Crystal Structure and Superhydrophilic Property of TiO 2 Thin Film Coated on Si(100) Wafer

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1 Krean J. Crystallgraphy Vl. 12, N. 3, pp.177~181, 2001 Si(100) TiO 2 * *, * Crystal Structure and Superhydrphilic Prperty f TiO 2 Thin Film Cated n Si(100) Wafer Sarah Kim, Wn-J Ch*, Jae-Gwan Park* and Yng-Chul Lee Department f Chemical Engineering, Sungkyunkwan University, Suwn , Krea *Krea Institute f Science and Technlgy, P.O.BOX 131, Chengryang, Seul , Krea TiO 2. Sl-Gel!" #$ (100) % & ' (. 1) *+, 500 C, + -./ anatase 0, 1000 C, -./ rutile C, - 9:; anatase rutile 0 <= >?. + -./@ UVA B CD7 EF, G 750 C, -./ 5 HIJK. 1;./@ L# 4,,G M> * NO>P, UVA BQ 1.5 J RSG TU; :- E. Abstract We have studied superhydrphilic prperties f TiO 2 thin films in relatin with thse crystal structures due t the heat treatments. Thin films were fabricated n Si (100) wafers using a cnventinal Sl-Gel methd. Fllwing drying and sintering prcesses, TiO 2 film had an anatase phase with additinal heat treatment at 500 C, an rutile phase at 1000 C, and a mixture f anatase and rutile phase at 750 C. All these films gt hydrphilic even withut any UV illuminatin. Especially the sample treated at 750 C had a superhydrphilic cntact angle f 5. We suggested that the superhydrphilic films shuld have a mixture f anatase and rutile phase fr the best perfrmance. The hydrphilic TiO 2 films were slwly degraded int the hydrphbic state in the dark rm but quickly recvered back with less than 1 hur f UV illuminatin. 1. TiO 2!" #$! %& '() *+,-. /0! 1" TiO : ; /*<, ; ; AB)CD E *+1+F G " %F H, I! JK LM TiO 2 N+ O& P ; A%&) QR S '&T UV W XYZ[, +. 'Q\ ]^, _ abc d: I. 1-3) e U f gh TiO 2 Aid j k lm n9p! qr& s t8 uv wxyw z' { } ID F ~ /. p 8 $ ƒcd Qt J f gh 177

2 178. 4) ˆ Š" TiO 2 8 Q $.H) Œ W Ž< & w T" + 8 /0 š" D J /.8 pd J + œ gh. 5) TiO 2 8 Ž< &8 ž ) Ÿ 8 }ª Q $ F A id a[ 9:«! lm gh. n9 'QF T Ž<&.HD t. p W± ² ³ µ +. F² < 8 U ¹ «A. Aid F º U 400 nm -» {8 +¼½ ¾ }I A º ( 8 À Á * A F H! +¼½ 8 I d: }IA8 9: U Ã! º 8 F +¼½ A Ä 1mW/ cm 2 " * }IA8 1% '. T" A ÅW ÆÇ" Š! ÈÉ! F +¼½8 FD Q² <.Ê ËÌ. _! Í TiO 2 8 AQR Î TiO 2 bandgap energy(3.4 ev) Ï A{ Ð< 8 Ñ& electrn) hle)8 Î 8 wñ ¾, electrn) hle Ò E Š! electrn pair 8 Óy ³) dping Ô8 JKD F bandgap energy ÕyW U U8 A{ %FÖ ³ $±8 Øq lm ÙÚT ² <. Û" Si(100).Ü M TiO 2 8 Ž < & ÝVD xyw ÆÞ ß Yà á 678 L D ' âàã0 ƒ) äir åq P ž æ ß. 2. Û ÆÞ8 TiO 2 sld &. F! ç alkxide Ti žg " TTIP(titaniumtert-isprpxide) F ß ethanl(99.9%) D Fd F èæté. _! &id HCl(35%)D F <$ 67êë8 YàD J.! >L" DMF(dimethyl frmamide) ì ß, íî< F î" <$ ß. TTIP (. 8 1 P <$)8 Î& d: E ÆÞ )'" 1 P <$) Î! 4 ß. _! spin cating. * ï' Si(100). ÜD *ã0. TCE, methanl, acetne, di-water8 ð" rr 3$ Ýñ òó ß N 2 gund F té. 67 M.Ü.S" 24t S Y[ µ aging té, ô7 0.6 C/min8 õî 500 C" 1t S 1 â 500 C 1M TiO 2 töd t 200, 500, 750, 1000 C" 1t S 1, *. " ø â, ù*ú ûrtü }" äir 8 åq ýæ t T jþ ß BLB UV lamp(365 nm) 678 Ž<&D w etü â t äird ÿ' ß. 678 Èòm P êë} FE-SEM(Field Emissin Scanning Electrn Micrscpe; S-4100, Hitachi) jþ ß. _! XRD(X-ray diffractmeter; Cu-Kα, Rigaku) F >r 2θ=10~80 " D. scanning step = 0.02, scan speed = 10 /min X½ wñž8 * =40kV P * = 126 ma. äir cntact angle meter " static J8 CCD(Nikn zm lens) ŸT ÇUM DGD Fast/60(GBX Scientific Instrument, France) F ß, windrp++ ^@]D F, : äi rd 5 Y ÿ' ß Û lm" w F8 8 CD '

