分子線エピタキシーにより作製され, 有機ガスで処理されたバナジルフタロシアニン薄膜の配向 

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愛 総 研 ・ 研 究 報 告 第3号 平 成13年

63

分子線エピタキシーにより作製され、有機ガスで処理されたパナジルフタロシア

ニン薄膜の配向

Orientation of Vanadyl-Phthalocyanine Film Prepared by Molecular Beam Epitaxy and Treated in Organic Gas

Hiroyuki NAKANO t, Akinori MAEDA t, Hideo FURUHASHI t 1", 中 野 寛 之 前 田 昭 徳 古 橋 秀 夫

Toshio YOSHIKAWA t t t Yoshiyuki UCHIDA t t, Kenzo KOJIMA t ,

吉 川 俊 夫 内田悦行 小嶋憲三

Asao OHASHI t and Shizuyasu OCHIAI t 大 橋 朝 夫 落 合 鎮 康

Absirad: In this paper, the VOPc film was prepared on KBr substrate by OMBD圃Afterthat, it was treated in organic

gas. The thickness of VOPc film was 96 nm圃 Themorphologies of VOPc film before and after the gas treatrnent were

characterized with optical absorption (VIS/UV) spectra and SEM image. The third占armonicgeneration ( THG) of VOPc film before and after the gas treatment were also measured by Maker fringe method using a Nd-YAG laser.

Keywords: epitaxy, VOPc film, organic gas treatment, phase transition, THG 1. Introduction Organic nonlinear optical materials, which can yi巴ld large third-order nonlinearties, have been widely studied to achieve optical devices like on optically gated optical switch. Organic thin films are prom -ising for the application to various kinds of optical devic巴sbecause of their巴xcellentprocessability. However

most thin films are usually fabricated by sp加castingor by the Langmuir-Blodgett method. These thin films do not necessarily take full advarト tage of the1arge nonlinearities of the materials, since these methods cannot be easi1y applied to molecules with poor solubility. Organic molecular beam deposition (OMED) has recently attracted a lot of in -terest because it is applicable to molecules with poor solubility and its deposition is easy to control (1-4)圃 Moreover, OMED is considered to hav巴otheradvan -tages to provide good crystal quality

high optical transmittance

and/or large optical nonlinearity. However, optical IC requires that the film thickness ofnonlin巴aroptical film is thicker than 1mm and that

the film must be grown with epitaxy. The second and third harmonic generations of the film grown 巴pitaxiallyare higher than those of the film grown pseudoepitaxia11y and the film thickness related to the T愛 知 工 業 大 学 電 気 工 学 科 (豊田市)

t

t

愛知工業大学情報通信工学科(豊田市) t t t愛知工業大学総合技術研究所(豊田市) performance of optical IC. In this paper, we investigate the characteri -zation and nonlinearities of the thick film prepared on KBr by OMBD and treated in organic gas. 2. Experiments

The source material used was VOPc powder supplied from Eastman Kodak Company. After VOPc pow-der was inserted into a Knudsen-c巴11,it was preheated

at 3000C for two hours. The substraie of KBr was

cleaved just before it was attached on the holder. The main chamber of OMBD was at about 1O-7pa

and the KBr substrate was preheated for one hour. The preheat泊gtemperature of阻 rsub蜘 te(Tp) was at 150oC. The evaporating temperature was kept at T巴:300oC. The substrate temperature (Ts) was at 200oC. The evaporating time (t)

the film thikness (d)

the tim巴treatedin organic gas (tv)

the temperature treated in organic gas (Tv) and the OI-ganic gas used are at 240 minutes, 36nm, 25hrs, 240C and 1,2・Dichloroethane,respectively.

2

.

Results and Discussion Fig圃1shows the structure of a vanadyl-phthlocyanine molecule. The height is 0.2 nm and the diameter is 1.4nm. Fig. 2 shows VIS/UV spectra. The absorp幽

tion spectrum of VOPc film has an absorption peak at 780nm before th巴organicgas treatment and at 810nm

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64 愛知工業大学総合技術研究報告第

3

号 平成

1

3

年,

V

o

l.

