• Journal of the Korean Ceramic Society
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• v.35 no.3
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• pp.294-302
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• 1998

$Pb_{1+x}$($Fe_{0.5}$$Nb_{0.5}$)$O_3$ films have been synthesized on Pt/Ti/$SiO_2$/Si substrates using rfmagnetron sputtering Concentration of Fe and Nb in the deposited films was adjusted to near stoichiometry through the control of target composition, Films deposited with adjusted to near stoichiometry showed better electrical properties such as dielectic and leakage characteristics. Crystallinity and dielectric constant increased with increasing excess PbO upto 9 mol% This study also showed that dielectric constant and leakage current characteristics improved by optimum content of $O_2$ flow during deposition.

• Korean Journal of Materials Research
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• v.7 no.5
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• pp.381-385
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• 1997

PEMOCVD에 의해서 SrBi$_{2}$Ta$_{2}$O$_{9}$밥막이 낮은 온도에서 성공적으로 Pt/Ti/SiO$_{2}$Si위에 증착되었다. 5$50^{\circ}C$에서 증착된 200nm박막은 치밀하고 작은 결정립을 보였으며 3V의 인가전압하에서 이력곡선은 포화되기 시작하였다. 3V에서 박막은 잔류분극 (P$_{r}$)과 항전계(E$_{c}$)는 각각 15$\mu$/$\textrm{cm}^2$과 50kV/cm이었다. 6V bipolar square pulse의 피로측정에서 박막은 1.0x$10^{11}$cycles까지 피로 현상을 보이지 않았다. PEMOCVD에 의해서 5$50^{\circ}C$에서 증착된 SBT박막은 비휘발성 기억소자에 충분히 활용할 수 있다.다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.4
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• pp.362-368
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• 2023

Multilayered actuators using Pb(Mg_1/3Nb_2/3)O₃-Pb(In_1/2Nb_1/2)O₃-PbTiO₃ (PMN-PIN-PT) crystals have demonstrated excellent properties, but are costly and lack mechanical strength. Textured PMN-PIN-PT ceramics exhibit robust mechanical strength and comparable properties to their single crystals form. However, the development of multilayered actuators using textured PMN-PIN-PT ceramics has not been achieved until now. This study presents the development of a multilayered actuator using textured 0.37PMN-0.29PIN-0.34PT ceramics with an Ag_0.9/Pd_0.1 inner electrode, co-fired at 950℃. A random 0.37PMN-0.29PIN-0.34PT ceramics multilayered actuator was also developed for comparison. The multilayered actuator consisted of 9 ceramic layers (36 ㎛ thickness) with an overall actuator thickness of 0.401 mm. The textured and random 0.37PMN-0.29PIN-0.34PT ceramics-based multilayered actuators achieved displacements of 0.61 ㎛ (0.15% strain) and 0.23 ㎛ (0.057% strain) at a low applied peak voltage of 100 V. These results suggest that the developed multilayered actuator using high-performance textured 0.37PMN-0.29PIN-0.34PT ceramics has the potential to replace expensive single crystal-based actuators cost-effectively.

• Journal of the Korean Ceramic Society
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• v.34 no.2
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• pp.202-208
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• 1997

Bi-layered SrBi2Ta2O9(SBT) films were deposited on Pt/Ti/SiO2/Si sibstrates by rf magnetron sputt-ering at room temperature and then were annealed at 75$0^{\circ}C$, 80$0^{\circ}C$ and 85$0^{\circ}C$ for 1 hour in oxygen at-mosphere. The film composition of SrBi2Ta2O9 was obtained after depositing at room temperature and annealing at 80$0^{\circ}C$. Excess 20mole% Bi2O3 and 30 mole% SrCO3 were added to the target to compensate for the lack of Bi and Sr in SBT film. 200 nm thick SBT film exhibited and dense microstructure, adielectric constant of 210, and a dissipation factor of 0.05 at 1 MHz frequency. The films exhibited Curie temperature of 32$0^{\circ}C$ and a dielectric constant of 314 at that temperature under 100 kHz frequency. The remanent polarization(2Pr) and the coercive field(2Ec) of the SBT films were 9.1 $\mu$C/$\textrm{cm}^2$ and 85 kV/cm at an applied voltage of 3V, resspectively and the SBT film showed a fatigue-free characteristics up to 1010 cy-cles under 5V bipolar pulse. The leakage current density of the SBT film was about 7$\times$10-7A/$\textrm{cm}^2$ at 150 kV/cm. Fatigue-free SBT films prepared by rf magnetron sputtering can be suitable for application to non-volatile memory device.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.170-173
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• 2001

