Nghiên cứu chế tạo cảm biến khí H2 và H2S trên cơ sở màng SnO2 biến tính đảo xúc tác micronano

LI CAM OAN Tụi xin cam oan õy l cụng trỡnh nghiờn cu ca riờng tụi di s hng dn ca GS TS Nguyn Vn Hiu v PGS TS Nguyn Vn Quy Cỏc s liu, kt qu nghiờn cu l trung thc v cha tng cụng b bt k cụng trỡnh no khỏc Tp th Giỏo viờn hng dn Tỏc gi i LI CM N iu u tiờn tụi xin by t li cm n chõn thnh ti th giỏo viờn hng dn GS.TS Nguyn Vn Hiu v PGS.TS Nguyn Vn Quy, cỏc thy ó chp nhn tụi l nghiờn cu sinh v hng dn sut quỏ trỡnh tụi thc hin bn lun ỏn ny Cỏc thy ó ch bo, hng dn cho tụi tụi c tip cn mt lnh vc ang c s quan tõm ca ton nhõn loi, ú l cụng ngh vi in t v cụng ngh nano Tụi ó hc c rt nhiu t nhng iu ch dn, nhng bui tho lun v t nhõn cỏch ca cỏc thy Tụi cm phc nhng hiu bit sõu sc v chuyờn mụn, nhng kh nng cng nh s tn tỡnh ca cỏc thy Tụi cng rt bit n s kiờn trỡ ca cỏc thy ó c cn thn v gúp ý kin cho bn tho ca lun ỏn ny Tụi xin cỏm n PGS TS Nguyn c Hũa, TS Nguyn Vn Duy, ThS Nguyn Vit Chin cựng th cỏn b, NCS, ThS ca nhúm cm bin khớ Vin ITIMS ó ng viờn, giỳp tụi rt nhiu quỏ trỡnh thc hin cỏc cụng vic thc nghim ca ti cng nh tho lun gii thớch thnh cụng kt qu thc nghim Tụi cng trõn trng cm n GS Thõn c Hin, GS Nguyn c Chin, PGS Phm Thnh Huy nguyờn l nhng cỏn b lónh o ca Vin ITIMS Cỏc thy ó ng viờn v giỳp tụi rt nhiu quỏ trỡnh lm vic v hc Tụi xin chõn thnh cm n ti BG v th cỏn b nhõn viờn Vin ITIMS Cỏc thy, cỏc anh cỏc ch ó ng viờn giỳp v chia s nhng kinh nghim quý bỏu cho tụi sut quỏ trỡnh thc hin cỏc cụng vic thc nghim ca ti, ng thi cú nhng tho lun gi m quý bỏu quỏ trỡnh tụi vit hon thin lun ỏn With Tom A.a.i.rnink from Twente University, Thanks for your help! Tụi xin trõn trng cm n Ban giỏm hiu, Vin Sau i hc, Trng i hc Bỏch khoa H Ni ỏn 911 ca B Giỏo dc v o to Ni dung nghiờn cu ca lun ỏn ny nm khuụn kh thc hin v c ti tr bi Qu Phỏt trin Khoa hc v Cụng ngh Quc gia (Nafosted) mó s 103.99-2012.31 v mó s 103.02.2014.18; D ỏn chng trỡnh sỏng kin nghiờn cu VLIR-UOS under code ZEIN2012RIP20; ti cp Trng HBK H Ni mó s T2014-119 v T2015-068 Cui cựng, tụi mun dnh cho nhng ngi thõn yờu nht, bn lun ỏn ny l mún qu quý giỏ tụi xin c tng cho b m, v v cỏc thõn yờu ca tụi Tỏc gi lun ỏn ii MC LC LI CM N II MC LC III DANH MC CC Kí HIU V CH VIT TT V DANH MC BNG BIU VI DANH MC HèNH VII M U 1 Tớnh cp thit ca ti Mc tiờu ca lun ỏn Ni dung nghiờn cu i tng nghiờn cu Phng phỏp nghiờn cu í ngha thc tin ca ti Nhng úng gúp mi ca lun ỏn Cu trỳc ca lun ỏn Kt lun CHNG TNG QUAN 1.1 Gii thiu chung v cm bin khớ da trờn ụxớt kim loi bỏn dn 1.2 Gii thiu v vt liu SnO2 ng dng cho cm bin khớ 10 1.3 Nguyờn tc hot ng, hin tng un cong vựng nng lng v c ch tng tỏc b mt 12 1.4 Cỏc phng phỏp bin tớnh b mt mng mng cho cm bin khớ 16 1.4.1 Cm bin mng mng ụxớt bin tớnh vi xỳc tỏc kim loi 16 1.4.1.1 Mụ hỡnh cỏc cht phõn b cht bỏn dn 17 1.4.1.2 C ch nhy khớ ca mng mng bin tớnh vi xỳc tỏc kim loi 17 a) C ch nhy hoỏ 18 b) C ch nhy in t 18 1.4.2 Cm bin mng mng ụxớt bin tớnh vi o xỳc tỏc khỏc loi ht ti 25 1.4.3 Cm bin mng mng ụxớt bin tớnh vi o xỳc tỏc cựng loi ht ti 30 1.5 Kt lun 32 CHNG THC NGHIM LINH KIN CM BIN KH V CễNG NGH CH TO 33 2.1 Gii thiu 33 2.2 Thit k, ch to cm bin 33 2.2.1 Thit k cm bin 33 2.2.2 Tớnh toỏn cụng sut tiờu