DAI HOC QUOC GIA HA NOI
TRUONG OAI HOC KHOA HOC TU NHIEN
• • • •
* * *
V\
bl
TA\l!
KHA NANG
LTNG
DUNG CAC DAY NANO ZnO
Dl/OC
CHE TAO BANG
PHl/ONG
PHAP BOG BAY NHIET
MA
SO: QT - 06 - 09
CHU TRI DE
TAI: PCS. TS. Ta Dinh Canh
I
CAN
BO
THAM
GIA: CN. Tran Thi
Quynh
Hoa
CN.
Nguyen
Viet Tuyen
HA
Ndi
- 2006

Diiili
Canh
Can bo tham gia: CN. Tran Thi Quynh Hoa
CN. Nguyen Viet Tuyen
1.
Muc tieu de tai:
Hien nay vat lieu cau
true
nano mot chieu (day nano, thanh nano,
bang nano) dang
du-ffc
quan tam dac biet vi tiem nang ung dung cua no
trong
ITnh virc
linh kien dien tir va quang dien
tir
co kich
thu-ffc
nano.
Vat lieu cau
true
nano mot chieu co the dune
nhu*
cac cau
true
thanh
•
•
•
C3

lien ket
exciton
co*
60 meV. Cac day nano, thanh nano ZnO la cac vat lieu co
nhieu trien
vpng
trong viec che tao cac lade, diot phat quang vung
tii*
ngoai
(sii-
dung hieu
ling
exciton nhiet do phong), cac transit© hieu ung
tru-crng,
chuyen mach quang va cac
senso'
khi
Trong bai bao cao nay, chiing toi tr
inh
b ay cac ket qua che tao day
nano,
thanh nano ZnO bang phuong phap van chuyen tir pha
hai
kh
ong
V
a
CO
chat xiic tac Au trong moi truong
khi

Khi
mang Ar co do sach 99%
+
Tdng hop
ca'u true
nano ZnO
1-chieu
tCr
pha
hai-ran
(VS)
+ Tong hop cau
true
nano ZnO
1-chieu
tir
pha
hai-long-ran
(VLS)
bang
each sir
dung mang vang
(chai
xuc tac) nhu
m6t
dung moi tai nhiet
do
cao.
+ Khao sat
tinh

phirang
phap VS va VLS co dung m6i
trircmg
thoi
khi
tra Ar.
+
khao sat
tinh chA'l
cau true
ciia ca'u triic
nan6 ZnO phu thuoc vao
nhiet
d6
de,
th5i
gian tao
mSu,
do day ciia cha't
xiic
tac vang.
-I-
Khoa sat
tinh
chat huynh quang va kfch thich huynh quang
ciia
cac
day nan6 ZnO da che tao.
H-Birdc
dau phat hien hieu ung nhay am ciia ZnO,

quang
ph6
toan
(liioe hin (hiV
IV,
('iiii
llu),
S/2()()(),
(il;l iilifm
in).
+ Cong tac dao tao :
* Da
hiromg
dan 2 khoa luan tot nghiep
-Vu Tien
L6c"che
tao mot sd cau triic nano ZnO bang phuang phap
b6'c
bay
nhiet" (2006)
-NguySn
Viet Tuyen "Che tao va khao sat dTa nano dang
I6i/v6 ciia
Zn/ZnO
bang phuang phap boc bay nhiet" (2006)
* Da hu6ng
dSn
2 luan van cao hoc:
-TrSn
Thi Quynh Hoa,

Thue mu6n : 6.000.000 d
Chi
phi
vat tu hoa chat: 7.800.000 d
Chi
phi
khac (QLCS): 600.000 d
Da th6ng qua
chijng
ttj*
tai phong tai vu.
Xac nhan
ciia
ban chu nhiem Khoa
(Ky va ghi ro ho ten)
?5
Chia tri
de tai
(Ky va ghi ro ho ten)
PGS.TS.NguyIn
The
Binh
PGS.TS.Ta
Dinh
Canh
Xiic nhAn ci'ui 'IVircnig
DI
IKI II'N
OHO HiEu
IRU6N&

