分子線エピタキシ-法により NaCl 基板上に作製されたバナジルフタロシアニン膜の 3 次高調波

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愛知工業大学研究報告

第36号B 平成13年 15

分子線エピタキシ一法により

N

a

C

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基板上に作製されたパナジルフタロシアニン膜の

3 次高調波

Third Harmonic Generation of Vanadyl~Phthalocyanine Film Prepared on NaCl Substrate by Molecular Beam Epitaxy

Hi royuki NAKANO t， Akinor i MAEDA t， Hi deo FUR日IASHIt t，

中野寛之前田昭徳古橋秀夫

Toshio YOSHlKAWA "it t Yoshiyuki UCHIDA t t， Kenzo KOJIMA t ，

古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

Abstrad

The incident angle dependence of τ百intensityof VOPc fi1m irradiaied with P polarized laser beam shows an upper

∞

nvex curve that has a maximum value at -15 degree. It suggest that the tensor ofτH susceptibility of VOPc film is dominated with the components ofχ(xxxx) and χ(yyyy) and also indicates that the VOPc血ole

-cules deposited on NaCl have a tilt angle. These may give us information about τHG. loIntroduc針。阻 Organic nonlinear optical materials

，

which can yield a large third-order nonlinearity

，

have been widely studied to develop optical devices such as op -tically gated optical switches1₎_. _O_r_g_a_n_i_c_m_a_t_e_r_i_a_l_s with extensively delocalizedπ-eleclron systems have aitracied significant attention because a big of χ(3) lS expected if appropriately oriented molecules can be manufactured in film form. It has been demmト straied that organic maierials with π圃conjugatedsys圃 tems show anomalously large optical nonlinearities and ultrafast responses which are due to delocalized π圃electron2). Conjugated linear chains such as polydiacetylenes (PDA) possess a ve可 largethird -order nonlinear optical susceptibility， as reported in both theoretical and experimental pioneeringworks~J. In linear chain structures， the major contribution to the microscopic third-order optical susceptibility γ(ijkl)(圃ω4;ωbω2，ω3)main chain axis compo-nentγ(xxxx))(ーω4;ωbω2

，

ω3)with all electric fields aligned along the chain axis (x-axis). Inchanging企omlinear to cyclic conjugated structures， one must take new tensor components such as γ(yyyy)，γ(xxyy)，γ(xyxy)γ(xyyx)，γ(yyxx)ョ

T 愛知工業大学電気工学科 (豊田市)

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) γ(yxyx) and γ(yxxy) into consideration.τ'here出 fore， the nonline昌roptical properties of the organic 白血filmson thermally treated substrate were investi -gated. 20 Experiment

百lesource material used was VOPc powder sup-" plied from Eastman Kodak Company. After VOPc powder was邸側edinto a Knudsen叩 11

，

it was p時

heated at 300vC for one hour. The substrate of NaCl

was deaved just before a setting to a holder. After that， the substrate was attached on the holder. The main chamber of MBE was at about 10-7 _Pa

_，

_a_n_d_t_h_e

NaCl substrate was preheated for one hour. The pre -heating was done at 1500C and 2500C. The ev~po・

rating temp. was kept at Te (evaporating temp.) : 300VC.百lepreparing conditions ofVOPc thin films were the substraie temp. (Ts : 200vC)， evaporat_担g time(1:240 min.)

，

annealing temp. (Ta : 200u_C)_a_n_d annealing time (ta : 240 min

よ

respectivel子 Thefilm thicknesses were 115mn for Sample 1 (preheating temp of substrate:1500C)and 130nm fOIlsample2 (250v_C₎_. 30 Results and discussion Figure 1 shows the VIS凡JVspectra of Sample 1 and 2. The VIS尺JVspect即m of Sample 1 has an

absorption peak at 800nm血 theQ band region.内It suggests that the VOPc film is deposited with pseudo

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愛知工業大学研究報告，第36号民平成 13年，Vot-36B， Mar， 2001

located 21t 5 degree. Itsuggests that the molecules in the VOPc film have a tilt旦ngleon NaCl substrate.