th cho cm bin 34 2.3 Quy trỡnh ch to cm bin 37 2.3.1 Mụ hỡnh v s cụng ngh ch to 37 2.3.2 Cỏc bc cụng ngh ch to 38 a) X lớ b mt 38 b) ễxy húa nhit 38 c) Quang khc mt n th nht (Mask 1, ch to lũ vi nhit v in cc) 39 d) Phỳn x catot to in cc v lũ vi nhit 41 e) Quang khc Mask v phỳn x to mng mng nhy khớ SnO2 42 f) Quang khc Mask v phỳn x o xỳc tỏc 43 2.4 Kho sỏt t trng nhy khớ ca cm bin 44 2.5 Quỏ trỡnh úng v cm bin 46 iii 2.6 Kho sỏt cụng sut tiờu th ca cm bin 48 2.7 Th nghim cm bin trờn bo mch tớch hp 48 2.8 Kt lun 49 CHNG CM BIN KH H2 TRấN C S MNG MNG SNO2 BIN TNH PD (SNO2/PD) 50 3.1 Gii thiu 50 3.2 Kt qu v tho lun 51 3.2.1 Kho sỏt hỡnh thỏi, cu trỳc vt liu cm bin mng mng SnO2 51 3.2.2 Kho sỏt hỡnh thỏi, cu trỳc vt liu cm bin mng mng SnO2/Pd 55 3.3 Kho sỏt c trng nhy khớ ca cm bin 56 3.3.1 Cm bin mng mng SnO2 56 3.3.2 Cm bin mng mng SnO2 kt hp o xỳc tỏc Pd (SnO2/Pd) 65 3.3.3 Cm bin mng mng SnO2 cú o xỳc tỏc Pt, Au 75 3.4 Thit k v chun húa thit b o khớ H2 trờn c s mng mng SnO2/Pd 78 3.5 Kt lun 82 CHNG 4: CM BIN KH H2S TRấN C S MNG MNG SNO2 BIN TNH CUO (SNO2/CUO) 83 4.1 Gii thiu 83 4.2 Kt qu v tho lun 86 4.2.1 Kt qu kho sỏt hỡnh thỏi v cu trỳc vt liu 86 4.2.2 Kt qu kho sỏt c trng nhy khớ 88 C ch nhy khớ ca cm bin 98 4.3 Kho sỏt ng u cm bin khớ H2S 103 4.4 Kho sỏt kh nng nhy khớ ca cm bin sau khớ úng gúi 103 4.5 Kt lun 106 KT LUN CHUNG V KIN NGH ERROR! BOOKMARK NOT DEFINED DANH MC CC CễNG TRèNH CễNG B CA LUN N 109 TI LIU THAM KHO 110 iv DANH MC CC Kí HIU V CH VIT TT Ký hiu, vit tt Tờn ting Anh Ngha ting Vit CVD Chemical Vapour Deposition Lng ng húa hc pha hi VLS Vapour Liquid Solid Hi-lng-rn VS Vapour Solid Hi-rn Mask Mt n TT MFC Mass Flow Controllers B iu khin lu lng khớ ppb Parts per billion Mt phn t ppm Parts per million Mt phn triu SEM Scanning Electron Microscope Kớnh hin vi in t quột TEM Transmission Electron Microscope Kớnh hin vi in t truyn qua 10 XRD X-Ray Diffraction Nhiu x tia X 11 FESEM Field Emission Scanning Electron Microsope Kớnh hin vi in t quột phỏt x trng 12 EDS/EDX Energy Dispersive X-ray Spectroscopy Ph nhiu x in t tia X 13 SMO Semiconducting Metal Oxides ễxớt kim loi bỏn dn 14 JCPDS Joint Committee on Powder Diffraction Standards y ban chung v tiờu chun nhiu x ca vt liu 15 Ra Rair in tr o khụng khớ 16 Rg Rgas in tr o khớ th 17 S Sensitivity hi ỏp/ ỏp ng 18 Donors Cỏc tõm cho in t 19 Acceptors Cỏc tõm nhn in t 20 Prototype Sn phm th nghim 21 sccm Standard Cubic Centimeters per Minute mL/phỳt 22 ITIMS International Training Institute for Materials Science Vin o to Quc t v Khoa hc Vt liu v DANH MC BNG BIU Bng 1.1 Mt s lnh vc ng dng ca cm bin khớ Bng 1.2 Di nng c quan tõm ca cỏc nng khớ [117] Bng 1.3 Thng kờ v loi vt liu ụxớt kim loi bỏn dn cho cm bin dng mng mng t nm 2000 n 11 Bng 1.4 Mt s cụng b tiờu biu v cm bin khớ trờn c s mng mng ụxớt bin tớnh vi o xỳc tỏc kim loi 20 Bng 1.5 dn in ca cm bin vi 300 ppm khớ CO theo nhit [76] 22 Bng 1.6 ỏp ng 200 ppm khớ LPG ca cm bin SnO2/Pt vi cỏc chiu dy o xỳc tỏc [25] 23 Bng 1.7 ỏp ng 200 ppm khớ LPG ca cm bin SnO2/Pt chiu UV/khụng chiu UV [26] 23 Bng 1.8 Mt s cụng b tiờu biu v cm bin khớ trờn c s mng mng ụxớt bin tớnh vi o xỳc tỏc khỏc loi ht ti 26 Bng 1.9 ỏp ng v in tr tng ng ca cm bin khụng