Bi4Ti3O12(BIT) is ferroelectric ceramics material. It¡¦s application on capacity, conductor, memory device, and sensor. It¡¦s curie point at 675oC. When the temperature above 675oC, the structure of BIT is tetragonal (space group is I4/mmm). As temperature below 675oC, because BIT effected by inner strain, the structure of BIT transform from tetragonal to orthorhombic (space group is B2cb). And then, it may transform from orthorhombic to monoclinic. The texture assuming the structure of BIT is orthorhombic. This texture use x-ray anglicizing to determine component of BIT. On the other hand, using optical microscopy and scaning electron microscopy to observe the surface structure. Because of phase transformation, this texture confirm BIT have 101 twin by images and diffraction pattern of transmission electron microscopy. Further, this texture also find that BIT may have 180o domains on some grains.

In this thesis, Bi4Ti3O12 thin films are deposited on ITO/glass and Pt/Ti/SiO2/Si substrates using RF magnetron sputtering at room temperature and two kinds of targets with different compositions of Bi4Ti3O12 and Bi4Ti3O12+4wt% Bi2O3, respectively, and then heated by a rapid thermal annealing (RTA) process in an oxygen atmosphere. Three topics are focused in this research, they are: (1) to study the effects of different fabricated conditions and substrates on the physical and electrical characteristics of Bi4Ti3O12; (2) to investigate the influence of bismuth evaporation during thermal process on the characteristics of thin films, and seeking for the methods of bismuth compensation; and (3) applying the Bi4Ti3O12 film as the insulting layer of AC thin film electroluminescence device with the phosphor layer of ZnS:TbOF, and investigating the interaction between the two films. The experimental results indicate that intensities of X-ray diffraction (XRD) peaks of the films are evident when annealing at 650¢J for 15 min or at 700¢J for 10 min using RTA process, and the optimal properties of polycrystalline Bi4Ti3O12 thin films can be obtained at 700¢J for 15 min. No dielectric breakdown phenomenon of the films is detected in the filed of 500 kV/cm, and the leakage current density was lower than 10-6 A/cm2. The dielectric constant can attain to 307, and the loss factor is 0.02 at 1 kHz. The residual polarization and coercive field are 3.7 £gC/cm2 and 80 kV/cm with a sinusoidal wave of 500 Hz, respectively. The optical transmittance of the film is close to 100% at the wavelength of 550 nm. Scanning electronic microscopy (SEM) observation reveals that the microstructures, grain sizes and thicknesses of the thin films strongly dependent on the substrates, that is, the Pt/Ti/SiO2/Si substrate provides a more suitable interface layer than ITO/glass substrate for the growth of Bi4Ti3O12 thin films. The energy dispersive spectrometer (EDS) results indicate that the Bi/Ti atomic ratio of the films is less than that of target, which suggests that evaporation loss of bismuth occurs during the heating process. Whereas, this phenomenon occurs near the surface of thin film, it is not apparent in the inner of film. Excess 4wt% Bi2O3 additive in the target or additional Bi2O3 powder in the annealing process can compensate the loss of bismuth in the films, and improve the characteristics of thin films. Finally, the interdiffusion and chemical reactions take place among the element Bi, S and O at the interface during the deposition of ZnS:TbOF on Bi4Ti3O12 films, which degrades the optical transmittance of thin films. A 100 nm SiO2 buffer layer sandwiched between the ZnS:TbOF and Bi4Ti3O12 films can prevent the interdiffusion of the two layers, and enhance the optical transmittance and dielectric breakdown of Bi4Ti3O12 films.

