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Nghin cu v ch to b lc quang (bng rng v bng hp) da trn mng a lp silic xp
Nguyn Thy Vn
Trng i hc Cng ngh
Lun vn Thc s ngnh: K thut in t; M s: 60 52 70 Ngi hng dn: TS. Bi Huy
Nm bo v: 2011
Abstract: Tng quan v tinh th quang t v tinh th quang t mt chiu da trn silic xp. Tin hnh m phng cc c tnh quang hc ca b lc quang. Trnh by cc kt qu thc nghim ch to b lc quang hc giao thoa da trn quang t mt chiu v m phng
Keywords: in t - Vin thng; K thut in t; B lc quang; Mng a lp silic xp
Content
M U
Tinh th quang t l mt loi vt liu mi c nhiu nt tng ng tinh th bn dn -
mt vt liu lm nn cuc cch mng mi v s pht trin ca cng nghip vi in t (IC).
Chnh nh s pht trin ca ngnh cng nghip ny chng ta ch to c nhng my tnh
c nhn gn, nh vi tc cao, nhng h thng thng tin vin thng siu tc bng thng
rng. Tinh th quang t l mt cu trc khng gian tun hon ca cc vt liu c hng s in
mi khc nhau. S bin i tun hon ca hng s in mi lm xut hin vng cm quang
(photonic bandgap - PBG) trong cu trc vng (c hiu l mi lin h gia tn s v s
sng) ca tinh th quang t. PBG trong tinh th quang t c vai tr ging nh vng cm v
nng lng trong tinh th in t.
Chng ta c th s dng tinh th quang t iu khin, giam gi v kim sot nh
sng trong khng gian ba chiu. Tinh th quang t c th cm hon ton cc sng in t c
bc sng trong PBG lan truyn qua n m khng ph thuc vo s phn cc ca nh sng.
Tinh th quang t c th to ra s dn sng t b mt mt nng lng hng dng nh sng
truyn theo mt hng c th (thm ch vi nhng ch r cong n 900) Trn thc t, tinh
th quang t c xem nh linh kin then cht cho cc mch tch hp quang trong thng tin
quang v cc h thng my tnh lng t trong tng lai. Vi kh nng kim sot s lan truyn
v bc x t pht nh sng, tinh th quang t c nh hng to ln n s pht trin cng ngh
2
ch to cc b lc quang, cc chuyn mch quang tc cao, cc hc quang, cc it quang,
cc laser ngng thp, cc ng dn sng vi cc nhnh r nh sng t ngt ng dng trong
thng tin quang v cc sensor ha, sinh hc
Trong cc loi tinh th quang t, tinh th quang t mt chiu l loi tinh th n
gin nht. Tuy nhin tinh th mt chiu li c nhng u im ring nh d dng ch to hn,
c th s dng nghin cu mt s kha cnh ca tinh th quang t nhiu chiu hn v c th
dn n nhng ng dng v cc linh kin m chng khng yu cu phi cm hon ton (v
mi hng) s lan truyn qua hay bc x nh sng. Tinh th quang t mt chiu vi chit sut
ng nht trong mi lp c bit n di tn gi l tm phn x Bragg phn b hay thng
dng hn l b lc quang hc giao thoa. Loi b lc ny l mt trong cc linh kin quang hc
kh thng dng, trc y thng c ch to bng phng php phn x hay bay hi nhit
mt cch ln lt cc oxt to ra mng mng a lp c chit sut thay i tun hon. Ngy
nay, da trn cng ngh in ha phin silic chng ta c th ch to c mng silic xp a
lp c tnh nng nh mt b lc quang hc giao thoa. Cc b lc quang bng rng hot ng
da trn nguyn l phn x Bragg ch to t mng silic xp a lp c th t c rng
ph t vi chc n vi trm nano mt. Trn c s b lc quang bng rng ny, chng ta c th
ch to c cc b lc bng hp c rng ph ch vi nano mt vi suy hao thp di
dng cc bung vi cng hng. u im ca cc b lc ch to bng phng php ny l tch
hp thun li vi cng ngh vi in t to ra mch tch hp quang vi vng ph hot ng
c tri rng t nhn thy, qua hng ngoi n tn vng siu vi ba.
Vi nhng l do trn v ng thi da vo trang thit b hin c ca phng th nghim
ti chn ti cho lun vn thc s l:
Nghin cu v ch to b lc quang (bng rng v bng hp) trn c s mng a lp
silic xp.
