Chế tạo và khảo sát các senso khí trên cơ sở vật liệu zno

+ Che tao mang Pd bang phuang phap bde bay nhiet trong chan khdng, do day eiia mang kim loai bien ddi tir vai chue den ban mot tram nanomel.. + Chd tao thanh edng mang Pd vdi cac do day

DAI HOC QUOC GIA HA NOI TRLfONG DAI HOC KHOA HOC 11/ NHIEN

* * *

bl TAI t

CHE TAO VA KHAO SAT GAG SENSO KHl'

TREN GO S6 VAT LIEU ZnO

Ma so: QT - 01 - 32

CHl) TRI DE TAI: PGS TS Ta Dinh Canh

CAC CAN BO THAM GIA: ThS Nguyen Duy Phuong

ThS Nguyen Sy Hai

•-•' , J- •• : S O I

H.A NOI - 2002

3AO CAO TOM TAT

Chu tri de tai: PGS TS Ta Dinh Canh

1 Muc tieu de tai:

Trong gan mudi lam nam nay, da cd rat nhilu net cd gang de phat triln cac loai sensa boa hgc mdi va tot han Thue te cac sensa ban dan val ran da ird

thanh ddi tugng quan trgng de phat hien va xac dinh nong do cac khi dt chay va

doe [1] Trong dd, nhiJng cd gang mdi da nghien cuu che lao cac sensa nhay khi hydro, vi rang khi nay la mot trong cac khi nguy hiem va rat dl chay

Tir y6u eau thue te dd, muc tieu cac dl tai la bude dau nghien cuu che tao 2 loai eau triie sensa nhay khi hydro: Pd/ZnO/p-Si va Pd/ZnO/Zn, de c6 the phal hien khi hydro vdi nong do tir 20.000 ppm trong khdng khi d nhiet do phong Vdi sir ban che vl thdi lugng, vl kinh phi, dl tai chi gidi han d muc lieu la danh gia sa bd cac tinh chat nhay khi hydro ddi vdi cac eau true sensa con danh gia mot each dinh lugng va tinh lap lai va dn dinh eiia cac sensa nhay khi hydro nay eon la van dl can duge tiep tuc nghien cuu

2 Noi dung nehien curu:

De thue hi6n duge muc tieu neu d tren, dl tai da giai quyet duge cac van dl sau:

+ Che tao mang ZnO cd eha't lugng cao bang phuong phap phiin xa r.f magnetron tren thiet bi Univex - 450 eiia hang Leybold

- Lam chu duge thiet bi Univex - 450 eiia hang Leybold

- Che tao bia ZnO tir bgt ZnO eiia hang Merck bang phuang phap gdm truyin thdng tren cac thiet bi eiia du an OPEC

+ Che tao mang Pd bang phuang phap bde bay nhiet trong chan khdng, do day eiia mang kim loai bien ddi tir vai chue den ban mot tram nanomel + Khao sat tinh chat eiia mang ZnO va mang Pd

+ Che tao to hgp eiia eau true sensa nhay khi Pd/ZnO/p-Si va Pd/ZnO/Zn + Danh gia do nhay eiia cac sensa da che tao trong buong do vdi cac nong

do khi hydro khae nhau

3 Cac ket qua dat duuc:

+ Dua cac thiet bi che tao mang mdng bang phiin xa catdt Univex-450 va bde bay nhiet trong chan khdng Univex-300 vao boat dgng cd hieu qua (tuy rang van eon trong thdi gian bao hanh )

+ Che tao thanh edng cac loai bia ZnO va ZnO pha tap bang phuang phap gdm truyin thdng

+ Tim duge che do edng nghe de che tao mang ZnO va mang ZnO pha tap tren

de p-Si va de thiiy tinh bang phuang phap phiin xa r.f magnetron iren ihiel

bi Univex-450

+ Chd tao thanh edng mang Pd vdi cac do day khae nhau bang phuang phap bde bay nhiet trong chan khdng tren thiet bi Univex-300

