
12-11Hydrogen Gas Sensors
acoustic wave [20]. To modify the propagation of SAW by changing the electric conductivity, semi-
conducting
MO
Xs
su
ch
as WO
3
[21], InO
x
[22], and SiN
x
[23] are used. In order to improve the sensitiv-
ity
of th
e
se
nsitive
la
yer
in SA
W
de
vices,
th
e
ga
s
de
tection
la
yer
is na
nostructured
to in
crease
th
e
su
rface-to-volume
ra
tio
an
d
he
nce
ha
ving
mo
re
su
rface
co
ntact
wi
th
th
e
hyd
rogen
th
at
pe
rmits
a fa
st
re
sponse
to th
e
ga
s[24]
. Na
nostructured
Zn
O
as we
ll
as pa
lladium
na
nowires
ha
ve
be
en
in
vestigated
[2
5,26]
sh
owing
an en
hancement
in th
e
se
nsitivity
co
mpared
to l
m
st
ructures
of th
e
sa
me
ma
teri-
als
. To im
prove
th
e
se
lectiv ...