柔性ITO透明导电薄膜的研究
摘要
透明导电氧化物(TCO)薄膜兼具透明性和导电性两大特性，能广泛应用于平面显示器、太阳能电池、节能视窗、透明电磁屏蔽等领域。当前，显示技术越来越趋向于柔性化、超薄化，这大大促进了人们对柔性TCO薄膜的研究，其中在低软化点的柔性衬底上低温制备优质的ITO薄膜，已经成为国际上的热门研究课题。
本文通过对柔性ITO薄膜的特性、制备工艺研究，设计出并低温制备出了透光率大于75％、电阻率为8×10~(-5)Ω·cm的SiO_2/ITO/Ag/ITO膜系的PET基柔性ITO薄膜。论文取得的成果和创新点主要有：
1．针对低温溅射难以生成低电阻率的ITO薄膜这一难题，通过理论分析和实验研究，创造性地提出了“在线紫外辐照”提高反应气体氧在低温下活性的工艺路线，大幅度降低了ITO的电阻率也提高了ITO薄膜在可见光区透射率，为PET等柔性基底上低温生长优质的TCO薄膜提出了一种十分有效的方法。这一工艺方法有较大的理论指导意义和实用价值，在国内外尚未见报道。
2．针对有机衬底在溅射时容易裂解、放气大的问题，提出了在PET衬底上先镀覆SiO_2阻挡层的结构方案，有效地阻止了有机裂解物对ITO薄膜的污染，也阻挡了有机衬底的放气，并增强了薄膜的附着力。这为柔性ITO技术提出了一种新颖的结构。
3．为了进一步提高薄膜的电导率，我们根据薄膜光学理论并通过对纳米金属薄膜特性的研究，设计出SiO_2/ITO/Ag/ITO的膜系结构，在衬底不加热的工艺条件下大大提高了薄膜的电导率，同时，通过理论计算和系列实验摸索出了透明导电Ag层的制备参数。
4．在上述研究的基础上，我们用磁控溅射法在常温下制备出了光电性能良好的柔性SiO_2/ITO/Ag/ITO膜系，其最低电阻率达到8×10~(-5)Ω·cm，可见光区透射率大于75％，达到了国内先进水平。
本研究对低温制备柔性ITO膜技术有较大的理论指导意义和重要的实用价值。
Transparent conductive oxide (TCO) films with both transparent and conductive characteristics, have been widely used in graphic LCD, solar battery electrodes, and other energy-saving window. It developed rapidly in recent years. Along with the display technology developed toward flexible, thin-oriented, the research of flexible TCO films is undertaken accordingly. And one of the most important researches is to deposit ITO thin films with lower resistivity for analogous visible transmittance on organic substrates at room temperature.
Properties of flexible ITO films and preparation techniques are studied, and flexible SiO_2/ITO/Ag/ITO films with better optoelectronic properties had been successfully prepared at room temperature. The resistance achieved 8 × 10~(-5) Ω ? cm and the visible transmittance is greater than 75%. The major works and innovation in this paper are as follows:
1. To solve the difficulty of depositing ITO films with low resistivity at room temperature, we use UV irradiation to increase the oxidated activity of O_2, thereby enhancing the conductivity and transmittance in the visible region of the films. This is an effective way to deposit ITO films with better optoelectronic properties on PET substrates at room temperature. Until now, no investigation of this way has been reported, and it have great significance in both theoretic and application area.
2. To avoid the cracking of substrate during deposition, we use SiO_2 as a buffer layer on PET substrate, it decreases the higher substrate gas rate and enhances the film bonding. It's a novel structure which can effectively prevent the organic substrate gas and impurities through, and improve adhesion properties of flexible ITO films.
3. To seek lower resistivity, we designed SiO_2/ITO/Ag/ITO structures according to the thin film optical theory and the study of properties of metal nano-films. The structure can improve the conductivity of the films without heating. And the parameters for depositing a transparent
conductive layer of silver had also been got through a series of theoretical
calculations and experiments. 4. Based on the study above, flexible SiO_2/ITO/Ag/ITO films with high
performance has been successfully prepared with magnetron sputtering.
The resistance achieved 8 × 10~(-5) Ω ? cm and the transmittance in visible
region is greater than 75%.
