ポリイミド基板上に作製されたVOPc薄膜の形態と非線形光学特性へのコロナ帯電効果

愛総研・研究報告 第4号 平 成 14年

59

ポリイミド基板上に作製された

VOPc

薄膜の形態と非線形光学特性へのコロナ帯電効果

Effects of Corona Charging on

N

onlinear Optical Property and Morphology of VOPc

Th

in Film Prepared on Polyimide Substrate

by Molecular Beam Epitaxy

Hiroyuki NAKANO t

，

Y

可

iSAKAI t

，

Yoshiyuki UCHIDA t t t

，

Asao OHASHI t t

中野寛之 酒井雄二 内田悦行 大橋朝夫

Kenzo KOJIMA t t and Shizuyasu OCHIAI t t

小嶋憲三 落合鎮康

Abst

:

r

ad: - One important factor for a nonlin巳aroptical thin film having high second and third nonlinear optical susceptibilities is a high packing density. Vanadyl-phthalocyanin巴(VOPc)thin films were pr巴par巴don non-charged and corona-charged polyimide substrates by the molecular beam epitaxy (MBE). The VIS川V spectrum of Sample 1 on a non-charged substrate had a maximum absorption peak at 835nm. According to Griffiths et al吋 theVOPc thin film has a

maximum absorption peak at 830nm， after prepared on a glass at room t巴mperatureand heated at 325 oc for 2 hours. He called the morphology of Phase III. The maximum absorption peak of Sample 1 shifted longer by 5nm than that reported by Griffiths. This means that th巴packingdensity of Sample 1 is higher than that of the VOPc thin film reported by Grif -fiths. A maximum absorption peak in Q band region of Sample 4 on a corona charged substrate appeared at 845nm

，

which is longer by lOnm than that of Sample 1.This suggests that a strong interaction betw巴enVOPc mol巴culeand elec帯

triccl四 g巴onpolyimide s由strat巴makesa high molecular packing of Sampl巴4. The third harmonic (TH) generations of Samples 1 and 4 w巴remeasured by Mak巴rfring巴withP polarized laser ligh. The peak vt alu巴ofTH intensity of Sample 4 was larger by 2 tim巴sthan that of SampJe 1. This means that the nonlinear optical property of VOPc thin film is im

-proved by corona charging. Keywords: epitaxy

，

VOPc film

，

corona charging

，

phase transition

，

THG 1.

I

n

troduction Nonlinear op乱calmaterials are泊lpOrt阻tto develop optical devices such as laserフopticalswitch， modulation， and m巴mory. Ther巴fore，由eyhave recently at回ctedmuch attention. Va -nadyl-P色白aloc戸 血1巴 (VOPc)isone of them. Many re -S回rchぽshave reported出品tVOPc thin fi1ms were epitaxially grown on alkali halide substrates by恥田E1) -4). Moreover

，

Ochi泊巴tal po泊tedout出at由es泊glecrystal(pesudomorphic lay釘)hav泊gabsorptionpeakat 79伽minQband have notbe巴ninvestigated for也ethird-order nonlin巴紅optical properti回 阻d由巳morphologies勾 Th巴 pol

り出

de(PI) film is

T

愛知工業大学電気電子工学専攻 (豊田市)

t

t

愛 知 工 業 大 学 電 気 工 科 ヰ (豊田市) t t t愛知工業大学情報通信工特ヰ (豊田市) mor巴:flexible，better optical仕 組smittiviりTand much cheaper than KBr subs加teand also is a heat-resistant polym紅 白 血 . They mean that th巴VOPcfilm prep紅巳don polyimide film w世 b巴abl巴touse as a substrat巳toprepare VOPc白血filmτnere -fore

，

we investigat巴dthe morphologies姐dnonline紅 optical properties of VOPc thin films prep紅巳don polyimide臼m. Possible ways to improve the nonlinear optical sus

∞

ptib出

t

y

of VOPc thin film訂巴toincrease由巳filmthickness， to improve the orientation of mol巴culeson仕lesubstrat巴andto increase th巴 molecular packing densiけ.百lerefore，we willdiscuss the differen田 be何 回nthe nonlinear optical properties ofVOPc thinfi1ms prep紅吋 ona non-

∞

rona charged and

∞

rona charged PI subs回te. W巴willalso加vestigatethe relation be抑E巴nth巴morphologies田dnonl加巴aroptical properties of VOPcthin臼msbyVIS川Vspectros

∞

py， Scanning electron

60 愛知工業大学総合技術研究報告，第4号 平 成14年，Vo.14，M訂.200

ヨ

Illlαoscopy(SE

附 加

dMaker合inge.

