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1. tt: I --,*';r,.t77 *\.47 F characferisticsovel' a lvidc r angc 0I Electronegativeerlasmra*sherlth collisionnlitY I { . ' ! ' as s r ' r ianr ' - , s ' t r . . ' \ s lan i n c . i a d 2f,' l ] o r g h e i r , i \ I . t i s h g h a b a d i l [ tDel.tur.lrnenl Kartri Rrunr:h, Jslatnic ,'ltttd Universih. Karoi, Iran 6lf'lrlit,.sit:s, -\^c:iettc.e.l:'crctrlq', .P|,,',,,,.,.P/i1.sic.;Re'se.ttl.cltCelttre,5'ciettc:ettric|[|c'st:tlt.r:l'l}Jrottch,'[s]untic'4zttc{[jttil,et.s - llc c c r nb( ) r 2i) 09iAc r : c p t c c l . S J u 1 l , ', l 0 l t ) / l : 'l b l i . r h c r i : 2 0 S e p t c m b c r 2 0 l 0 i{ c c c i- , - c ij: ;\bstrrtct . l-h cn oll.n ctttt.lti:;i i. llt t hr c gionc r | scc 1io llr;ttthcl'c]o c i1y or r Lhc 1lr t l1. i1er ll. t hc 1r os i| i t , e-f ' ir:ct:lil1 'llcg atiV eiolt t c t ll1ler at it r - eenc llic i1at it , c l i o ; l C . . l l t c c t l t r a 1 i r l t l t ] n t h c l ] o S i 1 i \ 'c j r l l l . t : 1 o c i [ y arc inlcsli!j:ricrl fitl tliffcrc t I lc1 )t.cst:ttrlt:o{.tir c c o] lis i. : lt ls lc lr ] s t ot ht lt iir r liI li.s l t r r l g t l r c . s h c : r L ] l t | r i c k r l n] () fep fon ornrcc i rr h i g1r c r .oll r s ion ar uplit udc . c l ,A C ' s . 5 2 I5 .l )i : 5 2.,10 _52.20 v; 1(h; 1:l 52.-50 g D I{r:vrvords:Lllectronega/it,e ili.schlr:4e, Plct.srttit sltedtii;Genet'ctlr:ed }loht)tctitet'iott l. I ntro rlur:fio rr I I o u 'c v c r . l h c c l e s t i c c o i l i s i o l s b c t . , . , 'c c t h e p r r : i fi r c n i o n s l i n t l n c L r t r - l li t a r : k t : r 'o i u i (c l . r n ] r c c r i s L c d i r r t l r c l l.lnr lclslln rlrnl titr: sl t r : t it lr r r nut r r r rrrr f lt llr s nlr lr or r l,l i t , lf s l r c l i l r r i o . i o l . I n g c n c r i r J i.v c c i , r n - s i r i clr i t t l i . : l t i t s r r i v l tl f ic:i i; e )ricilii:ii-'iLrce c ir c lir iv ioi of lt llis t r iirr i' r Lllir r l . : ilr icn coiliston ct.L)ss cctlorl ltris lr lrrrttci llnv tl,-.lli:tt- lnclitrn is a iirnction of s hc at lr c lt allc t c r is r ic s [ 1- ( r J t l e n c c <) np o i i t i v c i 0 n v c l o r r i t , v1 2 ] . [ 'l Ir,: r,'lcctrit: otctr{i r l ol lhc r r ' r t ll is negat iv c w' it h r c - p 1 ] c r c .r l c f t t c L r s r r l r n c l c c t r o n c g i t t i v c h c a t l rr c . g r l r r o s spcct to th c p lLrsuta or c . - i- het c lolc ,t he pos it iv c :r c n s c r)r'er a r.viilcrarrgeof: collisionality and inr.estigate tirc accelcrateto\\.itf(i,elcctrons rcpcl from tlte rvall, autl i n t l u c n c e o f t h e d i s c h a r l l c p a f a n l e t e ro n n t i r c t r - ] s c L r p l c conse qu cn tiya no u- lleut r alr c gjot r is f or - nr ed ar 1l ) e nc v r u i a b l c o f p l a s n r as h c a t h . l n S ec . 