The investigation of depositing flexible ITO films at low temperature in this paper has great significance in both theoretic and application area.
本文通过对柔性ITO薄膜的特性、制备工艺研究，设计出并低温制备出了透光率大于75％、电阻率为8×10~(-5)Ω·cm的SiO_2/ITO/Ag/ITO膜系的PET基柔性ITO薄膜。论文取得的成果和创新点主要有：
1．针对低温溅射难以生成低电阻率的ITO薄膜这一难题，通过理论分析和实验研究，创造性地提出了“在线紫外辐照”提高反应气体氧在低温下活性的工艺路线，大幅度降低了ITO的电阻率也提高了ITO薄膜在可见光区透射率，为PET等柔性基底上低温生长优质的TCO薄膜提出了一种十分有效的方法。这一工艺方法有较大的理论指导意义和实用价值，在国内外尚未见报道。
2．针对有机衬底在溅射时容易裂解、放气大的问题，提出了在PET衬底上先镀覆SiO_2阻挡层的结构方案，有效地阻止了有机裂解物对ITO薄膜的污染，也阻挡了有机衬底的放气，并增强了薄膜的附着力。这为柔性ITO技术提出了一种新颖的结构。
3．为了进一步提高薄膜的电导率，我们根据薄膜光学理论并通过对纳米金属薄膜特性的研究，设计出SiO_2/ITO/Ag/ITO的膜系结构，在衬底不加热的工艺条件下大大提高了薄膜的电导率，同时，通过理论计算和系列实验摸索出了透明导电Ag层的制备参数。
4．在上述研究的基础上，我们用磁控溅射法在常温下制备出了光电性能良好的柔性SiO_2/ITO/Ag/ITO膜系，其最低电阻率达到8×10~(-5)Ω·cm，可见光区透射率大于75％，达到了国内先进水平。
本研究对低温制备柔性ITO膜技术有较大的理论指导意义和重要的实用价值。
Transparent conductive oxide (TCO) films with both transparent and conductive characteristics, have been widely used in graphic LCD, solar battery electrodes, and other energy-saving window. It developed rapidly in recent years. Along with the display technology developed toward flexible, thin-oriented, the research of flexible TCO films is undertaken accordingly. And one of the most important researches is to deposit ITO thin films with lower resistivity for analogous visible transmittance on organic substrates at room temperature.
Properties of flexible ITO films and preparation techniques are studied, and flexible SiO_2/ITO/Ag/ITO films with better optoelectronic properties had been successfully prepared at room temperature. The resistance achieved 8 × 10~(-5) Ω ? cm and the visible transmittance is greater than 75%. The major works and innovation in this paper are as follows:
1. To solve the difficulty of depositing ITO films with low resistivity at room temperature, we use UV irradiation to increase the oxidated activity of O_2, thereby enhancing the conductivity and transmittance in the visible region of the films. This is an effective way to deposit ITO films with better optoelectronic properties on PET substrates at room temperature. Until now, no investigation of this way has been reported, and it have great significance in both theoretic and application area.
2. To avoid the cracking of substrate during deposition, we use SiO_2 as a buffer layer on PET substrate, it decreases the higher substrate gas rate and enhances the film bonding. It's a novel structure which can effectively prevent the organic substrate gas and impurities through, and improve adhesion properties of flexible ITO films.
3. To seek lower resistivity, we designed SiO_2/ITO/Ag/ITO structures according to the thin film optical theory and the study of properties of metal nano-films. The structure can improve the conductivity of the films without heating. And the parameters for depositing a transparent
conductive layer of silver had also been got through a series of theoretical
calculations and experiments. 4. Based on the study above, flexible SiO_2/ITO/Ag/ITO films with high
performance has been successfully prepared with magnetron sputtering.
The resistance achieved 8 × 10~(-5) Ω ? cm and the transmittance in visible
region is greater than 75%.
The investigation of depositing flexible ITO films at low temperature in this paper has great significance in both theoretic and application area.
引文
[1]. K. Badeker, Transparent conducting CdO obtained by thermal oxidation of sputtered Cd films, Phys, 1907,22:749.
