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Supporting Information for:
Conduction Paths in Cu/Amorphous-Ta2O5/Pt
Atomic Switch: First-Principles Studies
Bo Xiao,*,† Tingkun Gu,‡ Tomofumi Tada,† Satoshi Watanabe†
†
Department of Materials Engineering, The University of Tokyo, Tokyo, Japan
‡
School of Electrical Engineering, Shandong University, Jinan, China
1
S1. The structural parameters and electronic properties of amorphous Ta2O5 (a-Ta2O5) with the
densities of 8.11 and 7.68 g/cm3, respectively. a-Ta2O5 with high density is less stable, which is
consist with previous studies.1,2 Meanwhile, if the lattice constants are relaxed during the
optimization, the volumes of both amorphous structures will be slightly increased with the
density 7.79 and 7.55 g/cm3, respectively, following by the increasing of their stabilities.
However, the structural parameters and electronic properties have been only slightly changed
before and after the relaxation of lattice constants.
a-Ta32O80 (8.11 g/cm3)
a-Ta32O80 (7.68 g/cm3)
Ta-Ta bond length (Å)
3.20
3.27
Ta-O bond length (Å)
1.93
1.90
O-O bond length (Å)
2.83
2.70
OTaO bond angle distribution
ranging from 70º to 110º
70%
72%
Coordination numbers of
Ta(O7) : Ta(O6) : Ta(O5)
3 : 20 : 9
4 : 17 : 11
Coordination numbers of
O(Ta3) : O(Ta2)
25 : 55
26 : 54
Effective charge on Ta (e)
2.57
2.58
Effective charge on O (e)
-1.03
-1.03
Band gap (eV)
2.82
3.08
Energy (eV)
-1080.44
-1082.21
2
S1 (Continued)
(a)
(b)
3
S1 (Continued)
(c)
(d)
4
S2. The structural parameters and electronic properties of amorphous Ta2O5 (8.11 g/cm3) with
the quenching speeds of 4K/3fs, 2K/3fs and 0.1K/3fs, respectively.
a-Ta32O80
(4K/3fs )
a-Ta32O80
(2K/3fs )
a-Ta32O80
(1K/3fs )
a-Ta32O80
(0.1K/3fs )
Ta-Ta bond length (Å)
3.20
3.43
3.23
3.21
Ta-O bond length (Å)
1.93
1.90
1.91
1.91
O-O bond length (Å)
2.83
2.66
2.68
2.80
OTaO bond angle distribution
ranging from 70º to 110º
70%
69%
72%
83%
Coordination numbers of
Ta(O7) : Ta(O6) : Ta(O5)
3 : 20 : 9
2 : 22 : 7
3 : 21 : 7
8 : 23 : 1
Coordination numbers of
O(Ta3) : O(Ta2)
25 : 55
25 : 55
25 : 55
40 : 40
Effective charge on Ta (e)
2.57
2.58
2.59
2.59
Effective charge on O (e)
-1.03
-1.03
-1.04
-1.04
Band gap (eV)
2.82
2.84
2.96
2.82
Energy (eV)
-1080.44
-1081.75
-1082.94
-1086.13
5
S3. In our previous study, a chain of interstitial Cu atoms in δ-Ta2O5 film forms a conductive
path in the heterostructure of Cu/δ-Ta2O5/Pt. As seen in this Figure, the local density of states
(LDOS) around the Fermi level consists of Ta, O and Cu atoms, but the corresponding partial
charge density is mainly delocalized on the alternate Cu-Ta bonds. Therefore, in the present
study, we propose that the alternate Cu-Ta bonding is considered to be the main conduction path
in the δ-Ta2O5.
Cu
Ta
6
S4. The density of state and partial charge density around the Fermi level (from E F-1 to EF) at
0.01 e/Å3 isovalue for the structures with (a) alternate Ta-Cu (Ta32O77Cu3) and (b) continued CuCu atomic chain (Ta32O76Cu4) in amorphous Ta2O5
Cu
Ta
(a)
(b)
(b)
7
S5. The density of state and partial charge density around the Fermi level (range from EF-1 to EF)
at 0.01 e/Å3 isovalue for the structures with interlaced (a) trigonal, (b) tetragonal packed and (c)
the thinnest Cu nanowires in amorphous Ta2O5 (7.55 g/cm3). The insets show the corresponding
Cu filament structures.
(a)
(b)
8
S5 (Continued)
(c)
(c)
9
REFERENCES AND NOTES
1. Crooks,D. R. M.; Sneddon, P.; Cagnoli, G.; Hough, J.; Rowan, S.; Fejer, M. M.; Gustafson, E.;
Route, R.; Nakagawa, N.; Coyne, D.; Harry, G. M.; Gretarsson, A. M. Excess mechanical loss
associated with dielectric mirror coatings on test masses in interferometric gravitational wave
detectors. Class. Quantum. Grav. 2002, 19, 4229-4229.
2. Penn, S. D.; Sneddon, P. H.; Armandula, H.; Betzwieser, J. C.; Cagnoli, G.; Camp, J.; Crooks,
D. R. M.; Fejer, M. M.; Gretarsson, A. M.; Harry, G. M.; Hough, J.; Kittelberger, S. E.;
Mortonson, M. J.; Route, R.; Rowan, S.; Vassiliou, C. C. Mechanical loss in tantala/silica
dielectric mirror coatings. Class. Quantum. Grav. 2003, 20, 2917-2928.
10
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