3 12 3, 2001 Si(100) TiO 2! "#$ %& 179 Table 1. Surface tensin and biling pint f each liquid slvent at 20 C Materials Frmula Surface tensin (γ) Biling pint ( C) DMF HCON(CH 3 ) Frmamide HCONH Ethanl CH 3 CH 2 OH Water H 2 O sld L â 67} SEMD F jþ ß. ú, sl Ç8 )8 8! YàD J. >L DMF ì ß. DMF Á D 9: ethanl) gel 8.( } µ ¾ gel 1 ethanl8 ½ sw.( S 8 & å µ M., )! & µ W 8 êë U s µ M. Š! êë U 8.( < ig Yà wñ µ ³. Table 1 r 8 êë U ) VD ZǾ ) frmamide DMF ethanl êë U Œ V Œ ;ñd 3 <. T" H 2 O êë U ë" V ; DMF sl8 ê ëu D > 678 YàD J <. Û lm" TTIP : Ethanl : DMF : HCl8 CD 1:4:2:0.05 't 8 ID 1, 2, 4 rr s t 500 C" 1t 1 ß 678 } jþ! SEM gd Fig. 1 rr ZÇ. 8 )! I 2ml (b)8 67 Yà Ñ 4 ml(c)8 9: TiO e Œ q ß. T" 8 I Yà wñ 1ml ' ß DMF8 I 2ml ß. Û ÆÞ" TiO 2 8!<! Í ' ß. Fig C" 1t 1! tö 8 êë P "8 SEM g. ÿ' ) TiO 2 8 grain size É 10~20 nm, " 200 nm 'ß. Wang8 XPS $æ 8 ë, UV 8 Fig. 1. SEM phtgraphs f TiO 2 thin film sintered at 500 C and prepared by varius H 2 O ml rati : (a) 1 ml (b) 2 ml (c) 4 ml.! 1 (( TiO 2 ï'8 É 75 Å Ç" wñ E 8 " êë ÂD #. #$ ÑrM. 6) 3-2. TiO 2 TiO 2 8 Ž<& band gap A{ g *+«'(D Ñ& ë" A/ M *+ Ž<&D /w! 345. ú *+ Ti +4 Ti +3 A/ ë" 1 $ %" êëâd Ñ& (. 8 )