Ngoi phn m u v kt lun, lun vn gm c ba chng vi ni dung nh sau:
Chng 1: Tng quan v tinh th quang t mt chiu
Chng 2: M phng cc c tnh quang hc ca b lc quang
Chng 3: Kt qu thc nghim v tho lun
CHNG 1
TNG QUAN V TINH TH QUANG T MT CHIU
1.1 Tinh th quang t
1.1.1 Khi nim tinh th quang t:
3
Tinh th quang t l mt cu trc tun hon trong khng gian ca cc vt liu vi hng
s in mi khc nhau c sp xp xen k nhau, c chit sut thay i theo chu k trn mt
thang chiu di c th so snh c vi bc sng nh sng ang c nghin cu.
1.1.2 Cc c tnh v thng s quan trng ca tinh th quang t
Tinh th quang t c c trng bi mt s thng s c bn sau: S chiu, s i
xng, hng s mng (a), h s lp y (f), chit sut hiu dng (neff), s tng phn chit sut
()
1.1.3 Cc ng dng ca tinh th quang t
S dng nh cc chuyn mch quang hc, b nh quang hc, pin quang-in-ha
Tinh th quang t mt chiu( 1D) c s dng trong vic kim sot v iu chnh nh sng
mc chnh xc c bc sng, nh vic to ra tinh th quang t 1D c s dng nh nhng
b lc quang hc, ng dn sng, cm bin sinh hc
1.2 Tinh th quang t mt chiu da trn silic xp
1.2.1 Tinh th quang t mt chiu c thit k nh mt b lc giao thoa
a. B lc quang giao thoa bng rng Gng phn x Bragg (Distributed
Bragg Reflectors)
B lc bng rng hay gng phn x Bragg l h gm nhiu lp in mi hot ng
da trn hin tng nhiu x Bragg ca mt chm nh sng sau khi phn x ti mt phn cch
gia cc lp in mi. M hnh n gin ca hin tng nhiu x c trnh by trong hnh
1.6 [9],[15], trong mng mng bao gm nhiu cp lp ging ht nhau, mi cp lp gm hai
lp c chit sut n1 v n2 khc nhau tng ng vi dy d1, d2.
Hnh 1.6: (a) Tia phn x v tia truyn qua trong trng hp mng n lp v (b)
trong trng hp mng a lp
B lc di rng c s dng nhiu nht l b lc (Gng phn x Bragg - DBR) phn
t bc sng, l loi b lc c di quang hc ca cc lp l nH.hH=nLhL=/4 v chu k
ca cu trc l =hH+hL
4
Hnh 1.8 Hnh minh ha ca cc hiu ng phn x ca mt b lc bng rng. a) nh
sng phn x ti mi mt phn cch gia cc lp c chit sut khc nhau, b) ph phn x ca
mt b lc bng rng da trn tinh th quang t mt chiu [9],[19].
b. B lc bng hp Bung vi cng hng (Microcavities)
Hnh 1.9. S ct ngang ca mt bung vi cng hng. Chit sut ca lp m l
ns v b dy ca lp ny l ds. Lp m c a vo gia hai DBR i xng vi chit sut
ca cc lp l nH, nL v b dy dH, dL
1.2.2 C s cho qu trnh hnh thnh b lc giao thoa trn c s mng silic
xp a lp
1.2.2.1 S hnh thnh silic xp
Silic xp ch yu c to ra t s n mn in ho cc phin Silic trong cc dung dch
axit HF [2],[13]. Hnh 1.10 l s ch to silic xp: anot l phin silic c b mt c tip
xc vi dung dch HF, catt c lm bng platin.
Hnh 1.10. S nguyn l ch to silic xp
1.2.2.2 Kch thc v hnh thi l xp
5
Hnh 1.12: Mt ct ngang hnh nh TEM cho thy s khc nhau c bn trong hnh thi
gia cc loi khc nhau ca mu. (a) silic pha tap loi p, (b) silic pha tp loi n, (c) silic pha
tap loi p+, (d) silic pha tp loi n+.
1.2.2.3 Cc thng s anot ha
Cc nghin cu s hnh thnh silic xp bng n mn in ha [1],[10] u cho thy cc
tham s nh hng ti qu trnh ny l:
- S pha tp ca phin silic gm: loi tp v nng tp;
- Mt dng;
- Nng HF: nng cng cao, kch thc l v xp cng nh. Nng
HF quyt nh JPS, l gii hn trn ca gi tr mt dng.
- Cc dung mi dng pha long HF: v silic xp l loi vt liu k nc nn
vic s dng ethanol lm cht pha long HF s m bo tnh ng nht v kh nng thm t
b mt tt hn so vi nc kh ion ha.
- Thi gian n mn: thi gian n mn di dn n cc lp dy hn, nu khng
c thi gian di s xy ra tnh d hng i vi chiu su trong lp do hot ng ha hc ca
cht in phn.
- S chiu sng trong sut qu trnh n mn: p dng cho silic loi n [10]
1.2.3 c im ca silic xp.
