Key Engineering Materials Vols. 421-422

Abstract: In this study, (Ba1-x,Srx)TiO3 thin films of various composition ratios were deposited on glazed Al2O3 substrates by the CSD method, and the temperature dependence of the dielectric property was analyzed. The dielectric property of the BST (80/20) thin film annealed at C was highly tunable, and the temperature dependence of the dielectric constant was stabilized at around room temperature. However, this BST (80/20) thin film exhibited intense ferroelectricity. Its tan intensified to 0.0511 in the high-frequency range (1 MHz). After the BST thin film was annealed at 600C, the grain size of the BST thin film was reduced to 40 nm and the ferroelectricity was alleviated. The dielectric constant, tan, and tunability of the BST thin film at 100 kHz were 158, 0.0170, and 39.6 (214 kV/cm, 6.0 V), respectively. The change rate of the dielectric constant, which indicates its temperature dependence, was ±7 or less in the range of -55 to 85C. Therefore, this BST thin film was considered to guarantee a wide operation temperature range for microwave tunable devices.

Abstract: This paper presents synthesized diamond films by using combustion activated chemical vapor deposition (CACVD) techniques. The characteristics of diamond films have been studied at wide ranges of temperature (30-400°C). The resistance of diamond films has been determined for hydrogen termination times of 5, 10, 15, and 20 minutes, and at the operation temperatures of 500, 600, and 700°C. The investigation found that, at 30°C a synthesized diamond film has a high resistance (1010 ), whereas at high temperatures (100-400°C) the resistance has decreased from 4.04 M to 2.42 M. The result obtained from the hydrogen termination showed that the resistance has decreased by 105-106  (at 30°C). Summarily, it can be stated that the higher the hydrogen termination times and operation temperatures, the lower the resistance of diamond films.

Abstract: Micro-patterned Pb(Zr,Ti)O3 (PZT) films with dot-pattern were grown by metal organic chemical vapor phase deposition (MOCVD). Micro-patterned Pb(Zr,Ti)O3 (PZT) films were formed on dot-patterned SrRuO3 (SRO) buffer layer that was prepared by MOCVD through the metal mask on (111)Pt/Ti/SiO2/Si substrate. The orientation of dot-patterned PZT films was ascertained by the micro-beam x-ray diffraction (XRD) and their crystallinity was characterized by Raman spectroscopy. It was found that PZT films were oriented to (111) on dot-pattern, while (100)/(001) out of dot-pattern and the amount of oxygen vacancies at the circumference of the dot-pattern were larger than that of center of dot-pattern.

Abstract: Artificial super-lattices of [(BaTiO3)/(SrTiO3)10]4 (BTO10/STO10) were fabricated on STO(001) substrate by the molecular beam epitaxy method (MBE), and the molecular layers of SrRuO3(SRO) was introduced into these superlattices as conductive layers. The superlattices introduced two conductive layers showed the enormous dielectric permittivity. On the other hand, the permittivity of the superlattice introduced one conductive layer was almost same as that of BTO10/STO10. In the case of introducing two conductive layers, the moving electrons between two layers induced the interfacial polarization. Especially, the superlattice with two SRO conductive layers, the distance between these layers in a superlattice is 18 molecular layers, showed the highest relaxation frequency 132 kHz and biggest capacitance.

Abstract: After depositing amorphous (Bi0.5La0.5)(Ni0.5Ti0.5)O3 (BLNT) films on BLNT seed layer/Pt(100)/ MgO(100) substrates by room-temperature sputtering, the crystallization of the perovskite-struc- tured films has been tried by hot isostatic pressing (HIP). The samples with a single-phase perovskite structure HIP-treated at 800°C for 1 h under gas pressures of 0.51.0 MPa showed good crystallinity of  = 0.960.98 without accompanying the precipitation of the secondary phase. It was confirmed that a large root mean square roughness value of 44.2 nm for the sample HIP-treated at 800°C for 1 h under gas pressure of 0.1 MPa is due to innumerable Bi4Ti3O12-like rod-shaped grains precipitated in the film surface, based on atomic force microscopy. It is shown that the BLNT sample HIP-treated at 800°C for 1 h under gas pressure of 1.0 MPa exhibits the best hysteresis loop shape with a remanent polarization of Pr = 5 C/cm2 and a coercive field of Ec = 150 kV/cm of the six.

