• Korean Journal of Materials Research
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• v.18 no.7
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• pp.373-378
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• 2008

$Ba(Ti,Sn)O_3$ thin films, for use as dielectrics for MLCCs, were grown from Sn doped BaTiO3 sources by e-beam evaporation. The crystalline phase, microstructure, dielectric and electrical properties of films were investigated as a function of the (Ti＋Sn)/Ba ratio. When $BaTiO_3$ sources doped with $20{\sim}50\;mol%$ of Sn were evaporated, $BaSnO_3$films were grown due to the higher vapor pressure of Ba and Sn than of Ti. However, it was possible to grow the $Ba(Ti,Sn)O_3$ thin films with {\leq}\;15\;mol%$ of Sn by co-evaporation of BTS and Ti metal sources. The (Ti＋Sn)/Ba and Sn/Ti ratio affected the microstructure and surface roughness of films and the dielectric constant increased with increasing Sn content. The dielectric constant and dissipation factor of $Ba(Ti,Sn)O_3$ thin films with {\leq}\;15\;mol%$ of Sn showed the range of 120 to 160 and $2.5{\sim}5.5%$ at 1 KHz, respectively. The leakage current density of films was order of the $10^{-9}{\sim}10^{-8}A/cm^2$ at 300 KV/cm. The research results showed that it was feasible to grow the $Ba(Ti,Sn)O_3$ thin films as dielectrics for MLCCs by an e-beam evaporation technique.

• Journal of the Korean Ceramic Society
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• v.33 no.11
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• pp.1195-1202
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• 1996

To prepare the dielectric thin films of (Pb1-xSrx)TiO3 (x=0.1, 0.2, 0.3, 0.35, 0.5) by the sol-gel process titanium (IV) isopropoxide (Ti[OCH(CH3)2]4) and Pb Sr, acetate were used therefore the thin films were fabricated by dip-coating method. Stability of the sol decreased with addition of Sr content thin films could be fabricated up to 35mol% Over this range precipitation of sol occured thin films couldn't be obtained. Transmittance of thin films at visible range decreased with the increase of heat-treatment temperature but exhibited transmit-tance above 60% in all case. Moreover transmittance of thin films at visible range slightly increased with of addition of Sr,. When thin film containing 30 mol% srontium was heated at 600℃ the best perovskite phase was obtained. The dielectric constant (ε) was 280 and dielectric loss factor (tan δ) was 0.021 and curie tempera-ture (Tc) decreased with the increase of addition of Sr.

• Journal of Surface Science and Engineering
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• v.37 no.6
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• pp.307-312
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• 2004

Extensive efforts have been made in an attempt to utilize photocatalytic properties of $TiO_2$ in visible range. $TiO_2$ and TiO-N thin films were made by the DC reactive magnetron sputtering method at $300^{\circ}C$. Various gases (Ar, $O_2$ and $N_2$) were used and Ti target was impressed by 0.6 kW-5.8 kW power range. The hysteresis phenomenon of the $TiO_2$ thin film as a function of the discharge voltage characteristic was observed to be higher as applied power increases. That of TiO-N thin film was occurred at the 5.8 kW power. The cross section and surface roughness of thin films were observed by FE-SEM and AFM. Average surface roughness of TiO-N thin film was observed as $15.9\AA$ and that of $TiO_2$ as $13.2\AA$. The crystal phases of both $TiO_2$ and TiO-N thin films were found to be anatase structure. The atomic $\beta$-N (396 eV peak in N 1s XPS) was shown in the rutile crystal of TiO-N and was considered acting as the origin of wavelength shift to the visible light.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.6
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• pp.410-415
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• 1999

$Ba_{1-x}Sr_xTiO_3$ thin films with various ratio of Sr (X = 0.4, 0.5, 0.6) were grown $Pt/TiN/SiO_2/Si$ subastrate by RF magnetron sputtering deposition. As, Ag, and Cu films were deposited on $Ba_{1-x}Sr_xTiO_3$ thin films as top electrodes by using a thermal evaporator. The electrical properties of $Ba_{1-x}Sr_xTiO_3$ thin films for various compositions were characterized and the physical properties at interface between $Ba_{1-x}Sr_xTiO_3$ thin films and top electrodes were evaluated in terms of the work function difference. At x =0.5, the degradation of capacitance is lower to the other compositions. As negative biasapplied, the specimen with Cu top electrode has board saturation region and low leakage current since work function of Cu is bigger than other electrodes.$ Ba_{0.5}Sr_{0.5}TiO_3$ thin films with Cu top electrode, the dielectric constant was measured to the value of 354 at 1 kHz and the leakage current was obtained to the value of $5.26\times10^{-6}A/cm2$ at the forward bias of 2 V.