1.2.3.1 xp (P)
Phng php n gin nht xc nh xp theo trng lng c th hin trong
cng thc 1.4:
1 2
1 3
%m m
Pm m
(1.4)
6
Hnh 1.13 : Mi quan h gia xp v mt dng ca tm silic loi p+ (~0,01 cm)
vi dung dch HF 15% trong ethanol. Tng mt dng dn n xp cao hn. xp nm
trong khong gia 45% v 85% l ph hp i vi mt dng thit lp t 5 mA/cm2 n 100
mA/cm2[23].
1.2.3.2 Chit sut hiu dng
1.2.3.3
Hnh 1.14: Gin minh ha khi nim chit sut hiu dng ca silic xp [22]
Hnh 1.15: Mi quan h gia xp v chit sut ca silic xp. S khc bit gia l
thuyt Bruggeman, Looyenga v Maxwell-Garnett l do nhng gi thit to ra cc hnh thi
ca vt liu hn hp gia silic v khng kh [23].
1.2.3.4 Tc n mn
1.2.3.5
7
Hnh 1.16: Gin mi lin h gia tc n mn vi mt dng in ca loi silic
P+ (0,01 cm ) vi dung dch axit HF 15% trong ethanol[23].
KT LUN CHNG 1
1. Tinh th quang t c cu trc khng gian tun hon v chit sut, c trng c bn
nht ca n l tn ti vng cm quang, tc dng quan trng nht l kim sot s lan truyn v
bc x nh sng.
2. Tinh th quang t mt chiu n gin nht l b lc giao thoa bng rng (DBR), c
cu trc gm cc lp in mi bin i tun hon v chit sut sao cho qung ng quang
hc mi lp tha mn iu kin Bragg. Da trn cu trc ca b lc bng rng, chng ta c th
pht trin ch to b lc bng hp. B lc bng hp c cu trc bung vi cng hng bao
gm hai b lc bng rng ging ht nhau t i xng vi nhau bi mt lp m c di
quang hc bng /2 hoc .
3. iu kin to ra silic xp bng in ho phin silic: dung dch in ho cha HF,
ch phn cc a-nt, mt dng thp hn ngng nh bng in cc v c s tham gia
ca l trng trong phn ng ho tan Si.
4. C s cho vic ch to mng silic xp a lp: (i) qu trnh hnh thnh cc nano tinh
th Si trong silic xp mang tnh cht t gii hn do mt khi nano Si c to ra hay mt lp
xp c to ra th chng s khng b nh hng ca cc qu trnh in ho tip theo; (ii)
xp ca lp xp ch ph thuc vo mt dng khi cc iu kin in ho cn li c duy tr
khng i; (iii) chit sut ca lp xp ph thuc n nht vo xp ca n; (iv) tc n
mn ph thuc n nht vo thi gian n mn khi cc iu kin in ho khc c duy tr
khng i. Cc iu kin ny cho php thay th vic kim sot chit sut theo chiu su ca
mng ngha l to ra mt mng a lp bng vic kim sot mt dng theo thi gian n mn.
5. L thuyt mi trng hiu dng a ra tiu chun cho vt liu xp gm hai pha
c th c xem nh l mi trng hiu dng n nht vi mt hng s cch in c trng
m n l trung bnh theo t trng ca hng s cch in ca hai vt liu hp phn khi khong
khng gian trng trong vt liu nn nh hn nhiu so vi bc sng ca nh sng ti.
8
CHNG 2
M PHNG C TNH QUANG HC CA B LC QUANG
2.1. C s ton hc phn tch v m phng mng a lp
Trc khi ch to b lc quang hc giao thoa, chng ti xy dng chng trnh m
phng c th thit k v d on c cc tnh cht quang hc ca b lc mt cch chnh
xc hn. Mi b lc quang hc giao thoa da trn mng a lp silic xp c c trng bi
cc thng s c bn nh: s lp N, chit sut n v dy quang hc d ca lp. C rt nhiu
phng php s phn tch b lc quang hc giao thoa (hay h thng mng a lp) nh:
Phng php ma trn truyn (Transfer Matrix Method - TMM), phng php sng phng
(Plane Wave Method - PWM), v phng php min thi gian khc bit hu hn (Finite
Difference Time Domain - FDTD). Da trn nhng u nhc im ca tng phng php
chng ti chn phng php Ma trn truyn m phng c trng ph phn x cho cc b
lc c nghin cu trong Lun vn.
2.1.1 Phng php ma trn truyn (Transfer Matrix Method - TMM)
Phng php ma trn truyn (TMM) l mt thut ton rt hu ch cho vic tnh ton
ph phn x v truyn qua ca cc cu trc a lp.
