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New ternary compounds cualx2 (x = te, se) buffer layers: large band gap
ELSEVIER
Synthetic Metals 103 (1999) 2644-2645
~
~~ ~~-~ ___~~
NEW TERNARY’ COMPOUNDS CuAl& (X = Te, Se)BUFFER LAYERS: LAliGE BAND GAP
propcrtics
of the ilms cbnfirrus
tl;:tt lhcy xc good cnhdidatcs
to rc&cc
CdS buiTcr la\crs in solar cc&,
It has been show that CuAlSclilms C:III bc obtained by atwaling uudcr SC atmosphcrc ol scqucntiall? dcpositcd Cu/AI/CdAI... Iiiycrs 1 1I.
The CuAl& films wcrc s~nthcsixd by rcactiou txtwcc11 the constituents during in post amealing ol- hatf 211 hour LIP773K under argou flow. The cvaporutiotl rules rind layer thicl~~~css wrc mcasurcd in-situ by the libratiug ~WIX method, The thickucss or the thiii Iwcrs or thc constituents wcrc culcuI:~Lcd in order to :&cvc the desired composition. The total thickwss II:E I >tlu. The films ncrc clwectcriscd b.\, X r;l>- dilTrxtion scani@ (NRC?). clcctroii nticroscopy (SEM). microprobe :uialgis and X-w photoclcctroil spectroscopy. The absorption coci%icnt of lhc iilms hs been dcduccd rrom lhc trxrwlission or 11x0 snwplcs with din‘crcut thickwss 121 jyhilc roow tctnpcraturc conductivity Ilwsurcn~c~lts 1x1s been done ul’tcr gold clcctrodc deposition OII pl:ular suuplcs. XRD spectra 0r OuAIXz lilins ;~fcr :inixiliiig xc slio~ II iii fig I
AlIcr the awcnliug h31l-z11lhour at 773K. ;1s usd ill chalcop~ritc compou~ids such as Cu!iiScz 131. llic f I 12) pc:lk is dominating which shows that the cqstallitcs of the films xc oricutcd along lhc (1 12) dircctioii, Morcovcr S;IIW others mall p%ks tgpicxl Or ihc chalcop?ritc structure xc visible fijjI.ThcrcTorc CuAIXz films cnskllliscd ii~ the ch:llcop~ritc structure hnvc bxn s~utllcs~scd I~!: the tcchniquc dcscribcd abo~xz The niicroprobc nwlysis hassho~ II tji:11 the fi!lus could bc strongly contamincd by oygcti (up to SOnl.%) duriug the dcposilion process. ‘i’hcrc~orc \\ hilt tlic deposition rxtc o~:~luminium has I$& incrcascd up 16~ 211111s”the dcpositcd :~lmmiuium lilms wcrc imntcdi;llcl? rccovcrcd with ;1 cl~nlcogcnc layer in order to prcuxt osidc lonnntioa. By using such proms tlw rclntivc atotilic couccntrnliou 0T osygw prcscnt ii1 tlic filuis at IIIC end or th process has been dccrcnscd 10 9 al.%. Typical Ihit film composiliou of B good tiirn is TFl6 al 96. Cu=21 at’%. Al=21 at% and OA-vgcn 9at.%. The small ulumiuiuu~ CSCCSSis boltdcd to osggzn to $w AIQ microdonx& mndoml~ rcpartitcd in CuAlTc:
0379-6779/99/$ - see front matter 0 1999 Elsevier Science S.A. All rights reserved, PII: SO379-6779(98)00656-O
K. Benchouk
et al. I Synthetic
Metals
IO3 (1999)
2644-2645
2645