20E珂狩，riments

百leso町 田 material凶edwas VOPc powder supplied企om

Eastman Kodak Company. Figure 1 shows批 molecular

S位uctureof VOPc molecule. Its powder was inserted into a

Knudsen-cell組dpr巴heatedat 3伺，

O

c

for one hOUL 百leS

Uf-fa田 ofPIsubs回tewas cleaned up with ac〆etone. After that

，

the subs回tewas attached on誼leholder.The main chamber of

MBE was at about 10・7pa， 四d批 PIsubs回tewas preheated

at 300

o

c

for one ho町.τ'heevapo国ingtempera加I巴 σ~)was kept at 3佃IOC. Syrnbols used眠 Ts:subs回tetemperature

，

t : evaporating t加le阻dd : film thickness

，

respectively.

グ

V

~ー N ベ主主

一

一

一

;

一

一

一

J

0.2n皿 、 、 . E F ' a 〆 ， 園 、 、 司王司C日正迫田.!l.e

¥

λ

人 人 人 ^

Á~申官b告とr弘、

AV.).

品明討がザ人

J

担

1

.

.

.

.

.

"

唆

品

売

γ

人

式 首 守A

"

'

y

弘

討

仏

￨

抽 出

￨

(b)Phase II Figure 1 (a) Mol巴，C蜘 蜘C畑氏ofVOPcmolec叫紅 (b)S加 ctur巴ofPhase

n

Th巴d紅伊19on PI subs回tewas done by a

∞

rona ch紅伊19 method using a needle-plate elec仕ode. The distance be附 田n 出eneedle and t巴h<plateelectrode was 2αn.τ'he tip radius of

出en田dlewas260μm.τ'hePIsubs回.tewas put on the plate just叩d紅 白eneedle阻d8 kV was applied to the needle for 30 minutes. 30 Results and di.scussions Firs

t

1

y

，

fue morphologi，田 ofVOPc thin filmspr叩M吋 onPI subs加tewere investigated by VIS，川Vspec仕aand SEM国司 ages observed under differenf conditions. Figure 2 shows fue VIS川V spec回 measuredunder different

∞

nditions. S

a

m

r

-ple 1 shows a broad band企om55伽 皿to78仇1m阻d阻 ab -sorption peak at 835nm.

A

∞

ordingωGri箇 fus

，

the

抑 制

hav泊gone peak at 820 nm in

Q

band region is叩lledPhaseII 6同. Its structure is shown in Figur，巴1. PhaseIIhas a仕I -clinicαystal struc制 民 出espa

∞

group P and is identified as a slipped stackarr佃gement. τ'heabsorption peak at 835nm of S但npl巴1shifts by 15nm th巴longerwavelength sid巴白血白紙 of Phase

I

I

.

Itreveals血atthe phase morpholo⑤TofSample 1 is not Phase

n

but has a di笠erentphase.τ'he phase having 阻 absorptionpeak at 83臼lIllis called Phase

m

6.同. PhaseIII has a te仕agonalαystals位uc刷工e. S但nple1 has叩 absorption peak at 835nm泊Qband region. 百lerefore

，

its phase is close to Phase III and may also illclude a deformationIrlVOPc出加 film. S但nple2 has an ab問 中tionpeak at 84伽 四 泊Qband region. 百1ISme姐S白at白epacking density of VOPc白血 血mishi俳 句 白 血thatof Sample 1. Inother words

，

it sug -gests白atisland crystals grow in VOPc thinfilm by molecular d出lSion. Sampl巴3has批 absorptionpeak at 845nm

。

泊

band region. Th巴substratetemperature of Sample 3 is hi偵巴E 曲四社Iatof S阻 .ple2園 Therefore

，

it su毘巴ststhat island αys

-tals加ぬ巴VOPcthin film of Sample 3 are much lager th組

曲os巴forSample 2. Sample 1 (Ts: 80"C， t:120min.， d: 75nm) 冨Sample 2 (Ts: 150oC， t:60皿in.，d: 54nm) 四Sample 3 (Ts: 20QoC， 仁 30min.，d: 35nm) 0.8

.

.

，

~ 0.6 帽 ，.c ι~ 0 ~ 0.4 〈

0

.

2

0 500 600 700 800 胃avelength [nm] 900

61 ポリイミド基板上に作製された

V

O

P

c

薄膜の形態と非線形光学特性へのコロナ帯電効果

Figure 3 SEM image of Sample 1.

Figure 3 shows也eSEM image of S阻 ple1.

τ

'he surfaαof

出巴thin

f

i

1

m

is smooth and a lot of grains釘eformed. 百lIs

su鹿 町tsthat出巴moleculardi血lsionof VOPc molecu1e on PI substrat巴islowand由巳interactionbetween adsorped molecu1e and自己PIsubs回teis班ong. These are dosely related to thヰ

phase morphology of Sample 1. Figure 4 shows the SEM image of Sample 2. A lot of island αystals grow on PI sub -strate. Thおおveals由at血emolec叫訂 diffusionof VOPc molecule on PI substrate is high紅 白 血thatof Sampl巴，1阻d白巴

interaction between deposited molecu1es and the PI subs回t巴is weakerth叩 thatof Sample 1. 百lese訂巴closelyrelatedω白巴

phase morphology of Sample 2園 Figure5 shows出eSEM

image of Samp1e3園 Islandcrystals grow bi，回目加Sample3

th四 加S翻 ple2. 日開 館ests伽t血巴moleculardiffusion of

VOPc molecule on PI subs回teis higher in Sanlple 3阻d白at

Figure4SEM加ageof Sample 2.