khớ v khớ H2S [74] 29 Bng 2.1 Giỏ tr in tr tớnh toỏn tng ng vi cụng sut 35 Bng 2.2 Giỏ tr in tr tng ng chiu dy mng Pt 35 Bng 2.3 Quy trỡnh cụng ngh quang khc 40 Bng 2.5 Thụng s phỳn x mng mng Cr/Pt 41 Bng 2.6 Thụng s phỳn x mng mng SnO2 42 Bng 2.7 Thụng s phỳn x o xỳc tỏc 43 Bng 4.1 nh hng ca khớ H2S n sc khe ngi (Ngun: American National Standards Institute (ANSI Standard No Z37.2-1972) 83 Bng 4.2 Mt s cm bin khớ H2S c bỏn trờn th trng 105 vi DANH MC HèNH Hỡnh 1.1 Cu to chung ca cm bin khớ Hỡnh 1.2 Mụ hỡnh cu trỳc ụ n v (a) v cu trỳc vựng nng lng ca SnO2 (b) 10 Hỡnh 1.3 Cỏc loi cm bin nhy khớ trờn c s vt liu ụxớt bỏn dn dng (a) v dng mng (b) 12 Hỡnh 1.4 Mụ hỡnh c ch nhy khớ ca cm bin mng mng bỏn dn [115] 13 Hỡnh 1.5 S nng lng v s thay i vựng nghốo in t ti biờn gii ht [115] 14 Hỡnh 1.6 nh hng ca kớch thc ht n c ch nhy khớ [117] 15 Hỡnh 1.7 Mụ hỡnh cỏc cht hp trờn b cht vo bỏn dn (a); dng (b) v dng mng (c) [115] 17 Hỡnh 1.8 Mụ hỡnh s cu trỳc nng lng bin tớnh xỳc tỏc kim loi: (a) khụng khớ v mụi trng cú khớ kh (b) 19 Hỡnh 1.9 nh SEM ca mng mng SnO2/Ag (a) v tớnh cht nhy khớ H2 ca mng mng Ag (dy nm) theo nhit (b) [122] 20 Hỡnh 1.10 Phõn b kớch thc ht theo t l kim loi pha (a) v c trng in tr ca mng khụng pha Rh v cú pha Rh (b) [76] 21 Hỡnh 1.11 ỏp ng khớ theo nhit ca mng mng SnO2 bin tớnh cỏc loi o kim loi khỏc (a) v thi gian ỏp ng, hi phc ca cm bin SnO2/Pt (b) [84] 23 Hỡnh 1.12 S mc nng lng sau kt hp hai vt liu bỏn dn loi p/n 25 Hỡnh 1.13 Cm bin mng mng SnO2 bin tớnh mng mng CuO (a) v cỏc o CuO (b) [11] 27 Hỡnh 1.14 ỏp ng ca cỏc cm bin theo nng (a) v theo nhit (b) [11] 27 Hỡnh 1.15 c trng I-V ca tip xỳc CuO (p)-SnO2 (n) [74] 28 Hỡnh 1.16 ỏp ng theo nhit ca mng mng SnO2 bin tớnh o khớ SO2 (a) 30 v chn lc ca cm bin (b) [100] 30 Hỡnh 1.17 S mc nng lng sau kt hp hai vt liu bỏn dn loi n/n 31 Hỡnh 2.1 Cỏc thụng s ca cm bin (n v o àm) 34 Hỡnh 2.2 Quan h gia cụng sut phỏt x v nhit 34 Hỡnh 2.3 B mt n thit k cho Si 4-inch: (a) mt n to hỡnh vi in cc v lũ vi nhit; (b) mt n to hỡnh o xỳc tỏc (5 àm); (c) mt n to hỡnh vựng nhy khớ 36 Hỡnh 2.4 Mụ hỡnh cm bin sau ch to (a) v quy trỡnh ch to cm bin trờn c s cụng ngh Vi in t (b) 37 Hỡnh 2.5 Cỏc thit b chớnh dựng quỏ trỡnh cụng ngh: Mỏy quang khc mt (PEM 800) (a); Mỏy quay ph 1H-D7 (b); Bp nhit (c) v Kớnh hin vi quang hc (d) phũng sch Vin ITIMS 39 Hỡnh 2.6 nh h phỳn x phũng sch Vin ITIMS 41 Hỡnh 2.7 Hỡnh nh in cc v lũ vi nhit sau ch to 41 vii Hỡnh 2.8 Quy trỡnh ch to mng nhy khớ: a) Quang khc mask 2; (b) Sau quang khc; (c) Phỳn x mng mng SnO2 42 Hỡnh 2.9 Hỡnh nh lp mng nhy khớ SnO2 trờn in cc sau ch to 42 Hỡnh 2.10 Quy trỡnh ch to o xỳc tỏc: a) Quang khc mask 3; (b) Sau quang khc; (c) Phỳn x mng mng Pd, Cu 43 Hỡnh 2.11 Hỡnh nh lp o xỳc tỏc trờn mng nhy khớ SnO2 sau ch to 43 Hỡnh 2.12 nh quang hc ca cỏc cm bin ch to trờn phin Si inch (a); nh ca mt cm bin (b) v mụ hỡnh cm bin mng mng kt hp o xỳc tỏc (c) 44 Hỡnh 2.13 S nguyờn lý h o tớnh cht nhy khớ ca cm bin (a), thit b o th v dũng (b) 45 Hỡnh 2.14 Giao din chng trỡnh VEE-Pro 46 Hỡnh 2.15 Quy trỡnh úng v cm bin: Mỏy hn dõy Westbond 7400C (a) v quy trỡnh úng gúi cm bin (b) bao gm cỏc cụng on: (1) Chớp cm bin ct ri; (2) Hn dõy cm bin vo bn mch; (3) Ph lp bo v bng keo