+ Khao sat eae tinh eha't cua cac mang ZnO tren de thiiy tinh

+ Che tao thanh edng 2 loai eau triie sensa nhay khi hydro Pd/ZnO/p-Si va Pd/ZnO/Zn va khao sat tinh chat nhay khi hydro vdi cac nong do hydro khae nhau tir 2000 ^ 20.000 ppm

+ Cdng tac nghien cuu:

1/ Ta Dinh Canh, Nguyen Ngoe Long, Nguyen Duy Phuong, Nguyen Si Hai ^' Preparation of ZnO films by R F magnetron sputtering", Comm in phys.,

12, N"2 (2002) p.p 1 0 4 - 1 1 0

2/ Ta Dinh Canh, "Che tao va khao sat sensa nhay khi hydro tren ca sd mang mdng ZnO d nhiet do phdng'\ Tuyen tap bao cao khoa hgc Hoi nghi khoa hgc ky thuat do ludng Viet Nam Ian thu 3, Ha Ngi - 10/2001, 509 - 514 + Cdng tac dao tao :

* Da hudng dan 2 khoa luan tdt nghiep:

1/ Nguyin SI Hieu, ''Che tao va khao sat mang ZnO de thiiy tinh bang bde bay nhiet kem axetat trong chan khdng" Ha Ngi - 6/2001

2/ Nguyin Hong Viet, ''Che tao va khao sat mang ZnO pha tap Al tren de thiiy tinh bang phuang phap phiin xa R F magnetron", Ha Ngi- 6/2002

* Da hudng dSn 1 luan van cao hgc:

1/ Nguyin Si Hai, " Che tao va nghien cuu mot sd tinh chat ciia mang ban d^m ZnO va ZnO pha tap Al bang phuang phap phiin xa R.F magnetron" - Ha Ngi, 9/2002

* Dang hudng dan 1 nghien cuu sinh trong hudng nghien cuu nay

4 Tinh hinh sur dung kinh phi

Tong kinh phi duge cap :

Thanh toan hgp dong va thue ehuyen gia

Trang thidt bi khdng phai TSCD :

Da thdng qua ehiing tir tai phong tai vu

8.000.000 d (tarn trieu dong) 7.000.000 d

1.000.000 d

XAC NHAN CUA BCN KHOA

(Ky va ghi rd hg ten)

CHU TRI DE TAI

(Ky va ghi ro ho ten

^

PGS.TS Le Viet Du Khirong PGS.TS Ta dinh Canh

XAC NHAN CUA T R U O N G

OH6 H'E'J Tci'jnK'P

PGS.TS Nguyen Ngoc Long

BRIEF OF THE REPORT

1 The title of the project

Fabrication and Investigation of gas sensor based on ZnO material

The code number: QT - 01 - 32

2 Main responsible person: assoc prof Dr Ta Dinh Canh

3 Main implementation numbers:

Master Nguyen Duy Phuong Master Nguyen Si Hai

4 The objects

ZnO, a II-VI compound semiconductor and a prospective material for hydrogen

detection, has a very sensitive surface mainly due to surface adsorption of oxygen species

5 The content of research

Thin film ZnO (0.3 -^ 1.0 |im) has been deposited on various substrate by an r.f (13.56 MHz) magnetron sputtering of a ZnO target in an Ar atmosphere The film composition was characterized A Pd/ZnO/p-Si heterojunction and Pd/ZnO/Zn metal-active insulator-metal (MIM) were fabricated, and tested for hydrogen sensor apphieation

6 Results:

1/ Ta Dinh Canh, Nguyen Ngoe Long, Nguyen Duy Phuong Nguyen Si Hai ^' Preparation of ZnO films by R F magnetron sputtering", Comm in phys., 12,N**2(2002)p.p 1 0 4 - 1 1 0

2/ Ta Dinh Canh, " Preparation and Investigation of Room - temperature Hydrogen sensors based on ZnO ", proceedings of the 3''' Vietnam metrology conference, oct 25 - 26 (2001), 509 - 514, Hanoi, Vietnam