4 180 Fig. 3. XRD patterns f TiO 2 thin films sintered at (a) 500 C (b) 750 C (c) 1000 C fr 1 h. Fig. 2. SEM phtgraphs f surface (a) and thickness (b) f TiO 2 thin film (H 2 O ml rati = 1, sintered at 500 C). 1 0M } 9& êëâ Ð'! ( ç U /. êëâ }" 1- OH.8 Ð' Œ :) [W*. ª OH. 8 %nm êë O. 8 %nm êë- + S' 2., 1$+ %n W OH. - Œ à µ!., ýæ" - S töd.u µ ë TiO 2 8 êë t 1<& D /µ M. 7) TiO 2 ï') 'êë8 $+ Ð' defect site" Œ /0 µ [W* lm- Hendersn 8 lm. _! 8), TiO 2 8 defect site st JK UV T, î" 1, Ar îd 0123 JK Ô ¾, Û ÆÞ" 9) 500 C 8 î" 1² 9: UV }" Ž<& Ñ. ³D jþ ß. [ $8 TiO 2 8 Aid Î Degussa P25 _ anatase \" º A$ ƒ) U 4 ³ lm) Z g. ç TiO 2 «jkm f 5, Q$ \ ÝVD xyw lm gh TiO 2 8 'm«ž<&8 j6 j! lm d: ÈÐ! Æ'. :½ 500 C 1M TiO 2 sampled t 200, 500, 750, 1000 C" 1t S 1 *." ø â, ù*ú ûrtü }" ä ir8 åq jþ ß. _! XRD F î TiO åq jþ ß. Fig. 3 î åq XRD F $ æ! ³. T500 tö º anatase\, T1000 tö º rutile \ :ò ß T750 tö 8 7 \} Z8. Fig. 4 Z* «9 1 â8 Ž<& D jþ! ) T750 tö àã0 â 4 U 4:, T jþ. ª 200 C«1000 C" àã0! â Ž<& 8 Z :. ;< tö ýæ".u ß t T Vg 1<&D t T1000 tö 3[ S UV ã0t Ž<&D

5 12 3, 2001 Si(100) TiO 2! "#$ %& 181 Fig. 4. Change f the water cntact angles f TiO 2 samples re-heated at varius temperature (a) 750 C (b) 500 C (c) 1000 C (d) 200 C accrding t the dark rm treatment and then UV (365 nm) illuminatin. Ç, rutile8 9: Ž<&8 ~ U?@. 4. Sl-GelK 8 &M TiO 2 AD Æ0B.Ü 0C LM 67D 500 C " 1 t S 1 1! ñ, âà ã0 ƒ) TiO Ž<&D jþ ß. 1) TiO êë } D 60 e á Y[ µ L U :<! A8 & 1 TTIP : 4 Ethanl : 1 H 2 O : 2 DMF : 0.05 HCl (ml) DMF F A8 êë U D LW ß. 2) LM TiO 2 67 UVã0 á àã0 8! 1(( 8 Ž<&D ZÇ, anatase ) rutile 7 WD Ý. ä ir U :D ª T ýæ ã0 8! EQ U?@. 3) Ž<& EQM TiO 2 67, Ý. äir 15 8 ÝŽ<&D : É 1 t 8 UVã0ª Fú ÝŽ<&D ~ ß. Fig. 5. CCD camera phtgraphs f the water drp n TiO 2 thin film (a) just after the first sintering at 500 C, and (b) after string in the dark rm fr 50 hurs. ~ ß tö 1t Ç 5 8 Ž<&D ~ ß. Linsebigler8 lm) ë, 500 K8 ; î àã0² 9: 1(( \& ³ 345, 11) Š! àã0 ) Ti 3+ Â " ½ $+8 Ð' =W > 8 Ž<& Z ¾ Û ÆÞ" 750 C" àã0! ³ U 4 &D Z 1) Nishide, T., J. Mater. Sci., 35, 465 (2000). 2) Shiga. A., J. phys. Chem. B., 102, 6049 (1998). 3) Fujishima, A. and Tata, N., J. Phtchem. Phtbi. C., 1 (2000). 4) Ishibashi, K. and Fujishima, A., J. Phtchem. Phtbi. A., 134, 139 (2000). 5) Watanabe, T., Thin Slid Films, 351, 260 (1999). 6) Wang, R., J. Phys. Chem. B., 103, 2188 (1999). 7) Wang, R., Adv. Mater., 10, 135 (1998). 8) Hendersn, M. A., Langmuir, 12, 5093 (1996). 9) Shen, H.-S., Chem. Mater., 5, 284 (1993). 10) Göpel, W., Surf. Sci., 62, 165 (1977). 11) Lu, G. and Linsebigler, A., J. Phys. Chem., 98, (1994).