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The fabrication of the thin films by chemical vapour deposition and the effect of the deposition parameters on the physical, electical, and optical properties of deposited films
No full text학위논문(박사) - 한국과학기술원 : 재료공학과, 1988.8, [ vi, 123 p. ]IV-3. 화학증착법을 이용하여 강유전체 재료인 Lead Titanate 박막을 제조하였다. IV-3-1. Substrate reaction Pbo와 모재인 티타늄과의 반응에서 Lead Titanate를 제조하여 다음 결과를 얻었다. 1. 증착층은 주상정 조직을 가지며 모재에 수직으로 성장한다. 2. 박막과 모재사이에 titanium dioxide의 interlayer가 형성되었다. 3. 의 유전상수와 유전손실은 박막두께에 관계없이 일정하며 양호한 성질을 나타낸다. VI-3. 의 혼합 기체를 이용한 Lead Titanate의 화학 화학증착에서 증착층의 화학 조성을 AES 와 XPS 를 사용하여 얻어서 다음과 결론을 얻었다. (1)표준 시편을 사용하여 증착층의 조성을 AES 와 XPS로 분석하였다.\\ Table.14 Comparison XPS and AES results for a sputter cleaned \varphi=45\,^\circ to the normal to the sample. \begin{center} \begin{tabular}{rrrr}\hline & \underline{Pb(at.\%)} & \underline{Ti(at.\%)} & \underline{O(at.\%)}\cos \varphi = 0.87) & 20.4 & 19.5 & 60.1\\ XPS(\varphi\qquad = 45\,\^circ) & 16.94 & 26.84 & 56.2 \\ \hline \end{tabular} \end{center} Deposition condition: deposition temperature, 750\,^\circ\!C;\; Ti(C_2H_5O)_4O_2PbTiO_3 films for various deposition temperatures (by XPS)\\ \begin{center} \begin{tabular}{|r|rrrr} \hline & \multicolumn{4}{|c|} Various deposition temperature (^\circ\!C)\\ \hline & \underline{600} & \underline{650} & \underline{700} & \underline{750}\\ Pb(a.c) & 0.183 & 0.171 & 0.179 & 0.167\\ Ti(a.c) & 0.261 & 0.263 & 0.270 & 0.269 & O(a.c) & 0.556 & 0.566 & 0.551 &0.564\\ \hline \end{tabular} \end{center} Table.16 Atomic compositions of the films for various fractions(by XPS)\\ \begin{center} \begin{tabular}{|r|rrr} \hline & \multicolumn{3}{|c|} Various fractions\\ \hline & & & \\ Pb(a.c) & 0.115 & 0.103 & 0.112 \\ Ti(a.c) & 0.219 & 0.208 & 0.237 \\ O(a.c) & 0.667 & 0.689 & 0.651\\ \hline \end{tabular} \end{center} (2) 반응기체유량 800sccm, 분율0.15, $한국과학기술원 : 재료공학과
SBT강유전체 박막 형성 방법
No full textA method for forming SBT ferroelectric thin film. Sr(C.sub.5 F.sub.6 HO.sub.2).sub.2, Bi(C.sub.6 H.sub.5).sub.3 and Ta(C.sub.2 H.sub.5 O).sub.5 are used as the precursors of Sr, Bi and Ta and bubbled at a temperature of 110-130.degree. C., 140-160.degree. C., and 120-140.degree. C., respectively. The deposition of the precursors on a substrate is carried out at 500-550.degree. C. in plasma by using an RF power of 100-150 W. Having a residual polarity (Pr) of 15 .mu.C/cm.sup.2 or higher and a coercive electric field (Ec) of 50 kV/cm or less and, the SBT ferroelectric thin film does not show a fatigue phenomenon until 1.times.10.sup.11 cycles as measured under 6V bipolar square pulse in the structure comprising Pt upper and lower electrodes and thus, can be applied for non-volatile memory devices
High-Performance Flexible Ultraviolet Photodetectors Based on Facilely Synthesized Ecofriendly ZnAl:LDH Nanosheets
No full textRecent studies have focused on the development of efficient, flexible, and highly sensitive ultraviolet photodetectors (UV PDs) with various wide band-gap materials. In the present study, the application of environmentally friendly zinc-aluminum layered double hydroxide (ZnAl-CO3:LDH) is demonstrated for a high-performance, flexible UV PD. The vertically oriented ZnAl:LDH nanosheets (ZnAl:LDH Ns) are facilely synthesized by dipping the sputtered 10 wt % aluminum-doped zinc oxide thin films in deionized water at room temperature. Without passivation, the UV PDs exhibit an exceptional light-to-dark current ratio of 104 and a responsivity of similar to 34.7 mA/W at a bias of 1 V. Moreover, the spectral responsivity and detectivity are enhanced to similar to 148.3 mA/W and 2.5 x 1012 Jones, respectively, by passivating the ZnAl:LDH Ns with polydimethylsiloxane (PDMS), thus making the device suitable for application in UV detectors. In addition, the ambient atmosphere effect on PD performance, which elucidates the clear understanding of the PD working mechanism, is also investigated. The passivation of the Ns by PDMS also helps to enhance the mechanical robustness and long-term stability of the PD. The methodology demonstrated herein highlights the potential of the ZnAl:LDH material in realizing the next generation of flexible