7 Conclusion

* Obtaining the aims of the project

* Training 2 graduate students, 1 master student and 1 Ph.D student

MUC lUC

trang

Mddau 1 Chutfng 1: Phuong phap thue nghiem 2

1.1 Che tao mang mdng ZnO 2

1.1.1 Phuang phap phiin xa catdt 2

1.1.2 Phuang phap bde bay nhiet 4

Chuung 2: Ket qua va bien luan 5

2.1 Mot sd tinh chat eiia mang ZnO 5

2.1.1 Tinh chat eau triie eiia mang ZnO 5

2.1.2 Tinh chat quang va huynh quang eiia mang ZnO 7

2.1.3 Tinh chat dien eiia mang ZnO 11

2.2 Che tao va khao sat sensa nhay khi hydro 13

2.2.1 Che tao mau do 13 2.2.2 Sa do eau triie va ban chat vat ly

eiia sensa nhay khi 15

2.2.3 Dae tinh eiia eau triie Pd/ZnO/p-Si va Pd/ZnO/Zn

ddi vdi ndng do khi Hj khae nhau d nhiet do phong 16

2.2.4 Do nhay khi phu thuge vao do day lap Pd 17

2.2.5 Gia edng nhiet trong mdi trudng hydro 20

Ket luan 22 Tai lieu tham khao 23

Phuluc 24

Md DAU

Nghi6n eiin do nong do eiia khi hydro la van dl khoa hgc va edng nghe vat lieu ha'p dan nhilu nd lue nghien cuu va ung dung trong nhihig nam gan day Khi hydrd duge su dung nhilu trong nhilu nganh cong nghe d nude ta eung nhu tren the gidi Viee six dung khi hydro trong thap ky qua da tang len ciing vdi cac phat minh

ra cac litig dung mdi vdi su trg giiip eiia ky thuat an toan Mot sd tinh chat vat ly va hoa hgc da duge khai thae de phat hien khi hydrd Cac cam bien hydrd vat ran dua tren cac tinh eha't dien nhi6t, ap di^n, quang dien, ban dan va dien hoa da duge thdng bao tren cac tap chi Mac dii rat nhilu trong sd cac cam bien nay sir dung kim loai Paladi (Pd) de bay hydrd, viee tim kiem cac vat lieu va cdng nghe che tao cam bien hydro van can thiet vdi nhirng dae tfnh nhu sau: do ehgn Igc hoa hgc, linh thuan nghich, dap ling nhanh, do nhay cao, kich thude nhd, che tao dan gian va khdng gay d nhilm mdi trudng Trong sd cac cam bien hydrd, phan Idn dua tren cac linh kien dien tir ket hgp vdi viee su dung Pd lam lap boat dgng

ZnO la chat ban dan thuge nhdm A^ B^\ la vat lieu ran day hiia hen de phal hien khi hydrd [2], cd bl mat rat dl hap thu khi oxy Tuy rang, ZnO da duge khao sat de ling dung rgng rai lam cac thiet bi nhu trong pin mat trdi chat lugng cao [3], diing mang ZnO lam ngudn phat thu song am bl mat [4] song ngay ca tinh chat nhay khi eiia ZnO vSn ehua duge khai thae hoan toan [5]

Trong dl tai nay ehiing tdi trinh bay phuang phap che tao mang ZnO bang phuang phap phiin xa r.f magnetron, che tag va khao sat sensa nhay khi hydro d nhiet do phong vdi eau triie lap ehuyen tiep di the Pd/ZnO/p-Si va eau triie kim loai

- dien mdi - kim loai (MIM) Pd/ZnO/Zn

CHUONG L PHUONG PHAP THUG NGHIEM 1.1 Che tao mang ZnO

1.1 Che tao m i u

Hien nay cd nhilu phuang phap de che tao cac mang ZnO phiin xa ca lot [6], epitaxy bang chum phan tir [7], sol-gel [8], phun tinh dien [9], oxy hoa mang kim loai Zn[10], bde bay nhiet trong chan khdng [11], phun dung dich tren de ndng [12]

