Effects of substitution with La and V in $Bi_4Ti_3O_{12}$ thin film by MOCVD using ultrasonic spraying

초음파분무 MOCVD법에 의한 $Bi_4Ti_3O_{12}$ 박막의 제조와 La과 V의 Co-Substitution 에 의한 효과

  • 김기현 (경북대학교 무기재료공학과) ;
  • 곽병오 (경북대학교 무기재료공학과) ;
  • 이승엽 (경북대학교 무기재료공학과) ;
  • 이진홍 (경북대학교 무기재료공학과) ;
  • 박병옥 (경북대학교 무기재료공학과)
  • Published : 2003.12.01

Abstract

$Bi_4Ti_3O_{12}$ (BIT) and $(Bi_{3.25}La_{0.75})(Ti_{2.97}V_{0.03})O_{12}$ (BLTV) thin films were deposited on ITO/glass substrates by metal organic chemical vapor deposition (MOCVD) using ultrasonic spraying. After deposition of the films in oxygen atmosphere for 30 min, the films were heated by rapid thermal annealing (RTA) method, especially direct insertion, at various temperatures. The films were investigated on phase formation temperature, microstructure and electrical properties. From x-ray diffraction (XRD) patterns, the perovskite phase formation temperature of BLTV thin film was about $600^{\circ}C$ which was lower than that of BIT, $650^{\circ}C$. The leakage current of the BLTV thin film was measured to be $1.52\times 10^{-9}$A/$cm^2$ at an applied voltage of 1 V. The remanent polarization (Pr) and coercive field (Ec) values of the BLTV film deposited at $650^{\circ}C$ were $5.6\muC/cm^2$ and 96.5 kV/cm, respectively.

초음파 분무에 의한 유기금속 화학증착법 (MOCVD)법으로 $Bi_4Ti_3O_{12}$(BIT)와 Bi와 Ti 대신에 La과 V을 동시에 치환시킨 ($Bi_{3.75}La_{0.75})(Ti_{2.97}V_{0.03})O_{12}$ (BLTV)박막을 ITO/glass 기판 위에 증착하였다. 산소 분위기에서 30분 동안 증착한 후, RTA 방식의 직접삽입법으로 열처리를 하였다. 박막은 페로브스카이트상 생성 온도, 미세구조, 전기적 성질에 관해서 조사하였다. XRD(X-Ray diffraction) 측정결과 BLTV 박막의 페로브스카이트상 생성 온도는 약 $600^{\circ}C$로써 BIT의 $650^{\circ}C$보다 더 낮았다. BLTV 박막의 누설전류는 인가전압 1 V에서 $1.52\times10^{-19}$ A/cm^2$로 측정되었다 또한, $650^{\circ}C$에서 증착했을 경우 잔류 분극값이 $5.6\mu$C/$cm^2$, 항전계값 96.5 kV/cm으로 명확한 강유전성을 보이고 있다.

Keywords

References

  1. Materials science of Thin Films(2nd ed.) M.Ohing
  2. Jpn. J. Appl. Phys. v.34 Preparation of ferroelectric thin films of bismuth layer structured compounds H.Watanabe;T.Mihara https://doi.org/10.1143/JJAP.34.5240
  3. Jpn. J. Appl. Phys. v.39 Valence band and bandgap states of ferroelectric SrBi₂Ta₂TEX>$O_{9}$ thin films K.Watanbe;A.J.Hartmann;R.N.Lamb.;R.P.Craig;S.M.Thurgate;J.F.Scott https://doi.org/10.1143/JJAP.39.L309
  4. Appl. Phys. Lett v.76 Dielectric properties of layered perovskite ${Sr}_{1-x}A_x$Bi₂Nb₂$O_{9}$ ferroelectrics (A=La, Ca and x=0,0.1) M.J.Forbess;S.Seraji;Y.Wu;C.P.Nguyen;G.Z.Cao https://doi.org/10.1063/1.126521
  5. J. Crystal Growth v.186 Growth of layered perovskite BI₄Ti₃$O_{12}$ thin films by sol-gel process H.Gu;C.Dong;P.Chen;D.Bao;A.Kuang;X.Li https://doi.org/10.1016/S0022-0248(97)00508-3
  6. J. Am. Ceram. Soc. v.81 Ferroelectric thin-films of bismuthcontaining layered perovskites - part ⅠBi₄Ti₃$O_{12}$ X.Du;I.Chen https://doi.org/10.1111/j.1151-2916.1998.tb02764.x
  7. Nature v.401 Lanthanum-substituted bismuth titanate for use in non-volatile memories B.H.Park;B.S.Kang;S.D.Bu;T.W.Noh;J.Lee;W.Jo https://doi.org/10.1038/44352
  8. J. Appl. Phys v.92 Ferroelectric properties of vanadium-doped Bi₄Ti₃$O_{12}$ thin films deposited by sol-gel method S.S.Kim;T.K.Song;J.K.Kim;J.H.Kim https://doi.org/10.1063/1.1494840
  9. Thin Solid Films v.427 On the physical properties of indium oxide thin films deposited by pyrosol in comparison with films deposited by pneumatic spray pyrolysis M.Girtan;H.Cachet;G.I.Rusu https://doi.org/10.1016/S0040-6090(02)01185-9
  10. J. Crystal Growth v.205 Oriented bismuth titanate thin films by single-solid-source metalorganic chemical vapor depolsition S.Sun;P.Lu;P.A.Fuierer https://doi.org/10.1016/S0022-0248(99)00261-4
  11. J. Korean Institute of Electrical and Electronic Material Engineering v.12 no.5 Properties of ZnO thim films by the ultrasonic spray pyrolysis technique Y.G.Lee;H.B.Kim;J.Y.Jung;M.H.Lee;H.C.Kwon;Y.R.Roh
  12. J. Crystal Growth v.248 Property design of Bi₄Ti₃$O_{12}$-based thin films using a site-engineered concept H.Funakobo;T.Watanabe;T.Kojima;T.Sakai;Y.Noguchi;M.Miyayama;M.Osada;M.Kakihana;K.saito https://doi.org/10.1016/S0022-0248(02)02047-X