16 On the other handフtheVQPc film (Sample 2) on the subs1rate treated with 250vC has an abso_中_層 Uonpe北畠t805nm in theQ band region. 曜動 @ @ 4器電器 @ 4島︹ @ E e 喝 ]

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2 8開 Sample 1 加吋 n 側伸 n 朗 K 5 H m

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2.5 2 50 Fig.3SH and 1百intensitiesvs. incident21l angle of Sample 2.

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On the other hand， the incident21l 21ngle dependence ofτH intensity of S21mple 1 irr21diated with P polar -ized l21ser beam shows 21n upper convex curve th21t h21s 2 1 m21ximum v21lue 21t・5degree. Figure 3 shows the incident 21ngle dependence of SH 21nd τH intensity of S21mple 2 irradiated with S 21nd P polarized laser beam. The SH intensity shows 2 s1 ymmetrical V curve 21t 0 degree but the SH intensity is not zero 21t 0 degree. 1t me21ns th21t the VOPc film cont21in the molecules nor -m21l to substrate in VOPc film. The τH intensity of S21mple 2 h21s 21n upper convex curve whose m21ximum value 21t is loc21ted四15degree園 τ'heysuggest that the

1H susceptibility tensors of VOPc film is domin21ted with the components ofχ(xxxx) 21nd χ(yyyy) 21nd 211so indic21te that the VOPc molecules deposited on N21Cl have 21 t臼t21ngle. These m21y give us inform21 -tion 21bout τHG. 4. Condu:!lions The VIS/UV spect四m of S21mple 1 h21s 21n abso 叩-tion pe21k 21t 800nm in theQ band region. Itsuggests that the VOPc film is deposited with pseudoepit21xy. On the other h阻 d，the VOPc film (S21mple 2) on the Fig.l VIS尺JVspectra of Sample 1 21nd 2. Itsuggests th21t the VOPc film is closely related to the structure of epitaxy. The SEM国21geof S21mple 1 shows a 10t of island crystals. lt8 orlentation h21s同TO 21xes. Figur己2shows the SEM im21ge of Sample 2. The island crystals are larger th21n those of Sample 1. From the distance between stre21ks of the RHEED pat -tern of Sample 2， VOPc molecu1es inthe t出h血 film gr

伊f即O W附n0叩立 N陥畠￡抑C臼1s叫u曲bs拙t紅E蹴a

(10)悶土均27戸o The second 21nd third harmonic g開 a er21tions (TH and SH) of VOPc films were measured by Maker fringe. The incident angle dependence of SH intensily of Sample 1 irr21diated with S polarized l21ser beam shows 21 V curve whose minimum v21lue 1S

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分子線エピタキシ一法により

N

a

C

l

基板上に作製されたパナジルフタロシアニン膜の

3

次高調波 o subslrate treat己dwith 250vC has an absorption peak at 805nm in the Q band region. H suggests that the VOPc film is closely related to the structure of epitaxy. We indicated that the VOPc田oleculesin the thin film grown on N aCl substrate formed two latti印 s(10)1/2X (10)1/2土270_f_r_o_m_t_h_e_d_i_s_t_{組問} _b_e_t_w_e_e_ns_t_r_e_a_k_s_o_f_t_h_e

RHEED pattem of Sample 2.τbis paper was pub -lished by International conference of Nonlinear Optics Materials， Fundamentals and Applications held on 2000. Refer垂直開S 1) H.}匂lbara

，

T. Maruna

，

A. YamashitaフS.Matsu国 moto， T. Hayashi H. Konami and N. T旦，naka，"Third-order nonlinear optical Properties of phthalocyan恒eand fullere，"J. Appl.Phys. 80， 3674-3682 (1996).

2) M. HosodaヲT.Wada， A. YamadaラA.F.Garito and

H. Sasabe， "Phases and third-order nonlinearities in tetravant metallophthalocyanine thin films

，

"

Jpn. J. Appl.Phys. 30， L1486園L1488(1991)

3) S. FangラK.Kohama， H. Hoshi and Y. Maruyama，

"Dependence of off-Diagonal Components ofχ(3) on subsirate temperature of epitaxially grown vanadyl圃 phthalocyan血efilms，"Jpn. J. Appl.Phys. 32， L1418 -L1420 (1993)。 (受理平成13年3月19日) 17