Supporting Information for:
2
5
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 Ta
2
O
5
(a-Ta
2
O
5
) with the densities of 8.11 and 7.68 g/cm 3 , respectively. a-Ta
2
O
5
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/cm 3 , 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.
Ta-Ta bond length (Å)
Ta-O bond length (Å)
O-O bond length (Å)
OTaO bond angle distribution ranging from 70º to 110º
Coordination numbers of
Ta(O
7
) : Ta(O
6
) : Ta(O
5
)
Coordination numbers of
O(Ta
3
) : O(Ta
2
)
Effective charge on Ta (e)
Effective charge on O (e) a-Ta
32
O
80
(8.11 g/cm 3 ) a-Ta
32
O
80
(7.68 g/cm 3 )
3.20
1.93
2.83
70%
3.27
1.90
2.70
72%
3 : 20 : 9
25 : 55
2.57
4 : 17 : 11
26 : 54
2.58
-1.03
2.82
-1.03
3.08 Band gap (eV)
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 Ta
2
O
5
(8.11 g/cm 3 ) with the quenching speeds of 4K/3fs, 2K/3fs and 0.1K/3fs , respectively.
a-Ta
32
O
80
(4K/3fs ) a-Ta
32
O
80
(2K/3fs ) a-Ta
32
O
80
(1K/3fs ) a-Ta
32
O
80
(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)
OTaO bond angle distribution ranging from 70º to 110º
Coordination numbers of
Ta(O
7
) : Ta(O
6
) : Ta(O
5
)
Coordination numbers of
O(Ta
3
) : O(Ta
2
)
Effective charge on Ta (e)
Effective charge on O (e)
Band gap (eV)
Energy (eV)
2.83
70%
3 : 20 : 9
25 : 55
2.57
-1.03
2.82
-1080.44
2.66
69%
2 : 22 : 7
25 : 55
2.58
-1.03
2.84
-1081.75
2.68
72%
3 : 21 : 7
25 : 55
2.59
-1.04
2.96
-1082.94
2.80
83%
8 : 23 : 1
40 : 40
2.59
-1.04
2.82
-1086.13
5

S3.
In our previous study, a chain of interstitial Cu atoms in δ-Ta
2
O
5
film forms a conductive path in the heterostructure of Cu/δ-Ta
2
O
5
/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-Ta
2
O
5
.
Cu
Ta
6

S4.
The density of state and partial charge density around the Fermi level (from E
F
-1 to E
F
) at
0.01 e/Å 3 isovalue for the structures with (a) alternate Ta-Cu (Ta
32
O
77
Cu
3
) and (b) continued Cu-
Cu atomic chain (Ta
32
O
76
Cu
4
) in amorphous Ta
2
O
5
Cu
Ta
(a)
(b)
(b)
7

S5.
The density of state and partial charge density around the Fermi level (range from E
F
-1 to E
F
) at 0.01 e/Å 3 isovalue for the structures with interlaced (a) trigonal, (b) tetragonal packed and (c) the thinnest Cu nanowires in amorphous Ta
2
O
5
(7.55 g/cm
Cu filament structures.
3 ). The insets show the corresponding
(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