3

M

a

r

.

2

0

0

1

after the gas treatment, resp巴ctively. The p巴akshift suggests that the crystal structure of a VOPc film changes from昌pseudoepitaxialgrowth to epitaxial growth during organic gas treatment園 Fig3 shows

the SEM image of VOPc film befor巴thegas treat -ment. The SEM image shows that the VOPc film consists of gra担s. The surface density of grain is high. Therefore

the grains deform in VOPc film so that the VOPc film pseudoepitaxially grows on KBr substrate. Fig. 4 shows the SEM image of VOPc film after the gas treatment. The SEM image shows a soomth surface of VOPc film圃 Thegrains disap

-pear from the surface of VOPc film and a few single crystals exist there. The percentage of single crystal to the日atarea of VOPc film is small. Thereforeフ we will not discuss the effect of single crystal in this paper. As mentioned above, the surface of VOPc film is smooth and the grains disappear during the gas treatment

今ず、マコ

3>デモ三

o ~ 1 1 1 O. 2 [凹] ---v ' 唾一一一一一一一 1. 4 [日]一一一一一一予 Fig. 1 Structur巴ofvanadyl・phthalocyaninemolecule 2.5 ' "乞2 ;; l.5 ,且 』 。 明 l dコ 〈 0.5 500 600 700 800 900 1000 Wavelenglh [n田] Fig. 2 Absorption spectra of VOPc film after and before the gas treatment. Fig. 3 SEM image of VOPc film before the gas treatment in organic gas. Ther巴fore

the gas treatment may relax the deforma -tion in VOPc film and induce the change in film from a pseudoepitaxial growth to epitaxial growth. Fig. 4 SEM image of VOPc film after the gas treatment. O. 025 n l ρ u n μ m e b t m 刷 一 a t e a 一 r e 一 t r 一 e 一 r r 一 o e -e f nDAA lL ﹁ l b l 2 0 0 [ ロ Eヨ ] ー0.015 @ """, " ." .

2

1 @ @ 2 @ ど 111'11

L

.

.

_

~..",. G - O.S> .:: v. V l

r

.

.

.

.

.

lsle屯J@ 三o ~ ,ç,~O 国 I ..(j/'J~GQ0 ロ v弘 二 世 @ H

以屯J

1

1

:

h

t

予缶詰笠

「 品 耳 w ロ ロ 国 吉 田 口 ロロ Incident Angle [deg.] Fig.5 SH intensity vs. incident angle of VOPc film. (P polarized laser light) Fig園6・(a)Crystal coordinaies.

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分子線エピタキシイーにより作製され、有機ガスで処理されたパナジルフタロシアニン薄膜の配向 65

X

Z

~ '7

Y

Figふ(11)Laboratory system of Cartesian coordinate The VOPc film treated with organic gas is epitaxy and has the 4mm structure with C4 axis along the KBr surface normal [5]. Fig. 6 (a) shows the epitaxial str附 ureofVOPc square lattice on回 r(001)whe民 間rions蹴 shown as op巴nand solid circles. The x and y in Fig. (a) are the crystal coordinates. To describ巴anexperimental condition

a Laboratory system of Cartesian coordi開 nates (X

YフZ)is introduced

where the Z in Fig. (b) is in the direction of the incideni las巴rbeam andX is the rotation axis of Maker fringe experiment. The tensor components ofχobey the following equation for our film [6]固 For the irradiated laser beam polarized S, χ1111=χ1111...……・0 ・ e・e・... (1) In the case of the irradiated laser b巴ampolarized P, χフ2222=COS4θχ 1111+3coS2

e

sin2

e

χ1331+3coS2θ sin2

e

χ3113+sin4

e

χ3333 ・ … ー … (2) The comparison beiween calculated and experim巴ntal values of the third harmonic (TH) intensity vs. inci -dent angle in Fig. 7 suggests that the TH intensity is domin且tedby aχ1111 in tensor components.