Thin films of phase-pure perovskite (P $b_{0.72}$L $a_{0.28}$) $Ti_{0.93}$ $O_3$(PLT) were deposited in-situ onto Pt/Ti/ $SiO_2$/Si substrates by pulsed laser deposition. We have systematically investigated the variation of grain sizes depending on the process condition. Both in-situ annealing and ex-situ annealing treatments have been compared depending on the annealing time. Two-step process to grow (P $b_{0.72}$L $a_{0.28}$) $Ti_{0.93}$ $O_3$(PLT) films was adopted and verified to be useful to enlarge the grain size of the film and to enhance the leakage current characteristics. The grain sizes of PLT thin films were successfully controlled 260 to 350 nm by changing process parameters. Electrical properties including dielectric constant, ferroelectric characteristics, crystallization and leakage current of PLT thin films were shown to be strongly inf1uenced by grain size. Also PLT thin films on p-type(100) Si substrate will be fabricated by pulsed laser deposition technique using a Nd:YAG laser with different wavelengths of 355, 532 and 1064 nm. Effect of the variation of laser wavelength on dielectric properties will be discussed. Microstructural and electrical properties of the film were investigated by C-V measurement leakage current measurement and SEM.ent and SEM.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.359-360
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• 2013

The effect of electrode and deposition methods on non-linear interfacial resistive switching in HfO2 based $250{\times}250$ nm2 cross-point device was studied. HfO2 based device has the interfacial resistive switching properties of non-linearity and self-compliance current switching. The operating current in HfO2 based device was increased with negatively increasing the heat of formation energy in top electrode. Also, it was investigated that the operating current in HfO2 based device was changed with deposition methods of O3 reactant ALD, H2O reactant ALD and dc reactive sputtering, resulting the magnitude of the operating current and on/off ratio in order of HfO2 films deposited by dc reactive sputtering, H2O reactant ALD, and O3 reactant ALD. To investigate the effect of electrode and deposition methods on operating current of non-linear interfacial resistive switching in the cross-point device, X-ray photoelectron spectroscopy was measured. Through the analysis of O 1s spectra, non-lattice oxygen concentration, which is closely related to oxygen vacancies, was increased in order of Pt, TiN, and Ti top electrodes and in order of O3 reactant ALD, H2O reactant ALD, and O3 reactant ALD, and dc reactive sputtering deposition method. From all results, non-lattice oxygen concentration in ultra-thin HfO2 films play a crucial role in the operating current and memory states (LRS & HRS) in the non-linear interfacial resistive switching.

• Korean Journal of Materials Research
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• v.17 no.11
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• pp.574-579
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• 2007

Amorphous $BaTi_4O_9$ ($BT_4$) film was deposited on Pt/Si substrate by RF magnetron sputter and their dielectric properties and electrical properties are investigated. A cross sectional SEM image and AFM image of the surface of the amorphous $BT_4$ film deposited at room temperature showed the film was grown well on the substrate. The amorphous $BT_4$ film had a large dielectric constant of 32, which is similar to that of the crystalline $BT_4$ film. The leakage current density of the $BT_4$ film was low and a Poole-Frenkel emission was suggested as the leakage current mechanism. A positive quadratic voltage coefficient of capacitance (VCC) was obtained for the $BT_4$ film with a thickness of <70 nm and it could be due to the free carrier relaxation. However, a negative quadratic VCC was obtained for the films with a thickness ${\geq}96nm$, possibly due to the dipolar relaxation. The 55 nm-thick $BT_4$ film had a high capacitance density of $5.1fF/{\mu}m^2$ with a low leakage current density of $11.6nA/cm^2$ at 2 V. Its quadratic and linear VCCs were $244ppm/V^2$ and -52 ppm/V, respectively, with a low temperature coefficient of capacitance of $961ppm/^{\circ}C$ at 100 kHz. These results confirmed the potential suitability of the amorphous $BT_4$ film for use as a high performance metal-insulator-metal (MIM) capacitor.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.171-171
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• 2010