• Korean Journal of Materials Research
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• v.11 no.7
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• pp.537-544
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• 2001

Anatase $TiO_2$thin films as a photocatalyst were prepared by the reactive magnetron sputtering process. The $TiO_2$thin films were deposited on Si substrates under the various conditions : oxygen partial pressure, working pressure, sputtering time, and D.C. power. The photocatalystic degradation of $TiO_2$thin film have been studied to examine the contribution of surface morphology and crystallinity. The thin films with a good crystallinity or a rough surface showed a high photocatalytic degradation rate on phenol and E.coli 078 experiment. Compared with that of only UV radiation, the photocatalytic efficiency of $TiO_2$thin film under the UV radiation and the $O_2$ flow increased. We found that the crystallity and the morphology were the important factors on the photocatalytic efficiency of TiO$_2$thin film.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.9
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• pp.711-717
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• 1998

BST(70/30) and BST(50/50) thin films were prepared by Sol-Gel method and studied about the microstructural and dielectric properties with Pt and ITO bottom electrodes. The stock solution was synthesized and spin coated on the Pt/Ti$SiO_2$/Si and Indium Tin Oxide(ITO)/ glass substrate. the coated films were dries at 350$^{\circ}C$ for 10 minutes and annealed at $750^{\circ}C$ for 1 hour for the crystallization. The thin films coated on ITO substrate were crystallized easily and the packing density and roughness of surface were better that those of films coated on Pt substrates. In the BST(50/50) composition the structural properties were similar to the BST(70/30) composition and grain size were decreased with increasing the contents of Sr. The dielectric constant was higher in the BST(50/50) composition compared with the BST(70/30) composition. Using the ITO substrate, the dielectric constant was higher than the Pt substrate while the dielectric loss was showed a reverse trend. The dielectric constant with and increase of temperature was decreased slowly.

• JSTS:Journal of Semiconductor Technology and Science
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• v.8 no.1
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• pp.80-84
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• 2008

We systematically investigated the resistive switching properties of thin $TiO_2$ films on Pt/Ti/$SiO_2$/Si substrates that were embedded with a Co ultra thin layer. An in-situ sputtering technique was used to grow both films without breaking the chamber vacuum. A stable bipolar switching in the current-voltage curve was clearly observed in $TiO_2$ films with an embedded Co ultra thin layer, addressing the high and low resistive state under a bias voltage sweep. We propose that the underlying origin involved in the bipolar switching may be attributed to the interface redox reaction between the Co and $TiO_2$ layers. The improved reproducible switching properties of our novel structures under forward and reverse bias stresses demonstrated the possibility of future non-volatile memory elements in a simple capacitive-like structure.

• 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.

• Proceedings of the KIEE Conference
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• 2005.11a
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• pp.87-89
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• 2005

$Bi_{3.25}Y_{0.75}Ti_{3}O_{12}$[BYT] ferroelectric thin films were deposited by RF-Sputtering method on the $Pt/Ti/SiO_2/Si$. We investigated the effects of processing condition (especially post-annealing) on the structural and ferroelectric properties of the BYT thin films. Increasing the annealing temperature, the peak intensity of (117) increased and c-axis orientation decreased. The BYT thin films crystallized well at $600^{\circ}C$ for 30min. No secondary phases observed in the XRD pattern. At annealing temperature of $700^{\circ}C$, the thin films had no cracks and the grain was uniform. The calculated lattice constants of BYT thin films were a=0.539nm, b=0.536nm, c=3.288nm. The remnant polarization of the $Bi_{3.25}Y_{0.75}Ti_{3}O_{12}$ capacitor reached $1.8uC/cm^2$ at an applied field about 400kV/cm. The BYT thin films can be used as capacitors in Ferroelectric Random Access Memory device.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.8
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• pp.655-659
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• 2010

Nanoporous titanium dioxide ($TiO_2$) is very attractive material for various applications due to the high surface to volume ratio. In this study, we have fabricated nanoporous $TiO_2$ thin films on Si by anodic oxidation. 500-nm-thick titanium (Ti) films were deposited on Si by using electron beam evaporation. Nanoporous structures in the Ti films were obtained by anodic oxidization using ethylene glycol electrolytes containing 0.3 wt% $NH_4F$ and 2 vol% $H_2O$ under an applied bias of 5 V. The diameter of nanopores in the Ti films linearly increased with anodization time and the whole Ti layer could become nanoporous after anodizing for 3 hours, resulting in vertically aligned nanotubes with the length of 200~300 nm and the diameter of 50~80 nm. Upon annealing at $600^{\circ}C$ in air, the anodized Ti films were fully crystallized to $TiO_2$ of rutile and anatase phases. We believe that our method to fabricate nanoporous $TiO_2$ films on Si is promising for applications to thin-film gas sensors and thin-film photovoltaics.