In this study, the electrical properties of [Al/(Bi4Ti3O12+V2O5 ) /Ba(Zr0.1Ti0.9)O3/Silicon¡AMFIS ]structure using annealed-BZT films would be improved for the nonvolatile FeRAM device applications. The radio-frequency magnetron sputtering was used to deposit BTV ferroelectric films on Mo/Ti/SiO2/Si and BZT/Si substrates, respectively, and MFMIS and MFIS structures would also be fabricated. The various sputtering parameter effects of BTV films such as the oxygen concentrations, rf power and deposition time would be discussed. Besides, the electrical and physical properties of as-deposited BZT films for (BTV/BZT/Si¡AMFIS) structure would be improved by different rapidly thermal annealing temperature. The physical characteristics of BTV films and annealed-BZT films for various sputtering parameters were obtained from the XRD pattern and SEM morphology. Besides, the memory window, dielectric constant and leakage current of MFM and MFIS structure using BTV films and annealed-BZT films would be found from the HP4284A, RT66A and HP4156C. From the experimental result obtained, the maximum dielectric constant of BTV films for 40 % oxygen concentration and 130W power were 10.79. The leakage current density was about 10-5A/cm2, as the applied electrical field of 200 kV/cm. In addition, the coercive field (Ec) and remanent polarization (2Pr) were 750 kV/cm and 12 £gC/cm2 from the P-E curves, respectively. Finally, the maximum memory window and lower leakage current density of [Al/(Bi4Ti3O12+V2O5) /Ba(Zr0.1Ti0.9)O3/Silicon¡AMFIS) structure would be found and they were 25V and 10-8A/cm2, respectively.

Este trabalho descreve um estudo sistemático da influência da adição do átomo de lantânio na estrutura da fase Bi4Ti3O12 (BIT) e do átomo érbio na fase Bi3,25La0,75Ti3O12 (BLT075) no que tange seu processo de síntese e suas propriedades estruturais, microestruturais e elétricas. Cerâmicas de composição nominal Bi4-xLaxTi3O12 (BLTx) com 0 x 2 mol % e Bi3,25La0,75Ti3O12 (BLT075) com substituição no sítio do La3+ (BLExT) e no sítio do Ti4+ (BLTEx) com 0 x 0,06 mol %, foram preparadas através do método de síntese por reação do estado sólido. Os dados de difração de raios X (DRX) das amostras BLTx mostram a formação de uma solução sólida para todas as amostras, exceto para amostra contendo 2 mol% de La3+. Verificou-se que a adição de La3+ leva a um aumento da temperatura de sinterização e diminui o tamanho médio dos grãos, alterando sua morfologia de grão na forma de placas para uma forma mais esférica. Quanto às propriedades dielétricas, amostras BLTx com x 1 mol% apresentam um comportamento característico de um ferroelétrico normal, enquanto que quando x > 1 mol%, observa-se um pequeno deslocamento da temperatura de máximo da permissividade dielétrica (Tm) com a freqüência, indicando a existência de um comportamento típico de materiais ferroelétricos relaxores. Os resultados de espectroscopia Raman sugerem que os íons La3+ tendem a ocupar preferencialmente o sítio do Bi3+ das camadas peroviskitas quando x < 1,0 mol %, enquanto que quando x >1,0 mol %, o processo de incorporação também ocorre no sítio do Bi3+ nas camadas de Bi2O2. De acordo com a analise dos espectros XANES e XPS, a estrutura local e eletrônica dos átomos de Ti, Bi e La, não são afetadas de forma significativa pela adição de lantânio.Em relação às amostras dos sistemas BLExT e BLTEx, os dados de DRX mostram somente a presença de fases secundárias nas composições x= 0,04 e 0,06 mol% do sistema no BLTEx. A sinterização à 1115oC possibilitou obter amostras apresentando uma densidade relativa superior a da amostra não dopada BLT075. A adição de Er3+ causa mudanças na morfologia, diminuindo o tamanho médio dos grãos no sistema BLExT e aumentando no sistema BLTEx. Através de medidas elétricas, foi observado um decréscimo no valor Tm em ambos os casos. Quando x > 0,02 mol%, o comportamento de Tm é dominado pelo limite de solubilidade para o sistema BLExT. De acordo com os dados de XAS, a estrutura local e eletrônica dos átomos de Ti e Er não são afetadas de forma significativa pela adição de érbio. / This work describes a systematic study of the influence of the lanthanum atom addition in the Bi4Ti3O12 (BIT) phase and the erbium atom addition in the Bi3,25La0,75Ti3O12 (BLT075) phase in terms of their synthesis process and its structural, microstructural and electrical properties. Ceramics of nominal composition Bi4-xLaxTi3O12 (BLTx) with 0 x 2 mol% and Bi3,25La0, 75Ti3O12 (BLT075) with Er3+ replacing the La3+ atoms (BLExT) and replacing Ti4+ atoms (BLTEx) with 0 x 0, 06 mol%, were prepared by the solid state reaction method. X-ray diffraction (XRD) data of BLTx samples shows