In this work, we investigated the effect of the oxidation temperature on the unipolar and bipolar resistance switching behaviors of the oxidized TiO-x films. TiOx films on Pt electrodes were fabricated by the oxidation of Ti films at $550^{\circ}C$ for 1 to 3 hours. The unipolar and bipolar resistance switching properties were investigated with the oxidation temperature and time. Also, the crystal structure and the physical properties such as chemical bonding states of TiOx layers were characterized in addition to the resistance switching characteristics. The resistance switching behaviors of TiOx films oxidized at above $450^{\circ}C$ and below $650^{\circ}C$ was shown. So, we investigated that the resistance switching behaviors of TiOx films oxidized at $550^{\circ}C$ with the oxidation time from 1 to 3 hour. The memory windows of unipolar switching in the oxidized TiOx films were reduced with increasing the oxidation time, but those of the bipolar switching were slightly enlarged. The enlargement of rutile TiO2 peak with increasing the oxidation time and temperature was studied by X-ray diffraction. An increase of non-lattice oxygen and Ti3+ in the TiOx films with the oxidation times was investigated by X-ray photoemission spectroscopy. It was expected that the uipolar and bipolar resistive switching of the oxidized TiOx film was strongly related with the migration of non-lattice oxygen anions and schottky barrier height, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.9
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• pp.764-769
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• 2002

The effect of excess Bi contents on the ferroelectric properties of B $i_{3.25}$ L $a_{0.75}$ $Ti_3$ $O_{12}$ (BLT) thin films has been investigated. Bismuth lanthanum titanate thin films with excess Bi contents were prepared onto Pt/Ti/ $SiO_2$/Si substrate by metalorganic decomposition (MOD) technique. The structure and morphology of the films were analyzed using X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. From the XRD analysis, BLT thin films show polycrystalline structure and the layered-perovskite phase was obtained over 10% excess of Bi contents. As a result of ferroelectric characteristics related to the Bi content of the BLT thin film, the remanent polarization and dielectric constant decreased with increasing over Bi content of 10% excess. The BLT film with Bi content of 10% excess was measured to have a dielectric constant of 326 and dielectric loss of 0.024. The BLT thin films showed little polarization fatigue test up to 3.5$\times$10$^{9}$ bipolar switching cycling.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.51-54
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• 2003

Tb-doped lead zirconate titanate($Pb_{1.1}(Zr_{0.6}Ti_{0.4})O_3$; PZT) thin films on $Pt(111)/Ti/SiO_2/Si(100)$ substrates prepared by a sol-gel method. Films have a Zr/Ti ratio of 60:40 and perovskite phase structure. The effect on the structural and electrical properties of films measured according to Tb content. Dielectric and ferroelectric properties of PZT thin films were altered significantly by Tb-doping. The PZT thin film with higher dielectric constant and improved leakage current characteristic was obtained by adding 0.3 mol% Tb. At 100 kHz, the dielectric constant and the dielectric loss of the 0.3 mol% Tb-doped PZT thin film were 1611 and 0.24, respectively The remanent polarization(2Pr) of the 0.3 mol% Tb-doped PZT thin film was $61.4\;{\mu}C/cm^2$ and the coercive field was 61.9 kV/cm. Tb-doped PZT thin films showed improved fatigue characteristics comparing to the undoped PZT thin film.