Chemistry Reference
In-Depth Information
a
c
e
4.0
4.0
V b =400V
R L =3.25M
C =4.38
F
R L =3.25M
μ
V b =300V
C =4.38
4.0
Ω
Ω
F
R s =200k Ω
μ
L
R s =200k Ω
R s =200k Ω
9.86 k Ω
1.71 M Ω
open
250 V
3.0
3.0
3.0
985 nF
4.38
300 V
μ
F
3.25 M
Ω
400 V
2.0
2.0
2.0
500 V
4.17 M Ω
8.87 μ F
1.0
1.0
1.0
800 V
6.36 M Ω
20.5 μ F
0
0
0
0
100
200
0
100
200
0
100
200
Time (s)
Time (s)
Time (s)
b
d
f
80
80
40
60
calc.
60
30
exp.
40
exp.
exp.
calc.
calc.
40
20
calc.
exp.
20
20
10
0
0
0
0
10
20
300
400
500
1
2
3
4
5
Capacitance C (
(
μ
F)
Voltage V b (V)
Resistance R L (M
Ω
)
Fig. 6.5 Temporal profile of current oscillation and its period dependent on parallel capacitance,
applied voltage, and resistance R L for [Ni(chxn) 2 Br]Br 2 measured at 90 K. (a) Temporal profiles for
various capacitances (open, 985 nF, 1.38
m
F, 8.87
m
F and 20.5
m
F) at V b
¼
400 V, R L
¼
3.25 M
O
,
R s
,(b) The period values are plotted by filled circles .The solid line indicates the periods
calculated by Eqs. ( 6.1 )and( 6.2 )(c) Temporal profiles measured for various source voltages at
C ¼
¼
200 k
O
,(d) Periods dependent on the source voltage V b .
(e) Time profiles measured for various source voltages at V b
4.38
m
F, R L
¼
3.25 M
O
, R s
¼
200 k
O
;
(f) The period dependent on source voltages V b . The data of figures (a)and(b) are from [ 6 ]and
others (c)-(f)from[ 19 ]
¼
300 V, C ¼
4.38
m
F, R s
¼
200 k
O
( C ¼
985 nF), the oscillation does not occur. In these two cases, the circuit is stable
at the crossing point of the load line (shown by dotted line in Fig. 6.5a ) and the I - V
curve. On the other hand, with the large capacitance ( C
r
F), the oscillation
appears, whose periods are roughly proportional to the capacitance of the parallel
capacitor. In Fig. 6.5b , we show the capacitance dependence of the period by solid
circles compared with the calculated values using Eqs. ( 6.1 ) and ( 6.2 ). The calcula-
tion reproduces the experimental results satisfactorily. However, the adapted model
suggests that the oscillation should appear even at small capacitance. This discrep-
ancy between the experimental results and the calculations might be ascribed to the
time dependence of the nonlinear resistance behaviors. The sudden change in
resistance is similar to a phase transition from insulating to metallic states. When
the phase transition develops by domain growth, the formation of macroscopic
domains is governed by the time of domain growth. As a result, the I - V curves and
resistance would be time dependent. In the metal-insulator transition in a 3D Mott
insulator (VO 2 ), the domain growth is observed in real space and its growth limits
4
:
38
m
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