1.1.1 Phuang phap phun xa ca tdt

Cac mau mang mdng khao sat trong

dl tai nay duge che tao bang phuang

phap thdng dung la phiin xa catdt, ca

sd eiia phuang phap nay la su dung

cac ion eiia nguyen tu khi tra argon

(dang plasma eiia Ar duge chi ra d

hinh 1.1) de ban pha bl mat bia cua

vat lieu can lang dgng thanh mang

mdng lam bat cac nguyen tu ra khdi

bl mat eiia bia va sau dd duge lang

khoang each giixa anot va catdt la 6 cm, nhiet do de cd the thay doi duge nhd thay ddi the dat vao bep dien trd tdi nhiet do 250'G, plasma duge hinh thanh trong moi trudng khi Ar cd do sach 3N (99,9%) Bia gdm ZnO duge che tao tir bgt ZnO c6 do sach 3N (99,9%) cua hang Merck cd dang dia trdn cd dudng kinh day (j) = 75 mm

va do day la 3mm (hinh 1.3) Bia gdm ZnO duge che tao nhu sau: trdn diu bgt ZnO

vdi chat kit dinh, sau dd duge dua vao khudn ep hinh tru c6^ = S7 mm va nen dang

tde tren thiet bi nen thuy lire vdi ap lire 67 tan Bia gdm ZnO duge sir ly d 200'C trong 2 gid va duge thieu ket trong Id nung cd ehuang trinh xu ly nhiet do vdi toe

do tang nhiet do la 1,5'G/phut va giir bia d nhiet do 1300'C trong thdi gian 3 gid

Hinh 1.2: He phiin xa de va r.f

magnetron Univex-450

Hinh 1.3: Bia ZnO do chung toi

che tao

Mang mdng ZnO duge lang dgng tren de lamen cua Dii'c vdi kich thude 20x20x0.1

mm De thuy tinh duge lam sach bang sieu am vdi cac dung mdi thich hgp: Aceton, con tuydt ddi va duge say khd d 120'C Chilu day ciia mang duge xac dinh qua dau

do thach anh ed gan liln vdi thidt bi (gian tiep) hoae xac dinh true tiep qua anh SEM va qua su giao thoa cua pho truyin qua eiia mSu do

1.1.2 Phuong phap bde bay nhiet

Phuang phap nay dua tren nguyen tac lam ndng chay va bay hai (hoae thang

hoa) cac nguyen tir eha't ran va lang dgng cac nguyen tii hoa hai len mat de ran a

day sir dung nang lugng nhiet Joule sinh ra khi cd dong dien chay qua mot vat dan Cac vat dan di6n diing lam nguon nhiet thudng la cac la kim loai cd dien trd suat Idn va chiu duge nhiet do cao (> lOOO'G) nhu vonfram (W), mdlipden (Mo) tantan (Ta) d dang day hoae la mdng hoae cac hgp chat nhu nitarit, cacbit Nguon nhiet thudng duge tao dudi dang nhu cai gid, noi hay thuyin de dung vat lieu bay hai De tranh phan ling giCra vat lieu bay hai vdi cac kim loai lam nguon nhiet, ngudi ta thudng phii cac vat lieu nhu Al20^, B2O3 len day kim loai de tao thanh noi ehua vat lieu bde bay Cd the dl dang dilu khien

nhiet do lam bay hai vat lieu bang dilu

khien cudng do dong dien Do chan khdng

tdi thieu de tao ra mang mdng ed chat

lugng tdt la ed lO'*" Torr Vdi do chan

khdng nay, tinh theo quang dudng tu do

trung binh, thi cac nguyen tu tir nguon cd

the di thang duge khoang 5 m mdi va cham

vdi cac nguyen tu khae Vi the neu khoang

each tir nguon tdi de dien hinh la tir 10 ^

50 em, cac nguyen tu se di thang tdi de ma

khdng hi va cham

Cac mang kim loai Al tiep xiic omic vdi mang ZnO, hoae cac mang Ag, Zn

da duge che tao tir he chan khdng Univex-300 ciia hang Leybold (Hinh 1.4) He dal duge chan khdng la 10" Torr, cd trang bi do do day va tdc do lang dgng mang hang phuang phap dao dgng ban thach anh, cd he thdng tao nhiet do cho de tao mang

