Pt/SiO_2_/Si 기판위에 형성된(Pb , La) TiO_3_ 강유전체 박막의 특성 연구

서광종,김민영,장지근,장호정 한국마이크로전자및패키징학회 1998 추계 기술심포지움 논문집 Vol.1 No.1

졸-겔법에 의해 제작된 적외선 센서용 $(Pb,La)TiO_3$ 강유전체 박막의 특성

서광종,장호정,장지근,Seo, Gwang-Jong,Jang, Ho-Jeong,Jang, Ji-Geun 한국재료학회 1999 한국재료학회지 Vol.9 No.5

Pt/SiOz!Si의 기판위에 $(Pb,La)TiO_3$(PLT) 박막을 졸-겔 방법으로 제작하여 La 첨가량 및 후속열처리 온도에 따른 결정학적, 전기적 특성율 조사하였다. $600^{\circ}C$ 이상의 온도에서 열처리된 PLT 박막 시료의 경우 La 도핑량에 관계없이 전형적인 perovskite 결정구조를 보여 주었다. La이 전혀 첨가되지 않은 $(Pb,La)TiO_3$(PT) 시료에 10 mole% La을 첨가할 경우 (PLT-I0 시료) c축 배향도는 약 63%에서 26%로 크게 감소하였다. PLT-1O 박막시료의 깊이에 따른 AES 분석결과 박막내의 각 성분원소 들이 비교척 균일하게 분포되어 았고 하부전극(Pt)과 PLT 박막층 사이에는 상호반응없이 비교적 안정된 막을 형성하고 있음을 알 수 있었다. $600^{\circ}C$에서 열처리된 PLT-1O 박막의 유전상수$({\varepsilon}r)$ 와 유전정접 (tan$\delta$) 은 약 193과 0.02의 값을 나타내였다. 후속열처리 온도를 $600^{\circ}C 에서 700^{\circ}C$로 증가함에 따라 잔류분극$(2Pr,Pr_+-Pr_-)$은 약 $4\muC\textrm{cm}^2 에서 약 16\muC\textrm{cm}^2$로 크게 증가하였으며 잔류 분극값의 증가는 후속열처리에 의해 결정성이 개선되었기 때문이라 판단된다. $30^{\circ}C$ 온도부근에셔 초전계수($\gamma$)는 약 $4.0nC/\textrm{cm}^2{\cdot}^{\circ}C$의 값을 냐타내었다. $(Pb,La)TiO_3$(PLT) thin films were prepared on Pt/SiO$_2$/Si substrates by the sol-gel method and investigated the crystalline and electrical properties according to La concentration and post-annealing temperatures. The PLT films annealed at above $600^{\circ}C$ were exhibited the typical perovskite structures regardless of La contents. When the $(Pb,La)TiO_3$(PT) films were doped with La concentration up to 10mol%(PLT-10), the degree of z-axis orientation was greatly decreased from 63% to 26%. From AES depth profiles for the PLT-10 samples, no remarkable inter-reaction between PLT film and lower Pt electrode was found. The remanent polarization$(2Pr,Pr_+-Pr_-)$ were increased from $4\muC\textrm{cm}^2 to 16\muC\textrm{cm}^2$ as the annealing temperature increased from $600^{\circ}C to 700^{\circ}C$. This result may be ascribed to the improvement of crystallinity by the high temperature post-annealing. The dielectric constant$({\varepsilon}r)$ and tangent loss(tan$\delta$) of the PLT-10 films annealed at $650^{\circ}C$ were about 193 and 0.02, respectively with the pyroelectric coefficient($\gamma$) of around $4.0nC/\textrm{cm}^2{\cdot}^{\circ}C at 30^{\circ}C$.

Ga 첨가량이 (Zn,Mg)O 투명전극 막의 전기적, 결정학적 특성에 미치는 영향

서광종,와카하라 아키히로,요시다 아키라,Suh, Kwang-Jong,Wakahara, Akihiro,Yoshida, Akira 한국재료학회 2005 한국재료학회지 Vol.15 No.8

(Zn,Mg)O (ZMO) thin films doped with Ga $(0\~0.03mol\%)$ in the target source were prepared by pulsed laser deposition on c-plane sapphire substrates at $500^{\circ}C$, and the effect of Ga contents on the properties of the electrical, optical and crystal properties of the deposited films was investigated. From X-ray diffraction patterns, ZMO film doped with $0.02 mol\%$ Ga showed crystal structure with c-axis preferred orientation, showing only the (0002) and (0004) diffraction peaks. In contrast, ZMO film doped with $Ga=0.03 mol\%$ showed a randomly oriented crystal structure. All the samples were highly transparent, showing the transmittance values of above $85\%$ in the visible region. For all the Ga doped ZMO films, the value of energy band gap was found to be about 3.5 eV, regardless of their Ga contents. From the Hall measurements, the resistivity and the carrier density for the ZMO film doped with $0.01 mol\%$ Ga were about $5\times10^{-4}\Omega-cm$ and $2\times10^{21}cm^{-3}$, respectively.