the formation of a solid solution for all samples, except for sample containing 2 mol% of La3+. It was found that the addition of La3+ leads to an increase in the sintering temperature, a decrease in the average size of grains and a modification on the grain from plates to a more spherical morphology. The dielectric properties of BLTx samples with x 1 mol% show a behavior characteristic of a normal ferroelectric whereas when x> 1 mol%, there is a small displacement of the temperature of maximum dielectric permittivity (Tm) with the frequency, indicating the existence of a typical behavior of a relaxor ferroelectric material. The Raman spectroscopy results suggest that La3+ ions tend to preferentially occupy the Bi3+ site in the peroviskite layer when x <1.0 mol%, whereas when x> 1.0 mol%, the process of incorporation occurred also in the Bi3+ site of the Bi2O2 layer. According to the analysis of XANES and XPS spectra, the local structure of atoms and electronic structure of Ti, Bi and La atoms of BLTx samples are not affected significantly by the addition of lanthanum. For samples of BLExT and BLTEx systems, the XRD data shows only the presence of a secondary phase in the x = 0.04 and 0.06 mol% compositions of the BLTEx system. The sintering at 1115 °C allowed to obtain samples presenting a relative high density than the sample BLT075 undoped sample. The addition of Er3+ induces significative changes in grain morphology by decreasing the average size of grains in the BLExT system and by increasing the BLTEx system. Through electrical measurements, it was observed a decrease in the Tm value in both cases. In the BLExT system, when x> 0.02 mol%, the behavior of Tm is dominated by the solubility limit. According to the XAS data, the local and electronic structure of Ti and Er atoms are not affected significantly by the addition of erbium.

Este trabalho descreve um estudo sistemático da influência da adição do átomo de lantânio na estrutura da fase Bi4Ti3O12 (BIT) e do átomo érbio na fase Bi3,25La0,75Ti3O12 (BLT075) no que tange seu processo de síntese e suas propriedades estruturais, microestruturais e elétricas. Cerâmicas de composição nominal Bi4-xLaxTi3O12 (BLTx) com 0 x 2 mol % e Bi3,25La0,75Ti3O12 (BLT075) com substituição no sítio do La3+ (BLExT) e no sítio do Ti4+ (BLTEx) com 0 x 0,06 mol %, foram preparadas através do método de síntese por reação do estado sólido. Os dados de difração de raios X (DRX) das amostras BLTx mostram a formação de uma solução sólida para todas as amostras, exceto para amostra contendo 2 mol% de La3+. Verificou-se que a adição de La3+ leva a um aumento da temperatura de sinterização e diminui o tamanho médio dos grãos, alterando sua morfologia de grão na forma de placas para uma forma mais esférica. Quanto às propriedades dielétricas, amostras BLTx com x 1 mol% apresentam um comportamento característico de um ferroelétrico normal, enquanto que quando x > 1 mol%, observa-se um pequeno deslocamento da temperatura de máximo da permissividade dielétrica (Tm) com a freqüência, indicando a existência de um comportamento típico de materiais ferroelétricos relaxores. Os resultados de espectroscopia Raman sugerem que os íons La3+ tendem a ocupar preferencialmente o sítio do Bi3+ das camadas peroviskitas quando x < 1,0 mol %, enquanto que quando x >1,0 mol %, o processo de incorporação também ocorre no sítio do Bi3+ nas camadas de Bi2O2. De acordo com a analise dos espectros XANES e XPS, a estrutura local e eletrônica dos átomos de Ti, Bi e La, não são afetadas de forma significativa pela adição de lantânio.Em relação às amostras dos sistemas BLExT e BLTEx, os dados de DRX mostram somente a presença de fases secundárias nas composições x= 0,04 e 0,06 mol% do sistema no BLTEx. A sinterização à 1115oC possibilitou obter amostras apresentando uma densidade relativa superior a da amostra não dopada BLT075. A adição de Er3+ causa mudanças na morfologia, diminuindo o tamanho médio dos grãos no sistema BLExT e aumentando no sistema BLTEx. Através de medidas elétricas, foi observado um decréscimo no valor Tm em ambos os casos. Quando x > 0,02 mol%, o comportamento de Tm é dominado pelo limite de solubilidade para o sistema BLExT. De acordo com os dados de XAS, a estrutura local e eletrônica dos átomos de Ti e Er não são afetadas de forma significativa pela adição de érbio. / This work describes a systematic study of the influence of the lanthanum atom addition in the Bi4Ti3O12 (BIT) phase and the erbium atom addition in the Bi3,25La0,75Ti3O12 (BLT075) phase in terms of their synthesis process and its structural, microstructural and electrical properties. Ceramics of nominal composition Bi4-xLaxTi3O12 (BLTx) with 0 x 2 mol% and Bi3,25La0, 75Ti3O12 (BLT075) with Er3+ replacing the La3+ atoms (BLExT) and replacing Ti4+ atoms (BLTEx) with 0 x 0, 06 mol%, were prepared by the solid state reaction method. X-ray diffraction (XRD) data of BLTx samples shows the formation of a solid solution for all samples, except for sample containing 2 mol% of La3+. It was found that the addition of La3+ leads to an increase in the sintering temperature, a decrease in the average size of grains and a modification on the grain from plates to a more spherical morphology. The dielectric properties of BLTx samples with x 1 mol% show a behavior characteristic of a normal ferroelectric whereas when x> 1 mol%, there is a small displacement of the temperature of maximum dielectric permittivity (Tm) with the frequency, indicating the existence of a typical behavior of a relaxor ferroelectric material. The Raman spectroscopy results suggest that La3+ ions tend to preferentially occupy the Bi3+ site in the peroviskite layer when x <1.0 mol%, whereas when x> 1.0 mol%, the process of incorporation occurred also in the Bi3+ site of the Bi2O2 layer. According to the analysis of XANES and XPS spectra, the local structure of atoms and electronic structure of Ti, Bi and La atoms of BLTx samples are not affected significantly by the addition of lanthanum. For samples of BLExT and BLTEx systems, the XRD data shows only the presence of a secondary phase in the x = 0.04 and 0.06 mol% compositions of the BLTEx system. The sintering at 1115 °C allowed to obtain samples presenting a relative high density than the sample BLT075 undoped sample. The addition of Er3+ induces significative changes in grain morphology by decreasing the average size of grains in the BLExT system and by increasing the BLTEx system. Through electrical measurements, it was observed a decrease in the Tm value in both cases. In the BLExT system, when x> 0.02 mol%, the behavior of Tm is dominated by the solubility limit. According to the XAS data, the local and electronic structure of Ti and Er atoms are not affected significantly by the addition of erbium.

No description available.

<p>Bismuth titanate Bi₄Ti₃O₁₂, is one of the bismuth based layered ferroelectric materials that is a candidate for replacing the lead based ferroelectric materials in for instance non-volatile ferroelectric random access memories (FRAM). This is due to the fact that the bismuth based ferroelectrics consists of pseudo perovskite units sandwiched in between bismuth oxide layers, which gives them a better fatigue nature.</p><p>In this thesis thin films of Bi₄Ti₃O₁₂have been deposited by chemical vapour deposition (CVD) using the metal iodides, BiI₃ and TiI₄ as precursors. Films grown on MgO(001) substrates were found to grow epitaxially. The electrical properties were determined for films grown on Pt-coated silicon and good properties such as a high dielectric constant (ε) of 200, low <i>tan</i> δ of 0.018, a remnant polarisation (<i>P</i>_r) of 5.3 μC/cm² and coercive field (E_c) as high as 150 kV/cm were obtained. Thin films in the Bi-Ti-O system were also deposited by atomic layer deposition (ALD) using metalorganic precursors.</p><p>In addition to the ternary bismuth titanates, films in the binary oxide systems <i>i.e.</i> bismuth oxides and titanium oxides were deposited. Epitaxial TiO₂ films were deposited both by CVD and ALD using TiI₄ as precursor. The rutile films deposited by ALD were found to grow epitaxially down to a temperature of at least 375 ¢ªC on α-A1₂O₃(0 1 2) substrates. The TiO₂ ALD process was also studied <i>in-situ</i> by QCM. Different bismuth oxides were deposited by halide-CVD using BiI₃ as precursor on MgO(0 0 1) and SrTiO₃(0 0 1) substrates and the results were summarised in an experimental CVD stability diagram. The Bi₂O_2.33 phase was found to grow epitaxially on both substrates.</p>

Bismuth titanate Bi4Ti3O12, is one of the bismuth based layered ferroelectric materials that is a candidate for replacing the lead based ferroelectric materials in for instance non-volatile ferroelectric random access memories (FRAM). This is due to the fact that the bismuth based ferroelectrics consists of pseudo perovskite units sandwiched in between bismuth oxide layers, which gives them a better fatigue nature. In this thesis thin films of Bi4Ti3O12 have been deposited by chemical vapour deposition (CVD) using the metal iodides, BiI3 and TiI4 as precursors. Films grown on MgO(001) substrates were found to grow epitaxially. The electrical properties were determined for films grown on Pt-coated silicon and good properties such as a high dielectric constant (ε) of 200, low tan δ of 0.018, a remnant