chu nhit v (4) Cm bin úng v hon chnh 46 Hỡnh 2.16 Cm bin ch to sau hn lờn (a); mch tớch hp linh kin (b) 49 Hỡnh 3.1 Cu trỳc mt trờn ca cm bin ch to chp bng kớnh hin vi (a) v hỡnh nh phúng to (b) 52 Hỡnh 3.2 Hỡnh nh b dy mng mng SnO2 thu c t Profilometer (a) Hỡnh nh chp t mỏy Profilometer; (b) Mụ hỡnh mt ct ngang 52 Hỡnh 3.3 Kt qu o chiu dy mng mng SnO2: (a) 20 nm; (b) 40 nm; (c) 60 nm v (d) 80 nm 53 Hỡnh 3.4 Gin nhiu x tia X ca mng SnO2 53 Hỡnh 3.5 nh FESEM ca mng mng SnO2 cỏc chiu dy khỏc nhau: (a) 20; (b) 40; (c) 60 v (d) 80 nm 54 Hỡnh 3.6 nh FESEM ca mng mng SnO2/Pd: (a) Cm bin SnO2/Pd; (b) Ma trn o xỳc tỏc Pd; (c) Hỡnh nh mt o xỳc tỏc v (d) Hỡnh nh biờn ca o xỳc tỏc Pd trờn nn SnO2 55 Hỡnh 3.7 Ph EDS ca cm bin mng mng SnO2/Pd: hỡnh chốn bờn l nh FESEM ca o Pd v thnh phn cỏc nguyờn t tng ng 56 Hỡnh 3.8 Cỏc c trng nhy khớ H2 ca cm bin mng mng SnO2 dy 20 nm: (a) c trng ỏp ng ca cm bin 300, 350 v 400 C; ỏp ng biu din ph thuc vo nng khớ (b) v nhit lm vic (c) 57 Hỡnh 3.9 Cỏc c trng nhy khớ H2 ca cm bin mng mng SnO2 dy 40 nm: (a) c trng ỏp ng ca cm bin 300, 350 v 400 C; ỏp ng biu din ph thuc vo nng khớ (b) v nhit lm vic (c) 58 Hỡnh 3.10 Cỏc c trng nhy khớ H2 ca cm bin mng mng SnO2 dy 60 nm: (a) c trng ỏp ng ca cm bin 300, 350 v 400 C; ỏp ng biu din ph thuc vo nng khớ (b) v nhit lm vic (c) 59 viii Hỡnh 3.11 Cỏc c trng nhy khớ H2 ca cm bin mng mng SnO2 dy 80 nm: (a) c trng ỏp ng ca cm bin 300, 350 v 400 C; ỏp ng biu din ph thuc vo nng khớ (b) v nhit lm vic (c) 59 Hỡnh 3.12 th so sỏnh ỏp ng ca cỏc cm bin mng mng SnO2 cú chiu dy khỏc nhau: ỏp ng biu din ph thuc vo nng khớ (a) v nhit lm vic (b) 61 Hỡnh 3.13 Thi gian ỏp ng v hi phc theo nhit ca mng mng SnO2 cú chiu dy 40 nm vi nng 1000 ppm khớ H2 61 Hỡnh 3.14 c trng nhy khớ: 250 ppm CO (a); 2500 ppm LPG (b) 250 ppm NH3 (c); 62 v 250 ppm H2 (d) ca cm bin mng mng SnO2 dy 40 nm ti nhit 400 C 62 Hỡnh 3.15 chn lc khớ ca cm bin mng mng SnO2 dy 40 nm 63 Hỡnh 3.16 c trng nhy khớ H2 ca cm bin mng mng SnO2 thay i lu lng khớ phỳn x theo nng khớ Ar : O2 (sccm) khỏc nhau: 100% (30 sccm) Ar (a); t l (25 sccm) Ar v (5 sccm) O2 (b); (c) t l (20 sccm) Ar v (10 sccm) O2; (d) t l (10 sccm) Ar v (20 sccm) O2 64 Hỡnh 3.17 ỏp ng khớ H2 ca cm bin mng mng SnO2 dy 40 nm thay i lu lng khớ phỳn x ti nhit 400 C 65 Hỡnh 3.18 Cỏc c trng nhy khớ H2 ca cm bin mng mng SnO2 (40 nm)/Pd (5 nm): (a) c trng ỏp ng khớ ca cm bin 200, 250, 300, 350 v 400 C v (b) ỏp ng biu din ph thuc vo nng khớ 66 Hỡnh 3.19 c trng nhy khớ H2 ca cm bin mng mng SnO2/Pd (dy 10 nm): (a) c trng ỏp ng khớ 200, 250, 300, 350 v 400 C v (b) ỏp ng biu din ph thuc vo nng khớ 67 Hỡnh 3.20 c trng nhy khớ H2 ca cm bin mng mng SnO2/Pd (dy25 nm): (a) c trng ỏp ng khớ 200, 250, 300, 350 v 400 C v (b) ỏp ng biu din ph thuc vo nng khớ 68 Hỡnh 3.21: c trng nhy khớ H2 ca cm bin mng mng SnO2/Pd (dy 40 nm): (a) c trng ỏp ng khớ 200, 250, 300, 350 v 400 C v (b) ỏp ng biu din ph thuc vo nng khớ 69 Hỡnh 3.22 ỏp ng ca cỏc cm bin SnO2/Pd biu din ph thuc vo nng khớ (a) v nhit lm vic (b) 69 Hỡnh 3.23 Mụ hỡnh c ch nhy khớ ca cm bin SnO2/Pd: (a) Khụng o Pd; (b) o Pd = nm; (c) o Pd = 10 nm v (d) o Pd 25 nm 72 Hỡnh 3.24 Thi gian hi phc (a) v ỏp ng (b) ca cỏc cm bin SnO2/Pd vi chiu dy khỏc theo