electron crystallographic study of bi-based superconductors using multi-dimensional direct methods...
TRANSCRIPT
Electron Crystallographic Study
of
Bi-based Superconductors
using
Multi-dimensional Direct Methods
Electron Crystallographic Study
of
Bi-based Superconductors
using
Multi-dimensional Direct Methods
Why Electrons ?Why Electrons ?
1. Electrons are better for studying minute and imperfect crystalline samples
2. Electron microscopes are the only instrument that can produce simultaneously EM’s and ED’s for the same crystalline sample at atomic resolution
3. Electrons are better for revealing light atoms in the presence of heavy atoms
1. Electrons are better for studying minute and imperfect crystalline samples
2. Electron microscopes are the only instrument that can produce simultaneously EM’s and ED’s for the same crystalline sample at atomic resolution
3. Electrons are better for revealing light atoms in the presence of heavy atoms
Scattering of X-rays and Electronsby Different Elements
Scattering of X-rays and Electronsby Different Elements
Relative scattering power
Relative scattering power
OO OO
Sin/Sin/
BiBi
SrSr
CaCaCuCu
X-raysX-rays
ElectronsElectrons
Bismuthbi-layer
Perovskitelayer
Bismuthbi-layer
Bi-based SuperconductorsBi-based Superconductors
n = 1 n = 2 n = 3Bi2201 Bi2212 Bi2223
Bi-OBi-O
Sr-OCu-OSr-O
Sr-OCu-OCa-OCu-OSr-O
Sr-OCu-OCa-OCu-OCa-OCu-OSr-O
Bi-OBi-O
Bi-OBi-O
Bi-OBi-O Bi-O
Bi-O Bi-OBi-O
c
Bi2Sr2Can1CunO2n+4+xBi2Sr2Can1CunO2n+4+x
Electron diffraction analysis ofthe Bi-2223 superconductor
Electron diffraction analysis ofthe Bi-2223 superconductor
Space group: P [Bbmb] 1 -1 1a = 5.49, b = 5.41, c = 37.1Å; q = 0.117b*
*The average structure is known*
Bi-2223 [100] projected potentialBi-2223 [100] projected potentialSpace group: P [Bbmb] 1 -1 1a = 5.49, b = 5.41, c = 37.1Å; q = 0.117b*Space group: P [Bbmb] 1 -1 1a = 5.49, b = 5.41, c = 37.1Å; q = 0.117b*
RsymM = 0.12 (Nref. =42)RsymS = 0.13 (Nref. = 70)
Rm = 0.16
Rs = 0.17
a3
a4
Bi-2223Bi-2223
cut at a2 = 0 and projected down the a1 axis
cut at a2 = 0 and projected down the a1 axis
Space group: P [Bbmb] 1 -1 1a = 5.49, b = 5.41, c = 37.1Å; q = 0.117b*
a1 = a, a2 = b 0.117d,a3 = c, a4 = d
4-dimensional metal atoms4-dimensional metal atoms
Image Processing of Bi-2212Image Processing of Bi-2212Space group: N [Bbmb] 1 -1 1
a = 5.42, b = 5.44, c = 30.5Å;q = 0.22b* + c*
EM image from Dr. S. Horiuchi
FTFT
FT-1FT-1Phase extension
Phase extension
Image Processing of Bi-2212 (continued)Image Processing of Bi-2212 (continued)
BiBiSrSr
CuCuCaCa
CuCuSrSrBiBi
bb
cc
22
8844
11
Oxygenin Cu-O layerOxygenin Cu-O layer
Original image
Enhanced image
b
c
O atoms on the Cu-O layer
O atoms on the Cu-O layer
Bi-OBi-OSr-OSr-O
Sr-OSr-OBi-OBi-O
Cu-OCu-O
O (extra)O (extra)
Electron diffraction analysis of Bi-2201Electron diffraction analysis of Bi-2201
RT = 0.32 Rm = 0.29 RS1 = 0.29 RS2 = 0.36 RS3 = 0.52
RT = 0.32 Rm = 0.29 RS1 = 0.29 RS2 = 0.36 RS3 = 0.52
Space group: P[B 2/b] -1]; a = 5.41, b = 5.43, c = 24.6Å,= 90o; q = 0.217b* + 0.62c*Space group: P[B 2/b] -1]; a = 5.41, b = 5.43, c = 24.6Å,= 90o; q = 0.217b* + 0.62c*
Bi-2201Bi-2201
Influence of Influence of thermal thermal
motion motion ((BB)) and and
Modulation Modulation ((MM)) to the to the dynamical dynamical diffractiondiffraction
Bi-2201Bi-2201
Influence of Influence of thermal thermal
motion motion ((BB)) and and
Modulation Modulation ((MM)) to the to the dynamical dynamical diffractiondiffraction
Experimental B and M
B set to zero
M set to zero B,M set to zero
Sample thickness: ~5Å Bi-2201Bi-2201
The effect of sample
thickness
Bi-O
Bi-O
Sr-O
Sr-OCu-O
~100Å~200Å~300Å
Extra oxygenOxygen inCu-O layer