2 , u , c p r c s c n t t h c l)lit s n]abo un cla rits. ln f t r c t , t his r c gior r is r es pons ib l c : g o v c m i n g e q u a t i o l t sa r r c li n t r o c l u c ct h c s c t o J 't l r n t c n to t he ch er';rclcr.ist ic : sit r le t ior r of t he lt lus t r iaiv iti i s i o n l c s s ( l l r i l l t i l i c - \ .I i r S c c . J . l v c s o l v c t h c e q r n t t u r r s of llc absortriitg surro rrttlr r . r wall- I n adr lilir x , t hc pr es c nr : c g l u r l i n v c s t i g i r i ct h c l t i t r v c r l i r r v c l c p c r r r l c n co f 'c o l l i s i o n y oi the n eg ati\/c ioils in t hc dis c har ge has gr er t inf iL r - c r O s - s ec i t o n a S \ [ e i l a s n e g i r t i \e i o r r c o n c r n t t i L t i ( ) la 1 l ( l t cncc olt Lhis tron-ncutralregion. T'he plasrnls contallt- l i e . q a t i v cl o l l t c | i i p c r a t u r eo n t i t c p o s i t i v c i o n ! c l o c i t y , e l c c t r i c p o t c n t i a l a n c l t h e s h e a t h t h i c k n e s s .'f h e t l t a j n ing tlie nersati\,e ions arc r.viclely, used in inciLrst.ry sucli zrsd 11 etchin g ol silic on- bas c ( ln) at c r ials l7- 111. ' I h c are srunl]tarized Scc. tl. rcsLllts in shceth eclgc sepaterting the ncutral plasrntl fr.orn the non-ueutralsheath is govefned by thc BolilI cr.itcr.ion. 2. Ilasic equationsand assrunptions T hc p rescn c--c o f'thc negat iv c ions nt odif ies lhis c r r t c - rit n an cl as an initia l v aluc f br pos it ile ion r , c ioc i t y \\'e assuilrc that the nesative specics ohcy tlic onc sh ou lcl nsitlertlr at r r r odif ic at iot r . co []oltznran rclati(l11: One o f th c iru ltc r lr ant har ac t er is t ic s t he s heu t h c of ic,L t - / 1 , t 's 1 t is thc lach ol' the ionizing r:ollisions. l'l.rc irtnrzrnli r ( l) 0 [ ; . '- l , / \ lP tnt : unficc p ath is la r c c l t hln t he s c alc of t hc s lt c a t l r / e(r\ at t d ltcrr,:ctlrc flur o f t hc po: r it iv c ion r c r t lr ir r s c : , 1 1 1 ri - ? r i e x P {; ; ,J . ( ') . ) s: t nrt. l.'h critle r ri il 1. [l2] _s t Lr r ller l r c lc c lr . Lr pr t s r t r r t '_ ar \t / lt llt sttta,tltctrtltiir lli c I r c Sc t r i: r :it i' t lr t eollt , s j( , r 1S'r lr u h c r . er r , - : , r n t i t t p i r f c t l t c r . i t r r r r b crrl - r t s i t i t so l ' r : l c r . : - l c r' ,iiir :hlltir liLrtlro r,; r . lt lr inir , : s iir : lt t r l , : it illLt c r t , ; r t l lric llt e 1 r 'o ra n c ll c i l i r t i r e i o n a t r j t c s h e i r t l tc r j c - c , 7 . a n r l / , l i r , : r liie Ctrl-sS Scctii'n 11 ilt Llrr ) n ihc s lr . ' , r r itl! , llllit llO it . I t i c tlte clcctronsitn(l llijgatt\c iolts tclltIctittlles. tc.-sllcc- Itcl Ii3 1. th e slicath r c gion ol' i] n elec t f Lijt c ger ir ,djs - e t i v c l y a r t d 1 6 i s t h e e l e c t r i c p o t c n t i a l i n t h e s h e a t l rr c - char.g els irrr e stig ar ed in r hc iibs e e of c ollis r ( ln s . nc g i o r r . I k : r 'ci t i s a s s t u - n c t h r t c a c h p a r t i c l e s p c c i c sp o s - d ir t-- gc € . hat ' L- L , r c::p c'l rl1 rq :1 p l rL -rr: gt 1.:r S. Kt Ya::icr iil -scs,s t l : . . , I i .r';:r rf \.,.1 i l .,r .i !.:.1il r c.r r I n l h e s h e a t h . i h e r e i s n . r i o n r z i n q c o i l i s i t - . na n c l l e l . 1r 1 1 8 ) 5 l ,1 t 5 2 i 0 6 l t l t c r c f o r . c h c p r - r s t t i r eo n f l L r r i s a n i : r v a r i a n c cq u a u i l - i i f i i ] . : t r 9 :l l /r I 4 l rl l l 0 6 iV,