• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.205-206
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• 2006

(BaSr)$TiO_3$ thick films were prepared by tape casting method, using $BaTiO_3$ and $SrTiO_3$ powder slurry in order to investigate dielectric properties. With MgO additives, the sintering density was 5.8 $g/cm^3$ and the BST sample exhibited the maximum dielectric constant, tunability at temperatures near phase transition point. Dielectric loss be on the decrease because the interface is not a pore. BST sample be applicable on tunable device.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.243-246
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• 1998

(Ba, Sr)TiO$_3$[BST] thin films were fabricated on Pt/SiO$_2$/Si substrate by RF sputtering technique. The structural, dielectric and electrical properties of BST thin films were investigated with Ar/O$_2$ ratio. Dielectric constant and dielectric loss of the BST thin film were about 1020 and 2.0[%], respectively. (at RF power 80W, post annealing temperature $650^{\circ}C$, deposition pressure of 5mTorr and Ar/O$_2$=80/20). For the BST(Ar/O$_2$=80/20) thin film with Polarization switching cycles of 10$^{10}$ , remanent polarization and coercive field were 0.084[$\mu$C/cm$^2$], 1.954[kV/cm], respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.04a
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• pp.309-313
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• 1997

(Ba$_{x}$Sr$_{l-x}$)TiO$_3$(BST) thin fi1ms with various Ba/Sr ratios were deposited on Pt(80nm)/SiO$_2$(100nm)/Si by RF magnetron sputtering. BST thin films which have x=0.6, 0.5, 0.4 were studied dielectric properties with temperature variation. The frequency was used from 100Hz to 1MHz for measuring dielectric constant. The measurement conditions of dielectric constant with Temperature Variation were 1KHz and 2$0^{\circ}C$. As a result, the dielectric constant of BST thin film was about 425 and loss factor was 0.013. Also, with increasing Temperature, the dielectric constants of BST thin films were gradually decreased.sed.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.2
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• pp.60-66
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• 2001

($Ba_x$$Sr_{1-x}$)$TiO_3$ (x=0.9, 0.7, 0.5) thin films were prepared on ITO-coated glass by sol-gel method. Perovskite phase formation temperature of BST thin films seemed to be higher than $600^{\circ}C$. Peaks of perovskite phase shift to high diffraction angles as the Sr/(Ba+Sr) ratio was increased, due to the smaller ionic size of $Sr^{2+}$ than $Ba^{2+}$ . As a heating temperature was increased, the grain became coarser. And as Sr/(Ba + Sr) ratio was increased, the grain became finer. Dielectric constants of the BST(50/50) thin film are higher and dielectric losses of that are lower than those of the others. Dielectric constant and dielectric loss of the BST(50/50) thin film were 652 and 0.042 at 1kHz, respectively.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1879-1881
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• 1999

(Ba,Sr)$TiO_3$[BST] thin films were fabricated on Pt/Ti/$SiO_2$/Si substrate by RF sputtering. We investigated the effects of substrate temperature on the structural and dielectric properties of BST thin films. Increasing the substrate temperature, barium multi titanate phases were decreased, and BST (100), (200) peaks were increased. The relative dielectric constant and dielectric loss of the BST thin films at the substrate temperature of $500^{\circ}C$ were 300 and 0.018, respectively at l[kHz]. In all films, the dielectric constants decreased. Dielectric losses increased as increasing the frequency. The switching voltage was 5V of the BST thin films at the substrate temperature of $500^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.04b
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• pp.18-21
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• 2004

An alkoxide-based sol-gel method was used to fabricate $Ba_{0.6}Sr_{0.4}TiO_3$ thin films doped by Bi from 5 to 20 mol% on a $Pt/Ti/SiO_2/Si$ substrate. The structural and dielectric properties of BST thin films were investigated as a function of Bi dopant concentration. The dielectric properties of the Bi doped BST films were strongly dependent on the Bi contents. The dielectric constant and dielectric loss of the films decreased with increasing Bi content. However, the leakage current density of the 10 mol% Bi doped $Ba_{0.6}Sr_{0.4}TiO_3$ thin film showed the lowest value of $5.13{\times}10^{-7}\;A/cm^2$ at 5 V. The figure of merit (FOM) reached a maximum value of 32.42 at a 10 mol% Bi doped $Ba_{0.6}Sr_{0.4}TiO_3$ thin films. The dielectric constant, loss factor, and tunability of the 10 mol% Bi doped $Ba_{0.6}Sr_{0.4}TiO_3$ thin films were 333, 0.0095, and 31.1%, respectively.