Phng php ma trn truyn c th x l cc cu trc c ch s tng phn cao gia hai
vt liu hn hp. iu ny khin cho TMM tr thnh phng php ph hp cho m phng cc
cu trc mng a lp, l cc cu trc c s tng phn cao gia cc lp.
2.1.2 Chng trnh m phng:
Trong lun vn ny, chng ti s dng phng php ma trn truyn m phng ph
phn x ca b lc quang giao thoa.
Hnh 2.1. S cu trc b lc quang giao thoa 1 chiu bng rng
9
Hnh 2.2 S cu trc ca b lc quang hc giao thoa 1 chiu bng hp
2.2. Kt qu m phng b lc quang hc giao thoa da trn tinh th
quang t 1 chiu:
Mc ch nh gi kt qu thc nghim vi kt qu tnh ton ca l thuyt, chng
ti m phng chi tit khi thay i tng thng s ca b lc. u tin trong phn ny, ti a
ra cc kt qu m phng v b lc quang bng rng, sau l cc kt qu v b lc quang
bng hp.
2.2.1 Kt qu m phng v b lc quang giao thoa 1 chiu bng
rng[3],[8],[21]:
1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 22000
0.2
0.4
0.6
0.8
1
Pho phan xa cua bo loc quang bang rong 1D
Buoc song (nm)
Do
ph
an
xa
(R
)
Hnh 2.3 Ph phn x ca b lc quang bng rng 1D vi chu k l 12,
nH=2,5,nL=1,55,dH=155nm v dL=258,3nm.
Nghin cu cc thng s ca b lc quang:
a) T l chit sut nH/nL:
1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 22000
0.2
0.4
0.6
0.8
1
1.2Pho phan xa cua bo loc quang bang rong 1D
Buoc song (nm)
Do p
han
xa (
R)
(a)
1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 22000
0.2
0.4
0.6
0.8
1
1.2Pho phan xa cua bo loc quang bang rong 1D
Buoc song (nm)
Do
ph
an
xa
(R
)
(b)
10
1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 22000
0.2
0.4
0.6
0.8
1
1.2Pho phan xa cua bo loc quang bang rong 1D
Buoc song (nm)
Do
ph
an
xa
(R
)
(c)
Hnh 2.4. Ph phn x ca b lc quang bng rng vi s chu k N=12. dy ca
mi lp c tnh ton sao cho bc sng trung tm 1550nm. T l chit sut nH/nL ln lt
l:(a) 2/1,55; (b) 2,3/1,55; v (c) 2,5/1,55
1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 22000
0.2
0.4
0.6
0.8
1
1.2Pho phan xa cua bo loc quang bang rong 1D
Buoc song (nm)
Do p
han
xa (
R)
(1) 2.0/1.55
(2) 2.3/1.55
(3) 2.5/1.55
(1)(2)(3)
Hnh 2.5 Ph phn x ca b lc quang bng rng 1D khi t l chit sut n1/n2 ca cp
lp trong mt chu k thay i
b) S chu k ca b lc:
1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 30000
0.2
0.4
0.6
0.8
1
1.2Pho phan xa cua bo loc quang bang rong 1D
Buoc song (nm)
Do p
han
xa (
R)
(1) N=4
(2) N=6
(3) N=8
(4) N=25
(1) (2) (3) (4)
Hnh 2.6. Ph phn x ca b lc quang bng rng 1D vi n1=2,3; n2=1,55 v s
chu k ln lt l 4, 6, 8 v 25 chu k
Bng 2.1 Bng gi tr th hin s ph thuc ca phn x vo s chu k
S chu
k N
H s
phn x
S chu
k N
H s
phn x 1 0.5172 9 0.9932
2 0.6904 10 0.9961
3 0.8113 11 0.9978
4 0.8886 12 0.9988
5 0.9354 13 0.9993
6 0.9692 14 0.9996
7 0.9789 15 0.9998
11
8 0.9880 16 0.9999
Hnh 2.7: S ph thuc ca h s phn x vo s chu k
Nhn xt: khi s chu k N tng ln, h s phn x tng dn ti gi tr 1
Nghin cu s nh hng ca s chu k ln bn rng ph
Bng 2.2 Bng gi tr th hin s ph thuc ca bn rng ph
vo s chu k
S chu
k N
bn
rng ph
S chu
k N
bn
rng ph 2 698 9 363
3 551 10 353
4 481 11 345
5 440 12 338
6 411 13 332
7 392 14 327
8 375
Hnh 2.8. S ph thuc ca bn rng ph vo s chu k
Nhn xt: khi s chu k N tng ln th bn rng ph c xu hng gim xung v
dn ti gi tr xc nh.
c) Nghin cu s nh hng ca bc sng nh sng trung tm ln bn
rng ph
12
1000 1500 2000 2500 3000 35000
0.2
0.4
0.6
0.8
1
1.2
Pho phan xa cua bo loc quang bang rong 1D
Buoc song (nm)
Do
ph
an
xa
(R
)
(1) 1000nm
(2) 1550nm
(3) 2500nm
(1) (3)(2)
Hnh 3.12. S ph thuc ca bn rng ph vo bc sng nh sng trung tm. (1)
0 = 1000 nm, (2) 0 =1550 nm, (3) 0 = 2500 nm.