nng 72 Hỡnh 3.25 c trng hi ỏp ca cm bin SnO2/Pd (10 nm) ti nhit 300 C vi cỏc loi khớ: (a) 250 ppm khớ CO, (b) 2500 ppm khớ LPG, (c) 250 ppm khớ NH3 v 250 ppm khớ H2 (d) 73 ix Hỡnh 3.26 chn lc khớ ca cm bin SnO2/Pd (10 nm) ti 300 C v 400 C (a); ỏp ng ca cm bin cú v khụng cú o ti 300 C (b) 74 Hỡnh 3.27 n nh ca cm bin SnO2/Pd (10 nm) sau 10 chu k thi / ngt 75 Hỡnh 3.28 Ph EDS ca cm bin SnO2 cú o xỳc tỏc Pt (a) v Au (b) 76 Hỡnh 3.29 Cỏc c trng nhy khớ ca cm bin SnO2/Au (dy10 nm): (a) c trng nhy khớ; ỏp ng biu din ph thuc theo nng khớ (b) 76 Hỡnh 3.30 Cỏc c trng nhy khớ ca cm bin SnO2/Pt (dy10 nm): (a) c trng nhy khớ; ỏp ng biu din ph thuc theo nng khớ (b) 77 Hỡnh 3.31 th so sỏnh ỏp ng theo nng khớ o ca cm bin SnO2 cú cỏc loi o xỳc tỏc dy (10 nm) ca Pt, Pd v Au 78 Hỡnh 3.32 S nguyờn lý mch o cm bin 78 Hỡnh 3.33 Thit k mt trờn (a) v mt di ca mch o (b) 79 Hỡnh 3.34 Cm bin sau hn dõy (a); sau úng v (b); mch o ca thit b (c) v thit b o khớ H2 hon chnh (d) 79 Hỡnh 3.35 c trng ỏp ng khớ H2 ca cm bin SnO2/Pd: Cụng sut tiờu th ph thuc theo thi gian (a) v biu din c trng nhy khớ theo cụng sut (b) 80 Hỡnh 3.36 c trng ỏp ng khớ H2 theo cỏc nng khỏc ca cm bin SnO2/Pd: (a) c trng hi ỏp theo cụng sut lũ vi nhit l 180 mW; (b) ỏp ng biu din ph thuc theo nng khớ 81 Hỡnh 3.37 chn lc khớ ca cm bin SnO2/Pd ti cụng sut 180 mW 81 Hỡnh 3.38 ỏp ng khớ H2 ca cm bin SnO2/Pd theo thi gian 82 Hỡnh 4.1 nh quang hc ca khong 400 cm bin trờn phin Si inch sau ch to (a); nh SEM ca mt cm bin (b); nh FE-SEM hỡnh thỏi b mt ca lp vt liu nhy khớ (c); nh quột chp EDS ca vt liu CuO v ph tỏn xc nng lng EDS ca vt liu CuO/SnO2 (d) 87 Hỡnh 4.2 Ph nhiu x tia X ca mng mng SnO2 (a) v ph Raman Shift ca vt liu SnO2/CuO (b) 88 Hỡnh 4.3 Cỏc c trng nhy khớ H2S ca cm bin SnO2 dy 40 nm: (a) c trng hi ỏp v ỏp ng biu din ph thuc theo nng khớ (b) 89 Hỡnh 4.4 Cỏc c trng nhy khớ H2S ca cm bin SnO2/CuO (dy nm): (a) c trng hi ỏp vi khớ H2S 250, 300, 350 v 400 C; ỏp ng biu din ph thuc v nng khớ (b) 90 Hỡnh 4.5 Cỏc c trng nhy khớ H2S ca cm bin SnO2/CuO (dy 10 nm): (a) c trng hi ỏp vi khớ H2S 250, 300, 350 v 400C; ỏp ng biu din ph thuc v nng khớ (b) 92 Hỡnh 4.6 Cỏc c trng nhy khớ H2S ca cm bin SnO2/CuO (dy 15 nm): (a) c trng hi ỏp vi khớ H2S 250, 300, 350 v 400C; ỏp ng biu din ph thuc vo nng khớ (b) 92 x Kt qu ny tng t nh i vi mng mng SnO2 thun khit Tuy nhiờn ỏp ng khớ H2S ca cỏc cm bin mng mng SnO2 bin tớnh o Cr2O3, Fe2Ox thp hn rt nhiu so vi mng khụng bin tớnh v so vi mng bin tớnh bng o CuO Khỏc vi cm bin mng mng SnO2/CuO (dy 20 nm), nhit hot ng ti u ca cm bin mng mng SnO2/Fe2Ox (dy 20 nm) l 400C ( ỏp ng S = 6,2 o ppm H2S ti 400 C) Trờn Hỡnh 4.18 l th so sỏnh ỏp ng ca cỏc cm bin mng mng SnO2 (40 nm) bin tớnh vi cỏc loi vt liu xỳc tỏc khỏc Chỳng ta d dng nhn thy cm bin mng mng SnO2/CuO khụng ch cú ỏp ng cao nht vi khớ H2S m cũn cú nhit hot ng thp hn so vi cỏc o xỳc tỏc khỏc Ta nhn thy, cm bin vi lp o xỳc tỏc CuO dy 20 nm trờn lp mng mng SnO2 dy 40 nm cú ỏp ng l cao nht, nhit hot ng ti u gim xung cũn 250 C Vi nhng u im ny chỳng tụi nhn thy cm bin cú th ng dng vo thc tin ch to thit b o quan trc ụ nhim mụi Cú th thy, Fe2Ox, Cr2O3, v CuO u l cỏc ụxớt kim loi bỏn dn loi p Khi bin tớnh trờn b mt mng mng SnO2 u to tip