[2]．史济群，周京英，马稚尧，马洪磊，电子束法沉积ITO透明导电膜的研究，华中理工大学学报，1998，26(3)：10-12．
[3]. T. Maruyama and K. Tabata, Jpn. J. Appl. Phys. Lett, 1990,29(2 ):355.
[4]. R. P. Howson, J. N. Avadsiotis, M. I. Ridge and C. A .Bishop, Thin Solid Films, 1979, 63:163.
[5]. R. P. Howson, and R .L. Ridge, Thin Solid Films, 1981,77:119.
[6]. Machet, J. Guille, P. Saulmier and S. Robert, Thin Solid Films, 1981,80:149.
[7]. Yasutaka Takahashi, Shinya Okada etal. Dip-coating of ITO films. Journal of Non-crystalline Solids. 1997,218:129.
[8]. MJ Alam, D. C. Cameron etal. Thin Solid Films. 2000,00:45.
[9]. L. Davis, Thin Solid Films,1993,236:1.
[10]. W Fukarek and H .Kersten, J. Vac. Sci. Technol,1994,A12:523.
[11]. L.J. Meng and M.P. Dos Santos, Mater. Res. Soc. Symp. Proc.,1996,42:643.
[12]. Z. Ovadyahu and H .Wiesmann, J. Appl. Phys. 1981,52:5865.
[13]. Ginley DS, Bright C. Transparent conducting oxides. MRS Bulletin, 2000,25(8):15-18.
[14]. Katayama M. TFT-LCD technology. Thin Solid Films, 1999,341 (1-2): 140-147.
[15]．石桥晓，杉浦功，堀隆英等．彩色STN用超低电阻透明导电膜．见：姜燮昌编，ITO膜的溅射沉积技术，沈阳：《真空》杂志社，1998：34-38．
[16]. Park JY, Kim HS, Lee DH et al. A study on the etch characteristics of ITO thin film using inductively coupled plasmas. Surface & coatings technology,2000,131 (1-3):247-251.
[17]. M. A. Martinez, J. Herrero, M. T. Gutierrez, Thin solid films, 1995, 269: 80.
[18]. X. Wu, W. P. Mulligan and T. J. Coutts, Thin Solid Films,1996,286:274.
[19]. T. Minami, H. Kumagai, T. Kakumu, S.Takata, and M. Ishii, J. Vac. Sci. Technol,1997, A 15(3):1069.
[20]. T. Minami, K. Oohashi and S. Takata, Thin Solid Films 1990,721:193-194.
[21]. H.L Ma, D.H. Zhang, P. Ma, S. Z. Win, S.Y. Li, Thin Solid Films,1995,263:105.
[22]. E. Fortunato, P. Nunes, D. Costa, D. Brida, I. Ferreira, R. Martins Vacuum 2002,64:233-236.
[23]. M. Buchanan, J. B. Webb and D. F. Williams, Appl. Phys. Lett,1980,37:213.
[24]. John C. C. Fan. [J]. Appl. Phys. Lett, 1979,34 (8) :515-517.
[25]. Chiou. B S, Hsieh S T. [J]. Thin Solid Films, 1993,229:146-155.
[26]. Freeman AJ,Poeppelmeier KR, Mason TO et al.Chemical and thin-film strategies for new transparent conducting oxides, MRS Bulletin,2000, 25(8):45-51.
[27]. Pan CA, Ma TP, High-quality transparent conductive indium oxide films prepared by thermal evaporation. Applied Physics Letters, 1980,37:163-165.
[28]. Kostishko BM, Orlov AM, Gonchar LI, Stoichionmetry and properties of undoped indium oxide films prepared by reactive evaporation.Inorganic materials, 1997, 33:816-819.
[29]. George J, Menon CS, Electrical-properties of thermally evaporated indium oxide thin-films. Indian Journal of Pure & Applied Physics, 1995,33:700-705.
[30]. Bellingham JR, Mackenzie AP, Phillips WA, Precise measurements of oxygen content oxygen vacancies in transparent conducting indium oxide-films. Applied physics letters, 1991, 58(22):2506-2508.
[31]. Coutts TJ, Young DL, Li XN. Characterization of transparent conducing oxides. MRS Bulletin,2000,25-8:58-65.
