Sol-gel법으로 제조된 PbTiO 3   박막의 온도에 따른 수축 및 응력거동

박상면; Sang Myun Park

Korean Journal of Materials Research, Vol.9, No.7, 735-739, July, 1999

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Sol-gel법으로 제조된 PbTiO 3 박막의 온도에 따른 수축 및 응력거동

In Situ Shrinkage and Stress Development for PbTiO 3 , Films Prepared by Sol-gel Process

박상면

한국항공대학교 항공재료공학과

Sang Myun Park

Department of Materials Engineering, Hankuk Aviation University, Korea

초록

본 연구에서는 sol-gel법으로 제조된 PbTiO 3 (PT) 단층박막내의 실시간 응력과 두께 수축거동, 그리고 다층박막의 미세경도를 온도의 함수로 측정하여 열처리에 따른 PT박막내의 물리화학적 변화를 설명하였다. 단층박막은 상온에서 220 ? C 까지 급격한 수축을 보였으며 총수축량의 83%가 이 온도구간에서 일어났다. as-spun된 박막 내에는 이미 75MPa의 인장응력이 존재하였으며 13 0 ? C 부터 뚜렷이 증가하여 250 ? C 에서 147MPa의 최대 인장응력을 나타냈다. 인장응력의 급격한 감소가 일어나는 370 ? C 부터는 본격적으로 치밀화된 PT박막과 Si 기판과의 열팽창계수 차이가 주로 박막내의 응력을 결정하며, 이것은 다층박막의 미세경도가 300 ? C 이후에서 급격히 증가하는 사실로도 뒷받침된다. 한편 다층박막에서 단층박막과 달리 550 ? C 까지 열처리후 Perovskite 상이 많이 생성되었으며 이는 박막 두께의 증가에 따른 homogenous 핵생성 site의 증가 때문이라고 생각된다.

In this study we investigated stress development and shrinkage of thickness for a single PbTiO 3 (PT) layer prepared by sol-gel processing. Changes of microhardness for multideposited PT layers with temperatures are also monitored to understand the densification of thin films. Single PT layer shrank rapidly from room temperature to 220 ? C yielding 83% of total shrinkage observed up to 500 ? C . A tensile stress of ~75MPa developed in an as-spun layer, and increased steadily beyond 130 ? C until it reaches the maximum value of 147MPa at 250 ? C . The significant decrease of tensile stress in the film beyond 370 ? C indicates that thermal expansion mismatch between the film and the substrate dominates the stress behavior in this temperature range. Microhardness of the multideposited coatings also increased rapidly above 300 ? C regardless of the pyrolysis temperatures used. Large amount of perovskite phase formed in multideposited coatings after 550 ? C may be due partly to enhanced homogeneous nucleation in the thicker coating.

[References]

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Voncken JHL, Lijzinga C, Kumar KP, Keizer K, Burggraaf AJ, Bonekamp BC, J. Mater. Sci., 27, 472 (1992)
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Park SM, unpublished
Sengupta SS, Park SM, Payne DA, Allen LH, J. Appl. Phys., 83, 2291 (1998)

[1] Newnham RE, Ruschau GR, J. Am. Ceram. Soc., 74, 463 (1991)

[2] Paz de Araujo CA, Taylor GW, Ferroelectrics, 116, 215 (1991)

[3] Land CE, J. Am. Ceram. Soc., 72, 2059 (1989)

[4] Dey SK, Payne DA, Budd KD, IEEE Trans.Ultrason. Ferroelectr. Freq. Control., 25, 80 (1988)

[5] Parill TM, J. Mater. Res., 9, 723 (1994)

[6] Fardad MA, Yeatman EM, Dawnay EJC, Green M, Horowitz F, J. Non-Cryst. Solids, 183, 260 (1995)

[7] Lakeman CDE, Ph.D. thesis/ University of Illiois at Urbana-Champaign, 1994 (1994)

[8] Garino TJ, Harrington M, Mater. Res. Symp. Proc., 243, 341 (1992)

[9] Desu SB, Phys. Status Solidi A, 141, 119 (1994)

[10] Spierings GACM, Dormans GJM, Moors WGJ, Ulenaers MJE, Larsen PK, J. Appl. Phys., 78, 1926 (1995)

[11] Tuttle BA, Voigt JA, Garino TJ, Goodnow DC, Schwartz RW, Lamppa DL, Headley TJ, Eatough MO, Proceeding of the IEEE 8th International Symposium on Applied Ferroelectrics, 344 (1992)

[12] Schwartz RW, Voigt JA, Buchheit CD, Boyle TJ, Ceram. Trans., 43, 145 (1994)

[13] Keddie JL, Braun PV, Giannelis EP, J. Am. Ceram. Soc., 77, 1592 (1994)

[14] Keddie JL, Giannelis EP, J. Am. Ceram. Soc., 74, 2669 (1991)

[15] Chen J, Udayakumar KR, Brooks KG, Cross LE, J. Appl. Phys., 71, 4465 (1992)

[16] Voncken JHL, Lijzinga C, Kumar KP, Keizer K, Burggraaf AJ, Bonekamp BC, J. Mater. Sci., 27, 472 (1992)

[17] Keizer K, Kumar KP, Lijzenga C, Zaspalis VT, Burggraaf AJ, Key Eng. Matls, 61(62), 433 (1991)

[18] Budd KD, Dey SK, Payne DA, Br. Ceram. Proc., 36, 107 (1985)

[19] Park SM, unpublished

[20] Sengupta SS, Park SM, Payne DA, Allen LH, J. Appl. Phys., 83, 2291 (1998)