Ind i; 1Il Journal or Pure & Applied Phy~i c~ Yol. :lX. ;\ugu~t 2()OO. pp. 000-61 () Studies on deposition of antimony triselenide thin films by chemical method: SILAR B R Sankapal , V Ganesan * & CD LokhanLie Thin Film Ph y~ i c, Llhoratory. Department orphy~ic~. Sl li v; lji Uni ve rsity. Kolhapur 4 1() !)()4 Rece ived 7 Fehruary 2()OO: rev i ~e d 16 M ;IY 200(): accepted 17 Jilly 2()()!) Thin rillll ~ or Sh ~ S C . l ha ve hec n d epo~ it cd using a simple and Ics s in vcsti ga ted chemical mClhod namcly. ~ u ccc~s i vc ioni c 1;l ycr adsorption ;I nd reaclion (SILAR). The prcparat ive paramcters such as co nccntration. numhcr Dr inullcrsiollS . illllll c r ~ i()n lime ctc. arc oplimized to get good qllalily andwcll adherent Sh2Sc, th in rilms. Thc rilm ~ arc char;lctcrized hy Illea ns or X-ray dillr;lclion. ~ca nn i n g elcclron micro ~copy (SEM). atomic rorce Illicro ~co p y (A FM ). optical ah~orp ti nn aIII I elec tri ca l measll rc­ lrIenl ~. XRD st ud y ~ ho lVs Ih at rilm ~ ;Irc or Sh ~ S Cl with orthorhomhic crys t;tI ~ I ructure . SEM and AFr", inl;lgcs show th;1I ri lm, arc n ; lIlo cry~ l;tllill e . The optic:ti h;l nd g; lp i~ e~ tilllatcd 10 he I .X eY . The room tcmperatu l'c d;lIt elecl ri c; tI res isti \, ily is or Iltl' order or I 0) ~l Cill. Introduction chaicogen ion s. The ri Im format ion takcs place \\' hen The selenide of antimony is a good pOlential absorb­ ioni c product exceeds so luhility prod uc t. Thi s al so re­ in g material in photoacti ve conve rsion device of solar sul ts into precipitatc forillati on into th e solution and energy with an opt ical ba ndgap inlhe range or 1.06-1 .88 cont ro l over the process is losl. In order to avo id sucil l eV in crys tal s and polycrys tallinc thin rilms -" with difficu lti es, SILAR meth od was deve loped. It is based V ,- VI , compositi ons. According to prince Loferski ef­ on th e illlmersion of th e suhstrate into selxl rat e ly pbced fici cncy bandgap diagranyl a conver1i on crrici ency or cationic and anionic precursors and rin sin g hetween > 20 0'r is possible in solar cell s cmploying absorber or every immcrsion with ion exchanged water to ;Ivo id thi s bandgap. homogeneous precipitation in solution. It i .~ modifi ed A numher or mcth ods have heen employee! ror th e vcrsion or chemical bath deposition <lnd ma y al so he prepara tion or Sh,Sc l compound thin rilms. Wood ('I call cd ;IS stepwise chem icalliL:posit i()n. T he Sh .:' Sc \ thin ul. ~ · ha ve preparccl aillorphous Sh-Sc thin rilills by vac ­ fi lm s ~I r c characterized hy me;lIls of ~ tru ct ural. surface UUIll c()- e v ap o r~ltion technique. Rajpure el 01 -"' , ha ve morphological , optical ;Ind elect ri cal prup,rties ;Ind re­ ohtain cd amorphous thin fi lm~ hy spray pyrolys is tech­ su lt s arc re portcd. nique. Nikam and P,lwar(' ha ve prepared amorphous thin rilills of Sb-Se using th crmal cvaporation method. 2 ExpCI"imcntal Details 7 x 0.1 M dm-' antimony potassiullltartra tc was taK en a ~ Tor,lt1 c ('I u/ . and Dcsai (' I ul. , ha vc dcpos it ed po ly­ cati oni c precursor for depos iti on of Sh Se, thin film ~. crystallinc Sh,Se l thin films ont o FTO coated glass 2 substrate by Ill eans of e lectrodcposition tcchniquc. The compl exing agcnt used in c;l ti oni c precursor W~ I S PramaniK and Bhattachary} ha ve prcpared amorphous tartaric ac id and I} I-I - 3 W; IS <lcljllst ed. The sou rce for S b ~ Sc \ thin filills hy chcmi cal bath dcpositi on tec hnique. anionic precursor was 0 .1 M dm- \ sod iulll seiL: nosul ­ In the prese nt paper. an all empt h<l s hecn made to phite wit h pH - 8.5. For th e deposition ni" Sh.:' Se l thin deposit Sh,Sl' l thin films hy .