[32]．叶良修，半导体物理学(下册)，北京，高等教育出版社，1987．
[33]. Rauf IA, A comparison of scanning-tunneling-microscopy weith conventional and scanning-transmission electron-microscopy using tin-doped indium oxide thin-films. Surface Science, 1995, 325(1-2):L413-L419.
[34]. Chen M, Pei ZL, Wang X et al. Instrinsic limit of electrical properties of the transparent conductive oxide films. Journal of physics D, 2000,33:2538-2548.
[35]. Manivannan P, Subrahrnanyam A. Studies on the electrical and optical properties of reactive electron beam evaporated indium tin oxide films. Journal of Physics D, 1993,26:1510-1515.
[36]. Kulkarni AK, Schulz KH, Lim TS et al. Dependence of sheet resistance of indium-tin-oxide thin films on grain size and grain orientation determined from X-ray diffraction techniques. Thin Solid Films, 1999, 345(2):273-277.
[37]. Liu J, Radlein E, Frischat GH. Preparation, nanostructure and properties of indium tin oxide(ITO) films on glass substrates. Part 1.Preparation and nanostructure. Physics and chemistry of glasses, 1999,40(5):277-281.
[38]. Parent P, Dexpert H, Tourillon G et al. Structural study of tin-doped indium oxide thin-films using X-ray absorption-spectroscopy and X-Ray-Diffraction. 2. Tin environment. Journal of the electrochemical society, 1992,139(1):282-285.
[39]. Yamada N, Yasui I, Shigesato Yet al. Donor compensation and carrier-transport mechanisms in tin-doped In_2O_3 films studied by means of conversion electron Sn-119 Mossbauer spectroscopy and Hall effect measurements. Japanese Journal of Applied Physics Part 1, 2000,39(7A):4158-4163.
[40]. Tahar RBH, Ban T, Ohya Yet al, Tin doped indium oxide thin films: electrical properties. Joumal of Applied Physics, 1998, 83(5):2631-2645.
[41]. Kulkami AK, Knickerbocker SA, Estimation and verification of the electrical properties of indium tin oxide based on the energy band diagram. Journal of vacuum science & technology A, 1996, 14(3):1709-1713.
[42]. Shimakawa K, Hosono H, Kikuchi N et al. Free carrier absorption in highly conducting amorphous oxides. Journal of Non-Crystalline Solids, 1998, 230:513-516.
[43]．方俊鑫，陆栋，固体物理学(下册)，上海：上海科学技术出版社，1981．
[44]．刘恩科，罗晋生，半导体物理学，上海：上海科学技术出版社，1984．
[45]．孟扬，扬锡良，陈华仙等，高价态差掺杂氧化物透明导电薄膜的研究．光电子技术，2001，3：19．
[46]．孟扬，沈杰等，透明导电IMO薄膜的载流子浓度测量，光电子技术，2001，12：246．
[47]．王建恩，王运涛，王军等，三氧化二铟基透明导电薄膜光、电特性的研究．功能材料，1995，26(2)：141．
[48]．陈猛，白雪冬等，ITO薄膜的光电特性研究，金属学报，1999，9：936．
[49]. Hamberg I,Granqvist C G. Evaporated Sn-doped In_2O_3films:Basic optical properties and applications to energy-efficient windows.Journal of Applied Physics, 1986, 60(11):R123-R159.
[50]. GuptaL,Mansingh A,Srivastava PL.Band gap narrowing and the band structure of tin doped indium oxide films,Thin Solid Films,1989,176:33-44.
[51]．光学薄膜编写组，上海：上海人民出版社，1976：3-18．
[52]．顾培夫．浙江：浙江大学出版社，1990．
[53]．孔庆升．北京：电子工业出版社，1994：35-36．
[54]．程知群，高启安，低温退火工艺对柔性基上ITO膜透光率的影响，半导体光电，1996，17(1)：53-55．
[55]. Michael Boehme, Christoph Charton, Properties of ITO on PET film in dependence on the coating conditions and thermal processing, Surface & Coatings Technology, 2005,200:932-935.
[56]．茅昕辉，直流磁控反应溅射沉积ITO透明导电膜的研究，光电子技术．
[57]. Weast RC. Handbook of chemistry and physics(54th edition). Cleveland. Ohio, CRS Press, 1973.