5.
The content of research.
ZnO has a direct bandgap
of
3.37 eV and high mechanical and thermal
stabilities at room temperature. One-dimensional nanostructured ZnO
materials have recently stimulated great interest due to their importance in
basic scientific research and potential applications in numerous areas such as
nanoscale electronic and photonic. The traditional approaches to synthesize
one-dimensional ZnO nanostructures are the vapor - phase transport process
with the assistance of metal catalysis, thermal evaporation and template -
assisted growth [1].
The humidity control is essential for various fields of industry as well
as human life. In this work, ZnO
films
composed of nanowires and nanorods
were fabricated, respectively, on the Si substrate by the vapor - phase
transport process, and their humidity sensitivity characteristics have been
investigated.
6. Results:
1/Tran
Thi Quynh Hoa, Ta Dinh Canh, Nguyen Ngoc Long, Nguyen Viet
Tuyen,
"Zinc
oxide nanostructure for humidity sensor", VNU Journal
ofScience,
Mathematics - Physics, 2006 (in press).
2/Ta Dinh Canh, Nguyen Ngoc Long, Nguyen Viet Tuyen, Tran Thi
Quynh Hoa, Cao Van Tuan, "Multiform ZnO nanostructures
fabricated by vapor-phase transport method without catalyst", VNU

ran
(VS)
,
*
^
L2.L
Co che hai - long - ran(VLS)
7.2.2 Hien
tugng
can bang nhiet dong
Ciurang 2: Thuc
nghiOin
7
Chuang 3: Ket qua va bien luan 12
Ket luan: : 19
L5i
cam an: 19
Tai lieu tham khao: 20
Md DAU
Hien nay tren the gidi da va dang
hinh
thanh mot nganh khoa hoc va cong nghe
mdi,
CO
nhieu trien vong va
dir
doan se co nhirng tac dong manh me den
ta't
ca cac
ITnh

nano (nanoscale).
C)
kfch thudc nano, hieu ung giam gui luong tu
bdt
dau anh hudng tdi tinh chat cua vat
Heu. Cai gi tao cho vat lieu nano su quan
tSm
dac biet, va cai gi da
dan
den su bung no
nhung nghien cuu trong
linh
vuc nay, nhung vat lieu nay cd the
nSng
cao va thay doi
tinh
chat nhu do chung cd su giam gui
lugng
tu trong mot, hai, hoac ba chieu.
Nghien cuu trong
linh
vuc nay se cung ca'p hau het nhung phat minh trong ky
thucU,
Kha nang de lam viec vdi nhirng nguyen tu d
kich
thudc nano, va vdi nguyen tu xac
dinh, huu hen md ra mot
linh
vuc mdi
ciia

lidu
nano da thu dugc
Igi fch
tir
trandilo phat xa trudng
(FETs)
cho nhung thiet vi dien
tii
nhd
ban,
nhe han, va
nhanh hon. va
cCing
md ra m()t
linh
vuc mdi gidng
nlur
spintronic.
Tuy
nhiCii,
khoa
ligc nano
va ky
thuAl
nano
vAn
Hong giai doan
clAu
phat
tridn.

ly
thuyei chi phdi mot ldp rieng cua nhung vat
lieu nay phai dugc phat hien.
Nghien cuu phai dugc tAp trung hon va
ihAin
dd trong
ccrch^kiCm
soat nhung
tinh
chat va
sir
phat trien rieng biet cua nhirng
cA'u true
nay. Chung ta phai luu y
kl
dc' hieu
nhung phat hien dang kinh ngac nay; chiing ta phai khao sat, do, va md hinh, nhung quan
trgng hon, chiing ta phai cd khd nang du doan.
CHl/ONG
I
PHirONG
PHAP
cut
TAO CAU TRUC NANO
1-CHIlSUTirPHAKHI
1,1.Cac
phirong
phap che tao ZnO nano
Cdng nghe
chS

