L2 and L3 spectra clearly deviates from 1:2. (b) Schematic electronic energy state of CuO and the process of L2 and L3 transitions. V.B. represents the valence band and C.B. represents the conduction band. The red and the pink parts respectively show the occupied and the unoccupied states of the Cu-3d orbit. The Cu-4s orbital component exists over a relatively broad energy range in C.B. and its density of states is small. Thus, the transition spectra to the 4s orbital component are observed as the broad background.
 The difference of the M4 and M5 energy levels of sixth-period elements is 10 to 120 eV. Two spectra with similar shape successively appear with the energy difference in the EELS spectrum. The intensity ratio of the M4 and M5 spectra is expected to be 2:3 from the occupation ratio of the inner-shell 3d electron levels.
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 Fig. 2 (a) M4 and M5 (absorption edge) spectra of Ba in barium titanate (BaTiO3). The M5 transition peak appears at 780 eV, and the M4 peak at 795 eV. The intensity ratio of the M4 and M5 spectra is approximately 2:3, indicating that the experimentally obtained ratio is close to the expected ratio. (b) Schematic of the electronic energy state of BaTiO3 and the process of M4 and M5 transitions. The pink part shows Ba-4f orbital component. Since 14 seats of Ba-4f orbitals are unoccupied, the M4 and M5 peaks are observed extremely strong. The Ba-6s and Ba-6p orbitals form a relatively broad conduction band and the density of states is small. The transition to the 6s orbital is forbidden. The transition spectra to the 6p orbitals form broad background. The background is very weak comparing with the M4 and M5 peaks.
 For the third periodic elements (Al, Si, etc.), L2 and L3 spectra are created by the transitions from the inner-shell 2p levels to 3s components in the conduction band. Since the energy difference between the L2 and L3 levels is less than 1 eV, L2 and L3 spectra are observed as one absorption edge spectrum without splitting. Then, L2 and L3 spectra in such a case are written as L2,3.
 (By Associate Professor Yohei Sato, Tohoku University)

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 characteristic X-ray, semiconductor detector (solid-state detector), SSD, escape peak, sum peak, wavelength-dispersive X-ray spectroscopy, WDS</pre>
 ==17. (L2, L3), (M4, M5)…spectra ==
-Absorption edges characteristic of elements, which appear in an energy region higher than 50 eV in an EELS spectrum. These absorption edges arise due to excitations of inner shell electrons to the conduction band. They are called "K, L, M…" shell excitation spectra depending on the excited inner shell. The inner-shell levels have fine structures due to the spin orbit coupling. The split levels are expressed as K(1s1/2), L1(2s1/2), L2(2p1/2), L3(2p3/2), M1(3s1/2), M2(3p1/2), M3(3p3/2), M4(3d3/2), M5(3d5/2), …. Since the difference of the L2 & L3 energy levels of 3d transition metals is 5 to 20 eV, two spectra with similar shape successively appear with the energy difference in the EELS spectrum. For Si and Al, the L2 & L3 spectra form a non-separated absorption-edge spectrum because the energy separation of the L2 & L3 levels is 1 eV or less. Thus, they are denoted as L2,3. The intensity ratio of the L2 & L3 spectra is expected to be 1:2 from the occupation ratio of the levels. However, the ratio experimentally observed is different from the ratio expected due to non-flat configuration of the conduction band and the core-hole interaction. In the case of the excitation of M shell electrons of 4d transition metals, M4 and M5 spectra appear successively with an energy difference of 2 to 10 eV.
+EELS spectra associated with electronic excitation from the L2 and L3 levels of elements or the M4 and M5 levels to the conduction band. Two similar-shaped spectra appear with an energy difference between the L2 and L3 levels. The spectra set is called (L2 and L3) spectra. For example, the energy difference between the L2 and L3 levels of the 3d transition metals is about 5 to 20 eV. The M4 and M5 spectra show a similar feature to (L2 and L3) spectra.
 <pre>Related term
 electron energy-loss spectroscopy, EELS, core-loss spectrum, spin orbit coupling, core-hole interaction</pre>

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 [[文件:Surface plasmon 01.jpg]]
 Fig. 1 (a) Schematic of surface plasmon for metal. Due to an external charged-particle or a light wave, the positive (+) and the negative (–) charges are induced. With an electric field generated by these charges (Ex (z=0±) in Fig. 1) as a driving force, a longitudinal oscillation wave of free electrons is created. (b) Illustration of the electric-field component vertical to the interface between a metal and a dielectric material (with vacuum) Ez=0± and the electric-field component parallel to this interface Ex (z=±0). Both of the continuity for the vertical component of the electric flux density εMEz=0-= εdEz=0+ and the continuity of the parallel component of the electric field are satisfied.
 [Experimentally-obtained surface plasmon]