[2]．史济群，周京英，马稚尧，马洪磊，电子束法沉积ITO透明导电膜的研究，华中理工大学学报，1998，26(3)：10-12．
[3]. T. Maruyama and K. Tabata, Jpn. J. Appl. Phys. Lett, 1990,29(2 ):355.
[4]. R. P. Howson, J. N. Avadsiotis, M. I. Ridge and C. A .Bishop, Thin Solid Films, 1979, 63:163.
[5]. R. P. Howson, and R .L. Ridge, Thin Solid Films, 1981,77:119.
[6]. Machet, J. Guille, P. Saulmier and S. Robert, Thin Solid Films, 1981,80:149.
[7]. Yasutaka Takahashi, Shinya Okada etal. Dip-coating of ITO films. Journal of Non-crystalline Solids. 1997,218:129.
[8]. MJ Alam, D. C. Cameron etal. Thin Solid Films. 2000,00:45.
[9]. L. Davis, Thin Solid Films,1993,236:1.
[10]. W Fukarek and H .Kersten, J. Vac. Sci. Technol,1994,A12:523.
[11]. L.J. Meng and M.P. Dos Santos, Mater. Res. Soc. Symp. Proc.,1996,42:643.
[12]. Z. Ovadyahu and H .Wiesmann, J. Appl. Phys. 1981,52:5865.
[13]. Ginley DS, Bright C. Transparent conducting oxides. MRS Bulletin, 2000,25(8):15-18.
[14]. Katayama M. TFT-LCD technology. Thin Solid Films, 1999,341 (1-2): 140-147.
[15]．石桥晓，杉浦功，堀隆英等．彩色STN用超低电阻透明导电膜．见：姜燮昌编，ITO膜的溅射沉积技术，沈阳：《真空》杂志社，1998：34-38．
[16]. Park JY, Kim HS, Lee DH et al. A study on the etch characteristics of ITO thin film using inductively coupled plasmas. Surface & coatings technology,2000,131 (1-3):247-251.
[17]. M. A. Martinez, J. Herrero, M. T. Gutierrez, Thin solid films, 1995, 269: 80.
[18]. X. Wu, W. P. Mulligan and T. J. Coutts, Thin Solid Films,1996,286:274.
[19]. T. Minami, H. Kumagai, T. Kakumu, S.Takata, and M. Ishii, J. Vac. Sci. Technol,1997, A 15(3):1069.
[20]. T. Minami, K. Oohashi and S. Takata, Thin Solid Films 1990,721:193-194.
[21]. H.L Ma, D.H. Zhang, P. Ma, S. Z. Win, S.Y. Li, Thin Solid Films,1995,263:105.
[22]. E. Fortunato, P. Nunes, D. Costa, D. Brida, I. Ferreira, R. Martins Vacuum 2002,64:233-236.
[23]. M. Buchanan, J. B. Webb and D. F. Williams, Appl. Phys. Lett,1980,37:213.
[24]. John C. C. Fan. [J]. Appl. Phys. Lett, 1979,34 (8) :515-517.
[25]. Chiou. B S, Hsieh S T. [J]. Thin Solid Films, 1993,229:146-155.
[26]. Freeman AJ,Poeppelmeier KR, Mason TO et al.Chemical and thin-film strategies for new transparent conducting oxides, MRS Bulletin,2000, 25(8):45-51.
[27]. Pan CA, Ma TP, High-quality transparent conductive indium oxide films prepared by thermal evaporation. Applied Physics Letters, 1980,37:163-165.
[28]. Kostishko BM, Orlov AM, Gonchar LI, Stoichionmetry and properties of undoped indium oxide films prepared by reactive evaporation.Inorganic materials, 1997, 33:816-819.
[29]. George J, Menon CS, Electrical-properties of thermally evaporated indium oxide thin-films. Indian Journal of Pure & Applied Physics, 1995,33:700-705.
[30]. Bellingham JR, Mackenzie AP, Phillips WA, Precise measurements of oxygen content oxygen vacancies in transparent conducting indium oxide-films. Applied physics letters, 1991, 58(22):2506-2508.
[31]. Coutts TJ, Young DL, Li XN. Characterization of transparent conducing oxides. MRS Bulletin,2000,25-8:58-65.