Hmh
1.10:
Phuang thuc bottom-up va top-down
/.2.
/
Phuong
thuc top -
down
I)Ai
vdi cdng nghv
naiu>,
dc
\i\n\
dugc
nhiYng
kich tlnrdc nhd cd I
nni -100
nm,
ngirdi ta phai khac nano bang chum electron, chum ion hdi lu, chum tia X Cd
nh&ng
trudng hgp can kich thudc cd nguyen
tii*,
ngudi ta phai dung bg quet d thiet
bj
hien vi de
quet dau dd dieu kien mui nhgn ve theo cac hinh mong mudn, diing dien trudng d dau dd
de lay di hoac them vao cac nguyen
tii.
Nhiing
each

phap
hieu qua rat cao nhung
ton kem do
sir
dung chan khdng sieu cao.
Ngoai ra, cac
phuoiig
phap hoa hoc khac ciing dugc coi la phuong thiic bottom -
up.
Cac phuong phap hda hgc cd nhieu
hiia
hen vi gia re, che tao dugc sd lugng
Idn
va cd
thS di6u khiSn
kich thudc chinh xac. Ban chat
ciia
viec hinh thanh cac cau tnic nano theo
phuong phap bottom - up chinh la qua trinh tinh the hda thdng qua hai budc co ban: tao
mSm va phat
triSn.
Khi ndng do
ciia cdc
khoi vat chat (nguyen
tir,
ion
hoac
phan tu)
dii
cao,

LTU
diem
ciia
phuang phap nay la co che don gian, tdc do lang dgng
cao,
mang cd do day ddng deu, cd the dieu khien dugc kich thudc. De che tao hon hgp
hoi Zn va 0 trong phuang phap lang dgng tu pha hoi ngudi ta cd the thuc hien mgt sd
each
sau:
Phuang phap phan
hiiy true
tiep ZnO
rSn
thanh hoi Zn va
O
ZnO
(ran)
>
Zn
(ho,)
+O2
(hai) (
1
•
14)
Day la phuong phap dan gian, tuy nhien nd cd han che
la
nhiet dd che tao phai
cao
(^1400

cflng
nhu dang hinh hgc
ciia cac
cau tnic nano.
Phuang phap gian tiep de tao ra hoi Zn bao gdm epitaxy tu pha hoi cua kim loai
hiju
CO, ma trong dd hgp chat kim loai
hiju
co Zn, vi du nhu
diethyl-zinc,
dugc su dung
vdi luu lugng khi oxy hay
N2O
thich hgp.
Phuong phap hien nay dugc ap dung nhieu nhat
la
phuong phap nhiet cacbon,
sir
d\nig
bgt ZnO
dirge Iron
vdi bgt
('
d5
lam
v(it Ii$u
nguon.
U'u
diem ciia
phuang phap nay

ch6
phat
triSn
day
nano ZnO cd
xiic
tac thudng la co
ch^
hoi -
Idng
-
ran
(VLS). Trong khi co
chg
phat
trign
day nano khdng cd
xiic tac
thudng la co
chfi
h(yi
- rAn
(VS).
I.2.C0
che
pliAe trien dfiy
hAii^
phuong phap hoc bay
nhiyt
don

xiic
tac.
Ban diu co
chi
nay dugc cho
la
do cac sai hdng mang, nhung
vi?c
xuat
hi?n
cac
day nano khdng sai hdng da chung minh dieu
nguge
lai. Them vao dd ngudi ta thay tdc
dg phat trien day cao hon loc dg ngung ty tu pha hoi. Co che nay cd the dugc giai thich
la
do ZnO cd
ciiu
tnic dj hudng,
\v\\c
uu
tien lA (0
0 2| -
tryc mA
dgc
tiico
nd
iiAng
lugng
chu