Bng 2.3: Bng gi tr th hin s ph thuc ca bn rng ph vo bc sng nh
sng trung tm trong vng 1000nm n 2800 nm:
Bc
sng nh sng
trung tm (
nm)
bn
rng ph
Bc
sng nh sng
trung tm (nm)
bn
rng ph 1000 289 2000 442
1200 265 2200 487
1400 310 2500 530
1550 353 2600 573
1800 398 2800 618
Hnh 3.13: th th hin s ph thuc ca bn rng ph vo bc sng sng
trung tm.
Nhn xt: bn rng ph ph thuc gn nh tuyn tnh vo bc sng ca nh sng
ti, khi bc sng nh sng ti tng, th bn rng ph cng tng
2.2.2 Kt qu m phng b lc quang giao thoa 1 chiu bng hp da
trn tinh th quang t 1 chiu [21]:
500 600 700 800 900 1000 11000
0.2
0.4
0.6
0.8
1
1.2Pho phan xa cua bo loc quang giao thoa bang hep 1D
Buoc song (nm)
Do
ph
an
xa
(R
)
13
Hnh 2.7. Ph phn x m phng ca mt b lc quang giao thoa bng hp 1D vi
bc sng cng hng 0 =650nm. T l ca nH/nL l 2,5/1,55 v dss= 0 /2ns.
Nghin cu cc thng s ca b lc quang giao thoa bng hp 1D
a) dy ca lp khng gian (dss):
500 600 700 800 900 1000 11000
0.2
0.4
0.6
0.8
1
1.2Pho phan xa cua bo loc quang giao thoa bang hep 1D
Buoc song (nm)
Do p
han
xa (
R)
(a)
500 600 700 800 900 1000 11000
0.2
0.4
0.6
0.8
1
1.2Pho phan xa cua bo loc quang giao thoa bang hep 1D
Buoc song (nm)
Do
ph
an
xa
(R
)
(b)
Hnh 2.8 Ph phn x ca mt vi hc cng hng bao gm 2 DBR vi dy quang
hc l /4 v mt lp khng gian dy l a), b)/2.
b) Chit sut phn x ca lp gia
Hnh 2.9 Ph phn x ca b lc quang giao thoa da trn tinh
th quang t 1 chiu bao gm 2 DBR vi nL=1,55 v nH =2,5. dy
ca lp khng gian l /2 v chit sut phn x ca n ln lt l a)1,4,
b)1,55, c) 1,8, d) 2,5.
d) S chu k ca DBR
400 500 600 700 800 900 1000 1100 12000
0.2
0.4
0.6
0.8
1
Pho phan xa cua bo loc quang hoc bang hep
Buoc song (nm)
Do
ph
an
xa
(R
)
N=2
N=4
N=6
N=8
(4)(3)(2)(1)
Hnh 2.10 Ph phn x ca b lc quang hc giao thoa bng hp da trn tinh th
quang t mt chiu ti bc sng trung tm 650nm trong cc DBR c s chu k khc nhau.
14
2 3 4 5 6 7 80
2
4
6
8
10
12
14
16
18
20
FH
WM
lin
e w
idth
of
cavit
y (
nm
)
The number of periods N
Hnh 2.11 S ph thuc ca bn rng
ph vo chu k ca b lc quang hc giao thoa bng hp ti bc sng 650nm.
KT LUN CHNG 2
1. Trong chng ny, chng ti chng minh c rng phng php ma trn
truyn l phng php rt hu ch v n gin cho vic m phng mng a lp. Da vo
phng php ny, chng ti m phng c cc c tnh quang hc ca b lc quang bng
cch thay i cc thng s u vo nh chit sut v dy ca cc lp, s chu k, gc ti v
khong bc sng. Cc c trng ca ph phn x ca b lc quang hc giao thoa bng rng
v bng hp c nghin cu trong vng bc sng t 600nm n 3000 nm.
2. Trong lun vn ny, mc d vic m phng trng tm cho cc lp silic xp
nhng vi bt k vt liu no chng ta cng c th m phng c bi v chit sut c th
c thay i ty vo mi vt liu khc nhau.
