Dielectric Properties of Bismuth Layer-Structured Oxide Thin Films with Preferential Crystal Orientation at High-Temperature

Thin films of MBi4Ti4O15 (M = Ca and Sr) with preferential crystal orientation were fabricated using underneath perovskite layers on various substrates. One-axis BLSD films on (100)LaNiO3/(111)Pt/Ti/(100)Si and epitaxial BLSD films on (100)SrRuO3//(100)SrTiO3 were fabricated by chemical solution deposition (CSD). Dielectric constants of the CaBi4Ti4O15 and SrBi4Ti4O15 films on (100)LaNiO3/(111)Pt/Ti/(100)Si were approximately 250, while those on (100)SrRuO3//(100)SrTiO3 were 220, respectively. The temperature coefficients of capacitance (TCCs) of these films were below 10% in atmospheric temperature range between R.T. and 300°C, which is significantly smaller than those of conventional (Ba,Sr)TiO3-based capacitors.

The Ferroelectric and Electrical Properties of CaBi4Ti4O15 Thin Films Prepared by Sol-Gel Technology

In this study, thin films of CaBi4Ti4O15with preferential crystal orientation were prepared by the chemical solution deposition (CSD) technique on a SiO2/Si substrate. The films consisted of a crystalline phase of bismuth-layer-structured dielectric. The as-deposited CaBi4Ti4O15thin films were crystallized in a conventional furnace annealing (RTA) under the temperature of 700 to 800°C for 1min. Structural and morphological characterization of the CBT thin films were investigated by X-ray diffraction (XRD) and field-emission scanning electron microscope (FE-SEM). The impedance analyzer HP4294A and HP4156C semiconductor parameters analyzer were used to measurement capacitance voltage (C-V) characteristics and leakage current density of electric field (J-E) characteristics by metal-ferroelectric-insulator- semiconductor (MFIS) structure. By the experimental result the CBT thin film in electrical field 20V, annealing temperature in 750°C the CBT thin film leaks the electric current is 1.88x10-7A/cm2and the memory window is 1.2V. In addition, we found the strongest (119) peak of as-deposited thin films as the annealed temperature of 750°C

Dielectric Properties of Highly (001)-Plane Oriented SrBi4Ti4O15 Thin Films

Thin films of a bismuth layer-structured dielectric oxides (BLSD), SrBi4Ti4O15, with preferential crystal orientation were prepared by means of chemical solution deposition (CSD) technique on (111)Pt/(100)Si substrate with bottom nucleation layers of conductive perovskite oxides, LaNiO3 and SrRuO3. CSD technique was utilized for the film preparation of SrBi4Ti4O15. These films possessed highly crystal orientation of (00l) BLSD planes parallel to the substrate surface. The leakage current densities of the SrBi4Ti4O15 films on (100)SrRuO3//(100)LaNiO3/(111)Pt/Ti/(100)Si and on (100)LaNiO3/(111)Pt/Ti/(100)Si were approximately 10-6 and 10-7 A/cm2 respectively. The dielectric constants of these films in a frequency range of 102 - 106 Hz were from 310 to 350 and 250 to 260 respectively. The value of capacitance change of these films in the range from 20 to 300 oC was about +8 and +5% respectively.

Synthesis of Apatite Ceramics with Preferential Crystal Orientation

Biological hard tissues show preferential alignment of the c-axis of biological apatite (BAp) crystallites depending on the shape and stress distribution in vivo, but apatite-base bioceramics developed for bone grafting have no preferential BAp orientation. Thus, the crystal orientation was controlled for developing novel bioceramics with apatite (Ap) texture similar to biological hard tissues. Since cortical portion in a bovine femur shows a one-dimensional orientation along the longitudinal direction of long bone, the effect of heat treatment on Ap orientation was investigated in the femur bone as a starting material. Heat treatment was performed first at 600°C for 1h to remove organic constituents and subsequently at each temperature between 700°C and 1300°C. Crystal orientation and texture of BAp were measured by the micro-beam X-ray diffractometer. Size of BAp crystallites increased remarkably after a heat treatment even at 600°C for 1h and a great amount of pore remained in the Ap ceramics in exchange for the organic constituents. Several Ap grains were surrounded as a group by the pores, but additional heat treatment in a temperature range up to 900°C reduced the number of Ap grains in the group, and finally became a single grain region at 1000°C. Pore density decreased with increasing annealing temperature, especially above 1000°C. One-dimensional preferential alignment of the c-axis in Ap maintained during all the heat treatment and the degree increased with increasing annealing temperature because a lot of low-energy low angle boundaries against the c-axis existed in the starting material and preferentially remained in the synthesized Ap ceramics. It was therefore concluded that adequate heat treatment of bovine femur can give the preferential crystal orientation in Ap ceramics.

Dependence of Crystallographic Texture of C54 Tisi2 on Thickness and Linewidth In Submicron Cmos Structures

Preferential crystal orientation of low-resistance C54 TiSi2 formed in the reaction of polycrystalline and single crystal silicon with titanium was investigated for Ti thicknesses ranging from 15 to 44 nm. Using in situ synchrotron x-ray diffraction during heating of 15 nm of Ti on single crystal Si, we observed that the C54 TiSi2 silicide film showed predominantly <040> grains oriented normal to the sample. In thicker silicide films the <311> orientation dominated or film was randomly oriented. An ex situ four circle diffractometer was used to investigate the strong <040> texture in narrow line arrays of C54-TiSi2 formed on polycrystalline silicon with linewidths from 0.2 to 1.1 μm. We observed that the angular distribution of <040> Ti Si2 grains is dependent on the line direction, where the majority of grains had their (100) planes oriented parallel with the line direction. These findings support a model of the C49 to C54 TiSi2 transformation involving rapid growth of certain orientations favored by the one-dimensional geometry imposed by narrow lines.