• Korean Journal of Materials Research
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• v.11 no.4
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• pp.290-293
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• 2001

The SrBi$_2$Nb$_2$O$_{9}$ (SBN) thin films were deposited on p-type(100) Si substrates by rf magnetron sputtering to confirm the Possibility of Pt/SBN/Si structure for the application of nondestructive read out ferroelectric random access memory (NDRO- FRAM). The SBN thin films were deposited by co-sputtering method with Sr$_2$Nb$_2$O$_{7}$ (SNO) and Bi$_2$O$_3$ ceramic targets. The SBN thin films deposited at room temperature were annealed at $700^{\circ}C$ for 1hr in $O_2$ ambient. The structural and electrical properties of SBN with different power ratios of targets were measured by x-ray diffraction(XRD), scanning electron microscopy(SEM), capacitance-voltage(C-V), and current-voltage(I-V). The C-V curves of the SBN films showed hysteresis curves of a clockwise rotation showing ferroelectricity. When the Power ratio of the SNO/Bi$_2$O$_3$ targets was 120 W/100 W, the SBN thin films had excellent electrical properties. The memory window of SBN thin film was 1.8 V-6.3 V at applied voltage of 3 V-9 V and the leakage current density was 1.5 $\times$ 10$^{-7}$ A/$\textrm{cm}^2$ at applied voltage of 5 V The composition of SBN thin films was analysed by electron probe X-ray micro analyzer(EPMA) and the atomic ratio of Sr:Bi:Nb with pawer ratio of 120 W/100 W was 1:3:2.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.248-249
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• 2007

The $V_{1.9}W_{0.1}O_5$ thin films deposited on Pt/Ti/$SiO_2$/Si substrates by RF sputtering method exhibited fairly good TCR and dielectric properties. It was found that film crystallinity, dielectric properties, and TCR properties were strongly dependent upon the annealing temperature. The dielectric constants of the $V_{1.9}W_{0.1}O_5$ thin films annealed at $300^{\circ}C$ were 37.7, with a dielectric loss of 2.535, respectively. Also, the TCR values of the $V_{1.9}W_{0.1}O_5$ thin films annealed at $300^{\circ}C$ were about -3.7%/K.

• Korean Journal of Materials Research
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• v.5 no.7
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• pp.850-857
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• 1995

VO$_{x}$ and V$_{1-x}$ Sn$_{x}$O$_2$thin films were fabricated on a glass under various $O_2$pressure by reactive e-beam evaporation method. Thermochromism and transition temperatures of these thin films were examined by measuring spectral solar transmittances with spectrophotometer at various temperatures, and their stoichiometries were analyzed by RBS. Oxygen pressure of 5$\times$10$^{-5}$ . Torr was found to be optimum to fabricate near stoichiometric VO$_2$thin film by reactive e-beam evaporation. Rapid thermal annealing(RTA) was adopted to crystallize the thin films and annealing at 40$0^{\circ}C$ ~45$0^{\circ}C$ for 20 ~ 30 seconds was found to be the optimum annealing condition for the crystallization of VO$_2$thin film of 100nm-300nm thickness. 1~6 atomic percent of Sn was doped into VO$_2$thin films to fabricate V$_{1-x}$ Sn$_{x}$O$_2$thin films. These V$_{1-x}$ Sn$_{x}$O$_2$thin films showed distinct thermochromism and significantly higher transition temperatures than VO$_2$thin film.

• Proceedings of the KIEE Conference
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• 2007.11c
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• pp.138-140
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• 2007

$TiO_2-V_2O_5$ sol was fabricated using sol-gel method and $TiO_2-V_2O_5$ thin films were fabricated using dip-coating method. $V_2O_5$ sol was added 0.01mo1e, 0.03mo1e, 0.05mo1e into $TiO_2$ sol. Viscosity of sol increased fast from about 1,000 minutes and sol began gelation from about 10,000 minutes. As a results of crystalline properties, $V_2O_5$ peaks were not found despite of $V_2O_5$ addition. Endothermic reaction occurred due to evaporation of solvent and dissociation of OH at $80^{\circ}C$. Exothermic reaction occurred due to combustion and oxidation of solvent at $230^{\circ}C$, occurred to combustion and oxidation of alkyl group at $350^{\circ}C$. Thickness of thin films increased $0.1{\sim}0.25{\mu}m$ every a dipping.

