• Journal of the Korean Ceramic Society
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• v.39 no.8
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• pp.750-757
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• 2002

Self-patterning of thin films using photosensitive sol solution has advantages such as simple manufacturing process compared to photoresist/dry etching process. In this study, ferroelectric $Sr_{0.9}Bi_{2.1}Ta_2O_9$ thin films have been prepared by spin coating method using photosensitive sol solution. Strontium ethoxide, tertramethylheptanedionato bismuth and tantalum ethoxide were used as starting materials. As UV exposure time to the SBT thin film increased, the UV absorption peak intensity of metal ${\beta}$-diketonate decreased due to reduced solubility by M-O-M bond formation. Solubility difference by UV irradiation on SBT thin film allows to obtain a fine patterning of thin film. Also, The ferroelectric properties of the UV irradiated SBT thin films were superior to those of the no-UV irradiated films.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.12
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• pp.1054-1059
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• 2002

A great deal of research has been done in the field of characterization for piezoelectric thin films after the first report on the measurement for the piezoelectric coefficient of thin films in 1990. The main idea of this research is to provide a distinctive solution for the measurement and standardization of both the longitudinal and the transverse piezoelectric d-coefficients, d33 and d31, of ferroelectric thin films. In general, to get these two coefficients of thin films, two different measuring systems are required. Here, we propose the improved method for the evaluation of these two coefficients with single equipment and with the relatively convenient procedure. The two-step loading process of applying the both positive and the negative pressure has been introduced to acquire the piezoelectric coefficients. These results have been calibrated for both the longitudinal and 4he transverse piezoelectric d-coefficients, d33 and 431, of thin films by comparison with the virtual standard created from FEM. In this experiments, we have obtained d33 of 331pC/N and 031 of -92.2pC/N for the PZT thin films.

• Korean Journal of Materials Research
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• v.30 no.2
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• pp.99-104
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• 2020

Recent discoveries of ferroelectric properties in ultrathin doped hafnium oxide (HfO₂) have led to the expectation that HfO₂ could overcome the shortcomings of perovskite materials and be applied to electron devices such as Fe-Random access memory (RAM), ferroelectric tunnel junction (FTJ) and negative capacitance field effect transistor (NC-FET) device. As research on hafnium oxide ferroelectrics accelerates, several models to analyze the polarization switching characteristics of hafnium oxide ferroelectrics have been proposed from the domain or energy point of view. However, there is still a lack of in-depth consideration of models that can fully express the polarization switching properties of ferroelectrics. In this paper, a Zr-doped HfO₂ thin film based metal-ferroelectric-metal (MFM) capacitor was implemented and the polarization switching dynamics, along with the ferroelectric characteristics, of the device were analyzed. In addition, a study was conducted to propose an applicable model of HfO₂-based MFM capacitors by applying various ferroelectric switching characteristics models.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.109-112
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• 1999

The PZT(10/90)/(90/17) heterolayered thin films were fabricated by the spin-coaling on the Pt/Ti/SiO$_2$/Si substrate using the PZT(10/90) and PZT(70/10) metal alkoxide solutions. The effect of heterolayered thin films on the ferroelectrics and electrical properties have been investigated. The lower PZT layers provided the nucleation site for the formation of a perovskite phase of the upper PZT films. Dielectric constant increased with increasing the number of coatings, and it was about 569.9 at PZT-6 heterolayered films.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.9
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• pp.783-787
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• 2002

In recent year, B $i_{4-}$x L $a_{x}$ $Ti_3$ $O_{12(BLT)}$ is one of promising substitute materials for the ferroelectric random access memory(FRAM) applications. But the systematic composition is still insufficient, so this experiment was carried out in ceramic ambient sintering process which has the very excellent ferroelectric property. Samples were prepared by a bulk and the purpose which was estimated with a suitability of thin films applications. The density of B $i_{3.75}$ L $a_{0.25}$ $Ti_3$ $O_{12}$ was high and the XRD pattern showed that the intensity of main peak (117) was increased at the argon ambient sintering. Controlling the quantity of oxygen, crystallization showed a thin, long plate like type, and we obtained the excellent dielectric and polarization properties at the argon atmosphere sintering. Also this sintering process was effective at the bulk sample. Argon ambient sintered sample produced higher permittivity of 154, the remanent polarization(2Pr) of 6.8 uC/$\textrm{cm}^2$ compared with that sintered in air and oxygen ambient. And this sintering process showed a possibility which could be applied to thin films process..

