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Preparation and properties of sol-gel derived ferroelectric thin layers
Vacuum~volume 42/number 16/pages 1035 to 1098/1991 Printed in Great Britain
0042-207X/91 $3.00+.00 Pergamon Press plc
Abstracts Invited paper Preparation and properties of sol-gel derived ferroelectric thin layers D A Payne, Department of Materials Science and Engineering,
Materials Research Laboratory, and Beckman Institute, University of Illinois at Urbana-Champaign, 105 S Goodwin, Urbana, IL 61801, USA In this paper we report on the polymeric condensation ofmetalloorganic precursors for the formation of inorganic network structures and the low temperature densification of ferroelectric ceramics. The chemical precursors include alkoxides and acetates, and the processing route is by the sol-gel method. Processing temperatures are sufficiently reduced for the integration of ferroelectric insulators on semiconductors. The sol-gel method allows for the mixing of solution precursors at the molecular level with purity and stoichiometry control. Molecular pathways are induced by hydrolysis and condensation reactions, which in turn are influenced by chemical additives. The role of pH and water concentration on oligomer and cluster formation, and polymerization, is illustrated for the synthesis of ferroelectric ceramics. Data are reported for transition metal oxide containing materials (i.e. titanates, zirconates, niobates . . . . ) of increasing complexity e.g. BaTiO3, PbTiO3, PZT, PLT, PLZT, LiNbO 3, Pb(Mg 1/3Nb 2/3)O3, PZN, etc. The importance of reflux and distillation conditions, for mixed alkoxide synthesis, and homogeneous hydrolysis of heterometal systems, is illustrated for PbTiO3 and LiNbO3. Single crystal data are reported for mixed metal alkoxides. The evolution of structure in solution, through condensation, is followed by N M R and F T I R methods. Formation of metal-oxygen-metal bonds is a prerequisite for low temperature synthesis and densification behavior. Features which influence viscoelastic densification, followed by crystallization at reduced temperatures, are reported. Finally, structure-property relations are given for MOS capacitors, ferroelectric non-volatile memories and electro-optic waveguides integrated on semiconductors. The implications for future intelligent material systems are outlined. The method is a potential upset technology in ceramic processing since it avoids the handling of fine powders, and is particularly suited for the fabrication of thin-layer devices.
Invited paper Advanced thin films for optical storage Gan Fuxi, Shanghai Institute of Optics and Fine Mechanics,
Academia Sinica, PO Box 800-211, Shanghai 201800, China Since the computer was invented, storage and retrieval of digital information has been a major challenge. The emergence of optical disk recording technology was a great event in these fields. Erasable optical recording is a new technology for achieving high density data storage. Advanced thin films are of interest for use
in optical data storage. The two leading contenders are magnetooptical (M-O) and phase change (P-C) recording thin films. Recently a great number of studies was performed concentrating on laser induced magnetic micro-domain formation of rare-earth-transition metal (RE-TM) alloy films for M-O recording. In this paper the mechanism of M-O recording, optical and recording properties of R E - T M thin films were introduced. The effects of the temperature profiles on magneto-optical polar Kerr rotation angle and recording domain size have been discussed in detail. Current research results of design and performances of multi-layer R E - T M films were also presented. The writing and erasing characteristics of the thin films for phase change type are determined by plotting changes in film reflectivity against the parameters of laser power and pulse width. In this paper a phase transformation kinetics diagram illustrating the phase change process of thin films for otical data storage is introduced. We draw heavily on our own data on InSb-based and GeTe-based alloy thin films. The most important features of properly selected P-C recording thin films, such as signal intensity, minimum crystallization time from amorphous to crystalline state, and the stability of the amorphous stage against crystallization, are discussed. The new experimental results of phase change at unequilibrium condition and appearance of metastable phases of metallic alloy thin films are also reported.
