• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1997.11a
• /
• pp.48-51
• /
• 1997

(Pb. La)TiO$_3$ thin films were fabricated by sol-gel Processing and spin-coated on the Pt substrate. The spin-coated PLT films were sintered at 75$0^{\circ}C$ for 5min by rapid thermal ann La content dependence of the electrical properties of the PLT thin films are discussed. Wit La mole% from 20 to 36mo1e%. the dielectric constant of the PLT thin films decreased f 570. P-E hysteresis loops changed from ferroelectric to paraelectric. and the charge storage charging time decreased. The Curie Point decreased with increasing La content. The leak density also decreased and La 36mo1% species shows mood characteristics less than 10- electric field 500 (KV/cm) Because of the broad range of composition-controlled ferroelectric PLT thin films are suitable for memory application.

• Proceedings of the KIEE Conference
• /
• 1998.11a
• /
• pp.378-381
• /
• 1998

PLT(28) ($Pb_{0.72}La_{0.28}Ti_{0.93}O_3$) dielectric thin films have been deposited on Pt/Ti/$SiO_2$/Si substrates in situ by a laser ablation. We have systematically changed the laser fluence from $0.5\;J/cm^2$ to $3\;J/cm^2$, and deposition temperature from $450^{\circ}C$ to $700^{\circ}C$. The surface morphology was changed from planar grain structure to columnar structure as the nucleation energy was increased. The PLT thin film with columnar structure showed good dielectric properties. It is shown that the deposition temperature strongly affect the film nucleation compared with the laser fluence.

• Proceedings of the Korean Vacuum Society Conference
• /
• 1995.06a
• /
• pp.38-39
• /
• 1995

• Journal of Surface Science and Engineering
• /
• v.33 no.2
• /
• pp.77-86
• /
• 2000

In this study effects of La starting compounds and substrates on the densification of (P $b_{0.92}$L $a_{0.05}$)Ti $O_3$ thin films were investigated. After the heat treatment on platinized silicon at $650^{\circ}C$ for 30min thickness of PLT(i) thin films (from La-isopropoxide) shrank by 27%, while 33% reduction occurred for PLT (a) thin films (from La-acetate). These PLT(i) films showed less densified surface microstructure compared to the PLT (a) . Lower shrinkage of the films on platinized silicon than on bare silicon (41% and 40% for PLT (i) and PLT (a) respectively) is attributed to the earlier development of crystallinity in the film, which arrests film densification. In order to maximize sintering before crystallization, heat treatment at $400^{\circ}C$ for 3 hours followed by $650^{\circ}C$ for 30 min was attempted. This method increased the shrinkage of the PLT (i) and PLT (a) films two times and 1.5 times as much as that observed for the films heat treated at $650^{\circ}C$ for 30min, respectively. FTIR results indicated that first pyrolysis in the film is associated with the burning of acetate ligands. Condensation reaction between OHs was found to occur preferentially between $350^{\circ}C$ and $450^{\circ}C$, whereas majority of polycondensation between ROH-OH appears to occur until $300^{\circ}C$ and be completed below $450^{\circ}C$.EX>.

• Korean Journal of Materials Research
• /
• v.7 no.3
• /
• pp.196-202
• /
• 1997

Perovskite lanthanum doped lead titanate ($(Pb,La)TiO_{3}$ or PLT) thin films were successfully fabricated on Pt/TijSiO.iSi substrates at the temperatures as low as $440~500^{\circ}C$ by eleclron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR PECVII). Since the volatilities of the MC sources arid oxide molecules (especially Ph oxide) increased with increasing deposition temperature, the film deposition rate and the (I'b + La)/'Ti ratio decreased Stoichiometric perovskite PL'T films with good dielectric and leakeage current properties were obtained at the temperatures of $460~480^{\circ}C$. The lanthanum content of the film was nearly directly propotional to $La(DPM)_{3}$ flow rate. As the La/Ti ratio increased from 3.0 to 9.5%, the dielectric constant increased from 360 to 650 and the leakeage current density at 100kV/cm electric field decreased from $4{\times}10^{-5}$ to $4{\times}10_{-8}A/cm^2$.

