• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05c
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• pp.182-185
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• 2003

Etching characteristics of (PB,Sr)$TiO_3$(PST) thin films Were investigated using inductively coupled chlorine based plasma system as functions of gas mixing ratio, RF power and DC bias voltage. It was found that increasing of Ar content in gas mixture' lead to sufficient increasing of etch rate and selectivity of PST to Pt. The maximum etch rate of PST film is 562 ${\AA}$/min and the selectivity of PST film to Pt is 0.8 at $Cl_2/(Cl_2+Ar)$ of 20 %. It was proposed that sputter etching is dominant etching mechanism while the contribution of chemical reaction is relatively low due to low volatility of etching products.

• Journal of Sensor Science and Technology
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• v.27 no.1
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• pp.1-5
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• 2018

Two-dimensional (2D) niobate-based nanosheets have attracted attention as high-k dielectric materials. We synthesized strontiumsubstituted calcium niobate ($Ca_{0.8}Sr_{1.2}Nb_3O_{10}$) nanosheets by a two-step cation exchange process from $KCa_{0.8}Sr_{1.2}Nb_3O_{10}$ ceramic. The $K^+$ ions were exchanged with $H^+$ ions, and then H+ ions were exchanged with tetrabutylammonium ($TBA^+$) cations. The $Ca_{0.8}Sr_{1.2}Nb_3O_{10}$ nanosheets were then exfoliated, decreasing the electrostatic interaction between each niobate layer. Furthermore, $Ca_2Nb_3O_{10}$ nanosheets were synthesized in same process for comparison. Each exfoliated nanosheet shows a single-crystal phase and has a lateral size of over 100 nm. The nanosheets were deposited on a $Pt/Ti/SiO_2/Si$ substrate by the electrophoretic deposition (EPD) method at 40 V, followed by ultraviolet irradiation of the films in order to remove the remaining $TBA^+$ ions. The $Ca_{0.8}Sr_{1.2}Nb_3O_{10}$ thin film exhibited twice the dielectric permittivity (~60) and lower dielectric loss than $Ca_2Nb_3O_{10}$ thin films.

• Korean Journal of Materials Research
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• v.31 no.9
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• pp.488-495
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• 2021

Solid state grain growth (SSCG) is a method of growing large single crystals from seed single crystals by abnormal grain growth in a small-grained matrix. During grain growth, pores are often trapped in the matrix and remain in single crystals. Aerosol deposition (AD) is a method of manufacturing films with almost full density from nano grains by causing high energy collision between substrates and ceramic powders. AD and SSCG are used to grow single crystals with few pores. BaTiO₃ films are coated on (100) SrTiO₃ seeds by AD. To generate grain growth, BaTiO₃ films are heated to 1,300 ℃ and held for 10 h, and entire films are grown as single crystals. The condition of grain growth driving force is ∆G_max < ∆G_c ≤ ∆G_seed. On the other hand, the condition of grain growth driving force in BaTiO₃ AD films heat-treated at 1,100 and 1,200 ℃ is ∆G_c < ∆G_max, and single crystals are not grown.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.28-28
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• 2007

Ferroelectric $(Ba_{0.5}Sr_{0.5})TiO_3$ (BST) thin films of thickness 500nm were deposited on $LaAlO_3$, (LAO) substrates by at $800^{\circ}C$. BST films were characterized for structure using X-ray diffraction (XRD). The surface morphology and thickness of BST the films were characterized by atomic force microscopy (AFM) and field emission scanning electron microscope (FESEM). We measured the dielectric properties at microwave frequencies (1~3 GHz) using a symmetrical stripline resonator with shorted ends and terahertz frequencies (0.2~2.5 THz) using a time-domain terahertz spectroscopy. The real and imaginary parts of the complex dielectric constant of the BST thin films on LAO substrates were in agreement with those previously reported.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.297-297
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• 2008

Buffer layers play an important role in the development of high critical current density coated conductor. $LaMnO_3$, $SrTiO_3$ and $BaZrO_3$ buffer layers were compatible with MgO surfaces and also provide a good template for growing high current density REBCO(RE=Rare earth) films. Systematic studies on the influences of pulsed laser deposition parameters (deposition temperature, deposition pressure, processing gas, laser energy density, etc.) on microstructure and texture properties of $LaMnO_3$, $SrTiO_3$ and $BaZrO_3$ films as buffer layer deposited on ion-beam assisted deposition MgO (IBAD_MgO) template by pulse laser deposition method, were carried out. These results will be presented together with the discussion on the possible use of this material in HTS coated conductor as buffer.

