Upload
eduardo-antunez
View
215
Download
0
Embed Size (px)
Citation preview
8/10/2019 Electrical Switching in VO2 Sol-gel
1/2
8/10/2019 Electrical Switching in VO2 Sol-gel
2/2
8
a
4
4
2
0 10 20
30
40
5
60
V N
Fig.
3
Variation
of
the threshold voltage,
Tih
with temperature
is higher than the transition temperature,
i e
as long as the
current is larger than the holding current , IhZO6mA
(point
C)
Beyond this point, the film switches back to the
OFF
state (line CO)
This electrical switching is due to the well know n in sulator-
metal transition
of
VO, It is thermally driven and the
threshold voltage depends on the amount of heat required to
reach the transition temperature This amoun t depends on the
difference between the ambient tem perature and the transition
temperature,
T ,
Therefore V decreases regularly when the
temperature increases (Fig 3 The switching behaviour disap-
pears when the room temperature reaches T , The whole film
is then in the metallic state
Electrical switching devices can be made easily with
V O z
thin films deposited from vanadium alkoxides Th e switching
mechanism is the same as previously reported for devices based
on aqueous
V,O,
* 18H20 xerogels In this case, a
VO,
filament was electrochemically formed through the xerogel
upon applying an over-voltage to the device The diameter of
this filament was difficult to control as it was not formed
homogeneously between the gold electrodes It was therefore
difficult to build devices showing a given thresh old voltage
In this paper, the whole film is made of
VO,
The size of
the active materials and the threshold voltage, T/h, depend on
the geometric characteristic of the
VO,
film between the
electrodes, R ps /A where R is the resistance,
p
the bulk
resistivity, the interelectrode separation and A the electrode
contact area They are defined by the ge ome tnc characteristics
of the mask used for the deposition of the gold electrodes
Reproducible results can then be obtained when these charac-
teristics are carefully controlled Mo reover, the transition
temperature can be easily modified when doped VO, films ar e
used Such dop ed thin films can be made easily by mixing
molecular precursors with the alkoxide solution We have
shown, for instance, that T , decreases with high-valent cations
(NbV,Wv ) a nd increases with low -valent cations such as
The switching behaviour of
VO,
thin films, recorded on an
oscilloscope, can be observed continuously for several weeks
or even months (Fig
2)
This points out the high reversibility
of such devices based on
V O z
thin films Bulk materials do
not withstand many cycles Th e structu ral distortion associated
with the insulator-metal transition rapidly leads to a degra-
datio n of the materials Large crystals break after few cycles
only
A11116 8
References
1 J Bullot, Gallais, M Gauthier and Livage, Phys Status Solzdz
A,
1982,71,k l
2 J G Zhang and
P C
Eklund,
Appl
P h y s 1988,64,729
3 G Zhang and P C Eklund,
Mater Res
1993,8,558
4 Livage, Chem Mater 1991,3,681
5 G Guzman, R Morineau and Livage,
Muter Res Bull
1994,
29,509
6 G Guzman, F Beteille, R Monneau and
J
Livage, Eur J
Solid
State Inorg Chem 1995,32,851
7
F
J M o m , Phys R e v L e t t
1959,3,34
8
Livage, G Guzman, F Beteille and P Davidson, J Sol-Gel Scz
Techn n
press
Communication 5/073491, Received 8th November 1995
5 6
J
Mater Chem 1995, VOL 6
Publishedon01January1996.DownloadedbyFACDEQUIMIC
Aon12/08/201400:50:18.
View Article Online
http://dx.doi.org/10.1039/jm9960600505