펄스 레이저 증착법을 이용한 $Zn_{1-x}Mg_xO$ 박막의 제작과 특성연구

서광종,Suh, Kwang-Jong 한국마이크로전자및패키징학회 2005 마이크로전자 및 패키징학회지 Vol.12 No.1

To widen the band gap of ZnO, we have investigated $Zn_{1-x}Mg_xO(ZMO)$ thin films prepared by pulsed laser deposition on c-plane sapphire substrates at $500^{\circ}C$. From X-ray diffraction patterns, ZMO films show only the (0002) and (0004) diffraction peaks. It means that the flints have the wurtzite structure. Segregation of ZnO and MgO phases is found in the films with x=0.59. All the samples are highly transparent in the visible region and have a sharp absorption edge in the UV region. The shift of absorption edge to higher energy is observed in the films with higher Mg composition. The excitonic nature of the films is clearly appeared in the spectra for all alloy compositions. The optical band-gap ($E_g$) of ZMO films is obtained from the ${\alpha}^2$ vs Photon energy plot assuming ${\alpha}^2\;\propto$ (hv - $E_g$), where u is the absorption coefficient and hv is the photon energy. The value of $E_g$ increases up to 3.72 eV for the films with x=0.35. It is important to adjust Mg composition control for controlling the band-gap of ZMO films.

산소압력이 테프론 휨성 기판위에 형성된 ZRO 투명박막의 전기적 특성에 미치는 영향

서광종,장호정,Suh Kwang Jong,Chang Ho Jung 한국재료학회 2005 한국재료학회지 Vol.15 No.4

We investigated the crystalline and electrical properties of ZnO thin films for transparent electrode as a function of the oxygen pressures during the deposition. The ZnO thin films were deposited on a flexible teflon substrates by the pulsed laser deposition. From the X-ray diffraction, ZnO films showed c axis oriented ZnO(0002) crystal structure. The FWHM (full width at half maximum) values decreased from $0.51^{\circ}\;to\;0.34^{\circ}$ as the oxygen pressure increased from 0.1 mTorr to 10.0 mTorr showing the improvement of crystallinity. The resistivity and hall mobility of ZnO film deposited at the oxgen pressure of 0.1 mTorr at $200^{\circ}C$ was about $5\times10^{-4}\Omega{\cdot}cm\;and\;20cm^2/V{\cdot}s$, respectively. The optical transmittance of the ZnO films on flexible teflon substrate was found to be above $85\%$.

비휘발성 메모리용 SrBi$_{2}$Ta$_{2}$ $O_{9}$강유전체 박막의 제조 및 특성연구

장호정,서광종,장기근 대한전자공학회 1998 電子工學會論文誌, D Vol.d35 No.3

SrBi$_{2}$Ta$_{2}$O$_{9}$ (SBT) ferroelectric thin films for nonvolatile memory were prepared on Pt/Ti/SiO$_{2}$/Si and RuO$_{2}$/SiO$_{2}$/Si substrates by RF magnetron sputtering. The dependences of crystalline and electrical properties on the lower electrode type(Pt and RuO$_{2}$) and the annealing temperatures were investigated. SBT films regardless of their electrode types showed typeical Bi layered peroviskite crystal structures. The crystalline quality of as-deposited SBT films was improved by the rapid thermal annealing at 650.deg. C for 30 sec. The remanetn polarization of 2Pr (Pr+-Pr-) of the annealed SBT films deposited on Pt/Ti/SiO$_{2}$/Si substrates were about 11 .mu.C/cm$^{2}$ and 3 .mu.C/cm$^{2}$, respectively. The leakage currents at 3 V bias voltage were about 0.8 .mu.A/cm$^{2}$ for SBT/ Pt/Ti/SiO$_{2}$/Si and about 1 .mu.A/cm$^{2}$ for SBT/RuO$_{2}$/SiO$_{2}$/Si sample. SBT films annealed at 650 .deg. C showed no degradation in Pr values after 10$^{11}$ polarization switching cycles, indicating good fatigue properties. In addition, for SBT samples deposited on Pt/Ti/SiO$_{2}$/Si, Pr values increased to more than that of initial state, suggesting the increament of leakage current caused by repeated polarization.