Invited paper Recent progress in Si thin film technology for solar cells Yukinori Kuwano, Shoichi Nakano and Shinya Tsuda, Functional
Materials Research Center, SANYO Electric Co., Ltd, 1-18-13, Hashiridani, Hirakata, Osaka 573, Japan Solar cells gather much attention, because of recent great interest in the global environment. Among the many materials available for solar cells, thin film silicon, such as amorphous silicon (a-Si), has received much attention because of the enormous resources, low fabrication energy, low fabrication costs, and limited pollution. In this paper, the recent progress in a-Si solar cell technology is summarized. The first point is the preparation method, mainly plasma CVD, which is the major process for fabrication of a-Si solar cells. Improvements in film quality by new material gases, optimization of reactant radicals, and impurity reduction are described. Improvements in the deposition rate and stability of a-Si films are also mentioned. The second point is solar cell structures. Both single-junction cells and multi-junction cells are discussed along with recent improvements in interface properties. The performance of various kinds of a-Si solar cells is also summarized. In addition, our latest investigative results on poly-crystaUine silicon thin film solar cell technology are discussed, along with the application of such technology as a near-future solar cell material to be used in stack-structured solar cells with a-Si. Various applications and future prospects on Si thin film solar 1035
0042-207X/91 $3.00+.00 Pergamon Press plc
Abstracts Invited paper Preparation and properties of sol-gel derived ferroelectric thin layers D A Payne, Department of Materials Science and Engineering,
Materials Research Laboratory, and Beckman Institute, University of Illinois at Urbana-Champaign, 105 S Goodwin, Urbana, IL 61801, USA In this paper we report on the polymeric condensation ofmetalloorganic precursors for the formation of inorganic network structures and the low temperature densification of ferroelectric ceramics. The chemical precursors include alkoxides and acetates, and the processing route is by the sol-gel method. Processing temperatures are sufficiently reduced for the integration of ferroelectric insulators on semiconductors. The sol-gel method allows for the mixing of solution precursors at the molecular level with purity and stoichiometry control. Molecular pathways are induced by hydrolysis and condensation reactions, which in turn are influenced by chemical additives. The role of pH and water concentration on oligomer and cluster formation, and polymerization, is illustrated for the synthesis of ferroelectric ceramics. Data are reported for transition metal oxide containing materials (i.e. titanates, zirconates, niobates . . . . ) of increasing complexity e.g. BaTiO3, PbTiO3, PZT, PLT, PLZT, LiNbO 3, Pb(Mg 1/3Nb 2/3)O3, PZN, etc. The importance of reflux and distillation conditions, for mixed alkoxide synthesis, and homogeneous hydrolysis of heterometal systems, is illustrated for PbTiO3 and LiNbO3. Single crystal data are reported for mixed metal alkoxides. The evolution of structure in solution, through condensation, is followed by N M R and F T I R methods. Formation of metal-oxygen-metal bonds is a prerequisite for low temperature synthesis and densification behavior. Features which influence viscoelastic densification, followed by crystallization at reduced temperatures, are reported. Finally, structure-property relations are given for MOS capacitors, ferroelectric non-volatile memories and electro-optic waveguides integrated on semiconductors. The implications for future intelligent material systems are outlined. The method is a potential upset technology in ceramic processing since it avoids the handling of fine powders, and is particularly suited for the fabrication of thin-layer devices.
Invited paper Advanced thin films for optical storage Gan Fuxi, Shanghai Institute of Optics and Fine Mechanics,
Academia Sinica, PO Box 800-211, Shanghai 201800, China Since the computer was invented, storage and retrieval of digital information has been a major challenge. The emergence of optical disk recording technology was a great event in these fields. Erasable optical recording is a new technology for achieving high density data storage. Advanced thin films are of interest for use
in optical data storage. The two leading contenders are magnetooptical (M-O) and phase change (P-C) recording thin films. Recently a great number of studies was performed concentrating on laser induced magnetic micro-domain formation of rare-earth-transition metal (RE-TM) alloy films for M-O recording. In this paper the mechanism of M-O recording, optical and recording properties of R E - T M thin films were introduced. The effects of the temperature profiles on magneto-optical polar Kerr rotation angle and recording domain size have been discussed in detail. Current research results of design and performances of multi-layer R E - T M films were also presented. The writing and erasing characteristics of the thin films for phase change type are determined by plotting changes in film reflectivity against the parameters of laser power and pulse width. In this paper a phase transformation kinetics diagram illustrating the phase change process of thin films for otical data storage is introduced. We draw heavily on our own data on InSb-based and GeTe-based alloy thin films. The most important features of properly selected P-C recording thin films, such as signal intensity, minimum crystallization time from amorphous to crystalline state, and the stability of the amorphous stage against crystallization, are discussed. The new experimental results of phase change at unequilibrium condition and appearance of metastable phases of metallic alloy thin films are also reported.
Invited paper Recent progress in Si thin film technology for solar cells Yukinori Kuwano, Shoichi Nakano and Shinya Tsuda, Functional
Materials Research Center, SANYO Electric Co., Ltd, 1-18-13, Hashiridani, Hirakata, Osaka 573, Japan Solar cells gather much attention, because of recent great interest in the global environment. Among the many materials available for solar cells, thin film silicon, such as amorphous silicon (a-Si), has received much attention because of the enormous resources, low fabrication energy, low fabrication costs, and limited pollution. In this paper, the recent progress in a-Si solar cell technology is summarized. The first point is the preparation method, mainly plasma CVD, which is the major process for fabrication of a-Si solar cells. Improvements in film quality by new material gases, optimization of reactant radicals, and impurity reduction are described. Improvements in the deposition rate and stability of a-Si films are also mentioned. The second point is solar cell structures. Both single-junction cells and multi-junction cells are discussed along with recent improvements in interface properties. The performance of various kinds of a-Si solar cells is also summarized. In addition, our latest investigative results on poly-crystaUine silicon thin film solar cell technology are discussed, along with the application of such technology as a near-future solar cell material to be used in stack-structured solar cells with a-Si. Various applications and future prospects on Si thin film solar 1035