SON(rcHEMICAI, SYNIIIISIS AIID CIIARACTERIZATION OF PR.ECT ...

ctuic mat.rials like zno, ZtOu, erc., acr a! a sdi@ndrcting ud have b€en pt paEd
by tM.rcw ttr!@ likc spurcri4,q ' CvD ed tbmri spou!|i6,r $tapri!1i!&ro
so!8cl oulEsr5 Dd othd mcihods. Anong emic m5&nah, zno w6 the
first studied fo. sNing, b€caue tbe @nducliod prce$ in th.& maEnah can depend
hsvily on glin bou&ri*. Th€ gs sming .hatad€nnict of the ZnO lhjn IilG wd
$duaGd rhrcugb rhe 8s F6iriviry (sJ, d.fined by: i
s! = R'/R!
wh@ P! is th. iilm 6i$anc. in at dd P{ i5 the filn rcsist{c. in th. PEence of tbe
gd, ThB S. b noE thu sjty for EdEins rr*s, siE llc !.Mr sislone dcc66
in a FducinS.llosphre. Thc s4ilivity i5 tlso defned 6 R.Ait { in lhis csc ss is
Iess thd uiiy for educing 8q!.
1.4.2 Usitrg Dopants to f,trhrrce Sctrsor Sel4tivi.y
DEing css sdsing n*Gh@t, dqe!* in Fsista'e t!*cs pl@ shd coarqi
srbstate is €xposd io sqsing 8s d@ ro idduction of €l€cirons inlo @nduclion buds of
odalond. Gigw 8). Bease olthis lack of elalivity, a nMber of tchnjqu.s Mre
adopted to hinihjt lhc sigt l obt iFl ftoi uddirEd ge. On otmon foi@ ro
inirod@ $letivity i o a n.Ll oxid. $uor k additioD of $itablc melallic dopet hto
O. @t rial. Foi exmple. doping s.o wnh paltadiu lhat hs ben used as a cat l/sl
duing lh. oxidation of m.thd. uu.lly incrcs.s lhe s6itivitv towdds lhis gss in the
I. me cs6 il is rcl n@. Fd tupl., BirLcf€ld et ,1.," noted soDc ibporlanl
chde* in Tio:-bsed *nsos for CO .nd hy.ltos.n det€clion, whe. th6e dcvices weE
tuodified wilh AlrO3 or Y:Or dmugh a b.ch&i.at mixin8 pto4s vh.n Ahos wa
idrcduc.d ro thc sysr.m, rhc EsroN B only dependsl on the @n@nFadon of
hy{tro8d prcsot ed ws itudsitiv€ toqsds CO, whet d d additi@ of Y:Or
ir@d the s.lecliity lowdds CO. ntis cnld.enent ws thought io occu eithd
threugb oodiftelioB of rh. spae ch{gc cgton ol tii.r4 or bv .Ienna the gain
boun&y @ acrl or nek fotuatiotr tet@n th. cry$rllit s Dopdll hNe .le be€n
ued iD order to inhbn erarn Stosah duing hstins ln s srudv bv Bonrnr er al '0
niobiu dd lst lu wrc introd@d into TiO, beou. of th. sinild ionic aia or the
.alioB. Nol only did thc doped frlms h!v. a moE p.sittcnl eEre phe in tbe
Pr*ne of high c6FnnFs, bul th€ av.dg. gEin siu d*c.s.d &on 200 m i. pw
tl