• Journal of the Korean Vacuum Society
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• v.8 no.3A
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• pp.238-244
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• 1999

Pt/SBT/Pt capacitors were fabricated using the MOD-derived $SrBi_{2x}Ta_2O_9$ (SBT) films and their ferroelectic and leakage current characteristics were investigated with post annealing at 400~$800^{\circ}C$. Although the MOD-derived SBT film exhibited the hysteresis loop typical for the leaky film, the well-saturated ferroelectric hysteresis loop could be obtained by post annealing the Pt/SBT/Pt capacitors at $550^{\circ}C$~$800^{\circ}C$. The remanent polarization $2P_r$ of the SBT film exhibited a maximum value of 9.72$\mu\textrm{cm}^2$ with post annealing at $600^{\circ}C$, and then decreased with increasing the post annealing temperature above $600^{\circ}C$. The MOD-derived SBT films exhibited the high leakage current density of ~$10^{-3} \textrm{A/cm}^2$ at 75kV/cm. With post annealing the Pt/SBT/Pt capacitor at 600~$800^{\circ}C$, however, the leakage current density decreased remarkably to less than $10^{-6}\textrm{A/cm}^2$ at 75kV/cm.

• Current Applied Physics
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• v.18 no.12
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• pp.1486-1491
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• 2018

In recent years, mica has been successfully used as a substrate for the growth of flexible epitaxial ferroelectric oxide thin films. Here, we systematically investigated the flexibility of mica in terms of its thickness, repeated bending/unbending, extremely hot/cold conditions, and successive thermal cycling. A $20-{\mu}m-thick$ sheet of mica is flexible even up to the bending radius of 5 mm, and it is durable for 20,000 cycles of up- and down-bending. In addition, the mica shows flexibility at 10 and 773 K, and thermal cycling stability for the temperature variation of ca. 400 K. Compared with the widely used flexible polyimide, mica has a significantly higher Young's modulus (ca. 5.4 GPa) and negligible hysteresis in the force-displacement curve. These results show that mica should be a suitable substrate for piezoelectric energy-harvesting applications of ferroelectric oxide thin films at extremely low and high temperatures.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.140-140
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• 2009

The Metal-ferroelectric-semiconductor (MFS) structure has superior advantages such as high density integration and non-destructive read-out operation. However, to obtain the desired electrical characteristics of an MFS structure is difficult because of interfacial reactions between ferroelectric thin film and Si substrate. As an alternative solution, the MFS structure with buffer insulating layer, i.e. metal-ferroelectric-insulator-semiconductor (MFIS), has been proposed to improve the interfacial properties. Insulators investigated as a buffer insulator in a MFIS structure, include $Ta_2O_5$, $HfO_2$, and $ZrO_2$ which are mainly high-k dielectrics. In this study, we prepared the Dy-doped $La_2O_3$ solution buffer layer as an insulator. To form a Dy-doped $La_2O_3$ buffer layer, the solution was spin-coated on p-type Si(100) wafer. The coated Dy-doped $La_2O_3$ films were annealed at various temperatures by rapid thermal annealing (RTA). To evaluate electrical properties, Au electrodes were thermally evaporated onto the surface of the samples. Finally, we observed the surface morphology and crystallization quality of the Dy-doped $La_2O_3$ on Si using atomic force microscopy (AFM) and x-ray diffractometer (XRD), respectively. To evaluate electrical properties, the capacitance-voltage (C-V) and current density-voltage (J-V) characteristics of Au/Dy-doped La2O3/Si structure were measured.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.3
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• pp.166-173
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• 2001

Hysteresis loops of the ferroelectric thin films such as PLZT(10/30/70), PLT(10) and PZT(30/70) was simulated using the field-dependent polarization model and compared to the measured loops. In case of PZT(30/70) thin film, as the real saturation or polarization at the applied voltage or larger than 5V appears slack and its value is quite different from the simulated one, it is deduced that the ferroelectric polarization of PZT(30/70) is generated not only by the pure dipoles but also by various electric charges. The drain current of quasi-MFISFET is expressed by using the square-law FET and field-dependent polarization models. The modeling results are analogous to the experimental values. The channel of quasi-MFISFET using PZT(30/70) forms more quickly compared to that of quasi-MFISFET using PLZT(10/30/70) or PLT(10) in the state of 'write' gate voltage of -10V. This may be because the decrease rate of the polarization in the PZT(30/70) thin film is 3~4 times more rapid than that of the polarization in the PLZT(10/30/70) or the PLT(10) thin film in the retention characteristics.

• Journal of the Korean Vacuum Society
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• v.6 no.1
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• pp.36-43
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• 1997

FECAPS(ferroelectric capacitors) have been fabricated by RF magnetron sputtering deposition of 3000$\AA$ PZT thin films on the Pt/Ti/$SiO_2$/Si substrates and post-annealing with the temperature of $550^{\circ}C$~$650^{\circ}C$ for 10 sec~50 sec in a RTA system. The electrical characteristics of the fabricated capacitors showed the highest dielectric constant and remanent polarization[${\varepsilon_r(1kHz)$=690, $2P_r$(-5V~5V sweep)=22$\mu$C/$ \textrm{cm}^2$] in the samples annealed at $650^{\circ}C$ for 30 sec, while the lowest tangent loss and leakage current [$tan\delta(\ge10kHz)\le0.02, \; J_i(5V)=3\mu\textrm{A}/\textrm{cm}^2$]in the samples annealed at $600^{\circ}C$ for 30 sec.

