Ghare, D B

Jani, V A

Jani, VA

Ghare, DB

Name not available

Effect of Impurities on Tcr of Tin Oxide Thin-Films

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Indian J. Phyt. 52A, 293-298 (1978)Effect of impurities on TCR of tin oxide thin filmsV  A .Tant aiul D  B  OiiiAin'iDepnrlweni of High \'oUugf’ Eugincarrng, Ivdimi Jih^ iHiitc of Srievcc, Ba7igaJore-(i^0()\ 2{JifGcived 7 JnHp 107(1, rcrififd 2 Jinip 1077)Jrtm, oopp;:«- and Miilphur ion impuritioM wove intiodiu-od in iUi‘ laliitii* of ]i,eavily aiiiiinony dopod lin oxido thin liliiiK. di-^ poHitod hy tho cliomicaj vapour drpo.siiioii iinhinqno Tho oltW’-t of tln^  pii-sriuio of thosc^  additional inipiu itioH on tho toinpi ratnro c;ocfltcuMit oi'rewi.S' tanco (TCB) of Hndi liJms vvafi Htudiod Jt w a.s fonnd tUai, ihc Tt’iB. intiroariod in magnitude in ease of tJio iiitroduetion ol iron ions, and teiuled to become nogativi  ^ in ( ane of tlxe introduction of copper ions, while the introduction of suli»]nir ions seemed to make it moi’e. positive.] .  I n tr od u c tionThin films of semiconducting tin oxide an^  known t.o have numerous applications in various teclmologies (Ku/netsov 19(>0, Dodd 195(») snch, as high stainlit> resistors (Burket lOfil), 'Pi'an.sparent olectrod,es lor Semiconductor and liquid crystal devices (Tlaniiey 10(i0, Bosnidl Waghorne 1973), Transtuiront heating elements foi aeioplane and antoiuobije windshields (Raymond Dennison lOfiS, Y'onng 1955, Maniot pI al 1958 and Thomas 195S) as well as (3iemi(,al and indus­trial glass/cerainic wari'S (Kuznetsov H al 1959, 1957, Little 1953), Transparent abrasion resistant coatings (Ward 1975), Elotdjsm tubes (Schmidt & llohiMt 1958, RCA Coip 1973), “Phosphors (Otani it, HaSegawa 1957, Caisov 1959, (N)mx>agnie des Lampes 1954), Printed Circuits (Saiinders 195G), (;tcThin films of semiconducting i,in oxide can bo dex>ositcd on glass and ceramic substrate,s by pyiohydrolysis of tin cblondi’- solutions on hot substrates (Goiuer 1953, Tmai ]9Gl>, Arai 1990) or by Vacuum sputtering techniqui's (Sinclair al 1965, Vosson cl al 1971, 1972)In case of certain applications such as high stability resistors (Burkett 1961) aud low temperature thermometry (Lyon & Geballe 1950); the temperature coefficieut of resistance of suidi films play an important role We have stiiduxl the effect of introduction of iion, coi)pej and sulphur impurities on the temiiera- ture coefficient of resistance of such filmsProsontly with Gujarat Elcptririiy Board, Ulcai, Gujarat.293294 V .  A .  J a n i  a n d  D .  B .  G h a re2. ExperimentalTliiii films fjf Hi-mif.fmdiiu tint? tin oxi(L‘, wore (lopo,sited on glass samples by tlie oheniical vapour deposition tofJiniquo as flescril)e<l earlier (Hamamijam /t. OJiare U)74, i07d) CUeaiuxl glass samples were lioated in an et’ctiic liiinaee to dc^ sii'od substrate t(?mporature (550‘’C) The bot substrates were then sprayi^d with tht^  chisired tin ehloridc! sohitio]i, when a thin film of tin oxide gets deposited on th(r Hurfaeo- o( tlie substrate by the hydrolysis of tm chloj-ide on tjie hot sur/ace (Aitcliihon 1054, Kim & Laitinon 1975) Samidos witJi identic-al film composition b\it with widri vai iations in surfaecM'esistiviiy values Were nrepared by eontrolling th(? film thiekiK'SS ol the deposikd film A solution of stannous eliloride (AK  ) in hydioehloMe arid and doptid witJi 2 At percent of antimony was uscsl as tlu^  paient solution to which any othei' desii’ed impurities were added in appropriate  ^eone,(‘ntrations li'on and toppe r^ ions were iiitroducod by doping the pareoii solution with appropriate amounts of their chlorides while sulphur ions were nitrodueed through dilute sulphuric acidAfter deposition, the samjjleS w'ore annealed in an electric oven at 150d-l''C for 75 hours for stabilisation of llie resistivity of such films by tlieiinal annealing (Xlamanujam & Ghar(‘ 1974) Contacts wore then miule by ekotroplating niekel at desired positions and tln^  loads wm’e then soldered on io this riJcLeh The niMasuroments ol temperatiu’i^  eocificieiit of n s^isiancei of the film samplers were (uinu'd ont in tlu^  trunporatuiv rangi^  from room temxiei atuii* to ilO“C with tlui ludj) (d’ a OiSAW Wheatstone hi'idge and a constant t('mi‘erair'r(‘ oil bath theimostat3. R esults and R iscussionThe x>lots of the Tmnperature Coi f^itcient ot Resistance  ^ (TCR) o( the tin oxide filin'^  as a function of surface'' resistivity for variems eeimjiositjons are* sh,e)wn in figure^ s 1 io 3Tt can be' sensi from figurei 1 that in eiaSc* of the'* pi’e^ serico ol iron as the impfiii ity ions, ther TCR of almost all tlie films have? ve^ ry high magnitude (irre?spective of its Sign) Sue;h high magnitudes ol TCR ai'e eletrimental in certain applications such as high stahility low TCR re?sistors. However, in case of e'e?rtani othes' airpJicatioiis ,suc]i as the low teunpcratiirc' thermometry, the higlies- magnitudes of TCR might r^rove to her useful111 case of copper as the impurity ions (figmo 2), and at 0-01 pw cent impurity iem concentration, the TCR is positive' in magnitude in most case*s, evem upto a surfaces ivsistivity value of about 1500 O/sq However, when the impurity ion coiioeMitration is ineivt^ asesl tei 1 jiLS' cent, almost all samples with surface resistivity valuers higher than e?ven about 200 Q/sq. have exhibited negative TCR. TJie^  X“ne?S(‘nce' ol cojipe'r impurity ions theirefore seiems to influence the TCR to becomeTCli of tin oxide thin films 295J. Vuuiitioiia 111 Tmiipoiatuio Cuoliicioui- oI ItobibLuiico an a luiujiioii uf &uifut’C i-o.siytiviiy lur iron an iho iinpuiiiy ioiiid.ii.‘g.iUvc. at 1..W mii’faoo msi.slivity valuos Ihirlhi r^, it may al.s«. l.o itotcHlluiK^  tl'at at 1 Ijoiit iioiipor ion imxmnty conemitration and at biU'faoo I'ortiMtivity valim,s loivvr than ahimt 200 12As4 > magmUiclo o1’ TCll Jor all mu mimph'S IS very small 100 ppm/‘*C) and positive111 ease oi‘ sulphm* as the impurity ions, it eau ho soeii from figinc 3 tb.at at (>■ 01 por cent impurity ion coiUioiitration, the TCR of all tho samiilos (with a spriiail in siufaco resistivity value from 50 to 2000 0 /s (i) is veiy small in magni­tude (150-150 ]ipm/''0). Howiiver, as the eoneentralion of tlu; sulphur iiiixiurity iojis ib inu-ease<l to 0-1 x^ a’ ee,ni, tlu» magnitude of TCK also mu'eased suhstan- tially (300 to 500 i i^nnlfC) and its sign heuamo distmetly xiositiveTin oxide is knomi to lie a bi'oad band semieonduetor. Wlvni tlie mateiial is dolled with nontaveliiiit donoi impuiity ions it becomes an a tyiio seiiiicondin;- tor. Noav since all the donor imxiin-ity ions are expected to liavo donated their296 V .  