3. Cc kt qu nghin cu ph phn x ca b lc quang hc bng rng bng
chng trnh m phng nh sau:
- Ph phn x ph thuc ln vo t s nH/nL (t s gia chit sut lp cao v chit
sut lp thp), rng ph tng cng vi tng phn chit sut gia hai lp lin k
- Khi s chu k N tng, ph phn x ca cc b lc hp li v phn x tng
dn ti 1
- Khi s chu k N tng ln, h s phn x tng dn ti gi tr 1
- Khi s chu k N tng ln th bn rng ph c xu hng gim xung
- bn rng ph ph thuc tuyn tnh vo bc sng nh sng ti, khi bc
sng nh sng ti tng, th bn rng ph cng tng.
4. Sau khi m phng cc c tnh quang hc ca b lc quang hc giao thoa bng
hp ta thu c cc kt qu nh sau:
- Khi thay i dy quang hc ca lp khng gian th ph phn x trong c hai
trng hp v /2 l tng t nhau. nh truyn qua c t ti bc sng trung tm
650nm trong c hai trng hp v phn x trong c hai trng hp gn nh bng 0 ti bc
15
sng ny. Tuy nhin, vng cm ca b lc vi lp khng gian l /2 l rng hn vng cm ca
b lc c dy l v cc cc tr hai bn gn vi vng cm hn.
- Chit sut phn x ca lp khng gian gn nh khng c nh hng nhiu ti
vng cm hoc nh truyn qua. S khc nhau gia cc ph phn x khi ta quan st thy c
l cc side-lobes.
- rng ca nh truyn qua ph thuc vo s chu k ca cc DBR ca hc
cng hng. Khi N tng, nh truyn qua tr nn hp hn, phn x ca vng cm tng ln
v hnh dng ca ph sc nt hn.
CHNG 3
CC KT QU THC NGHIM V THO LUN
3.1 Nguyn l, qui trnh ch to mng a lp bng phng php n mn
in ha
3.1.1 Nguyn l ch to
3.1.2 Ch to b lc quang hc da trn mng a lp silic xp
Bc 1: Chun b mu, dng c v ha cht
Hnh 3.1: H l c dng tip xc cho phin silic bc bay nhm
Bc 2: Ch to PC 1D bng phng php n mn in ha
Hnh 3.2: H thng n mn in ha
16
Hnh 3.3: S h in ha AUTOLAB. PGSTAT 30 dng ch to PC 1D
3.2 Thit k ch to b lc quang hc giao thoa da trn tinh th quang t 1
chiu
3.2.1 Thit k b lc quang hc giao thoa bng rng
Hnh 3.4: Lc ch to mng a lp
3.2.2 Thit k b lc quang giao thoa bng hp
Hnh 3.5. (a) S minh ha cu trc ca mt b lc quang hc bng hp th hin bi
lp khuyt tt c di quang hc /2 xen gia hai DBR gm cc lp c chit sut cao v
thp c di quang hc /4 xen k ln nhau. (b) Ph phn x tng ng ca b lc cho thy
mt bc sng cng hng hp gia nh phn x cc i.
17
Hnh 3.6. S minh ha qu trnh n mn to ra silic xp. Qu trnh ha tan ca
silic c u tin xy ra nh cc l xp ni mi trng l m c nht v cc l trng (h+)
v cc ion F- phn ng vi nhau. Hn na cc vng pha trn sau khi b n mn khng b nh
hng bi cc ht ti in
Hnh 3.7. S ca quy trnh to ra cc lp silic xp. Thi gian v ln ca mt
dng in quyt nh dy v xp ca lp silic xp sau khi in ha. Khi p dng mt
dng theo thi gian ( th bn tri), cc lp silic xp c hnh thnh tng ng (hnh v bn
phi). Mt thi gian ngn c thit lp (vi mt dng bng 0) nng HF cn bng
trong sut cc l xp v ngn nga s hnh thnh ca gradient xp khng mong mun
Bng 3.1. Cc iu kin n mn ch to b lc quang hc bng hp da trn tinh
th quang t 1D
M t Mt dng
(mA/cm2)
Thi gian
(s)
18
Gng
trn
(N,5 chu
k)
15 6,35
50 3,63
Lp
khuyt tt
50 7,26
Gng
di (N+1 chu
k)
15 6,35
50 3,63
3.3 Cc kt qu ch to b lc quang hc giao thoa da trn tinh th quang
t 1D
3.3.1 Cc kt qu ch to b lc quang hc giao thoa bng rng da trn tinh
th quang t 1D
a. Cu trc b lc quang bng hp
(a)
(b)
Hnh 3.8: nh FE SEM ca 2 lp lin k c t s mt dng (a) 15/50mA/cm2 and
(b) 25/50mA/cm2
b. Cu trc ca cc PC mt chiu c s chu k khc nhau
Hnh 3.9: nh FESEM c cng h s khuch i ca mt ct ngang ca
mng a lp vi s chu k N l 6, 12 v 18, tong ng vi cc hnh (a), (b) v (c).