• Bulletin of the Korean Chemical Society
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• v.32 no.1
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• pp.141-144
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• 2011

We report the synthesis of $SrTiO_3$, $BaTiO_3$ and $Ba_xSr_{1-x}TiO_3$ (BST) nanoparticles (NPs) in various compositions (x = 0.25, 0.5 and 0.75) by an inorganic sol-gel method under a basic condition. Highly crystalline nanoparticles were formed at the reaction temperature of 25 - $100^{\circ}C$ from a stabilized titanium alkoxide in tetramethylammonium hydroxide (TMAH) and barium or strontium acetate in aqueous solution. Morphology and particle structure of the synthesized BST NPs were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The BST nanoparticles in various compositions were monodispersed without mutual aggregation, and their average sizes were in the range of 70 - 80 nm. Furthermore, they showed highly crystallized perovskite phase over the whole composition range from $SrTiO_3$ to $BaTiO_3$. We also proposed a mechanism for the low-temperature formation of BST NPs.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.51-54
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• 2000

In this paper, $Ba_{0.5}$Sr$_{0.5}$TiO$_3$ thin films were prepared on Pt/Ti/SiO$_2$/Si substrate by RF magnetron sputtering method. We investigated effect of deposition conditions (especially RF input power) on structural properties of BST thin films. Deposit conditions of BST films were set working gas ratio, Ar:O$_2$= 70 : 30, working pressure 10mTorr, and RF input power 25W, 50W, 75W and 100W. Post-annealing using rapid thermal annealing(RTA) performed at 45$0^{\circ}C$, 55$0^{\circ}C$, $650^{\circ}C$, and 75$0^{\circ}C$ in oxigen ambient for 60 sec, respectively. The structural properties of BST films on Pt/Ti/SiO$_2$/Si substrate analysed by X-ray diffraction(XRD).).).

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.4
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• pp.56-62
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• 1999

In this study, (Ba, Sr)$TiO_3$ thin films were etched with $Cl_2$/Ar gas mixing ratio in an inductively coupled plasma (ICP) by varying the etching parameter such as rf power, dc bias voltage, and chamber pressure. The etch rate was 56 nm/min under $Cl_2$/($Cl_2$+Ar) gas mixing ratio of 0.2, rf power of 600 W, dc bias voltage of 250 V, and chamber pressure of 5 mTorr. At this time, the selectivity of BST to Pt, $SiO_2$ was respectively 0.52, 0.43. The surface reaction of the etched (Ba, Sr)$TiO_3$ thin films was investigated with X-ray photoelectron spectroscopy (XPS). Ba is removed by chemical reaction between Sr and Cl to remove Sr. Ti is removed by chemical reaction such as $TiCl_4$ with ease. The results of secondary ion mass spectrometer (SIMS) analysis compared with the results of XPS analysis and the results were the same.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.12
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• pp.555-559
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• 2006

Using the $Ba_{0.5}Sr_{0.5}TiO_3$(BST) powders prepared by the Sol-Gel method, the BST thick films were fabricated on the $Al_2O_3 $substrates coated with Pt by the screen printing method. Compared with pure BST thick films, the structural and dielectric properties of the BST thick films doped with $1{\sim}10$ wt % MgO were investigated. It was observed that the Mg substitution into BST causes a shift in the cubic-tetragonal BST phase transition peak to a lower temperature. The microstructure of the BST substituted with Mg was homogeneous and dense. Mg substitution into BST had a significant effect on the grain size reduction. Dielectric constant was decreased with increasing the MgO content and temperature. In the case of BST thick films doped with 1 wt% MgO, the relative permittivity and dielectric loss were 1581 and 1.4 % at 1 MHz.