Hmh 1.4: Thiel bi boc bay nhiet

Univex-300

CHUONG n KET QUA VA BIEN LUAN

2.1 Mot sd tinh chat cua mang ZnO

2.1.1 Tinh ehdt eau true eua mdng ZnO

Bia gdm ZnO duge che tao tir ZnO dudi dang bgt eiia hang Merck vdi kich thude trung binh la 2,49 |^m duge xac dinh tir thiet bi eiia hang Manrern Mastersizer, duac chi ra tren hinh 2.1

ZnO Volume (%)

Hinh 2.1 Sir phan bd hat theo kich thude hat ciia bgt ZnO Cac mang ZnO duge che tao bang phiin xa r.f magnetron tren de thuy tinh vdi nhiet do de d nhiet do phong, ap xuat khi argon la 8,8.10"^ Torr cdng suat phiin xa r.f bien doi tir 70 -^ 200 W Cac mang ZnO la cac mang da tinh the vdi eau triic luc giac va phat irien theo hudng true c vudng gdc vdi mat phang de

Pho nhieu xa tia X ciia 5 inSu mang ZnO ngung ket tren de thuy linh vdi cac edng xuat phat khae nhau (P): 70 W , 100 W, 130 W, 160 W va 200 W duge chi ra tren hinh 2.2

Cac kit qua cua ehiing tdi phu hgp vdi cac ket qua thu duge tir cac phuang

phap khae [13] dinh (002) ed cudng do tang theo su tang ciia edng suat ciia nguon

phiin xa r.f Kich thude tinh the tucmg ung vdi do dai ket hgp dgc theo phu(tng

vudng gdc vdi de duge suy ra tir ban do rgng eiia dinh (002) theo cong thue sau day

[14]: Mm

D = 0,9A

p.CosO (2.1) i2 trong dd X la bude sdng eiia tia X, p la ban ^

:()()()-do rgng eiia dinh (002) va 6 la gdc nhilu xa

nghe khae duge giir nhu nhau) Anh SEM

eiia mang ZnO duge dua ra tren hinh 2.3

Anh SEM mang tuang ling vdi do day ciia

.^2 U M^ ^x 40

2 - Theta - Scale

Hinh 2.2 Phd tia X cua cac miing ZnO duge ngung ket tir cac cdng suat phun xa khae nhau:

p=70 W(a): P= 100 W (h):

p= 130 W(c): P= l60W(d):

P = 200 W(e)

mang la 1,59 \m\ vdi cdng suat r.f la 200 W ed the thay rang hat phan bd rat

dong dIu vi bl mat mang ngung ket rat tran tru

Hinh 2.4 la ket qua phan tich phd tan sac (EDS) ddi vdi mang ZnO ket

qua phan tich EDS ciia mSu cho thay cac dinh tan sac hoan loan phu hgp vdi

cac dinh tan sac ciia cac nguyen to ed trong thanh phan ciia bia duge ehiing toi

che tao

<^ J,.* { ^ ^ # ^ A

Eaergy (keV)

Hinh 2.3: Anh be mat eiia

mang ZnO tren ddihuy tinh vdi

edng suat ngudn r.f 200 W

Hinh 2.4: Phd tan sac nang lugng

(EDS) ciia mang

2.7.2, Tinh ehdt quang vd huynh quang eua cac mdng ZnO

Cac mang ZnO ngung ket bang phuang phap phun xa r.f.magnelron vdi cong suat 200 W ed bl mat ra't tran tru va ed do dinh vdi de tdt Cac mang cd do truyin

qua trung binh tren 90 % trong miln anh sang ed bude sdng 400 - 800 nm (Hinh 2.5)

Bude sdng eiia anh sang tdi mau litig vdi cac cue dai va cue tilu trong phd truyin qua eung duge su dung de do do day cua mang, sir dung mdi lien he [15] sau:

trong dd n la chiet suat eiia mang

1\X phd truyin qua tren hinh 2.5, ehiing ta cd the xac dinh do day d ciia mang ZnO Chang ban vdi cac bude sdng A,^.,, = 491,5 nm, \^^^^ = 433,3 nm va n = 2,06

[11] Do day d duge tinh tir bieu thue (4.2) cho gia tri bang 445 nm

Phd hap thu quang ciia mang ZnO d nhiet do phong duge danh gia d hinh 2.10 Dinh phd chung to su cd mat eua hap thu exciton