1
\
A
1
1
1
_
1
1
1
-I
|I2I|
I
201
/•7
'
1
1
1
1
1
1
>-
—
n
r
1
\
Hinh
1.11:

tac). Trong
cac
mau khdng cd
xiic
lac, Zn ddng vai trd
tir xiic
tac. Hoi Zn dugc khi Ar dua tdi viing
nhi^t
dp thap hon
sg
hda
Idng.
Cdn trong cac mau cd
sir
d\ing
xiic
tac
(chAng
h^n
Au), hai Zn
vA
/nOi.x
tdi
tAc
d\ing
vdi linh the Au
(lining
thai rAn)
[[}o ihAnh
hgp kim (cAc cau lu

dpng li;ii
d cudi
day. Do qua trinh phat trien thdng qua pha
Idng nen
dudng kinh
ciia cAc day
nano
phy
thudc vao
kich
thudc
ciia
giot chat long va khdng thay ddi trong sudt
qua
trinh
ch6
tao.
Hoi Zn va
ZnO|
Hoi Zn
vaZnOu,
1
w
O O
O,
^
P
De Si cd
phii
vang Gigt hgp kim Day nano,

Neu mau cd
xiic
tac vang,
gigt chat
Idng sg
la hgp kim Au - Zn -
ZnOi-x.
Khi gigt chat
Idng
dat tdi trang thai qua
bao
hda vdi nguyen
tir
Zn va
ZnO|.x
mam bat dau dugc hinh thanh. Trang thai can bang
nhiet dgng cua vat lieu cd the dugc md
ta
theo cdng thuc:
7rR'dL = —^Sdt
(]
16)
kT dx
^ ^ ^
trong dd D
lA
hC*
so
kluiyech lAii /n
-

A
trong dd
ACT
la irng suat trong ldp mang Zn - ZnOx
0)
la the tich nguyen tir Zn,
ZnOi.x
y
la nang
lugng
mAl
{v\\
Do bien thien the hda hieu dung
A//
chfnh bang tdng
ciia
hai
phan
nang lugng:
PhAn
nang lugng.dan hdi tren mgt nguyen tir do su phuc hdi
bi6n
dang tren gigt
chAt Idng
AOTy
va phAn nang lirgng mat di tren mgt nguyen tir do su
tAng
dien tich
hk
mat

IJ'ng
sudt xuat
hi?n chii
yeu trong phan gan gigt
vang.
Do
v^y
khoang
cAch ph\ic
hAi
irng
suAl lA
X (hinh
1.13),
khi dd:
di,i tS.^.L
dx
(1.19)
Cuoi Cling
IDa
/ScTCO^
'lr"'Ti7
2r
AaR
(1.20)
Vay chieu dai day ty le thuan vdi thdi gian phat trien / va ty
le nghieh
vdi ban
kinh day R.
Thdng thudng

Ban chAt
ciia
phuong phap
nAy
la
sir
lang dgng vat lieu tir pha hoi. LTu diem cua nd la co
chi
dan
giAn,
tdc dg
lAng
dgng cao,
mang
cd dg day ddng deu, cd the dieu khien dugc
kich thudc.
2.7,7.
Sa dd he boc bay nhiet dan gian [8]
Ld nung
t
Ar
oooooooooooo
Khi
Ong thach
<
cap
nhiet
n
^
B6t

Id
dat dugc la
1200
°C.
Dd la
nhi?t
dp do dugc d
tam
Id.
Thdng thudng
Id
dugc sir dung d nhiet do
1000
^C.
KhAo
sAt sir
phan bd nhiet
trong
Id
khi rihiet do dugc
giCr
dn dinh tai
1000 T
cho thAy nhiet do phAn bd lech ve phia
trai,
nhiet do tai tirng vi tri tren
Id khA
dn dinh theo thdi gian, sai sd nhiet do khdng qua
10
^C.