polj c~stalliilc matrice. Similar mulls hxc bccli obhcd u ith CuAIScz, The \ istulisatiou or tllc lilnls slionx llial hey are polyxyslalliiie \\,ilh a11 a\wagcd grain size about 150 mi. Some cyslallilcs arc rxidouil~ rcpartilcd OII~O tllc fibs. it cm bc seen b> microl7robc anal.vsis lItal hq~ C;III be attribtrlcd 10 SOIW Cu ,.: co~npmnds. Tlq ca11 bc ckllcd by KCN solulioll. I! ~111 bc SCCII b!, NPS a11:1l! sis III:IL I\ hilt [ilc carlxm peak dclcckd at lllc surfkc or lhc smplc dkrppcars slier OIK or I\\0 iiiiiiulcs of elcliiiig. lllc os!gcll peak is still prcsciil alkr liioi-c Ilwi 0 niin or clchilig. This rasull sl~n\s Ilial. if llic lilriis ;irc riot coiilamiiialcd b! c;lrlmi. soilic osygcii is prcsclil all owr Ihc lhickiicss 0T Lhc 17llllS
‘13:pical
cm cs or CuA1.Y fil111s arc 11~11 lllcrc is ;I red shirt crrm Troni lhc sclciiitini 10 tllc Lcll~iririiii co1llp3111ld. Tllc absorption cocl%icnls oC lhc CuAISz krtl;y, conqxmds dcduccd rrom IIK Lransmission dala or I\\ o films n ith dill-crcnl Lhickncss. Eking direct band gap scruiconduc~ors, ~llc oplical gaps or lhc CuAI,Xz fihns IWC ~CCCI~c.wqxhlcd rrom ~11~cwcs : ((Zll.\‘) = (Il.\~ - Eg)’ .’ The ~xlucs dcduccd for CuAlTc~ md CuAIScy xc rcspccli\ el!, 2.3 cV and 2.7 cV. II C:IIIk SCCH thal ~hcsc wlucs arc sliglilly liighcr llic cspxlcd \~:1Imx(2. I CV and 2.67 CV l-or CuAl’l’c~ :lnd CuAISc. rcspccti\cly), This wiall iricrcase 0r [lx opliwl gip cxi tx csplaiiicd IT> [he ~ICWI~~ 01' lltc small Al-Ol dolwills randonll~ dislrihrilcd iii Lhc C’krAlS: pol,tcrj skilliric iiialricc, III 311 Ilclarogcllcorls S! SlClll. I\C Gill ;IssIIIllc tl1ai lllU s:lllll,lc ~111 lx di\ idcd inlo L\\o phases :111d Icl N,,.,,,,,,, :lnd N,,,,,,, Iv lllc dcnsitics of [he C’uAIN~ and o.\idc rc&ons ill UK hlk of lllc lilm. cr. lllc cocfficicnl is assurncd io Ix gi\ui b> 141.: gi\w
ill
fig
lrollsmissiotl
2
.I[
cm
k
sew
11hcrc CY,~~,,,~~~~ aud t~~,~,,~~ ;lrc absorpLion cocflicictlk or lhc ChAIS: and o+Jc pl~ascs. From lhc cqunliorl. u. I! ill dcpcnd011 LIICabsorptioucocrlicim of UK oxide plmc hcrcrorc or its optical g;lp. Shcc Illc AI,Cb (Eg= X.7cV) gq is gralcr lhan ihat or the CuAIXz pl~asc.(E~~,,,~~,~ = 2. IcV. Eg,S..u.,rscz= 2.67cV). tllc nlcasurcd optical gap I\ ill Ix: broader 111;111UK eyxclcd 011~ r0l ;I pw-c chalcogciiidc coiii~x~~~iid hiorco\ci~ llic iiicrcasc is higher 11Ilcn ~llc g:~p dirrcrcllccIx‘l\\eul lllc lno g;~ps is I~iglw. ~h:1~ is Lo s:l! iI1 lllc cm 0r CuAl’T’c.,
I. S. hlarsillac. J.C. Bcrucde. 0. El Mochr. J. Powcl hla(crials Scicrlccs and Irlgcuccring. Sccl. 13 : Solid Slalcs Malcrials for Ad\mccd Tcclmolog,~. B 45 ( l’N7) 00-75. 2. A. M~~llouky and J. C. Bcmcdc Thiu Solid Filw. IS!, (198X) 285. 3. G.hlassC. K,Chcn~~ot~~~. K.D.jcssas. F.Guasla\~ino Thin Solid Film. 203 ( 1907) 45-S I 4. J. C. Bcrmlc. S. Marsiliac. A. Couan and A. Godo!