the interaction be抑eendeposited molecules阻d白巴 PIsub

-s回teis weaker血S沼nple3. These紅eclosely related to白e phase morphology of Sample 3. Figure 6 shows the VIS川V spec仕aof Samples

1

阻d4. S但nple

1

is a non-charged

VOPc

l

P

L Sanlple 4 is a VOPc/pI charged with

∞

rona char伊19.As desαibedabov巴ヲSample

1

has the morphology ofPhase IIL

Figure5 SEM回ageof Sample 3.

百leab田rptionp巴akin Q band region of Sanlple 4 shifts by

1

白 血tothe longer wavelen♂h ， side and it is larger th阻 thatof

Sample 1.百lewavel巴ng也oftheab田rptionpeak加Qband region of Sanlpl巴2and 3 agr田 withthat of S嗣 ple4. The VOPc白血血m prepared on PI substrate charged with

∞

rona char酔19at

8

0

0

_C

_{has island αystals阻d也emolecular diffu} -sion of VOPc molecules on PI substrate is much higher th阻 that ofS阻lple1. 輯Sample 1 (Ts: 80"C， t: 120min.， d:75nm) 園Sample4 (Ts: 80"C， t: 120min.， d:80nm) 品一一、 1つ ~~=<Nu~~"， '~~"W' W叩 町一 _~，.，_，._，~_~_.v ，~=~ ，^_ < W ~A__ 崎~.

首

O

.6

5司 唱

。

者

0

.

4

O

.

2

6

0

0

7

0

0

8

0

0

9

0

0

Wavelength.[腿n] Figure 6 spec回 ofSampl巴sl阻d2. Figure

7

shows the血cident

四回

ed巴pend回 目 of帥 dh訂 -monic

肝司加

tensityfor Samples

1

岨d4 irradiated with P po -I紅izedlaser light. 百lem砿 加lUffiTH intensity of S創nple4is

62 愛知工業大学総合揃研究報告，第 4号 平 成 14年， Vo.14，M紅.2即2

。

Sample 1 (Ts: 80"C， t: 120min.， d: 75nm) 争Sample 4 (Ts: 80"C， t: 120min.， d:80nm) 0.025 0.02 E .:!o.015 2 1 n u n u k 円三一回国曲相園甲同同 ] F 0.005 O -60 -40 -20 0 20 40 60 Incidle:nt a:ngle[d1eg.] Figure 7 Incident angle d巳pend四 回ofTH intensity for S泊 任 pll回 1組d4 irradiated with P polarized laser ligh.t larger by 2 times出 回 出atof S但nple1.τ'hisme阻sthat白E 也註dorder nonlinear opti回1property of VOPc thin filrn isIill -proved by the

∞

rona charging of PI subs住ateat 800C. The TH int四sityversus血cident

祖国

eis姐 柳 町 ∞ 町 巴xcurve ha吋nga m阻 出m mTH value at 0 d巴gree. It sugg田ts由at VOPc molec叫巴sdeposited on血ePI subs回teare p紅all巴1to thePI subs佐at巴. 4. CO.lll.clusions VOPc白血filrnshave a lot of gr討nsat the substrate tempera -旬reof 800C_姐da 10t of island αystals at the subs_回tetem -pera旬resof 1500_{C and 200 O}

c

.

百

_lefilrns_{having the gra泊s} or isl叩dαystalsare closely related to由巳redshift of the ab -sorption peak inQ band region. 百lered shift is larger for

∞

-rona-charged PI subs回teth叩 non-charg吋lone.τ'heshift of the absorption p巴ak.in Q band region of血eVOPc thinfilrn prepared at th巴subs住atetemperaぬreof 800_{C is similar to that} at 150 oC or 200 o

c

.

百 出 suggeststhat出emolecular diffu -sion of VOPc molecules deposited on吐lePI substrate ch紅ged by

∞

rona charging is higher th阻 thatof a non-charg巴d VOPc/PI. On由eother handフitis su毘ested出atthe packing density of island crystal is higher也 組 曲atof gr幻n. 百leτH intensity of出巴VOPc白血血m prep紅edon出巴PIsubstrate charged by

∞

rona ch紅伊19is hi俳句by2 times白血出剖ofa non-charged VOPc!PI. TheτE泊.tensityversus incideni an -gle is an upper convex curv巴havinga maximum

rn

valu巴針。 degree. 百1巴fonnerme組 sthat白epacking density of由e VOPc白血血mpr巴:paredon the PI substrate charged by corona charging is higher白 血thatof a non-charged VOPc!PI and白e la口町田毘eststhat VOPc moleαues deposit吋 onthe PI sub -S仕at巴areparallel to the PI subs位ate.

百rispaper was published by aIDP2001 held on Ameri四 .

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