4.The⑪reticaiA湿alys.isof Ten.sor Compo日記n.ts of χ(3) The third order tensor components of VOPc film grown with epitaxy were expressed by叫uation(1) and (2)圃 Thethird harmonic intensity is given by as following equation (3). 4ω'113 ,""o.o_o_sin'(ムkd)/2 1 3 = 4 2 { χ ( 3 ) } 'd'L 3T (nc)4Eo' ' ' V

-.'.0

(ムkd/2)2 。) where 1(3ω) is the third order harmonic intensity, I(ω)= 1.20E+8J/m2ldamentalla 悶 lightintensity, n1 =2.82 refractive index of the sample for funda -mentallaser light, n3= 2圃86re台acHveindex for third-order harmonics,λp=1064 [nm] fundamental wavelength

lc=4.43E喝6[m]

herence leng出ofthe sample

d=l

s

e

effective length

1 ='=7100E四9[m] film thickness

T1 . . 1 transmission factor of KBr

T2 ='=71 transmission factor of VOPc film

χ(3) =6.2E・17 [m2パ,{2]third-order optical susceptibility and

K phase mismatch between the fundamental and the harmonic frequencies泊sidethe film. The

.

d

.

K is given by

K=π/L=6π(nl-n3) /入p The incident angle dependence of the third order harmonic intensity was ca1culated by using equations (1), (2) and (3) and values described above. 1.6 1.4

Calculationres噛 1.2

c

1.0 CI1 +5CJ 0.8 ト~ 0.6 0.4 0.2 0.0 -50 -25

25 50 Incident Angle [deg] Fig. 7 Insident angle dependence of TH intensity and calculated value ( Irradiated laser beam polarized S ) 1固8 1.6 1.4 1.2

Experimentalvalue Calculation results: 争Firstterm of eq. (2) 企Secondterm of eq. (2)

Thirdterm of eq. (2)

o

Fourth term of eq. (2) ゼ〉、 1.0 立 u

q208 ト 工 0.6 0.4 0.2

-50 -25 0 25 50 Incident Angle [deg] Fig. 8 Incident angle dependenc号ofTH intensity and calculated value ( Irradiated laser beam polarized P )

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66 愛知工業大学総合技術研究報告第3号 平成13年,Vol. 3, Mar.20m The calculated values are normalized with TH p巴ak intensity. From the results of calculated curves and 巴xperimentalvalues in Fig. 8, the tensor components of epitaxial VOPc film ar巴notonly dominat巴dby χ1111>but also ar巴 E巴latedto the nonlinear optical susceptibilities ofχ1331 and χ3113. It means that the VOPc film treated with organic gas is grown with epIt呂xy. COCLUSIONS From experimental and calculated results, we sug -gested the VOPc film grown巴pitaxiallywas domi -nated by the nonlinear optical susceptibility of χ1111.The gas treatment improves the TH intensity. It suggests thai the phase iransition from pseudoepi -taxy to巴pitaxyof VOPc film is closely related to the improvement of the third-order harmonic intensity of VOPcfilm圃 Thispaper was published by Photon -ics-2000 held on India.

1. M. Hara, H. Sasabe, A.Yamada and A. F. Ga-rito:

Jpn. J. Appl.Phys、28

L306 (1989) 2. A. J. Dann, H. Hoshi and Y.Maruyama:, J. Appl.

Phys. 67

1371 (1990)

3. H圃Tada,K.Saiki and A.Koma:, Jpn. J. Appl.

Phys園30

L306 (1991)

4. L. K.Chau, C.D. England:, S. Ch巴nandN. R.

Armstrong, J圃Phys.Chem園97,2699 (1993)

5. H. Hoshi, K. Hamamoto, T. Yamada, K.Ishikawa, H. Takezoe, A.Fukuda, S. Fang, K.Kohama and Y. Maruyama:ヲJpn.1.App.lPhys. 33

Ll555

(1994)

6. H. Hoshi, N. Nakamura, and Y.Maiuyama, J. Appl. Phys. (1991) 7244

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