Pl1.v~. Condcns.Mawr 8 ( 1996)3439-345I.
Synthetic Metals 103 (1999) 2644-2645
~
~~ ~~-~ ___~~
NEW TERNARY’ COMPOUNDS CuAl& (X = Te, Se)BUFFER LAYERS: LAliGE BAND GAP
propcrtics
of the ilms cbnfirrus
tl;:tt lhcy xc good cnhdidatcs
to rc&cc
CdS buiTcr la\crs in solar cc&,
It has been show that CuAlSclilms C:III bc obtained by atwaling uudcr SC atmosphcrc ol scqucntiall? dcpositcd Cu/AI/CdAI... Iiiycrs 1 1I.
The CuAl& films wcrc s~nthcsixd by rcactiou txtwcc11 the constituents during in post amealing ol- hatf 211 hour LIP773K under argou flow. The cvaporutiotl rules rind layer thicl~~~css wrc mcasurcd in-situ by the libratiug ~WIX method, The thickucss or the thiii Iwcrs or thc constituents wcrc culcuI:~Lcd in order to :&cvc the desired composition. The total thickwss II:E I >tlu. The films ncrc clwectcriscd b.\, X r;l>- dilTrxtion scani@ (NRC?). clcctroii nticroscopy (SEM). microprobe :uialgis and X-w photoclcctroil spectroscopy. The absorption coci%icnt of lhc iilms hs been dcduccd rrom lhc trxrwlission or 11x0 snwplcs with din‘crcut thickwss 121 jyhilc roow tctnpcraturc conductivity Ilwsurcn~c~lts 1x1s been done ul’tcr gold clcctrodc deposition OII pl:ular suuplcs. XRD spectra 0r OuAIXz lilins ;~fcr :inixiliiig xc slio~ II iii fig I
AlIcr the awcnliug h31l-z11lhour at 773K. ;1s usd ill chalcop~ritc compou~ids such as Cu!iiScz 131. llic f I 12) pc:lk is dominating which shows that the cqstallitcs of the films xc oricutcd along lhc (1 12) dircctioii, Morcovcr S;IIW others mall p%ks tgpicxl Or ihc chalcop?ritc structure xc visible fijjI.ThcrcTorc CuAIXz films cnskllliscd ii~ the ch:llcop~ritc structure hnvc bxn s~utllcs~scd I~!: the tcchniquc dcscribcd abo~xz The niicroprobc nwlysis hassho~ II tji:11 the fi!lus could bc strongly contamincd by oygcti (up to SOnl.%) duriug the dcposilion process. ‘i’hcrc~orc \\ hilt tlic deposition rxtc o~:~luminium has I$& incrcascd up 16~ 211111s”the dcpositcd :~lmmiuium lilms wcrc imntcdi;llcl? rccovcrcd with ;1 cl~nlcogcnc layer in order to prcuxt osidc lonnntioa. By using such proms tlw rclntivc atotilic couccntrnliou 0T osygw prcscnt ii1 tlic filuis at IIIC end or th process has been dccrcnscd 10 9 al.%. Typical Ihit film composiliou of B good tiirn is TFl6 al 96. Cu=21 at’%. Al=21 at% and OA-vgcn 9at.%. The small ulumiuiuu~ CSCCSSis boltdcd to osggzn to $w AIQ microdonx& mndoml~ rcpartitcd in CuAlTc:
0379-6779/99/$ - see front matter 0 1999 Elsevier Science S.A. All rights reserved, PII: SO379-6779(98)00656-O
K. Benchouk
et al. I Synthetic
Metals
IO3 (1999)
2644-2645
2645