xỳc p-n Tuy nhiờn ỏp ng khớ H2S ca cm bin cú o xỳc tỏc Fe2Ox, Cr2O3 l khụng cao, hay cú th hiu õy khụng phi l loi vt liu xỳc tỏc tt i vi khớ H2S Ngc li, bin tớnh vi CuO thỡ ỏp ng khớ H2S ca cm bin c tng lờn ỏng k iu ny chng t vai trũ o xỳc tỏc CuO ca cm bin SnO2 cú ỏp ng vi khớ H2S l tt nht Hay cú th hiu, CuO d dng phn ng vi khớ H2S to thnh CuS, t ú thay i bn cht tip xỳc p-n gia CuO v SnO2 ng thi tng cng tớnh nhy khớ ca cm bin 100 80 250 C 300C 350 C 400 C = R /R ) SS (Raa/Rgg 60 40 @@@ 2,5 ppm khí H2S 20 SnO2- Cr2O3 SnO2- Fe2Ox SnO2- CuO Hỡnh 4.18 ỏp ng ca cm bin o khớ H2S trờn c s mng mng SnO2/CuO, Cr2O3, Fe2Ox 102 4.3 Kho sỏt ng u cm bin khớ H2S T kt qu kho sỏt c trng nhy khớ ca cm bin mng mng SnO2/CuO (dy 20 nm) chỳng tụi ó tin hnh ch to linh kin cm bin o khớ H2S ng thi kho sỏt tin cy ca quy trỡnh ch to Cỏc chớp cm bin ó ch to trờn phin Si (4 inch) c tỏch nh v phõn tớch nh trờn Hỡnh 4.19 Chỳng tụi tin hnh kho sỏt ng u ca cm bin bng vic ly 12 chớp cm bin o tớnh cht nhy khớ ti cựng iu kin l 300 C v nng khớ H2S l 2,5 ppm Kt qu c mụ t trờn Hỡnh 4.19 cho thy cỏc cm bin ó ch to cú ng u tng i cao Trong nghiờn cu ny, chỳng tụi s dng bia cú kớch thc 2inch phỳn x lờn kớch thc 4-inch ú ng u ca cm bin cha c ti u ch to hng lot tin ti sn xut cụng nghip, thỡ yờu cu bia phỳn x phi cú kớch thc tng ng hoc ln hn kớch thc ca wafer S (Ra/Rg) 100 10 m1 m2 m3 m4 m5 m6 m7 m8 m9 m10 m11 m12 Số mẫu Hỡnh 4.19 ng u ca cm bin SnO2/CuO (dy 20nm) 4.4 Kho sỏt kh nng nhy khớ ca cm bin sau khớ úng gúi kho sỏt kh nng lm vic thc ca cm bin, mi chớp cm bin tip tc c gn lờn theo quy trỡnh ging nh ó thc hin vi cm bin khớ H2 nh trỡnh by Chng Vi linh kin cm bin khớ H2S ó c úng gúi, chỳng tụi tin hnh kho sỏt s nh hng ca cụng sut tiờu th cng nh cỏc iu kin ph thuc vo nng cng nh chn lc ca cm bin Cỏc kt qu kho sỏt trờn linh kin c trỡnh by trờn cỏc Hỡnh t Hỡnh 4.20; Hỡnh 4.21; Hỡnh 4.20 103 100 3000 250 mW 500 1000 100 1500 300 mW 500 1000 10 10 100 1500 350 mW 500 1000 1500 100 400 mW 250 500 40 20 10 60 10 2000 @ 2,5 ppm H2S 80 V (Vin /V S = S in/Vout out) 2000 (b) 10 200 mW 1000 100 100 (a) 750 1000 200 Thời gian (s) 250 300 350 400 Công suất (mW) Hỡnh 4.20 c trng nhy khớ H2S ca cm bin SnO2/CuO: (a) c trng hi ỏp vi khớ H2S 200, 250, 300, 350 v 400 mW v ỏp ng biu din ph thuc cụng sut lũ vi nhit (b) Cm bin mng mng ụxớt kim loi bỏn dn thng hot ng nhit cao, ú lũ vi nhit c ch to vi mc ớch cung cp nhit cho vựng cha lp vt liu nhy khớ Cm bin ca chỳng tụi ch to cú lũ vi nhit l dõy Pt rng 20 m un quanh lp mng mng Vi vic cp in ỏp vo lũ vi nhit khong 4V 9V v o dũng in, ta cú th tớnh c cụng sut tiờu th ca lũ vi nhit Chỳng tụi tin hnh kho sỏt c trng nhy khớ ca linh kin cm bin khớ H2S ti cỏc mc cú cụng sut tiờu th khỏc l 200, 250, 300, 350, 400 mW v kt qu c th hin trờn Hỡnh 4.20 Khi o vi 2,5 ppm khớ H2S, cm bin cho thy cú ỏp ng cao v tng dn cụng sut tiờu th ca lũ nhit gim ỏp ng cao nht S = 93 ng vi cụng sut lũ nhit l 200 mW, mc dự thi gian hi phc di iu ny hon ton ph hp vi kt qu kho sỏt cm bin phn trc Khi cụng sut lũ vi nhit thp, ng ngha vi vic nhit hot ng ca cm bin thp, ỏp ng tng cao nhng thi gian cm bin hi phc li trng thỏi ban u di Sau kho sỏt tớnh nhy khớ ph thuc cụng sut, chỳng tụi la chn cụng