-Hinh 2.6: Phd hap thu quang

ciia mang ZnO tren de thuy tinh

hv(c\')

Hinh 2.7: D6 thi ciia [/,{v) hv]^ doi

vdi nang lugng ciia photon vdi mang ZnO

Ht sd ha'p thu vdi cac ban dan ehuyen miic thang, tuan theo mdi quan he sau:

a ( v ) / ? v = A(/?v-E^)'^- (2.3) trong dd A V la nang lugng photon, E^ la do rgng viing cam

Nang lugng viing cam duge ngoai suy tir phan tuyen tinh ciia dd thi [a(v)hv]

-ddi vdi hv tdi [a (V)/A^] ^ = 0 (hinh 2.7) Vdi cac mang ZnO khdng pha tap, nang

lugng vimg ca'm la 3,24 eV, ket qua nay phu hgp vdi nhilu tac gia khae [16]

Phep do phd huynh quang eiia mau bgt ZnO duge thue hien d nhiet do phong

300 K Khi kich thude mSu bang biic xa dien tir ed bude sdng 300 nm (viing nang

lugng kich thich Idn han nang lugng vung cam ciia ZnO) ehiing tdi thay phd huynh

quang xuat hien mot dinh rat yeu tai 382 nm (hinh 2.8) va mot dinh phd rat rgng

bao phii tir 450 H- 600 nm Do anh hudng cua ham bae hai eiia bude song kich thich

mau len phd huynh quang va phai sir dung bude sdng kich thich 300 nm de ghi

nhan dinh 382 nm, edn miln phd rgng duge ghi nhan ro ret han khi dung bude song

kich thich 365 nm (hinh 2.8)

va (b) A = 365 nm

Phd huynh quang ciia mang ZnO duge do d viing nhiet do tir 11 K den nhiet

do phong 300 K vdi bude sdng kich thich 300 nm [17] Phd huynh quang lieu hieu

ttr eae nhiet dd khae nhau duge ehi ra d hinh 2.9 Phd huynh quang cac mang ZnO d

11 K the hien 3 dinh tai cac bude sdng 370 nm (tuang ung vdi nang lugng hv = 3,350 eV ), 375 nm (tuang ling vdi nung lugng hv = 3,306 eV) va 390 nm (tuang ling vdi nang lugng hv = 3,17 eV)

Nhu thay d hinh ve trong phd huynh quang d 11 K cudng do d dinh 370 nm bang cudng do d dinh 375 nm (Hinh 2.9) Cac dinh huynh quang d cac vung bude sdng xanh va dd dIu ra't nhd so vdi dinh huynh quang d bude sdng 380 nm (miln tir ngoai gan), ehiing to eae mSu ZnO duge che tao bang phuang phap phiin xa eatot it sai hong va do hgp thiic cao ban so vdi phuang phap khae

10

ducfng vdi nang lugng Av=3.27eV) d 300 K Trai nguge vdi dinh ?L2=375 nm , dinh

^3= 390 nm md rgng sang viing sdng dai khi tang nhiet do ngay tir 50 K va dinh

ling vdi bude sdng la 403 nm (tuang duang vdi nang lugng hv =3.07 eV) d 100 K

va d nhiet do cao ban 160 K dinh nay se bi tat Dudi dilu kien nhu vay dinh phiil quang mdi vdi bude sdng 384 nm (tuang duang vdi nang lugng Av=3.228 eV) da duge phat hien (hinh 2.9b, c, d, e, f)- ^ nhiet do cao han 160 K dinh ?t.=375 nm md rgng vl phia sdng dai va ket hgp vdi dinh 384 nm, cho nen trong phd huynh quang eiia mSu do ehi ed mot dinh vdi bude sdng la 379 nm da duge quan sat (hinh 2.9)

Dinh ?.|=370 nm ed the quy cho la cap exciton lien ket donor - trung hoa (D'X) Dinh ^2-375 nm la nhd lai hgp ed biic xa ciia electron lien ket vdi donor va