A .  J a n i  a n d  D .  B .  G h a re2. Vuimiloiih 1 1 1  of IluHlhlauec! as a luiK-Lioii oi .surface rcsisliviiyJur LU|>pci as tlic iinpunty ioijb.SubiU ute lemp^^raturi? 5 50  C3. Variations in TcmiJoraturo Coellicionl of Kosibiancc uu a function of surface reaistiviiy for sulphur as the mipuiity ions.T O R  o f  tin oxide thin filim 297extra  electrons at room t(nup>.irtiturii and li' tl'.o niatovial is luaivily doped, the immbor ol eliargo earner,s is ex iv ite d  to lx; ip.di ixin<li*nl ■»[ ti'inperatnix, (armind R T )  Tko material is tlieridoie i»xpeeteil to exliilnt a small jiositivo T C R  arising Irom tlv' .scattering oi tke eliargc^ eairiers as a result of ineiX'asi'd lattice vibrations at liiglior tempv'iatuius Sue!', a Ix'l’.avioiM is md.ixid exlubitisl by tliUik sell!icondueting tin oxide tliin films 'I'lvs-i fon '. \vb,en tbe niati rial is lieavily doped with pintas'^alent antim ony urns, a small nuiul);S o f additional impurity ions (as in our presm t ease) acting as .e'clitional d o n o i, a.,ee])tor or tra}i eentios are not expected to have such a inai'Uod inlhsenee on the TCUl ot t,l\e m aterial as ha.s been experim entally evident ed (liguieS 1 , 2 , 3)However, tin oxide thni films of any given doping uoiieentration are known to exlubit both negativo and po.sitive TCR depe,nding upon the tliiekness of Sneh films The films exhibit negative TOR, at lower film tlnckniiss ami positive TCR at higher film tUiekneS.s even though the inijiurity doping eoiieeniralion IS maintained constant Ramanujam <?!: Gliaiv (11174, 197(5) have stmlied the. efhict of variation in various proiess pa'aniiitis's on tl'e (ionduetivity of .sueli films. Thev havir suggested that the va'ialion in the ele.itrieal proxicrtii s ol the till oxide thin films as a lunclion of film tlockness are due to tlie associatid variation in the lattieii defect dun.sity during tlui dei)''sitioii xiroe.ess TI\e films aie initially assoeiaterl with b.iglier lattice defect doiisitv which gradually d<‘ciea,se with the iiicteasc! in tbe film thiekness Th<',se variations in the lattice defect density are rellocted in tb,e cdisitrieal jiroiiert.ies sueJi as f), it, TCR, idi. Jaiii (& Gliare (to be publisluMl) have, found that the xiro,S(^ nce of Fip Cu and S as .small addU.ional iiilxiurity bins liave an influence on the lattice' defeid,”density profiler during tbe (h.positimi of such tin oxide tb.m films TJie eUcet of tlu* i)ro,Sonco of some foreign ions on the lattice defect profiles have also Thmui roxmited by .some xiiovioiis workers (Wugiiet 1950, 1052, Wagner 1974) H is tliereforo suggo.sted that tlie influence ol tliosi^  small additional impurity