淀积气压对脉冲激光淀积La掺杂钛酸铅薄膜介电性能的影响

利用脉冲激光淀积法在Pt/Ti/SiO2/Si衬底上制备了28mol%La掺杂钛酸铅薄膜.采用不同的淀积氧气压，并分析了其对薄膜微观结构和介电性能的影响.结果表明，在2Pa左右的气压下淀积的薄膜具有好的结晶度和介电系数.在频率为10kHz时28mol%La掺杂钛酸铅薄膜的介电系数达852，并且保持了较低的损耗.同时制备了其他La掺杂浓度的PbTiO3薄膜，发现它们也有类似的特点.对此作了定性解释. 关键词： 脉冲激光淀积 PLT薄膜 气压 介电增强     

利用脉冲激光沉积技术在双轴织构的Ni基带上外延CeO2薄膜

利用脉冲激光沉积技术在氢还原气氛下成功地在双轴织构的Ni基带上外延了高质量的CeO₂薄膜. x射线衍射θ—２θ扫描和ω扫描结果表明，CeO₂薄膜在Ni基带上呈c轴方向生长，存在很强的平面外织构；极图和φ扫描显示它具有良好的平面内织构. Ni基片上织构的CeO₂薄膜为进一步在其上外延高质量的YBa₂Cu₃O_7-x超导薄膜提供了很好的模板. 关键词： 双轴织构的Ni基带 2薄膜')" href="#">CeO₂薄膜 脉冲激光沉积     

Pb(Zr0.3Ti0.7)O3铁电薄膜激光感生电压效应

采用脉冲激光沉积(PLD)技术在LaSrAlTaO₃(LSATO),LaAlO₃(LAO)和SrTiO₃(STO)的单晶倾斜衬底上成功制备了Pb(Zr_0.3Ti_0.7)O₃(PZT)薄膜,在三种倾斜衬底上生长的PZT薄膜中都首次发现了LIV效应.对PZT/LSATO薄膜在a,c轴两种不同取向择优生长下的LIV效应做了研究,发现在薄膜c轴取向择优生长 关键词： 激光感生电压效应 铁电薄膜 薄膜生长取向 原子层热电堆     

Effects of repetitive polarization switching on the coercive voltage of Pt/Pb(Zr0.52Ti0.48)O3/Pt thin films analyzed using impedance spectroscopy

We investigated the effect of repetitive switching of polarization on the ferroelectric Pt/Pb(Zr_0.52Ti_0.48)O₃/Pt thin film capacitor by using impedance spectroscopy. From the Cole-Cole plot, the equivalent circuit is described as a combination of the bulk part (a capacitor), the interface part (the constant phase element (CPE), and a parallelly-connected resistor). The circuit parameters were analyzed at various stages of switching. An early increase and a subsequent decrease of the bulk capacitance may represent the wake-up and fatigue phenomena, respectively. The change in the interface part was characterized by an increase in resistance and the growth of n, the exponent of CPE, which may have come from a reduction of defects and the diminished inhomogeneity in the interfacial layer, respectively. The change in the resistance and the coefficient of the CPE in the interface part collectively resulted in an increase in the interfacial impedance. The coercive voltage, which may have intrinsically increased due to the repetitive switching, was even larger as a result of the increased interfacial impedance.     

不同衬底上Pb(Zr0.52Ti0.48)O3择优取向铁电薄膜的制备和研究

通过MOD法在Si(100)和Pt(111)/Ti/SiO₂/Si基片上制备出LaNiO₃ ( LNO)薄膜.再通过修 正的Sol-gel法，在Pt(111)/Ti/SiO₂/Si,LNO/Si(100)和LNO/Pt/Ti/SiO_{2< /sub>/Si三种衬底上 制备出具有择优取向的Pb(Zr0.52Ti0.48)O3铁电薄膜. 经XRD分析表明，L NO薄膜具有(100)择优取向的类钙钛矿结构；PZT薄膜均具有钙钛矿结构，且在Pt(111)/Ti/S iO2/Si衬底上的薄膜以(110)择优取向，在LNO/Pt/Ti/SiO2/Si和LN O/Si(100)衬底上的 薄膜以(100)择优取向.经场发射SEM分析和介电、铁电性能测试表明，在LNO/Si和LNO/Pt/Ti /SiO2/Si衬底上的PZT薄膜的平均粒径、介电常数以及剩余极化强度均比以Pt/T i/SiO2/Si为衬底的薄膜大. 关键词： 3}薄膜')" href="#">LaNiO₃薄膜 PZT铁电薄膜 择优取向 剩余极化强度     