c. Cc kt qu nghin cu ph phn x ca PC mt chiu da trn mng
silic xp a lp
19
iu khin bc sng trung tm ca ph phn x trong di hng
ngoi
1000 1500 2000 2500 3000
0
10
20
30
40
50
60
70
80
90
100D
o p
han x
a (
%)
Buoc song (nm)
Hnh 3.10: Ph phn x ca PC mt chiu ch to bng phng php n mn in ha vi
nng HF l 16%, tng phn mt dng 50mAcm-2/15 mAcm-2
Hnh 3.11: Ph phn x ca cc mng a lp c thit k vi bc sng trung tm
thay i trong di hng ngoi
nh hng ca s tng phn chit sut ln rng ca cc i ph
phn x
Hnh 3.12: Ph phn x ca cc PC M4 v M5 c ch to vi t s mt
dng J1/J2 tng ng l 50mAcm-2
/30mAcm-2
v 50mAcm-2
/15mAcm-2
C
n
g
p
h
n x
(%)
Bc sng (nm)
20
Nh vy bc u c th khng nh rng c th iu chnh tng phn v
mt dng in ca hai lp lin k trong qu trnh ch to b lc iu chnh rng ca
cc i trong ph phn x.
nh hng ca s chu k N ln ph phn x ca b lc da trn mng
silic xp a lp
Hnh 3.13: Ph phn x ca cc b lc a, b v c c ch to vi s chu k
N tng ng l 6, 18 v 12.
1000 1500 2000 25000
0.2
0.4
0.6
0.8
1
1.2
So sanh pho phan xa mo phong va thuc nghiem
Buoc song (nm)
Do p
han
xa (
R)
(1) mo phong
(2) thuc nghiem
Hnh 3.14. So snh ph phn x m phng (1) v thc nghim (2) ca cng mt mu
b lc quang hc bng rng da trn PC 1D vi bc sng thit k =1460nm
d. Cc kt qu ban u v ch to b lc quang hc bng rng hot ng
trong vng nhn thy da trn mng silic xp a lp ch to bng phng php n
mn in ha
Hnh 3.15. nh chp cc mu PC 1D hot ng trong vng nhn thy cc bc
sng khc nhau (tng ng vi iu kin ch to khc nhau)
C
ng
ph
n x
(%)
21
a b
400 450 500 550 600 650 700 750 800
10
20
30
40
50
60
70
80
90
Cu
on
g d
o p
ha
n x
a (
%)
Buoc sng (nm)
562.5nm
603nm
647.7nm
689nm
(1)(2)
(3)
(4)
Hnh 3.16. Ph phn x ca cc mu b lc quang hc hot ng trong vng nhn
thy
3.3.2 Cc kt qu ch to b lc quang hc giao thoa bng hp da trn tinh
th quang t 1 chiu
Hnh 3.17. nh FE-SEM ca mt ct ngang mt b lc quang hc giao thoa bng hp
da trn tinh th quang t 1D vi di quang hc ca lp m (lp khuyt tt) l /2 vi
bc sng cng hng 650nm v tng phn chit sut l 15/50mAcm-2 (a), v nh FE-
SEM cho thy kch thc ca cc l xp vo khong vi chc nanomet trong lp m ca b
lc (b)
Hnh 3.18. nh FE-SEM ca vi hc cng hng 1D vi bc sng cng hng
650nm, t s mt dng l 15/50mAcm-2, nng HF l 16% cho thy b dy ca lp m
l khong 174nm
22
400 500 600 700 8000
10
20
30
40
50
60
70
80
Do
ph
an
xa
(%
)
Buoc song (nm)
Hnh 3.19. Ph phn x ca vi hc cng hng 1D vi 20 lp silic xp. Bc sng
trung tm ca vi hc cng hng 643,27nm v rng tng ng ca di truyn qua l
20nm.
500 600 700 80020
30
40
50
60
70
80
90
Do
ph
an
xa
(%
)
buoc song (nm)
a
b
Hnh 3.20. Ph phn x ca hai vi hc cng hng c cc iu kin ch to ging
nhau nhng s chu k ca cc DBR trn/di l khc nhau ln lt l
6,5/7 (a) v 8,5/9 (b).