Abstract: On the basis of experimental data on the piezoelectric pinpoint composition of ceramics of the ternary system Pb(Mg1/3Nb2/3)O3-PbZrO3-PbTiO3 (PMNZT), which we investigated in our previous report, epitaxial PbMg0.047Nb0.095Zr0.416Ti0.442O3 thick films with thicknesses ranging from 0.4 to 1.9 m were fabricated on Pt(100)/MgO(100) substrates by metalorganic decomposition. The film- thickness dependence on the structural and electrical properties (dielectric, piezoelectric and ferroelectric properties) was investigated. All PMNZT films exhibited a highly uniform (001) orientation, regardless of the film thickness. The cross-sectional transmission electron microscope micrographs and all the physical data suggest that high-density PMNZT thick films with a thickness  1.0 m can be expected to function as highly electrically insulating capacitors with high potential for piezo- and ferroelectric applications.

Abstract: Cubic pyrochlore bismuth zinc niobate thin films are known to exhibit voltage dependent dielectric properties. In this paper, we are demonstrating the fabrication and characterization of interdigital (IDC) and circular patch (CPC) capacitors using the pulsed laser deposited Bi1.5Zn1.0Nb1.5O7 (BZN) thin films on sapphire and platinised silicon substrates respectively. The IDCs fabricated are having 12 fingers of width 12 m each and separated by a gap of 8 m. The CPC are having circular patches with inner radius of 100 m and concentric ground plane with a radius of 300m. The electrical properties of these capacitors were characterized both at low frequencies and at microwave frequencies. The CPC varactors were having a tunability of 25% at 15 Volts. The calculated capacitance of the IDC varactor at 5.3 GHz with 0 V dc bias was 1.1 pF, which has got changed to 0.99 pF by the application of 30 Volts exhibiting a tunability of 10%.

Abstract: We investigated the influence of an external magnetic field for the carrier injection process of a metal (Au) / insulator (Cr2O3/Fe/CeO2) / semiconductor (Si) (MIS) capacitor, in which the insulator consists of magnetic materials. By applying an electric field, electrons propagating through the CeO2 layer from Si were injected into the Fe or an oxygen deficiency layer formed around the Fe layer. When a magnetic field was applied, the hysteresis window width of this capacitor was reduced. I-V curve analyses under a magnetic field revealed that this reduction was more likely due to the magnetic state of the Fe layer and the interaction between Fe and Cr2O3.

Abstract: Silica, silica/polymethylmethacrylate (PMMA) hybrid, and silica-particle blend silica films were successfully prepared on polybutylene terephtalate (PBT) substrate by dip coating using perhydropolysilazane (PHPS) as a silica source. The effect of thermal treatment on conversion from PHPS to silica was investigated in detail by scanning electron microscopy and Fourier transform infrared spectroscopy. Mechanical properties of silica and silica/PMMA hybrid thin films also were examined by the pencil scratch hardness tests.

Abstract: In the aerosol deposition method (ADM), we investigated an influence of pre-treatments for barium titanate powders as raw material on the deposition rate of thick films. By sieving and drying the powder, deposition rate of the films fabricated by ADM was effectively enhanced. On the other hand, heating the powders at 400-800°C, the resulting powders caused low deposition rate of the films. When a planetary milling was performed prior to charge aerosol chamber, the deposition rate of the films was four times higher than that in deposition using the powder without milling. By changing the milling rotation rate, we control size of agglomerated particles consisting of powders, which results in the control of deposition rate of the films.