polarisation (Pr) of 5.3 μC/cm2 and coercive field (Ec) as high as 150 kV/cm were obtained. Thin films in the Bi-Ti-O system were also deposited by atomic layer deposition (ALD) using metalorganic precursors. In addition to the ternary bismuth titanates, films in the binary oxide systems i.e. bismuth oxides and titanium oxides were deposited. Epitaxial TiO2 films were deposited both by CVD and ALD using TiI4 as precursor. The rutile films deposited by ALD were found to grow epitaxially down to a temperature of at least 375 ¢ªC on α-A12O3(0 1 2) substrates. The TiO2 ALD process was also studied in-situ by QCM. Different bismuth oxides were deposited by halide-CVD using BiI3 as precursor on MgO(0 0 1) and SrTiO3(0 0 1) substrates and the results were summarised in an experimental CVD stability diagram. The Bi2O2.33 phase was found to grow epitaxially on both substrates.

The present research work mainly focuses on the fabrication and characterization of single and multilayer thin films based on Bismuth Vanadate (BVO) and Bismuth Titanate (BTO). The multi-target laser ablation technique was used to fabricate single layer thin films of BVO, BVN and BTO; and multilayers composed of BVO and BTO in different structures. The fabricated thin films exhibited dense microstructure and a sharp interface with the substrate. The lattice strain, surface roughness and grain size could be varied as functions of composition and individual layer thickness in different structure fabricated. The optical properties were studied by spectroscopic ellipsometry and optical transmission spectra. The various models that were used for ellipsometric data analysis gave an excellent fitting to the experimental data. The optical constants were determined through multilayer analyses of the films. The band gap of these films was studied by spectroscopic ellipsometry and optical transmission. The optical studies carried out on BVO-BTO bilayer indicated the presence of an interfacial layer in between the BVO and BTO layer, whose refractive index was different from that of the individual layers and is attributed to different nature of the interfacial layer. The ferroelectric nature of BVO films was confirmed by P-E hysteresis loop studies under different applied fields and at various probing frequencies. The same was corroborated via the C-V measurements of these BVO films which exhibited butterfly shaped C-V characteristics. Fatigue studies in these films indicated that the switchable polarization is essentially constant through 105 cycles, after which it starts increasing probably due to the ionic conduction in BVO thin films. The dielectric response of undoped and Nb doped BVO as well as BVBT ML thin films were studied over a wide range of temperatures. The BVO films exhibited remarkable dielectric dispersion at low frequencies especially in the high temperature regime. Further, the frequency and temperature dependence of the dielectric, impedance, modulus and conductivity spectra of these films were investigated in detail. The ac conductivity was found to obey well the double power law in case of ML, indicating the different contributions to the conductivity, the low frequency conductivity being due to the short range translational hopping and the high frequency conductivity is due to the localized or reorientational hopping motion. DC leakage conduction in BVO, BVN and BVBT ML thin films was studied over a wide range of temperatures and applied electric fields. The experimental data were analyzed in light of different models to investigate the dc conduction mechanism in these films which were broadly classified into electrode limited and bulk limited conduction processes. In the case of BVO thin films the dc leakage current exhibited an ohmic nature at low electric fields followed by an onset of the space charge limited conduction (>1). Further in case of BVN films, three distinct regions were observed in I-V characteristics signifying different types of conduction processes in these films. In case of BVBT ML thin films, bulk limited PF mechanism was found to determine the conduction behavior at moderate electric fields. At higher electric fields, a trap filled region was observed which was followed by SCL conduction at higher fields. Therefore the present observation indicates the presence of more than one bulk limited conduction process in BVBT ML thin films. BVO thin films exhibiting good structure and dense morphology were successfully prepared on p-type Si by chemical solution decomposition technique. The C-V characteristics were evaluated for Au/BVO/Si MFS structure which showed a typical high frequency feature of a conventional MFIS structure.