ions on the TCR of tbe heavily antimony doped tin oxidi* tlfin film.s re^ x^ orled in tJiis article iniglit liave its origin in their iiillueiici  ^ on the film lattice in addition to thoir beb,avioi/r as additional donor, accexitor oi tinpceiities4 OONCLNSIONHThe pro.sonce of iron ions in minute qnantitie.s leads to an increase in the magnitude ol Tomx>erature CoefliciiMit of Resi.stance of heavily antimony doped tin oxide thin film,s. Thii copx>er ions teiuls to make the TCR nega­tive in magnitude while the x^msence of sidiilnir ions tends to maki; it positive. Tt is suggested that such, iuaiki>tl influonoe on the TOR of such h,eavily doped tin oxide thin films as a re.sult of minor adrlitional impurity do]nng conconti ations is XKirhaos a consequence of the influence of tbesi foreign ioms on the lattice defect density profile during the deposition of such films.2298 V .  A .  J a n i  a n d  D .  B .  G h a reA c k n o w l e d g m e n t s’'Hio uutli,orH art t.i'ajiUiil to  Pi ofosfior R . S !N. R an for his kind, oncoiira'^c- m onl and snppnrt.K e f e r e n o e sAituhiH(*n A. E. 1{)/j4 Aml^ J. A-ppl. S'cf,, 5. 10.Aral T, 1000 ./. Phys, A'oc, Japan 15. OJG.Eommll .1. R  & Washorrio R. 1973 Thin Solid Pilms 15. 141.Rurkoi R. H. W. 1961 J Brit,, 1. R. K. 21. 301.Compagno dos Larapos 1954 Fr. Pat,. 1.062.791.Dodds S, M, 1956 Materials and Methods 44. 108.Gaihor R, A. 1959 W S. Pat., 2.919 212 Ooinor R, 1953 Rev,, Sci., Insirum, 24. 993.Imai T. 1960 J. Phys., Soc., Japan, 15 937,Jani V. A. & Gharu D. 13. Trans., [ndian Ceram. Soc., (Commuuicatod).KuznoLsov A. Ya. 1960 Sovt, Physics— Solid State 2. 30,Kuznntsov A, Ya,. Kruglova A, V, & KryzhanovsUii 1966 Zavodsicaya Lat), 22 993,Kuznotsfiv A, Ya, 1967 Zavadskaya Lab, 23 90,Kim H. & Laiimon H A. 1975 J. Amer., Ceram., Soc, 58. 23,Lyon D, N, & Gebalo T, H, 1950 Rev, Sci, Instrum, 21 769,Lyllo Wm., O. 1963 U.S. Pat., 2.648.754,MarrioLl .). G. FoR R. M. 13oicjoy J. H, & Ryan J D. 1958 Oer. Pat , 1 045.612,Ol^ nni H. & lltisogawa Y. 1967 Jap., Pat., 4852,KC'A Coip. 1973 1F.6' Pat., 3.713.884,Ramanujam M. A. & Gharo D. 13. 1974 J lustrum , Soc., India 4 17,Ramaiiujam M A & Ohaio D, 13. 1976 J 1.1 Sc , 58. 254,Rannoy M. W, 1969 Solar Cells. Noyo.s Data Corp.Raymond R, J*’ . & Donnisoii 13. J. 1952 W S. Pat, 2.6J7 745,Saundors A E. 1956 W.S. Pat, 2.762 725 and 2.762 726.Schmidt W. & Roborl L. 1958 Oer, Pat, 1.030 471.Sinclair W. R . Voter F. G . Stillingor D. W & Koonco S E. 1965 J Eleetrochern, Soc 112 1096. Thojoas L. D. 1958 Ger., Pat., 1.046.613.Vosaon J. L. 1971 RCA Review 32. 289.VoHHon J. L. & Polliniak E. S. 1972 YVim Solid Films 13. 281.Wagner C. 1950 J. Chem, Phys. 18 62.Wagnor C. 1952 J. Electroehem. Soc. 99. 346c.Wagiior J B 1974 Electrical Conductivity in Ceramics and Glass Pari B. Ed, by N. M. Tallan.Narcel Dekkor Inc,Ward J. B. 1975 Glass Technol. 16, 68.Young T. K. 1955 U.S. Pat. 2.703.767.

Effect of Impurities on TCR of Tin Oxide Thin Films

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Effect of Impurities on TCR of Tin Oxide Thin Films

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