polj c~stalliilc matrice. Similar mulls hxc bccli obhcd u ith CuAIScz, The \ istulisatiou or tllc lilnls slionx llial hey are polyxyslalliiie \\,ilh a11 a\wagcd grain size about 150 mi. Some cyslallilcs arc rxidouil~ rcpartilcd OII~O tllc fibs. it cm bc seen b> microl7robc anal.vsis lItal hq~ C;III be attribtrlcd 10 SOIW Cu ,.: co~npmnds. Tlq ca11 bc ckllcd by KCN solulioll. I! ~111 bc SCCII b!, NPS a11:1l! sis III:IL I\ hilt [ilc carlxm peak dclcckd at lllc surfkc or lhc smplc dkrppcars slier OIK or I\\0 iiiiiiulcs of elcliiiig. lllc os!gcll peak is still prcsciil alkr liioi-c Ilwi 0 niin or clchilig. This rasull sl~n\s Ilial. if llic lilriis ;irc riot coiilamiiialcd b! c;lrlmi. soilic osygcii is prcsclil all owr Ihc lhickiicss 0T Lhc 17llllS
‘13:pical
cm cs or CuA1.Y fil111s arc 11~11 lllcrc is ;I red shirt crrm Troni lhc sclciiitini 10 tllc Lcll~iririiii co1llp3111ld. Tllc absorption cocl%icnls oC lhc CuAISz krtl;y, conqxmds dcduccd rrom IIK Lransmission dala or I\\ o films n ith dill-crcnl Lhickncss. Eking direct band gap scruiconduc~ors, ~llc oplical gaps or lhc CuAI,Xz fihns IWC ~CCCI~c.wqxhlcd rrom ~11~cwcs : ((Zll.\‘) = (Il.\~ - Eg)’ .’ The ~xlucs dcduccd for CuAlTc~ md CuAIScy xc rcspccli\ el!, 2.3 cV and 2.7 cV. II C:IIIk SCCH thal ~hcsc wlucs arc sliglilly liighcr llic cspxlcd \~:1Imx(2. I CV and 2.67 CV l-or CuAl’l’c~ :lnd CuAISc. rcspccti\cly), This wiall iricrcase 0r [lx opliwl gip cxi tx csplaiiicd IT> [he ~ICWI~~ 01' lltc small Al-Ol dolwills randonll~ dislrihrilcd iii Lhc C’krAlS: pol,tcrj skilliric iiialricc, III 311 Ilclarogcllcorls S! SlClll. I\C Gill ;IssIIIllc tl1ai lllU s:lllll,lc ~111 lx di\ idcd inlo L\\o phases :111d Icl N,,.,,,,,,, :lnd N,,,,,,, Iv lllc dcnsitics of [he C’uAIN~ and o.\idc rc&ons ill UK hlk of lllc lilm. cr. lllc cocfficicnl is assurncd io Ix gi\ui b> 141.: gi\w
ill
fig
lrollsmissiotl
2
.I[
cm
k
sew
11hcrc CY,~~,,,~~~~ aud t~~,~,,~~ ;lrc absorpLion cocflicictlk or lhc ChAIS: and o+Jc pl~ascs. From lhc cqunliorl. u. I! ill dcpcnd011 LIICabsorptioucocrlicim of UK oxide plmc hcrcrorc or its optical g;lp. Shcc Illc AI,Cb (Eg= X.7cV) gq is gralcr lhan ihat or the CuAIXz pl~asc.(E~~,,,~~,~ = 2. IcV. Eg,S..u.,rscz= 2.67cV). tllc nlcasurcd optical gap I\ ill Ix: broader 111;111UK eyxclcd 011~ r0l ;I pw-c chalcogciiidc coiii~x~~~iid hiorco\ci~ llic iiicrcasc is higher 11Ilcn ~llc g:~p dirrcrcllccIx‘l\\eul lllc lno g;~ps is I~iglw. ~h:1~ is Lo s:l! iI1 lllc cm 0r CuAl’T’c.,
I. S. hlarsillac. J.C. Bcrucde. 0. El Mochr. J. Powcl hla(crials Scicrlccs and Irlgcuccring. Sccl. 13 : Solid Slalcs Malcrials for Ad\mccd Tcclmolog,~. B 45 ( l’N7) 00-75. 2. A. M~~llouky and J. C. Bcmcdc Thiu Solid Filw. IS!, (198X) 285. 3. G.hlassC. K,Chcn~~ot~~~. K.D.jcssas. F.Guasla\~ino Thin Solid Film. 203 ( 1907) 45-S I 4. J. C. Bcrmlc. S. Marsiliac. A. Couan and A. Godo!
Pl1.v~. Condcns.Mawr 8 ( 1996)3439-345I.