.
L(cm)
-13
-12
-11
-10
-9
:', /.
I'hdn
T
C'C)
902
922
940
955
969
hd nhlC'l ci()
Ihco
L(cm)
-4
-3
-2
-1
0
TC'C)
1000
1000
1000
998
996

770
810
846
872
-8
-7
-6
-5
977
984
991
996
1
2
3
4
991
984
979
971
10
11
12
13
869
842
815
785
19
20

1
.
1
.
1
—1—
trai
I
1
1
I
1
1
1
1
1
1
1
1
I I
Nira
16
1 1 1
•
'
1
•
1
:
•

trinh
che tao
2.1.2.3.
Chuan
hi
Vat lieu ngudn
la bdt ZnO (99,9 %) va bdt C (99 %). Cac bdt
ngudn dugc
can
bang carl chfnh
xAc.
Ty le bdt
ngudn
ZnO:C
tinh theo
moi
thay
doi
trong khoang
tir
1:0,05
den 1:0,2. Hon hgp bdt
ngudn dugc trdn
ky
trudc
khi cho vao
Id.
Vat
lieu ngudn
dugc

Id
tuan theo
quy
luat
tren hinh
2.2.
Viec chpn nhiet
dp
dl
phu
thudc
vao
each
chpn
vi tri dat de
trong
Id.
Nhiet
dp dl
thudng dugc
ehgn
trong khoAng
tir 500
°C
den
700
""C.
Nhu vay cac dl
dugc
dat d

am
U'ong
mdi
Inrdng
axcton khoAng
30
plit'il,
roi say khd
Uii W) "C
trong
Id
say.
\^i!t iiAng
cao
hieu
qiiA clic
lao, sau khi
ihAnh
phan
vai lieu
nguon dugc chon
phu hop,
mdi
ldp vang xiic
tac
mdng dugc
phiin
xa len
tren
bl

Trong
qua
trinh
che tao mau cdn cd
sir
tham
gia
ciia
khi
mang Argon
(Ar). Khi
dugc
dua tir
binh
wen
khi Ar
cdng
nghiyp
vao
mgl
dau ong
thach
anh, dAu kia
ciia
ong
thach
anh noi vdi mot
binh
dau
nhdn.

gigt,
ban
kinh
mdi gigt
la 0,5 cm. Vay luu
lirgng
khi
thdi trong binh
la:
8
v
= 60 ;r.(0,5)^=3K4cmVphut
(2.1)
2.L2.3.
Chetqo
NhiC'l
dg Id dugc dAl
Ihco
chuang trinh
{\x
ddng.
QuA
trinh nung dugc
lhi,rc hi^n
iheo
3 giai doan bieu dien tren hinh 2.3.
U
1200
1000
800

TAng nhi^^t
lu
nhi?t
dp phdng len tdi
1000 ''C Toe
dg
tAng nhi?t lA
25
°C/
phut,
d nhi?t
dg cao, bgt carbon (C) trong dieu
ki?n thilu
oxy tAc
dyng
vdi oxy
(O2)
sinh ra khf CO (chAt dgc, khdng mau, khdng
miii).
(ran)
+ 0
2 (khi)
/
cao
>
CO
(khi)
(2.2)
Khi nhiet do tang len khoang 400
°C

o
2 (khi;
850"r
Zn
(khi)
Trong qua trinh nay mam bat dau dugc hinh thanh.
> ZnOi-x (hoi)
(2.3)
(2.4)
(2.5)
(2.6)
Giai
doqn
II: On
dinli
nhivt, khdng
chO nhivl dp
d
1000 ''C
trong
60
phiil.
Trong
giai doan nAy loc do thdi khi Ar dugc khong che khoang 30
cm7phiit.
Viec dieu khien
tdc do khi
rat
quan trgng vi qua trinh
nay