sut lũ nhit 300 mW kho sỏt tớnh nhy khớ v chn lc ca linh kin ỏp ng ca linh kin cm bin khớ da trờn c s mng mng SnO2 (40 nm) cú o xỳc tỏc CuO (20 nm) vi nng khớ H2S khỏc c th hin trờn Hỡnh 4.21(a) Chỳng tụi kho sỏt vi cỏc nng khớ H2S rt thp ln lt l 0,5; 1; 2,5 v ppm Vi 0,5 ppm khớ H2S, ỏp ng t giỏ tr S = 2.6, kt qu ny cho thy cm bin cú kh nng phỏt hin khớ H2S nng thp hn ppm Kt qu trờn Hỡnh 4.21(b) cng cho thy c cm bin cú chn lc cao ỏp ng vi ppm khớ H2S cao gp 12 ln so vi 500 ppm khớ NH3 v gp 25 ln so vi 500 ppm khớ H2 v 500 ppm khớ C2H5OH 104 ppm @ 300 mW 100 100 (a) (b) 2,5 ppm 10 ppm SS(Vinin/Vout ) = V /Vout ppm H2S @ 300 mW 10 500 ppm NH3 0,5 ppm 500 ppm H2 1 500 1000 1500 500 ppm C2H5OH 2000 300 Thời gian (s) 600 900 1200 1500 Thời gian (s) Hỡnh 4.21 ỏp ng ca linh kin cm bin khớ H2S theo: nng khớ (a) v cỏc loi khớ (b) Bng 4.2 so sỏnh phm cht ca mt s loi cm bin H2S thng mi v sn phm phỏt trin ti Cú th thy cm bin chỳng tụi phỏt trin th hin nhng u im vt tri so vi cỏc sn phm thng mi nh ỏp ng cao, gii nng lm vic thp, v thi giỏn ỏp ng nhanh Cỏc cm bin chỳng tụi phỏt trin hon ton ỏp ng c yờu cu ng dng quan trc ụ nhim mụi trng khụng khớ Bng 4.2 Mt s cm bin khớ H2S c bỏn trờn th trng Hóng sn xut Khong o (ppm) Sierra Monitor - 100 Industrial Scientific - 500 Pemtech 0.1 ppm chớnh xỏc Thi gian ỏp ng (s) Khong nhit (oC) Khong m (%) - 10 15 n 90 -20 n 50 15 n 95 -20 n 50 15 n 90 < 16 ppm -40 n 50 < 30 s 0-100 Lun ỏn phõn gii n 38 35 n 92 < 35 s ppm 105 4.5 Kt lun Trờn c s cỏc kt qu ó t c, chỳng tụi xin a mt s kt lun sau: ó nghiờn cu ch to thnh cụng cm bin khớ H2S da trờn mng mng SnO2 cú o xỳc tỏc CuO bng cụng ngh vi in t Cụng ngh ny cho phộp ch to quy mụ ln cỏc chớp (~400 chớp/1 phin Si 4-inch) cm bin bng s kt hp gia phng phỏp phỳn x hot húa v k thut quang khc nh hng ca dy o xỳc tỏc CuO lờn tớnh nhy khớ ca cm bin mng mng SnO2 ó c kho sỏt vi cỏc nng khớ H2S khong t n ppm ti cỏc nhit 250, 300, 350 v 400 oC Cỏc kt qu ch rng cm bin mng mng SnO2/CuO (dy 20 nm) cho ỏp ng cao nht S = 128 ng vi ppm khớ H2S o ti 250 C Cm bin ó ch to cú chn lc tt kho sỏt vi mt s loi khớ khỏc nh H2, LPG, CO, v NH3 Cm bin khụng h b suy gim phm cht lm vic liờn tc vi 10 chu k o khớ khỏc nhau, v cho thy tim nng cao vic ng dng vo kho sỏt khớ H2S thc t S tng cng tớnh cht nhy khớ ca cm bin mng mng SnO2 cú o xỳc tỏc CuO c gii thớch da trờn hai c ch ú l c ch trn spillover v c ch phn ng húa hc, ú c ch nhy khớ cng c kim tra trờn cỏc loi o xỳc tỏc khỏc nh Fe2Ox, v Cr2O3 Tỏc gi ch rng c ch húa hc quyt nh chớnh n c ch ci thin tớnh nhy khớ H2S ca mng mng SnO2 bin tớnh o CuO ó ch to th nghim mt s linh kin cm bin khớ H2S trờn c s mng mng SnO2/CuO (dy 20 nm) v kho sỏt ti cỏc iu kin hot ng theo cụng sut, nng khớ cng nh chn lc vi cỏc loi khớ khỏc Kt qu cho thy linh kin cm bin cú cụng sut tiờu th thp c 200 mW Cm bin hon ton cú th ng dng vo vic o giỏm sỏt quan trc ụ nhim khụng khớ 106 KT LUN CHUNG V KIN NGH Vi s phỏt trin vt bc ca khoa hc v cụng ngh nano, nhiu loi vt liu cú cu trỳc nano khỏc ó c nghiờn cu nhm phỏt trin th h cm bin khớ mi vi nhiu tớnh nng u vit so vi cm bin khớ truyn thng nh cú nhy cao, chn lc tt, n nh cao v cụng sut tiờu th nh Tuy nhiờn, vic phỏt trin cỏc cụng ngh hiu qu cho phộp ch to