• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.1835-1837
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• 2005

$Bi_{3.25}Y_{0.75}Ti_3O_{12}$[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 dielectric properties of the BYT thin films. The BYT thin films were crystallized well at annealing temperature of $750^{\circ}C$ for 30min. Increasing the annealing temperature, the peak intensity of (117) and c-axis orientation were increased. The calculated lattice constants of BYT thin films were a=0.539nm, b=0.536nm, c=3.288nm. The thickness of the BYT thin films were 350nm. The dielectric constant and dielectric loss at a frequency of 100KHz were 73.3 and 0.021, respectively. The BYT thin films can be used as capacitors in the Ferroelectric Random Access Memory device.

• Korean Journal of Materials Research
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• v.13 no.2
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• pp.69-73
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• 2003

In this work, $IrO_2$thin films as bottom electrode of ferroelectric capacitors were deposited and characterized. The $IrO_2$films deposited in the conditions of 25, 40 and 50% oxygen ambient by sputtering method were annealed at 600, 700 and $800^{\circ}C$, respectively. It was found that the crystallinity and the surface morphology of $IrO_2$films affected the surface properties and electrical properties of SBT thin films prepared by the MOD method. With increasing temperature, the crystallinity and the roughness of $IrO_2$films were also increasing. This increasing of roughness degraded the surface properties and electrical properties of SBT films. We found an optimum condition of $IrO_2$films as bottom electrode for ferroelectric capacitor at 50% oxygen ambient and $600^{\circ}C$ annealing temperature. Electrical characterizations were performed by using$ IrO_2$bottom electrodes grown at an optimum conditions. The remanent polarization ($P_{r}$) of the Pt/SBT/$IrO_2$/$SiO_2$/Si structure was 2.75 $\mu$C/$\textrm{cm}^2$ at an applied voltage of 3 V. The leakage current density was $1.06${\times}$10^{-3}$ A/$\textrm{cm}^2$ at an applied voltage of 3 V.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.80-80
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• 2009

Recently, multiferroics have attracted much attention due to their numorous potentials. In this work, we attemped to utilize the multiferroics as an alternative material for ferroelectrics. Ferroelectric materials have been stadied to ferroelectric random access memories, however, some inevitable problems prevent it from inplementation. multiferroics shows a ferroelectricity and has low process temperature $BiFeO_3$(BFO) films have good ferroelectric properties but poor leakage characterization. Thus we tried, in this work, to adopt $HfO_2$ insulating layer for metal-ferroelectric-insulator-semiconductor(MFMIS) structure to surpress to leakage current. $BiFeO_3$(BFO) thin films were fabricared by using a sol-gel method on $HfO_2/Si$ structure. Ferroelectric BFO films on a p-type Si(100)wafer with a $HfO_2$ buffer layer have been fabricated to form a metal-ferroelectric-insulator-semiconductor (MFIS) structure. The $HfO_2$ insulator were deposited by using a sol-gel method. Then, they were carried out a rapid thermal annealing(RTA) furnace at $750\;^{\circ}C$ for 10 min in $N_2$. BFO films on the $HfO_2/Si$ structures were deposited by sol-gel method and they were crystallized rapid thermal annealing in $N_2$ atomsphere at $550\;^{\circ}C$ for 5 min. They were characterized by atomic force microscopy(AFM) and Capacitance-voltage(C-V) curve.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.135-136
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• 2006

Bismuth titanate ($Bi_4Ti_3O_{12}$, BIT) thin film has been studied intensively in the past decade due to its large remanent polarization, low crystallization temperature, and high Curie temperature. Substitution of various trivalent rare-earth cations (such as $La^{3+}$, $Nd^{3+}$, $Sm^{3+}$ and $Pr^{3+}$) in the BIT structure is known to improve its ferroelectric properties, such as remanent polarization and fatigue characteristics. Among them, neodymuim-substituted bismuth titanate, ((Bi, Nd)$_4Ti_3O_{12}$, BNT) has been receiving much attention due to its larger ferroelectricity. In this study, Ferroelectric $Bi_{3.3}Nd_{0.7}Ti_3O_{12}$ thin films were successfully fabricated by liquid delivery MOCVD process onto Pt(111)/Ti/$SiO_2$/Si(l00) substrates. Fabricated polycrystailine BNT thin films were found to be random orientations, which were confirmed by X-ray diffraction and scanning electron microscope analyses. The remanent polarization of these films increased with increase in annealing temperature. And the film also demonstrated fatigue-free behavior up to $10^{11}$ read/write switching cycles. These results indicate that the randomly oriented BNT thin film is a promising candidate among ferroelectric materials useful for lead-free nonvolatile ferroelectric random access memory applications.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.455-458
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• 2001

The thin films of high pemitivity in ferroelectric materials using a capacitor are applied to DRAMs and FRAMs. (Ba, Sr)$TiO_3$ thin films as ferroelectric materials were prepared by the sol-gel method and made by spin-coating on the Pt/Ti/$SiO_2/Si$ substrate at 4,000 [rpm] for 10 seconds. The devices of BST thin films to composite $(Ba_{0.7},Sr_{0.3})TiO_3$ were fabricated by changing of the depositing layer number on $Pt/Ti/SiO_2/Si$ substrate. The thin film capacitor to be ferroelectric devices was investigated by structural and electrical properties. The thickness of BST thin films at each coating numbers 3, 4 and 5 times was $2500[\AA]$, $3500[\AA]$, $3800[\AA]$. The dielectric factor of thin film when the coating numbers were 3, 4 and 5 times was 190, 400 and 460 on frequency l[MHz]. The dielectric loss of BST thin film was linearly increased by increasing of the specimen area.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.235-238
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• 1998