Ddng Ar
«o
*
• . •
•
^
•
'k-'^<^-
^
^
'Day ZnO
*****
L6i
Zn
ZnO
-V6^
~300T *
Giai doan 3
- ~800"C
Dong Ar
~
800
°C
Day ZnO
L3i
Zn -V6
'7 r\
~
300
°C **

ZnO tren de.
I linh
2.5: Mau sau khi
che
tao
CHUONG
III
KJ^T
QUA VA BI$N LUAN
3.1.
Ket qua phan tich cau
triic
ChAt lugng mgt mau phu thudc rAt nhieu
vao
cac thdng sd che tao nhu thanh phan
vat
li^u
ngudn, chat
xiic
tac,
nhi^t
dp, Cac thdng sd ve ty
1^
moi
giua cac
v^it
li?u
ngudn,
dO
dAy Idp vAng

trong trudng hgp
[\r
xiic
tAc
lA
thap. MAm tinh the trong cA hai co che deu ty le vdi lugng
hoi Zn,
ZnOi-x.
Lirgng hoi nAy lai phu thupc vAo lugng carbon. Do vay sd lugng va hinh
dang
ciia
dAy phu thudc vao lugng carbon. Khi lugng carbon trong bdt ngudn nhd (hinh
3.1 a), sd lugng
niAni
quA it, sd lugng dAy tinh the dugc hinh thanh khdng dang ke, chung
phAn bd khdng deu tren de. Khi lugng carbon qua Idn, sd lugng
vA
kfch thudc mAm
Idn
dAn den mat do va kich thudc cac tinh the
Idn
(hinh 3.1 d). Qua trinh oxy hda trong cac
thanh nano cd kfch thudc
Idn
nay
xay
ra khdng hoAn loan. Do dd trong
loi
thanh vAn
Idn

xuc tAc
vAng
cd the hinh thanh theo 2 co che
la
VS va VLS. Ty le carbon trong vat lieu
ngudn cd mgt vai trd
xiic
tac rat quan trpng. Lirgng carbon tAng thi lugng day nano cung
lAng.
Khi lugng carbon Idn, cAc mau thu dugc la cAc thanh nano da tinh the cd kich thudc
Idn,
trong mau van cdn thanh phan Zn do chua oxy hda het. Ty le
ZnO:C
thich hgp nhat
cho viec hinh thAnh day nano ZnO
IA
1:0,15.
3.1.1.
Anh
hwang ciia
chieu day lop
xiic
tdc vang tren de
Tir ket qua khao
sAl
cau triic theo ty le bdt ngudn ta chpn thanh phan bdt ngudn
1:0,15
cho tat ca cac mau che tao. De dieu kien
sir
hinh thanh va phat trien day nano,

ciia cac
dAy cung tang theo, ddng thdi chieu dai
ciia
cAc
dAy giAm. Khi chieu day Idp mang la 20 nm va 25 nm thi day dai vai |im, cd dudng kinh
trung binh cd 36 nm va 40 nm
tuxyng
irng. Khi
chieu
day ldp vang
len Idi
50
nni,
cac cau
12
tnic nano thu dugc cd dang day dudng kinh
Idn
cd 60 nm. Chieu day ldp
vAng Idn
nhat
dugc khAo sat la 100 nm. Khi dd tren mau thu dugc
cAc
thanh ZnO ngan
va
cd dudng
kinh cd
130
nm.
DI
tim

giAc
ciia
ZnO cdn xuAt hien them pha
vang vdi hai dinh
(III)
va (2 0 0). Chimg td trong mAu thuc
sir
cd vang. Trong phd
XRD
ciia
cAc
mau cd Idp vang day cung thay xuAt hien dinh dac trung cho tinh the Zn.
Diiu
nay cho thAy trong cac mau cd tinh the
Idn
vAn ton tai pha Zn.
Hinh
3.5:
Pho XRD
ciia
cdc mau ZnO che tao tren de cd phu lap vdng
vdi
d()
ild\'
khdc nhau:
(a)
20 nm,
(b)
25 nm, (c) 50 nm, (d)
100