~imple and less ex pensive fi llll , we ll clea nccl substrate W; IS imllll'rsed in Cit ionic successive ionic I<l ye r adsmptilln and reac ti on (S ILAR ) precursor so lution (an timony potassillill tartrat l' ) fpr mcthod. The chemical hath depositi on technique in 40s. Antimony ions get adsorhed nn th e suhstrate sllr­ whi ch deposition of metal chalcogcnid e scmiconductor face. The substrate was rinsed in fl owing distilled w; lt er thin film s occurs due to suhstrat es maintained in contact for 30 s to remove loosely bound or exccss antimony with dilulc chemi cal baths containing th' metal and ions. The conducti vity of th e fl owin g water was lInd er I ~ln - I.C Il1 - I. Then this substrate \,v as immersed in all­ "' i.ow T ernp C' r:llllrc 1.;lhor:llnr)'. Inl er t lni versi l y Consortium. DA rT. llldmc ioni c precursor so luti on (sodium sl'lcnnsu lpllit e) for 4() SANKAPAL ('1 (II.: ANTIMONY TRISELENIDE THIN FILMS 607 ~. The se lenide ions reacted with pre-adsorbed antimony T ahlc I - Optimizcd co nditions for th c dcposition of ions to form one layer of Sb,Se, material. The unreacted Sh2SC, thin fi lm Sc c- ions or powdery Sb c S~\ t ~ateria l ha ve been sepa­ Prcc ursors rated out by rinsin g th e subs trate again in hi ghly purified Dcpos ition cationic an ionic flow in g water for 3() s. This compl etes one SILAR-cycle conditions for th e depos iti on of Sb Sc, thin fi I ms. By repeating such 1 Sourccs an timony sodium SILAR cycl es for 350 times, Sb2Se, film of thi ck ness potassium sc lcnos ulphite O.Ot) ~lm under th e optimi zed depos iti on conditions has tartratc been obtained. Optimized depositi on conditi ons are Conccntr,ltion (M dm- ' ) 0.2 O. I give n in Table I for the depositi on of Sb1Se, thin film . pH - :I X.'i 3 Results and Discllssion Immcrsion timc (scc.) 40 40 Immcrsion cycles :I'i() ]'i() 3.1 Reaction mechanism Rinsing time (scc.) :10 :I() The form ati on of Sb1Se , involves following steps. In th c anio ns precursors soluti on, the hydrolys is of sodium T cmperaturc (oC) 27 27 selenosulphite takes place whi ch releases selenide ions as: Na 2SeSO, + OW ~ Na1S04 + HSe­ ... ( I ) 2 HS c- + OW ~ H,O + HS e - ... (2) layer. Thus the optimized value of concentration is taken as 0.2 M dm-' . and cati oni c so luti on releases Sb'\+ ions from compl exed For the optimization of number of immersion. the Sb-'+ as: graph of film thick ness against number of immersion (Sb '+ I tartaric acid} ) ~ Sb-' + + Tartaric ac id ... (3) cyc les was pl otted. In thi s, the number of immersion When substrate is immersed in Sb'+ containing solu ­ cycles varied from 100 to 450 cycles. At 35() cyc les. a ti on. Sb \+ ion s are adsorbed on the substrate surface. maximum value of thickness of Sb Se, was obtained 2 1 Art er immersi on of such a substrate in Se - ions contain ­ which may be call ed as terminal thickness. After 35() in g so luti on foll owin g reacti on takes place: cycles, the thickness decreases du e to peelin g off the 2 - 2 Sb 1+ + 3Se ~ Sb2Sc, ... (4) film from the substrate surface. During thi s va riation concentration, immersion time and rinsing time were 3.2 Optimization of preparative pammeters kept constant. The nominal growth rate was calculated In th e present study, equivolumes of cationic precur­ up to terminal thickness only and was found to be 0.56 sor so luti on antimony potassium tartrate and ani oni c nm cycle-Ion glass substrate. Valk onen1o found growth prec ursQ r W.I M dm-:') sod ium selenosulphite were rate 0.13 nm cycl e- I for CdS thin film ont o FrO coated ta ke n in separately placed two beakers for the optimiza­ glass substrate. ti on or concentration of Sly'+ ions. The pH of cati onic Immersion time of Sb2Se, was optimi zed by keeping precursor was maintai ned as 3 by adding compl ex in g concentration and immersi on cycles constant. It wa:-­ age nt as tartari c acid . By keeping number of immersion, found that film attains the maximum thi ckn ess at immer­ i rtlmcrsion time, rinsi ng ti me constant, the concentration sion time of 40 s. of cati oni c precursor soluti on was va ri ed from 0.025 Mdm- ' to 0.4 M dm-' and respecti ve thickness was 3.3 Sample characterization measured and graph of thi ckness against concentration The X-ray diffrac ti on studi es were conducted in the of antilllony potassium tartrate was pl otted . It was found ran ge of scanning angles from 10 to 100° with Cu Ka that thc Sb2Se, film formation starts from concentration radiation (A.