• Journal of Sensor Science and Technology
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• v.11 no.1
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• pp.48-53
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• 2002

Ferroelectric $Pb_{0.99}[(Zr_{0.6}Sn_{0.4})_{1-x}Ti_x]_{0.98}Nb_{0.02}O_3$(PNZST) thin films were deposited by a RF magnetron sputtering on $(La_{0.5}Sr_{0.5})CoO_3$(LSCO)/Pt/Ti/$SiO_2$/Si substrate using a PNZST target with excess PbO of 10 mole%. The crystallinity and electrical properties of the thin films with various composition ratio were investigated. The thin films deposited at the substrate temperature of $500^{\circ}C$ and the power of 80 W were crystallized to a perovskite phase after rapid thermal annealing(RTA) at $650^{\circ}C$ for 10 seconds in air. A PNZST thin films with Ti of 10 mole% showed the good crystallinity and ferroelectric properties. The remanent polarization and coercive field of the PNZST capacitor were about $20\;{\mu}C/cm^2$ and 50 kV/cm, respectively. The reduction of the polarization after $2.2{\times}10^9$ switching cycles was less than 10%.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.6
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• pp.504-510
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• 2002

Recently, thin film capacitors of high dielectric constant and low leakage current are applied to integrated devices. In this study, (Ba, Sr)$TiO_3$ (BST) thin films for low cost were prepared by Sol-Gel method. BST solution was spin-coated on Pt/$SiO_2$/Si substrate at 4,000 rpm for 10 seconds. Coating process was repeated 3 times and then sintered at $700^{\circ}C$ for 30 minutes. Structural and electrical characteristics of each specimen were analyzed by TG-DTA, SEM, fractal phenomenon, voltage-current and dielectric factor. Thickness of BST ceramics thin films are about 2,600~2,800 ${\AA}$ at depositing 3 times. Dielectric constant of thin films was decreased in 1 kHz~1 MHz. Dielectric constant and loss to frequency were 250 and 0.02 in $(Ba_{0.7}Sr_{0.3})TiO_3$ (BST3). Leakage current of BST3 was $10^{-9}\sim10^{-11}$/ A under 3 V.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.55-56
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• 2006

In this paper, we first applied the chemical mechanical polishing (CMP) process to the planarization of ferroelectric film in order to obtain a good planarity of electrode/ferroelectric film interface. BST ($Ba_{0.6}Sr_{0.4}TiO_3$), PZT ($Pb_{1.1}(Zr_{0.52}TiO_{0.48})O_3$) and BTO ($BaTiO_3$) ferroelectric film are fabricated by the sol-gel method. And then, we compared the structural characteristics before and after CMP process of BST, PZT, BTO films. Their dependence on slurry composition was also investigated. We expect that our results will be useful promise of global planarization for ferroelectric random access memories (FRAM) application in the near future.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.263-266
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• 2001

In this paper, we investigated dielectric properies for BST thin films that was deposited on MgO/Si substrates using RF magnetron sputtering. In here, MgO film was used to perform that a diffusion b arrier between the BST film and Si substrate and a buffer layer to assist the BST film growth. A d eposition condition for MgO films was RF Power of 50W, substrate temperature of room temperature and the working gas ratio of Ar:O$_2$ were varied from 90:10 to 60:47. Finally we manufactured the cap acitor of Al/BST/MgO/Si/Al structure to know electrical properties of this capacitor through I-V, C-V measurement. In the results, C-V aha racteristic curves was shown a ferroelectric property so we measured P-E. A remanent poliazation and coerceive electric field was present 2$\mu$C/cm$^2$ and -27kV/cm respectively at Ar:O$_2$=90:10. And a va clue of dielectric constant was 86 at Ar:02=90:10.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.776-779
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• 2004

The dielectric and electrical characteristics of Ce doped (Ba0.6Sr0.4)TiO3 (BST) thin films were investigated as a function of Ce content. Both atomic force microscopy (AFM) and x-ray diffraction (XRD) analysis showed that increasing the Ce doping ratio causes the decrease in grain size while the surface remains smooth and crack-free. The dielectric properties of the Ce doped BST films were found to be strongly dependent on the Ce contents. The dielectric constant and dielectric loss of the BST films decreased with increasing Ce content. However, it was also found that, compared with undoped films, the increase of Cecontent improves the leakage-current characteristics. The improvement of the electrical properties of Ce-doped BST films may be related to the decrease in the concentration of oxygen vacancies. The figure of merit (FOM) reached the maximum value of 48.9 at the 1 mol % of Cedoping. The dielectric constant, loss factor, and tunability of the 1 mol% Ce doped Ba0.6Sr0.4TiO3 thin films were 320, 0.011, and 46.3%, respectively.