vang.
d
nhiet do cao, hgp kim hda
Idng
va trd thanh mdi trudng thuan
Igi
(dung mdi) hap thu hon
13
hgp hoi Zn va
ZnOi.x.
Khi lugng hoi hap thu tang, the tich gigt chAt
Idng
tAng. QuA trinh
nay dimg lai khi chAt gigt
Idng
trd nen qua
bAo
hda vdi hon hgp hoi Zn
va
ZnOi-x-
Liic
nay mAm mdi bat dAu dugc hinh thanh va phat trien thanh day ZnO (the ran).
Trong sudt qua trinh phat trien, gigt hgp kim vang lien tuc bi day len. Do dd dinh
tinh the Au xuat hien trong tAt cA cac phd XRD (hinh 3.5). Hon the, the tfch gigt hgp
kim
vang khdng bi thay ddi trong quA trinh phat trien dAy nen dudng kinh day hAu nhu khdng
thay ddi trong sudt quA trinh che tao. Vay kfch thudc va vi tri gigt hgp kim vAng se quyet
dinh kich thudc va vi trf cac dAy nano. Do day ldp vang
eang
Idn,

lAn nira
khang djnh rang co che phat trien day
nano tren de cd
phii
vang
la
co che VLS. Trong qua trinh hinh thanh mau, vang phu tren
dl tham gia vao gipt hgp kim va ddng vai trd
xiic
tAc. Dp day ldp vang quyet dinh kich
thudc tinh the ZnO. Dp day ldp
vangcAng
Icin,
thiet dien
day
ZnO nano
eang Idn
va
chieu dai day
eang
nhd. Tinh the dAy ZnO kich thudc
Idn
thudng du kem do qua trinh
oxy
hda khdng hoan loan. Vay chieu day tdi uu
ciia
ldp vang thich hgp cho day nano phat
trien
la
trong khoAng tir 20 nm den 25 nm.

ciia
cac mau nhan dugc la can
ihict.
Cac quy luat bien thien
ciia
nAn^
lugng huynh quang
Ihco
nhiet dp do
mfiu sO
cho la
nhieu
thdng sd quy bau
\\c\\
quan den cAu tnic vimg
nAng
lugng
ciia
loai vat
lieu
nay. De hieu rd bAn chAt
ciia
cAc dinh huynh quang, mau ZnO tren
dl
phii
ldp Au day 20 nm da dugc do huynh quang tai nhiet do thAp. Cac phd huynh
quang dugc do trong dAi nhiet do tir 14,5 K den 300 K, sir dung budc sdng kfch thfch
X =
300 nm.
i.2.7.

lidi
cac loai sai hdng nhu mil khuylt oxi
{V^^),
nguyen
tir kem dien
kS
Zn,'\
mil khuyet oxi bj ion hda
(KJ
), nguyen tir
kgm diln
ke bi ion hda
Zn
'^
Zni'"".

cd the
ion
tai trong vung cam
ciia
ZnO
[20],
14
1.8x10
^
1.5x10"
-
1—I—f—I—I—1—1—I
1 r
^uvt

VB irng vdi 2.8 eV.
Vinui
dan
.y,
•
1
\
2.:
2.8
:
1
2.2
r
I—
3.13
3,3
1
IDA
113
3.3f
BF
D°}
t
Vime
hda tri
Hinh
3.10:
Mo hinh cdc
mice
dien tu trong ZnO

IS
,
r
« *
Viec giai thich ngudn gdc cua cac dinh mien tir ngoai trong phd huynh quang
ciia
ZnO dugc nhieu nha nghien
cim
quan tam, tuy nhien cd nhieu y kien khac nhau ve co
che phat quang. De khao sat ky han ve co che huynh quang mien
cue
tfm, dai phd tir 2,8
eV
din
3,8 eV cua mau ZnO do trong dAi nhiet do tir 15 K
din
300 K dugc chi tren hinh
3.11.
Cd the thay rang d
nhi^t
do thap, tai mien huynh quang tir ngoai, trong
cac
phd
deu xuAt hien 4 dinh. Tuy nhien do tuong quan cudng do phd nen cac dinh cd the
ehdng
chap nhau. Tai nhiet dp 61,6 K
sir
tach phd tu nhien cd the quan sAt tdt nhat. Hinh
3.12
bieu dien phd huynh quang tai nhiet dp nay.