• Journal of the Korean Ceramic Society
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• v.40 no.1
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• pp.46-51
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• 2003

Ferroelectric $Sr_{0.7}Bi_{2.1}Ta_{2.0}O_9$ thin films with 200 nm thicknesses were deposited on $Pt/Ti/SiO_2/Si$ substrate by liquid delivery MOCVD process. In these experiments, $Sr(TMHD)_2{\cdot}pmdeta,\; Bi(ph)_3$ and $Ta(O^i/Pr)_4(TMHD)$ were used as precursors, which were dissolved in n-butyl acetate and pentamethyldiethylenetriamine. Substrate temperature and reactor pressure of this experiment was $570^{\circ}C$and 5 Torr, respectively. The remanent polarization value (2Pr) of SBT thin film with annealed at $780^{\circ}C$was$7.247{\mu}C/cm^2$and$8.485 {\mu}C/cm^2$by applying 3 V and 5 V, respectively.

• Journal of the Korean Ceramic Society
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• v.39 no.4
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• pp.377-385
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• 2002

The possibility of $ZrO_2$ thin film as insulator for Metal-Ferroelectric-Insulator-Semiconductor(MFIS) structure was investgated. $SrBi_2Ta_2O_9$ and $SrBi_2Ta_2O_9$(SBT) thin films were deposited on P-type Si(111) wafer by R. F. magnetron sputtering method. The electrical properties of MFIS gate were relatively improved by inserting the $ZrO_2$ buffer layer. The window memory increased from 0.5 to 2.2V in the applied gate voltage range of 3-9V when the thickness of SBT film increased from 160 to 220nm with 20nm thick $ZrO_2$. The maximum value of window memory is 2.2V in Pt/SBT(160nm)/$ZrO_2$(20nm)/Si structure with the optimum thickness of $ZrO_2$. These memory windows are sufficient for practical application of NDRO-FRAM operating at low voltage.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.271-274
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• 2003

[ $Sr_xBa_{1-x}Nb_2O_6$ ] (SBN, $0.25{\leq}x{\leq}0.75$) ceramic is a ferroelectric material with tetragonal tungsten bronze (TTB) type structure, which has a high pyroelectric coefficient and a nonlinear electro-optic coefficient value. In spite of its advantages, SBN has not been investigated well compared to other ferroelectric materials with perovskite structure. In this study, SBN thin film was manufactured by ion beam sputtering technique using the prepared SBN target in $Ar/O_2$ atmosphere. SBN30 thin films of different thickness were pre-deposited as a seed layer on $Pt(100)/TiO_2/SiO_2/Si$ substrate followed by SBN60 deposition up to $4500\;{\AA}$ in thickness. As-deposited SBN60/SBN30 layer was heat-treated at different temperatures of 650, 700, 750, and $800\;^{\circ}C$ in air, respectively, The crystallinity and orientation behavior as well as electric properties of SBN60/SBN30 multi-layer were examined. The deposited layer was uniform and the orientation was shown primarily along (001) plane from XRD pattern. There was difference in the crystal structure with heat-treatment temperature, and the electric properties depended on the heating temperature and the seed-layer thickness. In electric properties of Pt/SBN60/SBN30/Pt thin film capacitor prepared, the remnant polarization (2Pr) value was $15\;{\mu}C/cm^2$, the coercive field (Ec) 65 kV/cm, and the dielectric constant 1492, respectively.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.5
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• pp.265-269
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• 2000

$(Ba, Sr)TiO_3$thin films were etched with a magnetically enhanced inductively coupled plasma (MEICP) at different CF4/Ar gas mixing ratios. Experimental was done by varying the etching parameters such as rf power, dc bias and chamber pressure. The maximum etch rate of the BST films was $1800{AA}/min$ under $CF_4/(CF_4+Ar)$ of 0.1, 600 W/350 V and 5 mTorr. The selectivity of BST to Pt and PR was 0.6, 0.7, respectively. X-ray photoelectron spectroscopy (XPS) results show that surface reaction between Ba, Sr, Ti and C, F radicals occurs during the (Ba, Sr)TiO3 etching. To analyze the composition of surface residue after the etching, films etched with different CF_4/Ar$ gas mixing ratio were investigated using XPS and secondary ion mass spectroscopy (SIMS).

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.2
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• pp.140-144
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• 2000

($Pb_{0.91}$$La_{0.09}$)($Zr_{0.65}$$Ti_{0.35}$)$O_3$ thin films were prepared on ITO-coated glass by spin-coating. As $Pb_{0.9}$$La_{0.1}$)$TiO_3$ thin films were used as seeding layers, formation temperature of perovskite was reduced and theUrosette" structure was disappeared. PLZT thin films with a seeding layer of 40 nm thick showed a (100) preferred orientation and better dielectric and ferroelectric properties.ties.