c s lng ln cm bin ng dng c sn sut cụng nghip ang l nhng thỏch thc t Cng xu hng ú, khuụn kh lun ỏn tin s ny, chỳng tụi trung phỏt trin cụng ngh ch to cm bin bỏn dn dng mng mng s dng cụng ngh vi in t v phỳn x hot húa ch to cỏc loi cm bin khớ cú ỏp ng cao, c th l chỳng tụi hon thin cụng ngh ch to hai loi cm bin khớ H2S v H2 s dng mng mng SnO2 kt hp vi cỏc o xỳc tỏc tng cng ỏp ng cng nhng chn lc ca hai loi cm bin ny Cỏc kt qua chớnh m chỳng tụi ó trỡnh by lun ỏn ny nh sau: - Thit k, ch to c b mt n (mask) v a c quy trỡnh chun phự hp vi cụng ngh vi in t ch to cm bin khớ mng mng dng mt mt (lũ vi nhit v in cc c tớch hp trờn cựng mt mt) trờn c s vt liu SnO2 Quy trỡnh cho phộp ch to c s lng ln cm bin cú quy mụ kớch c wafer (hn 350 chớp cm bin c ch to cựng mt t cụng ngh) Cỏc thụng s cụng ngh nh chiu dy mng v t l khớ O2/Ar qua trỡnh lng ng mng SnO2 bng phng phỏp phỳn x ó c ti u húa - Ch to thnh cụng cm bin o khớ H2 trờn c s mng mng bin tớnh b mt SnO2/Pd Ti u húa c chiu dy ca o xỳc tỏc Cm bin SnO2/Pd cú cỏc u im vt tri so vi cm bin SnO2 ú l: ỏp ng tt hn (t 27,8 ln nng 250 ppm), nhit lm vic ca cm bin gim n 300 C, cú chn lc tt vi cỏc loi khớ th khỏc nhau, hot ng n nh v cụng sut tiờu th thp Trờn c s cm bin ó kho sỏt chỳng tụi ó thit k v xõy dng c thit b o khớ H2 cnh bỏo s rũ r khớ H2 nhm th nghim kh nng ng dng thc t ca cm bin ch to c - Ch to thnh cụng cm bin o khớ H2S trờn c s mng mng bin tớnh b mt SnO2/CuO Ti u húa c chiu dy ca o xỳc tỏc Cm bin SnO2/CuO cú cỏc u im vt tri so vi cm bin SnO2 ú l: ỏp ng tt hn (t 128 ln nng ppm), nhit lm vic ca cm bin gim n 250 C, cú chn lc tt vi cỏc loi khớ th khỏc nhau, hot ng n nh v cụng sut tiờu th thp Trờn c s cm bin ó kho sỏt chỳng tụi ó thit k v xõy dng c thit b o khớ H2S cnh bỏo s rũ r khớ H2S nhm th nghim kh nng ng dng thc t ca cm bin ch to c - Trờn c s cm bin ó ch to c, chỳng tụi nhn thy cỏc loi cm bin H2 v H2S cú tim nng ng dng cao xõy dng c thit b o cnh bỏo chỏy n o khớ H2 gõy nờn v o khớ H2S phc v quan trc ụ nhim mụi trng 107 - Cỏc kt qu nghiờn cu ny mi ch l u, cn cú nhng nghiờn cu sõu sc v h thng hn nhm nh hng ng dng thc t cng nh tin ti thng mi húa sn phm Hng nghiờn cu tip theo: Kho sỏt nh hng ca cỏc thụng s mụi trng nh m, ỏnh sỏng,v.v lờn tớnh cht nhy khớ ca cm bin tin ti cú th ng dng thc t Hon thin quy trỡnh cụng ngh úng v ca cm bin, bao gm phỏt trin cỏc loi mng lc ci thin chn lc, tin ti ch to hng lot Nghiờn cu v hon thin thit b o cú th ng dng cm bin vic phỏt hin, cnh bỏo nguy c chỏy n v s cú mt ca cỏc khớ c mụi trng 108 DANH MC CC CễNG TRèNH CễNG B CA LUN N N V Toỏn, N V Chin, N V Quy, N V Duy, N V Hiu(2013)Nghiờn cu ch to s lng ln cm bin khớ NH3 trờn c s mng mng SnO2 bng phng phỏp phỳn x Tuyn bỏo cỏo Hi ngh Vt lý cht rn v Khoa hc Vt liu ton quc ln th 8, Thỏi Nguyờn, Vit Nam, Trang 333 336 N V Toan, N V Chien, N V Duy, N V Quy, N V Hieu (2014) Wafer-scale fabrication of planer type SnO2 thin film gas sensor The 2ndInternational Conference on Advanced Materials and Nanotechnology, Ha Noi, Viet Nam Page 244 248 N V Duy, N V Toan, N D Hoa, N V Hieu (2014) Synthesis of H2S Gas Sensor based on SnO2 Thin Film Sensitized by Microsize CuO Islands.The 2ndInternational 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