RF 스퍼터링에 의해 MgO/Si 기판위에 증착된 Pb(Zr, Ti)$\textrm{O}_3$ 강유전체 박막의 특성연구

장호정,서광종,장지근,Jang, Ho-Jeong,Seo, Gwang-Jong,Jang, Ji-Geun 한국재료학회 1998 한국재료학회지 Vol.8 No.12

PZT films without lower electrode were deposited on the highly doped Si(100) substrate with MgO buffer layer (Mgo/si) by RF magnetron sputtering method followed by the rapid thermal annealing at $650^{\circ}C$ . We investigated the dependences of the crystalline and electrical properties on the MgO thickness and the RTA post annealing. The PZT films on bare Si (without MgO) showed pyrochlore crystal structure while those on MgO(50 )/Si substrates showed the typical perovskite crystal structures. From SEM and AES analysis, the thickness of PZT films was about 7000 showing relatively smooth interface. The depth profiles indicated that atomic species were distributed homogeneously in the PZT/MgO/Si substrate. The dielectric constant($\varepsilon_{r}$ ) and remanent polarization(2Pr) were about 300 and $14\mu$C/$\textrm{cm}^2$;, respectively. The leakage current was about $3.2\mu$/A$\textrm{cm}^2$. 하부전극 없이 MgO 중간층을 갖는 고농도로 도핑된 Si(100) 기판(MgO/Si)위에 고주파 마그네트론 스퍼터링 방법으로 as-deposited PZT 박막을 증착한후 $650^{\circ}C$ 온도에서 RTA 후속열처리를 실시하였다. 제작된 PZT 박막시료에 대해 MgO 중간층의 두께 및 후속열처리에 따른 결정학적, 전기적특성을 조사하였다. XRD 분석결과 MgO층이 전혀 증착되지 않은 bare Si 기판위에 증착된 PZT 시료는 pyrochlore 결정상만이 나타났으나 50 두께의 M gO층 위에 증착된 PZT/MgO/Si 박막시료는 전형적인 perovskite 결정구조를 나타내었다. SEM 및 AES 분석결과 PZT 박막두게는 약 7000 이었으며 비교적 매끄러운 계면형상을 보여 주었다. PZT 박막내의 각 성분원소가 깊이에 따라 비교적 균일한 분포를 나타내었다. $650^{\circ}C$의 온도로 후속열처리된 PZT/MgO/Si 박막의 1KHz 주파수에서 유전상수 ($\varepsilon_{r}$ )와 잔류분극 (2Pr)은 약 300 및 $14\mu$C/$\textrm{cm}^2$의 값을 각각 나타내었으며 누설전류의 크기는 약 $3.2\mu$A/$\textrm{cm}^2$이었다.

스크린 인쇄법과 졸겔법에 의해 제작된 (Pb,La)TiO_3 강유전체막의 특성 연구

장호정,김민영,서광종,장지근 단국대학교 신소재기술연구소 1998 신소재 Vol.8 No.-

Pt/SiO_2/Si 기판구조위에 스크린인쇄법과 졸-겔법에 의해 as-coated (Pb, La)TiO_3(PLT), 후막과 형성하고 650℃ 후속열처리 온도에서 결정화한후 결정특성과 전기적 특성을 조사하였다. 650℃ 온도에서 후속열처리된 PLT시료의 경우 전형적인 perovskite 결정구조를 보여주었다. 후속 열처리된 PLT 후막과 박막의 두께는 약 3.5㎛와 0.8㎛로 각각 나타났으며 Pt 전극과 PLT막 사이에는 비교적 평활한 계면형상을 보여주었다. PLT 후막과 박막시료의 1 kHz 주파수에서 유전상수는 660과 190의 값을 나타내었으며 잔류분극(2Pr) 값은 약 1μC/㎠과 7μC/㎠을 각각 나타내었다. 후막 PLT 시료에 의해 박막시료에서 잔류분극값의 증가는 박막시료가 보다 양호한 결정성을 가지고 있기 때문으로 사료된다. 누설전류의 크기는 약 0.3∼0.8 μA/㎠의 값을 나타내어 비교적 양호한 누설전류 특성을 얻었다. The as-coated (Pb,La)TiO_3(PLT) thick and thin films were prepared on Pt/SiO_2/Si substrates by the screen printing and the sol-gel methods. The post-annealing was carried out at 650℃ for the crystallization. The crystal structures and electrical properties were investigated. The PLT films annealed at 650℃ showed the typical perovskite crystal structures. The thickness of PLT thick and thin films were about 3.5 ㎛ and 0.8 ㎛ respectively, showing relatively smooth cross-sectional surface between Pt electrode and PLT film. The PLT thick and thin films annealed at 650℃ indicated about 660 and 190 for the dielectric constant and 1 μC/㎠ for the remanent polarization(2Pr), respectively. The higher Pr value in the thin film sample compared to the thick film may attributed to the good crystal structure of the thin film. The leakage currents were about 0.3-0.8μA/㎠.

스크린 인쇄법과 졸겔법에 의해 제작된 (Pb,La)TiO3 강유전체막의 특성 연구

장호정(Ho Jung Chang),김민영(Min Yong Kim),서광종(Kwang Jong Suh),장지근(Gee Keun Chang) 단국대학교 신소재기술연구소 1998 신소재 연구논집 Vol.8 No.-