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 ? 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 Electrons by Different Elements Scattering of X-rays and Electrons by Different Elements Relative scattering power O O O O Sin  / Bi Sr Ca Cu X-rays Electrons

Bismuth bi-layer Perovskite layer Bismuth bi-layer Bi-based Superconductors n = 1 n = 2 n = 3 Bi  2201 Bi  2212 Bi  2223 Bi-O Sr-O Cu-O Sr-O Cu-O Ca-O Cu-O Sr-O Cu-O Ca-O Cu-O Ca-O Cu-O Sr-O Bi-O c Bi 2 Sr 2 Ca n  1 Cu n O 2n+4+x

Electron diffraction analysis of the Bi-2223 superconductor Electron diffraction analysis of the Bi-2223 superconductor Space group: P [Bbmb] a = 5.49, b = 5.41, c = 37.1Å; q = 0.117b* *The average structure is known*

Bi-2223 [100] projected potential Space group: P [Bbmb] a = 5.49, b = 5.41, c = 37.1Å; q = 0.117b* Space group: P [Bbmb] a = 5.49, b = 5.41, c = 37.1Å; q = 0.117b* R symM = 0.12 (Nref. =42) R symS = 0.13 (Nref. = 70) R m = 0.16 R s = 0.17

a3a3 a4a4 Bi-2223 cut at a 2 = 0 and projected down the a 1 axis cut at a 2 = 0 and projected down the a 1 axis Space group: P [Bbmb] a = 5.49, b = 5.41, c = 37.1Å; q = 0.117b* a 1 = a, a 2 = b  0.117d, a 3 = c, a 4 = d 4-dimensional metal atoms

Image Processing of Bi-2212 Space group: N [Bbmb] a = 5.42, b = 5.44, c = 30.5Å; q = 0.22b* + c* EM image from Dr. S. Horiuchi FT FT -1 Phase extension Phase extension

Image Processing of Bi-2212 (continued) Bi Sr Cu Ca Cu Sr Bi b b c c Oxygen in Cu-O layer Oxygen in Cu-O layer Original image Enhanced image

b c O atoms on the Cu-O layer Bi-O Sr-O Bi-O Cu-O O (extra) Electron diffraction analysis of Bi-2201 R T = 0.32 R m = 0.29 R S1 = 0.29 R S2 = 0.36 R S3 = 0.52 Space group: P[B 2/b] -1]; a = 5.41, b = 5.43, c = 24.6Å,  = 90 o ; q = 0.217b* c* Space group: P[B 2/b] -1]; a = 5.41, b = 5.43, c = 24.6Å,  = 90 o ; q = 0.217b* c*

Bi-2201 Influence of thermal motion (B) and Modulation (M) to the dynamical diffraction Bi-2201 Influence of thermal motion (B) and Modulation (M) to the dynamical diffraction Experimental B and M B set to zero M set to zero B,M set to zero

Sample thickness: ~5Å Bi-2201 The effect of sample thickness Bi-O Sr-O Cu-O ~100Å ~200Å ~300Å Extra oxygen Oxygen in Cu-O layer