400 500 600 700 80010
20
30
40
50
60
70
80
Do
ph
an
xa
(%
)
Buoc song (nm)
Cavity 11 Jan 146
540nm
576nm
Hnh 3.21. Ph phn x ca vi hc cng hng 1D gm hai di truyn qua trong vng
cc i ph phn x ti 540nm v 576nm
23
450 500 550 600 650 700 750 800 850 9000
0.2
0.4
0.6
0.8
1
Pho phan xa cua bo loc quang hoc bang hep
thuc nghiem va mo phong
Buoc song (nm)
Do
ph
an
xa
(R
)
(1) thuc nghiem
(2) mo phong
(1) thuc nghiem
(2) mo phong
Hnh 3.22. So snh ph phn x thc nghim (1) v m phng (2) ca cng mt mu
b lc quang hc bng hp da trn PC 1D vi bc sng thit k =644nm
KT LUN CHNG 3
1. Chng ti xy dng c quy trnh v ch to thnh cng mng silic a lp
ng u trn din tch c 1 cm2 bng phng php n mn in ho phin silic loi p+, c
nh hng tinh th (100) trong dung dch HF l 16% vi vi cu trc bao gm cc l xp ng
u nm trong khong 5 n 50 nm tng ng vi s thay i ca mt dng trong khong
t 15mA/cm2 n 150 mA/cm2.
2. S ph thuc ca tc n mn vo mt dng n mn v s ph thuc ca
chit sut vo mt dng n mn c nghin cu v cho cc kt qu tng t vi cc
cng b ca cc tc gi nc ngoi.
3. Chng ti ch to thnh cng cc b lc quang hc bng rng trn c s
mng silic xp a lp hot ng trong vng ph t hng ngoi n vng nhn thy vi h s
phn x ln ti 80%.
4. Ph phn x ca cc b lc ch to c s ph hp nht nh vi cc kt qu
nhn c t tnh ton m phng v nh hng ca tng phn chit sut ca cc lp lin
k v s chu k N ca b lc. S sai lch v ph gia thc nghim v m phng ch xy ra vi
cc b lc c s chu k qu nh hoc qu ln v c gii thch thng qua s thay i cu
trc ca cc lp xp trn b mt v di y ca b lc.
5. Chng ti cng ch to thnh cng b lc bng hp hot ng trong vng
nh sng nhn thy da trn PC 1D bng phng php n mn in ho phin silic. Cc b lc
quang hc ny c phn x cao, trong khong t 50% n hn 80%.
6. Cc kt qu thc nghim cng cho thy khi s chu k ca b lc quang bng
hp tng ln th cng ca nh ph phn x tng ln v rng na cc i ca di truyn
qua gim. Cc kt lun ny rt ra ph hp vi cc tnh ton bng m phng.
24
KT LUN CA LUN VN
Lun vn t c mc tiu ra vi nhng kt qu chnh nh sau:
1. Lun vn trnh by mt cch h thng khi nim, nhng c trng c bn cng
nh nhng ng dng quan trng ca tinh th quang t ni chung v c bit l ca tinh th
quang t mt chiu da trn mng silic xp a lp.
2. Lun vn xy dng c mt quy trnh n mn in ho n nh, to c mng
xp a lp ng u trn din tch mu l ng trn c ng knh 10mm.
3. Lun vn chng minh c rng phng php ma trn truyn l phng php rt
hu ch v n gin cho vic m phng mng a lp. Da vo phng php ny, chng ti
m phng c cc c tnh quang hc ca b lc quang bng cch thay i cc thng s u
vo nh chit sut v dy ca cc lp, s chu k, gc ti v khong bc sng. Cc c
trng ca ph phn x ca b lc quang hc giao thoa bng rng v bng hp c nghin cu
trong vng bc sng t 600nm n 3000 nm
4. tm c quy trnh n nh, ph hp ch to cc b lc quang hc bng rng
c cht lng tt hot ng trong mt vng di ph rng t vng nhn thy n vng hng
ngoi. Cc b lc ny c cu trc trt t dn n hnh thnh vng cm quang theo phng
truyn, phn x cao. Vng cm quang ca cc b lc quang hc ph hp vi cc tnh ton
t m phng. Ngoi ra, chng ti cng nghin cu nh hng ca cc yu t nh tng
phn chit sut, s chu k n ph phn x ca b lc quang hc. Kt qu cho thy:
- Khi tng tng phn chit sut gia cc lp th cc i ph phn x
s c m rng.
- Khi s chu k tng ln th cng phn x tng dn n 1 v bn
rng ca cc i trung tm s gim.
Cc kt qu ny cng cho thy s ph hp gia m phng v thc nghim.
5. ch to thnh cng cc b lc quang bng hp trn c s PC 1D. Cc b lc ny
c vng bc sng hot ng tri di trong vng nhn thy v c phn x t 50% n 80%.
Ph phn x t m phng v thc nghim c s ph hp vi nhau chng t cht lng ca b
lc ch to c. Cc kt qu thc nghim cng cho thy khi s chu k ca b lc tng ln th
cng ca nh ph phn x tng ln v rng na cc i ca di truyn qua gim. Cc
kt lun ny rt ra ph hp vi cc tnh ton bng m phng.
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25
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