• Journal of the Korean Vacuum Society
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• v.9 no.2
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• pp.136-143
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• 2000

$SrBi_2Ta_2O_9;(SBT)$ films were deposited on p-type Si(100) at room temperature by rf magnetron sputtering method to confirm the possibility of application of $Pt/SBT/Pt/Ti/SiO_2/Si$ structure (MFM) for destructive read out ferroelectric RAM (random access memory). Their structural characteristics with the various annealing times and Ar/$O_2$ gas flow ratios in sputtering were observed by XRD (X-ray diffractometer) and the surface morphologies were observed by FE-SEM (field emission scanning electron microscopy), and their electrical properties were observed by P-V (polarization-voltage measurement) and I-V (current-voltage measurement). The Ar/$O_2$ gas flow ratios of sputtering gas were changed from 1 : 4 to 4 : 1 and SBT thin films were deposited at room temperature. The films show (105), (110) peaks of SBT by XRD measurement. SBT thin films deposited at room temperature were crystallized by furnace annealing at 80$0^{\circ}C$ in oxygen atmosphere during either one hour or two hours. Among their electrical properties, P-V curves showed shaped hysteresis curves, but the SBT thin films showed the asymmetric ferroelectric properties in P-V curves. When Ar/$O_2$ gas flow ratios are 1 : 1, 2: 1, the leakage current density values of SBT thin films are good, those values of 3 V, 5 V, and 7 V are respectively $3.11\times10^{-8} \textrm{A/cm}^2$, $5\times10^{-8}\textrm{A/cm}^2$, $7\times10^{-8}\textrm{A/cm}^2$.After two hours of annealing time, their electrical properties and crystallization are improved.

• Journal of Korean Vacuum Science & Technology
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• v.2 no.2
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• pp.92-96
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• 1998

Ferroelectric Bi-layered oxides SrBi2Ta2O9 (SBT) thin films have been deposited on Pt/Ti/SiO2/Si substrates using multi-target sputtering. Structure, composition, and electrical properties have been investigated on films. The SBT films were deposited with the various bismuth sputtering powers. The SBT films deposited with the bismuth sputtering power of 20 W have the most dense microstructure and the remanent polarization (Pr) of 9.2 ${\mu}$C/cm and the coercive field (Ec) of 43.8 kV/cm at an applied voltage of 5V. The SBT films deposited with the bismuth sputtering power of 20W showed a fatigue-free characteristics up to 1.0${\times}$1010 cycles under 5V bipolar pulse and a leakage current density of 2.0${\times}$10-8 A/$\textrm{cm}^2$ at 200 kV/cm.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.13 no.6
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• pp.272-278
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• 2003

$Bi_4Ti_3O_{12}$ (BIT) and $(Bi_{3.25}La_{0.75})(Ti_{2.97}V_{0.03})O_{12}$ (BLTV) thin films were deposited on ITO/glass substrates by metal organic chemical vapor deposition (MOCVD) using ultrasonic spraying. After deposition of the films in oxygen atmosphere for 30 min, the films were heated by rapid thermal annealing (RTA) method, especially direct insertion, at various temperatures. The films were investigated on phase formation temperature, microstructure and electrical properties. From x-ray diffraction (XRD) patterns, the perovskite phase formation temperature of BLTV thin film was about $600^{\circ}C$ which was lower than that of BIT, $650^{\circ}C$. The leakage current of the BLTV thin film was measured to be $1.52\times 10^{-9}$A/$cm^2$ at an applied voltage of 1 V. The remanent polarization (Pr) and coercive field (Ec) values of the BLTV film deposited at $650^{\circ}C$ were $5.6\muC/cm^2$ and 96.5 kV/cm, respectively.