Ferroelectric $LiNbO_3$ thin films were grown directly on Si(100) substrates by 13.55MHz RF magnetron sputtering system using a ceramic target ($Nb_2O_5/Li_2C0_3$ = 51.4/48.6). Because high temperature process have to avoided to prevent degradation of the interface (insulator/Si), $LiNbO_3$ thin films were deposited below $300^{\circ}C$. After as-deposited films were performed RTA treatments in an oxygen ambient at $600^{\circ}C$ for 60s, electrical measurements performed films before and after anneal treatment. In high field region, the leakage current density of the films after annealing was deceased about 4order and the resistivity of these was increased to about 5\times 10^{11} \Omega \cdot cm$ at 500kV/cm. In accumulation region of C-V curve, we calculated dielectric constant of thin film $LiNbO_3$ as 27.9 which is close to that of bulk value.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.455-458
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• 2001

The thin films of high permitivity in ferroelectric materials using a capacitor are applied to DRAMs and FRAMs. (Ba, Sr)TiO$_3$ thin films as ferroelectric materials were prepared by the sol-gel method and made by spin-coating on the Pt/Ti/SiO$_2$/Si substrate at 4,700 [rpm] for 10 seconds. The devices of BST thin films to composite (Ba$\_$0.7/Sr$\_$0.3/)TiO$_3$ were fabricated by changing of the depositing layer number on Pt/Ti/SiO$_2$/Si substrate. The thin film capacitor to be ferroelectric devices was investigated by structural and electrical properties. The thickness of BST thin films at each coating numbers 3, 4 and 5 times was 2500[${\AA}$], 3500[${\AA}$], 3800[${\AA}$]. The dielectric factor of thin film when the coating numbers were 3, 4 and 5 times was 190, 400 and 460 on frequency 1[MHz]. The dielectric loss of BST thin film was linearly increased by increasing of the specimen area.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05c
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• pp.200-203
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• 2003

Ferroelectric europium-substitution $Bi_4Ti_3O_{12}$ thin films were fabricated by spin-coating onto a Pt/Ti/$SiO_2$/Si substrate. The $Bi_{3.25}Eu_{0.75}Ti_3O_{12}$ (BET) films have polycrystalline structure annealed at 700 C. We investigated that the influence of $Bi_4Ti_3O_{12}$ thin films by substituting for Bi ions with Bi ions using X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). From the XPS measurement, it was suggested that the stability of the metal-oxygen octahedral should be related to substitute for Bi ions with Eu ions at annealed $800^{\circ}C$. The BET thin films showed a large remanent polarization (2Pr) of $60.99C/cm^2$ at an applied voltage of 10 V. The BET thin films exhibited no significant degradation of switching charge at least up to $5{\times}10^9$ switching cycles at a frequency of 50 kHz.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.3
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• pp.190-194
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• 2003

Dielectric thin films of (P $b_{0.72}$,L $a_{0.28}$) $Ti_{0.93}$ $O_3$ (PLT(28)) have been deposited on Pt(111)/Ti/ $SiO_2$/Si(100) substrates in-situ by pulsed laser deposition using different annealing and deposition Processes. We have investigated the effect of hydrogen annealing on the ferroelectric properties of PLT thin films and found that the annealing process causes the diffusion of hydrogen into the ferroelectric film resulting in the destruction of polarization. We have tried to form the film by a two-step deposition process In order to improve electrical property. Two-step process to grow PLT films was adopted and verified to be useful to enlarge the grain size of the film and to reduce the leakage current characteristics. Structural properties and electrical properties including dielectric constant, ferroelectric characteristics, and leakage current of PLT thin films were shown to be strongly influenced by grain size. The film deposited by using two-step Process including pre-annealing treatment has a strongly(111) orientation. However, the films deposited by using single -step process with hydrogen annealing process show the smallest grain size. The film deposited by using two-step process including pre-annealing treatment shows the leakage current density of below 10$^{-7}$ A/c $m^2$ for the field of smaller than 100 kV/cm. However, the films deposited by using single-step process with hydrogen annealing process and pre-annealing process show worse leakage current density than the film deposited by using two-step process including pre-annealing treatment.tment.

• Journal of the Korean Ceramic Society
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• v.35 no.10
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• pp.1040-1048
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• 1998

Ferroelectric properties of{{{{ { { { {SrBi }_{2 }Ta }_{2-x }Nb }_{x }O }_{9 } }} (SBIN) thin films were affected by the amount of Bi content in SBTN. The addition of Bi into the SBTN films could be accomplished by heat treating SBTN/Bi2O3/SBTN het-erostructures fabricated by r.f. magnetron sputtering method. The variation of Bi content was controlled by changing the thickness of the sandwiched Bi2O3 in SBTN/Bi2O3/SBTN heterostructure from 50 to 400$\AA$. As changing the thickness of the sandwiched Bi2O3 in Bi2O3 films was increased from 0 to 100$\AA$ the grain grew faster and the ferroelectric pro-perties were improved. On the other hand when the thickness of Bi2O3 films was thicker than 150$\AA$ the fer-roelectric properties were deteriorated Especially for SBTN thin films inserted by 400$\AA$ Bi2O3 layer a Bi2Phase appeared as a second phase resulting in poor ferroelectric properties. The maximum remanent po-larization (2Pr) and coercive field(Ec) were obtained for the SBTN/Bi2O3/(100$\AA$)/SBTN thin films. In this case 2Pr and Ec were 14.75 $\mu$C/cm2 and 53.4kV/cm at an applied voltage of 3V respectively.