5x10-
OX}
c
cr
j=
c
'>»
3
-O-
I
4x10
3x10"
2x10'
-
1x10
I
' I
*
I ' I '
1
o
S0ll^ulhvcnghlCmtlolal6l,6K
" Dirdng
nt
long Ix/p
Kit dinh
I,
II.
III.
IV

3.12:
Phd huynh quang
ciia
mau ZnO nano day do tai nhiet do
61,6
K
De
lAm
sang td ngudn gdc cua cAc dinh phAt xa nay, cAc sd
lieu
thirc nghiem dugc
fit bdi hAm ddi xirng Pearson
Vll
(vdi dg tin cay > 99.3 %)
[14],
y
=
A
2Vm.e^'^
-"
nWe
r(m-0.5)
1
+
4 : '- - ^
W
{X-Xr)
•m
(3.1)
trong dd A

lA
dd thi bieu dien
sir
phu thudc cua
nang lugng cac dinh pho I, II, III, IV vao nhiet do.
Cd the thAy rd rang cAc giA tri thirc nghiem
ciia
dinh I kha
phii
hgp vdi cdng thuc
Varshni [28]:
E{T)=I':{Q)-^—
(3.3)
trong dd £(0) la
nSng
lugng irng vdi vi tri dinh tai 0 K
a wk /3
la cAc tham sd thuc nghiem
100
160 200 250 300
350
Nhiet do (K)
Hinh
3.13:
Sir
phu thuoc cua ndng lirang dinh vdo nhiet do
Dua vao cAc sd
lieu
fit dugc ta cd the tinh toAn
a

lA
vAn de
phAi
bAn luan. Mgt sd tAc giA cho
rAng
dinh
phAt
xa nay
lA
exciton lien
kit
vdi acceptor trung hda [18, 19, 26, 32, 33]. Mgt sd tAc
giA
khAc
l^i
cho rang dinh nAy
lA
do
svr
chuyen ddi hai
di?n
tir
ciia
exciton lien
kit
vdi
donor trung hda
[18,
28], do
lAi

do tai hgp
c^lp
donor - acceptor (phan tich ve
lAi
hgp cAp donor - acceptor se dugc ndi rd
d phan sau). Cd the dua ra gia
ihict
rAng dinh
II lA lAi
hgp
ciia
hat
lAi tren
tap chAt vdi mpl
hsil lAi Ur
do (Bound -
I'rcc
Bl'). Mau ZnO dugc
che
tao
lA
ban dan
lo^ii
n
nen
dinh II cd
thi
la dien lir lien
kit ircn doiu)r
lai hgp vdi lo trdng lu do trong viing hda

l^p
l*;ii
phonon
ciia
dinh II
(BF-LO).
DAi phd rdng cudi ciing (dinh IV) giAm rAt nhanh khi nhiet dp tAng. Dinh nAy dugc
giAi thich
lA
do
sir
tAi hgp phAt xa
ciia cAp
donor - acceptor (DAP). Nang lugng irng vdi
vi tri
ciia
dinh nay dugc xAc dinh theo cdng thirc (1.9):
hco
=
AE
-E^ -E^
+-
d nhi?t
do thap cac hat
lAi
tren donor va acceptor vdi khoAng
each
r nhd s5 bj tai
hgp trudc, nAng lugng phAt xa
Idn.