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.6
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• pp.1175-1177
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• 2011

The SBN thin films were deposited on Pt/Ti/$SiO_2$/Si and p-type Si(100) substrate by rf magnetron sputtering method using $Sr_{0.7}Bi_{2.3}Nb_2O_9$ ceramic target. SBN thin films deposited were annealed at 600~800[$^{\circ}C$] by furnace in oxygen atmosphere during 40min. The polarization characteristics have been investigated to confirm the possibility of the SBN thin films for the application to destructive read out ferroelectric random access memory. The maximum remanent polarization and the coercive voltage are 0.6[${\mu}C/cm^2$], 1.2[V] respectively at annealing temperature of 800[$^{\circ}C$]. The leakage current density was the $2.57{\times}10^{-6}[A/cm^2]$ at an applied voltage of 5[V] at annealing temperature of 650[$^{\circ}C$]. Also, the fatigue characteristics of SBN thin films did not change up to $10^8$ switching cycles.

• Journal of the Korean institute of surface engineering
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• v.29 no.6
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• pp.621-627
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• 1996

$SrBi_{2x}TaO_9$ ferroelectric thin films were prepared on platinized silicon substrates using MOD proces, and crystallization behavior of the films was investigated with variation of the annealing temperature and Bi content x. Crystalline phase of bismuth layered perovskite structure was formed even by baking the films at $800^{\circ}C$ for 5 minutes in air, and was not changed by annealing at temperatures raning from $700^{\circ}C$ to $900^{\circ}C$ for 1 hour in oxygen ambient. When $SrBi_{2x}TaO_9$ thin films ($0.8\lex\ie1.6$) were annealed at $800^{\circ}C$, Preferred orientation of the films along c-axis was observed with $x\ge1.2$. With increasing Bi content x, surface morphology of the films was changed from equiaxed grains to elongated grains.

• Journal of the Microelectronics and Packaging Society
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• v.11 no.4 s.33
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• pp.87-91
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• 2004

We have investigated the effects of W-N/Pt bottom electrode on the ferroelectric degradation of $Sr_{0.8}Bi_{2.4}Ta_2O_9(SBT)/Pt$ due to hydrogen annealing at $350^{\circ}C$ in $N_2$ gas atmosphere containing $5{\%}\;H_2$ gas for 1hr. As a result, inserting the W-N thin films between SBT and Pt, this W-N thin film prevents hydrogen molecules to be chemisorbed at the Pt electrode surface of at the electrode/ferroelectric interface during hydrogen annealing. These hydrogen atoms can diffuse into the SBT and react with the oxide causing the oxygen deficiency in the SBT film, which will result in the ferroelectric degradation. Experimental results show that W-N thin film is a good diffusion barrier during the hydrogen annealing.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.273-278
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• 2000

In order to study effects of interface layers between PZT films and electrodes for MFM(Metal-Ferroelectric-Metal) structure capacitors, we have fabricated the capacitors with the Pt/PZT/interface-layer/Pt/$TiO_2/SiO_2/Si$ structure. $PT(PbTiO_3)$ interface layers were formed by sol-gel deposition and PbO, $ZrO_2$ and $TiO_2$ thin layers were deposited by reactive sputtering. $TiO_2$ interface layers result in the finest grains of PZT films compared to $PbO_2$ and $ZrO_2$ layers. On the other hand, PT interface layers result in improved morphology of PZT films and do not significantly change ferroelectric properties. It is also observed that seed layers at the middle and top of PZT films do not give significant effects on grain size but the PT seed layer at the interface between the bottom electrode and the PZT films results in the small grain size.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.278-281
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• 1999

PLZT thin films on Pt/Ti/SiO$_2$/Si substrate were fabricated with different Thickness by pulsed laser deposition. 14/50/50 PLZT thin film showed a maximum dielectric constant value of $\varepsilon$$_{t}$=985 at 5000$\AA$, and $\varepsilon$$_{t}$=668 at 2000A. P-EI hysteresis loop of 14/50/50 PLZT thin film was slim ferroelectric. Leakage current density of 14/50/70 PLZT thin film was 10$^{-8}$ A/$\textrm{cm}^2$ at 2000$\AA$.EX>.