[32]．叶良修，半导体物理学(下册)，北京，高等教育出版社，1987．
[33]. Rauf IA, A comparison of scanning-tunneling-microscopy weith conventional and scanning-transmission electron-microscopy using tin-doped indium oxide thin-films. Surface Science, 1995, 325(1-2):L413-L419.
[34]. Chen M, Pei ZL, Wang X et al. Instrinsic limit of electrical properties of the transparent conductive oxide films. Journal of physics D, 2000,33:2538-2548.
[35]. Manivannan P, Subrahrnanyam A. Studies on the electrical and optical properties of reactive electron beam evaporated indium tin oxide films. Journal of Physics D, 1993,26:1510-1515.
[36]. Kulkarni AK, Schulz KH, Lim TS et al. Dependence of sheet resistance of indium-tin-oxide thin films on grain size and grain orientation determined from X-ray diffraction techniques. Thin Solid Films, 1999, 345(2):273-277.
[37]. Liu J, Radlein E, Frischat GH. Preparation, nanostructure and properties of indium tin oxide(ITO) films on glass substrates. Part 1.Preparation and nanostructure. Physics and chemistry of glasses, 1999,40(5):277-281.
[38]. Parent P, Dexpert H, Tourillon G et al. Structural study of tin-doped indium oxide thin-films using X-ray absorption-spectroscopy and X-Ray-Diffraction. 2. Tin environment. Journal of the electrochemical society, 1992,139(1):282-285.
[39]. Yamada N, Yasui I, Shigesato Yet al. Donor compensation and carrier-transport mechanisms in tin-doped In_2O_3 films studied by means of conversion electron Sn-119 Mossbauer spectroscopy and Hall effect measurements. Japanese Journal of Applied Physics Part 1, 2000,39(7A):4158-4163.
[40]. Tahar RBH, Ban T, Ohya Yet al, Tin doped indium oxide thin films: electrical properties. Joumal of Applied Physics, 1998, 83(5):2631-2645.
[41]. Kulkami AK, Knickerbocker SA, Estimation and verification of the electrical properties of indium tin oxide based on the energy band diagram. Journal of vacuum science & technology A, 1996, 14(3):1709-1713.
[42]. Shimakawa K, Hosono H, Kikuchi N et al. Free carrier absorption in highly conducting amorphous oxides. Journal of Non-Crystalline Solids, 1998, 230:513-516.
[43]．方俊鑫，陆栋，固体物理学(下册)，上海：上海科学技术出版社，1981．
[44]．刘恩科，罗晋生，半导体物理学，上海：上海科学技术出版社，1984．
[45]．孟扬，扬锡良，陈华仙等，高价态差掺杂氧化物透明导电薄膜的研究．光电子技术，2001，3：19．
[46]．孟扬，沈杰等，透明导电IMO薄膜的载流子浓度测量，光电子技术，2001，12：246．
[47]．王建恩，王运涛，王军等，三氧化二铟基透明导电薄膜光、电特性的研究．功能材料，1995，26(2)：141．
[48]．陈猛，白雪冬等，ITO薄膜的光电特性研究，金属学报，1999，9：936．
[49]. Hamberg I,Granqvist C G. Evaporated Sn-doped In_2O_3films:Basic optical properties and applications to energy-efficient windows.Journal of Applied Physics, 1986, 60(11):R123-R159.
[50]. GuptaL,Mansingh A,Srivastava PL.Band gap narrowing and the band structure of tin doped indium oxide films,Thin Solid Films,1989,176:33-44.
[51]．光学薄膜编写组，上海：上海人民出版社，1976：3-18．
[52]．顾培夫．浙江：浙江大学出版社，1990．
[53]．孔庆升．北京：电子工业出版社，1994：35-36．
[54]．程知群，高启安，低温退火工艺对柔性基上ITO膜透光率的影响，半导体光电，1996，17(1)：53-55．
[55]. Michael Boehme, Christoph Charton, Properties of ITO on PET film in dependence on the coating conditions and thermal processing, Surface & Coatings Technology, 2005,200:932-935.
[56]．茅昕辉，直流磁控反应溅射沉积ITO透明导电膜的研究，光电子技术．
[57]. Weast RC. Handbook of chemistry and physics(54th edition). Cleveland. Ohio, CRS Press, 1973.