Id trdng tu do trong vung hoa tri (BF) Khoang each giira cac muc nang lugng ciia eae vach vdi bude sdng 375 nm va bude sdng 384 nm la 78 meV, ciing bac vdi nang lugng phonon quang dgc trong ZnO Nhu vay, dinh ling vdi bude song 384 nm duge xem la lap lai phonon cua dinh vdi bude song la 375 nm (BF-LO) Con dinh vdi bude sdng 403 nm ed the duge giai thich nhu ket qua sir ehuyen biic xa nhd cap dono-axceptor (DAP)

2.1.3 Tinh ehdt dien cua ZnO

Ddi vdi mang ZnO, khi ehua pha tap, vdi do hgp thiic cao, mang ZnO la chat dien mdi Thdng thudng khi che tao mang ZnO vdi do hoan hao khong cao thuang

CO nhimg mil khuyet oxy Nguyen tu tap chat se lam thay ddi dang ke do dan cua mang

Mang mdng ZnO duge che tao bang phuang phap phiin xa r.f magnetron vai cdng suat 200 W, ap suat khi Ar 8,8 xlO'^^Torr, nhiet do degiu'd nhiet do

phong, dd day ed 445 nm (duge xac dinh bang cdng thiic 4.2) va dien trd mat 9x10

^ Q (duge xac dinh bang dien trd vudng ciia mang ZnO ) vdi cue tiep xiie omic bang mang nhdm (duge che tao bang phuang phap bde bay nhiet trong chan khdng), nhu vay di6n trd sua't eua mang vao ed 4 x 10' Qem

Dien trd mat eua mang ZnO giam tdi gan 3 den 4 bae khi tien hanh gia cong

nhift trong mdi trudng hydrd d nhiet do 350 C Dien trd mat ciia mang ZnO giam

khi thdi gian ii trong mdi trudng hydrd tang va bao hoa sau 30 phiit, duge ehi ra tren hinh 2.10

Treaimem lime Imin.)

Hinh 2.10: Dien trd mat eiia mang ZnO nhu ham ciia thdi gian gia edng nhiet trong mdi trudng hydrd

Su giam eiia dien trd suat eiia mang ZnO khi gia edng trong md trudng hydrd cd the do hieu ling nha oxy Hieu ling nha oxy cd thi theo ha each Thii nhat, sir nha oxy tren bien hat dan den the rao giam, donors do do linh dgng tang Thii hai, su nha oxy xay ra ngay tren bl mat , dSn den giam miln cd dien trd mat cao

12

Cac phep do Hall ddi vdi mang ZnO (mSu do duge ehi ra tren hinh 2 11) duge thue hien d nhiet do phong Tat ca cac mang dIu the hien linh dan dien loai n vdi nong do hat tai ed 2,1 x 10 '^ em"' va do linh dgng Hall cd 36 em'V-'s'

Hinh 2.11: Sa dd do cac thdng so dien bang hieu ling Hall tren mang ZnO

2.2 Che tao va khao sat sensa nhay khi hydro tren ca sd mang ZnO d nhiet do phong

2.2.1 Che tao m^u do

Ca'u triie Pd/ZnO/p-Si (Idp ehuyen tiep di the ) mang ZnO duge che tao bring phuang phap phiin xa r.f magnetron (cdng suat ngudn r.f la 200W, ap suat khi Ar la 8,8.10"''Torr, nhiet do de giii d nhiet do phong) tren de Silic dan tinh the (100) vdi nong do tap chat N^^ = 4x10'"" e m \ Lap tiep xiie phia trude vdi mang ZnO la mang

paladi duge chd tao bang phuang phap bde bay nhiet trong chan khdng (vdi miic do chan khdng la 10^ Torr)

Tuang tu, ca'u triie Pd/ZnO/Zn (MIM) duge che tao vdi cue tiep xiic phia sau mang ZnO la mang kim loai Zn tren de thiiy tinh (mang kim loai Zn duge che tao bang phuang phap bde bay nhiet trong chan khdng ed do day thay ddi) lap tiep xiic omic vdi de Si loai p la lap nhdm (Al) chilu day ed 100 nm duge che tao eung bang phuang phap bde bay nhiet trong chan khdng d mat sau eua phien Si