Heteroepitaxial growth of the ferroelectric Pb(Zr0.2Ti0.8)O3 thin films on SrRuO3/SrTiO3 structures for nano-data storage
No full textHigh-power nanogenerator of 2D-layered perovskite in a polymer matrix for self-charging battery-powered electronics
No full textRecently two-dimensional layered halide perovskites (2D-layered HPs) with superior piezo-/ferroelectric properties and exceptional environmental stability have become potential alternatives to 3D-HPs. Herein, air-stable 2D-layered 1,3-propanediammonium lead iodide (DAPPbI4) perovskite is introduced as a promising filler material in a poly(vinylidene fluoride) (PVDF) polymer for the development of a high-performance and mechanically robust DAPPbI4-PVDF composite triboelectric nanogenerator (TENG). The triboelectric output performance is noticeably enhanced for 15 wt% DAPPbI4 owing to its improved electro-active beta-phase PVDF (-90%), high dielectric constant (similar to 47.4), and high piezoelectric coefficient (similar to 26.6 pm/V). The TENG achieved a high output voltage of similar to 662 V, current density of similar to 18.7 mu A/cm(2), unprecedented high power-density of similar to 4.28 mW/cm(2), and excellent pressure sensitivity of similar to 13.31 V/kPa with outstanding mechanical durability and operational stability. The application of HP-based TENG as a sustainable power source for various portable electronics is demonstrated by charging a Li-ion battery (LIB) in a short time using the TENG output.
Harnessing Flexoelectric and Piezoelectric Effects for Self-Charging Power Systems
No full textStretchable mechanical energy harvesters are in high demand as sustainable power sources and self-powered systems for wearable electronics and biomedical devices. In this study, a stretchable flexoelectric-piezoelectric nanogenerator (FPENG) composed of a zinc-aluminum layered double hydroxide nanosheets-ZnO nanorods (ZnAl:LDH NSs-ZnO NRs) heterostructure is developed. The coupling of the flexoelectric effect of ZnAl:LDH NSs and the piezoelectric effect of ZnO NRs enhances the output performance of the FPENG. The FPENG generates an open-circuit voltage (V oc) of 41.5 V, a short-circuit current density (J sc) of 4.57 mu A/cm2, and a maximum power density of 68.2 mu W/cm2 with good mechanical durability, while the device under stretching at 60% strain generates a V oc of 1.85 V and J sc of 0.09 mu A/cm2. The energy generated from the FPENG is stored in a Li-ion battery, demonstrating a self-charging power unit. These findings present a simple method to develop FPENGs with enhanced performance by coupling flexoelectric and piezoelectric effects for wearable devices.
Wrinkle-free graphene electrodes in zinc tin oxide thin-film transistors for large area applications
No full textWrinkle-free graphene was used to form the source-drain electrodes in thin film transistors based on a zinc tin oxide (ZTO) semiconductor. A 10 nm thick titanium adhesion layer was applied prior to transferring a conductive graphene film on top of it by chemical detachment. The formation of an interlayer oxide between titanium and graphene allows the achievement of uniform surface roughness over the entire substrate area. The resulting devices were thermally treated in ambient air, and a substantial decrease in field effect mobility is observed with increasing annealing temperature. The increase in electrical resistivity of the graphene film at higher annealing temperatures may have some influence, however the growth of the oxide interlayer at the ZTO/Ti boundary is suggested to be most influential, thereby inducing relatively high contact resistance.
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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