
9-11CMOS Integrated Gas Sensors
Although metal oxides are popular as the sensing layer, a well-known problem with these sensing
ma
terials
is th
eir
la
ck
of se
lectivity
. i
s
sit
uation
is us
ually
de
alt
wi
th
by usi
ng
an ar
ray
of se
nsors
co
vered
wi
th
di
erent
se
nsing
la
yers,
mu
lticomponent
or pa
ttern
re
cognition
al
gorithms
(e.g., pr
incipal
co
mponent
re
gression
(P
CR)),
an
d
mu
ltiway
an
alysis
or by do
ping
th
e
se
nsing
ma
terials
(e.g., pa
lla-
dium
do
ping
ma
kes
me
tal
ox
ide
mo
re
se
lective
tow
ard
hy
drogen)
. i
s
do
ping
ca
n
be do
ne
by ei
ther
ph
ysical
(e.g., co
ating
th
rough
sp
uttering)
or ch
emical
(e.g., wi
th
pr
oper
ch
emical
so
lution)
me
ans
. i
s
fu
nctionaliz ...