Tinh chat nhay khi eiia cac mau che tao duge tien hanh nghien ciiu duge chi

ra tren hinh 2.13 [16] duge che tao tai trung tam dao tao qudc te ve khoa hgc val lieu (ITIMS) trong dai ap suat khi tir 10 den 760 Torr d nhiet do phong.Khi hydro duge dua vao trong budng thii nghiem va lay ra bang bam chan khong sa cap va he

14

thdng eae khoa chan khdng Dae trung Von - Ampe duge do bang he do 1-V HP 4156A Preision Semiconductor Parameter Analyzer va may tinh PC 486

2.2.2 Sa do can triie vd ban chat vat ly cua sensa nhay khi

Hinh 2.14 la sa do ciia su phan ly ciia cac phan tii hydro tren be mat Pd , trong dd H^ la nguyen tu hydrd Cac nguyen tii hydrd khuyeeh tan tdi phan bien Pd-ZnO tao thanh mot Idp ludng cue dien H; la cac nguyen tii hydrd hap thu tai phan bien [1]

ZnO

Hinh 2.14 Sa dd sir thay ddi trang thai ciia hydro

Trong qua trinh hoi phue cac nguyen tii hydrd se khuyeeh tan tii phan bien Pd-ZnO tdi bl mat ngoai eiia Pd de ket hgp vdi nguyen tii oxy tao thanh nude hoae hai nguyen tii hydrd ket hgp vdi nhau tao thanh phan tii H2 Cac phan lu nude va hydrd se thoat ra khdi bl mat Pd nam trong chan khdng hoae bang kich hoal nhicl

Hien tugng vat ly ca ban eua nhay khi hydro la qua trinh hap thu va giai hap thu Pd gay ra su phan buy tu phat cua phan tir hydrd tao ra cac nguyen tii' hydro d bien eiia lap bien eiia Pd/ZnO

Vat lidu nhay chinh la mang ZnO Nhu da biet, dxy duge hap thu tren bl mat ZnO nhu O ', O2 ngay ca d nhiet do phong bang cac dien tii bi bat giu [1] Nhirng nguyen tii hydrd phan ling vdi loai dxy nay tao thanh ra cac phan lii H.O

va eae di6n tu duge giai phong, gay nen su tang dong qua lap tiep giap Phan ling nay la phan ling toa nhiet (1,8 Kcal moi"') va phan tii nude thoat nhanh ra khdi bl mat:

(02)zno + (2HJ,,o ^ H20(g) + Phan ling tao thanh nude la phan ling rat phiic tap va ca che ehinh xac van edn ehua that chae chan

e-2.2.3 Dae tinh cua eau true Pd/ZnO/p-Si va Pd/ZnO /Zn ddi vdi nong do

khi hydro khae nhau a nhiet do phong

Tren hinh 2.15 md ta dae trung Von-Ampe ciia Idp ehuyen tiep p-n trong ca'u triie Pd/ZnO/p-Si (mang nhdm la cue tiep xiic omic vdi de Si ) d nhiet do phong

(hinh 2.15a) va vdi eae nong do hydrd khae nhau Tir cac do thj ta thay dong dd ciia Idp ehuyen tiep la Idn va thay ddi Song vdi cac nong do hydrd khae nhau do djeh ehuyen didn the rat rd rang

Dae trung I-V eiia eau triie sensa Pd/ZnO/Zn trong khdng khi va tir cac ndng

do hydrd khae nhau la dudng tuyen tinh, duge md ta tren hinh 2.16

Hinh 2.16: Dae trung Von-Ampe ciia eau true sensa Pd/ZnO/Zn

(a va c trong moi trudng chan khong, b - trong moi trudng khi hydro

vai ndng do 2000 ppm)

2.2.4 Do nhay khi phu thuoc vao do day lap Pd

Do day ciia lap Pd duge xac dinh dua tren hien tugng phan xa tia X (XRR) Chilu day mang mdng t duge xac dinh dua tren bieu thiic vl quang Ig giua cac lia phan xa tir mat mang mdng va dilu kien cue tri giao thoa Khi chum tia X eo bude