• Journal of the Korean Institute of Telematics and Electronics D
• /
• v.34D no.5
• /
• pp.22-31
• /
• 1997

We have measured the optical properties, thickness, and energy band gap of the P $b_{1-x}$/100/L $a_{x}$100/ $Ti_{1-}$0.25x/100/ $O_{3}$ (PLT(x)) thin film prepared by the sol-gel method with varying the La concentration, x, fyom 15 nto 33 mol%. We have obtained the values from the tranmission spectrum and employed the envelope method in anayzing the spectrum. We have also performed the simulation of the transmission spectrum on the PC (personal computer) to verify the accuracy of the values 15 to 33mol%, the refractive index (at .lambda.=632.8nm) increases from 2.39 to 2.44. The extinction coefficient does not depend on the la concentration but mainly on te wavelength, and has the values between 0.2 and 0.5 at the wavelength shorter than 330nm and between 0.001 and 0.008 at the wavelength longer than 700nm. The energy band gap of the PLT (x) thin film has been obtained on the assumption of the direct band-to-band transition. It decreases from 3.28 to 3.17eV as the La concentration increases from 15 to 33 mol%. The thickness of the PLT(x) thin film has been also obtained in high accuracy by the envelope method..

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.07a
• /
• pp.395-397
• /
• 2002

Dielectric thin films of Pb$\_$0.72/La$\_$0.28/Ti$\_$0.93/O$_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. Two-step process to grow PLT films was adopted and verified to be useful to enlarge the grain size of the film. Structural properties including dielectric constant, and ferroelectric characteristics 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 strong (111) orientation. However, the films deposited by using single-step process with hydrogen annealing process shows the smallest grain size.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.33A no.2
• /
• pp.87-95
• /
• 1996

We have studied the effects of La concentration on the optical and electrical properties of lead lanthanum titanate (PLT) thin films by using sol-gel method. Both the optical and electrical properties are greatly affected by the La concentration. The refreactiv eindices of the films varied from 2.23 to 1.93 with varying La concentration in the range from 15 to 33 mol%. The dielectric constants of the films vary form 340 to 870 with varying La concentration in the range form 15 to 33 mol%. Hysteresis loop becomes slimmer with the increase of La concentration form 15 to 28mol% and little fatter again with the increase of La concentration form 28 to 33 mol%. Among the films investigated in this research, PLT(28) thin film shows the best dielectric properties for the application to the dielectrics of ULSI DRAM's. At the frequency of 100Hz, the dielectric constant and the loss tangent of PLT(28) thin films are 940 and 0.08 respectively. Its leakage current density at 1.5${\times}10^{5}$V/cm is 1${\times}10^{-6}A/cm^{2}$. The comparision between the simulated and the experimental curves for the switching transient characteristics shows that PLT (28) thin films behaves like normal dielectrics.

• Proceedings of the KIEE Conference
• /
• 1994.07a
• /
• pp.66-68
• /
• 1994

강유전체 박막과 마이크로 가공기술을 이용하여 초전형 적외선 센서를 제작하였다. 초전형 적외선 센서는 $Pb_{1-x}La_xTi_{1-x/4}O_3$ (x=0.05) (PLT) 강유전체 박막 커패시터를 RF 마그네트론 스퍼터링 방식으로 백금 전극이 증착된 MgO 기판상에 결정 성장시킨 구조를 갖고 있다. 스퍼터링된 PLT 바닥은 높은 c-축 결정 구조를 가지므로 센서로 사용하기 위한 poling 처리 과정이 필요하다. 이는 적외선 이미지 센서를 구현함에 있어서 수율 향상에 필수적인 요소이다. 마이크로 가공 기술을 사용하여 센서의 열용량을 극소화 함으로서 센서의 효율을 최대화하였다. 제작된 센서의 상부에 폴리이미드를 코팅하고 MgO 기판을 선택적으로 식각하여 코팅된 폴리이미드가 강유전체 박막 커패시터를 지지하고 있는 구조를 구현하였다. 이렇게 제작된 센서의 감도는 상온에서 $8.5{\times}10^8cm{\cdot}{\sqrt}{Hz/W}$로 측정되었으며 이는 마이크로 가공 기술을 사공하지 않은 경우보다 약 100 때의 감도 향상을 가져왔다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2003.05a
• /
• pp.696-699
• /
• 2003

In this study, we suggested the model to precisely evaluate the ferroelectric hysteresis loop, using the modified Sawyer-Tower circuit and the ferroelectric capacitor with a MDFM(Metal-Dielectric-ferroelectric-Metal) structure. The mathematical expression of dipole polarization is applied to the numerical integration algorithm, and the fatigue property can be considered including the dielectric layer between ferroelectrics and bottom electrode. The validity of our model is proved comparing the estimated value of our model and the measured results of PLT(10) thin film.