• Korean Journal of Materials Research
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• v.10 no.12
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• pp.807-811
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• 2000

CeO$_2$ and SrBi$_2$Ta$_2$O$_{9}$ (SBT) thin films for MFISFET (Metal-ferroelectric-insulator-semiconductor-field effect transistor) were deposited by r.f. sputtering and pulsed laser ablation method, respectively. The effects of sputtering gas ratio(Ar:O$_2$) during deposition for CeO$_2$ films were investigated. The CeO$_2$ thin films deposited on Si(100) substrate at $600^{\circ}C$ exhibited (200) preferred orientation. The preferred orientation, Brain size and surface roughness of films decreased with increasing oxygen to argon gas ratio. The films deposited under the condition of Ar:O$_2$= 1 : 1 showed the best C- V characteristics. The leakage current of films showed the order of 10$^{-7}$ ~10$^{-8}$ A at 100kV/cm. The SBT thin films on CeO$_2$/Si substrate showed dense microstructure of polycrystalline phase. From the C-V characteristics of MFIS structure with SBT film annealed at 80$0^{\circ}C$, the memory window width was 0.9V at 5V The leakage current density of Pt/SBT/CeO$_2$/Si structure annealed at 80$0^{\circ}C$ was 4$\times$10$^{-7}$ /$\textrm{cm}^2$ at 5V.

• Journal of the Korean institute of surface engineering
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• v.25 no.6
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• pp.293-298
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• 1992

Various vanadium-oxide thin films were deposited by e-beam and thermal evaporation of V2O5, V2O3, and VO2 powders. Films with thickness of $2000\AA$ were subjected to annealing at $300^{\circ}C$~$450^{\circ}C$ in N2 atmosphere for the crystallization and desification purposes. For the films deposited from V2O5 and VO2 sources, sources, Magneli (VnO2n-1$ 4\leq$ $n\leq$ 8) and VO2 phase appeared at $300^{\circ}C$, respectively, but VO2 phase also transformed into Magneli phase at $450^{\circ}C$ by severe reduction. On the contrary, VO2/VO mixed phases resulted from congruent evaporation of V2O3 unchanged after the same annealing treatment due to the balanced reduction and oxidation of VO2 and VO whcih have different equilibrium O2 pressures. It is suggested that the annealing in the controlled oxidation atmosphere or the deposition using mixed oxide sources are necessary to get the film containing VO2 phase.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.186.1-189
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• 2001

Ferroelectric $Bi_{4-x}$La$_{x}$Ti$_3$O$_{12}$ (BLT)thin films with various compositions(x=0.65, 0.70, 0.75) were prepared on Pt//Ti/SiO$_2$/Si(100) substrate by metal-organic deposition. The electrical and structural characteristics of BLT thin films were investigated to develop ferroelectric thin films for capacitor layers of FRAM. After spin coating, thin films were annealed at $650^{\circ}C$ for 1hour in oxygen atomosphere. Scanning electron micrographs showed uniform surfaces composed of rod-like grains. The $Bi_{4-x}$La$_{x}$Ti$_3$O$_{12}$ (x=0.70) thin film capacitors with a Pt top electrode showed better ferroelectric properties than other films. At the applied voltage of 5V, the dielectric constant($\varepsilon$$_{r}$), dissipation factor(tan$\delta$),remanent polarization(2Pr), and coercive field(2Ec) of the $Bi_{4-x}$La$_{x}$Ti$_3$O$_{12}$ (x=0.70)thin films were about 272.54, 0.059, 32.4 $\mu$C/cm$^2$, 2Ec=119.9kV/cm. Also the capacitor did not show any significant fatigue up to 4.8$\times$10$^{10}$ read/write switching cycles.hing cycles.s.