Pulsed laser deposition and thermal characterization of Ni-doped La5Ca9Cu24O41 thin films

Highly b-axis oriented polycrystalline Ni-doped La₅Ca₉Cu₂₄O₄₁ thin films have been grown on (0 0 1) SrTiO₃ substrates using the pulsed laser deposition technique. EDX measurements have revealed nearly stoichiometric target-to-film transfer of Ni concentration up to 6.6 at.%. The 3ω method has been employed to carry out thermal conductivity measurements in the range 90-300 K. The results indicate that the out-of-plane thermal conductivity (κ_b) decreases with increasing Ni doping level. The temperature dependence of κ_b observed in pristine and Ni-doped films is similar to that observed in polycrystalline pellets indicating that the grain boundaries play a significant role in the heat transport.     

LiFePO4 thin films grown by pulsed laser deposition: Effect of the substrate on the film structure and morphology

Well crystallized and homogeneous LiFePO₄/C (LFPO) thin films have been grown by pulsed laser deposition (PLD). The targets were prepared by the sol-gel process at 600 °C. The structure of the polycrystalline powders was analyzed with X-ray powder diffraction (XRD) data. The XRD patterns were indexed having a single phase olivine structure (Pnma). LFPO thin films have been deposited on three different substrates: aluminum (Al), stainless steel (SS) and silicon (Si) by pulsed laser deposition (PLD). The structure of the films was analyzed by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM). It is found that the crystallinity of the thin films depends on the substrate temperature which was set at 500 °C. When annealed treatments were used, secondary phases were found, so, one step depositions at 500 °C were made.Stainless steel is demonstrated to be the best choice to act as substrate for phosphate deposition. LiFePO₄ thin films grown on stainless steel plates exhibited the presence of carbon, inducing a slight conductivity enhancement that makes these films promising candidates as one step produced cathodes in Li-ion microbatteries.     

Structure evolution and stoichiometry control of Pb(Zr, Ti)O3 thick films fabricated by electrospray assisted vapour deposition

Well-crystallized and stoichiometric Pb(Zr, Ti)O₃ (PZT) films, typically ∼5 μm thick, with pure perovskite-type rhombohedral structures have been successfully prepared via an electrospray assisted vapour deposition (ESAVD) method. Control of the deposition temperature within a narrow range of 300-400 °C resulted in films with the most desirable phases. PZT films with close stoichiometric match with the expected composition ratio and uniform element distribution were obtained by adding the appropriate levels of excess Pb in the precursor solutions. The annealed films were uniform, dense, compact and adherent to the substrates. The dielectric constant, ?_r, and loss tangent, tan δ, of the fabricated PZT films measured at 10 kHz were 442 and 0.09, respectively. The ESAVD deposited PZT films showed a remanent polarization, P_r, of 15.3 μC/cm² and coercive field, E_c, of 86.7 kV/cm. These results demonstrate the clear potential of the ESAVD method as a promising technique for the fabrication of thick PZT films.     

Visible-light photocatalytic activity of nitrogen-doped TiO2 thin film prepared by pulsed laser deposition

Nitrogen-doped titanium dioxide (TiO_2−xN_x) thin films have been prepared by pulse laser deposition on quartz glass substrates by ablated titanium dioxide (rutile) target in nitrogen atmosphere. The x value (nitrogen concentration) is 0.567 as determined by X-ray photoelectron spectroscopy measurements. UV-vis spectroscopy measurements revealed two characteristic deep levels located at 1.0 and 2.5 eV below the conduction band. The 1.0 eV level is attributable to the O vacancy state and the 2.5 eV level is introduced by N doping, which contributes to narrowing the band-gap by mixing with the O2p valence band. The enhanced degradation efficiency in a broad visible-light range was observed from the degradation of methylene blue and methylene orange by the TiO_2−xN_x film.     

Structural and electrical properties of lithium manganese oxide thin films grown by pulsed laser deposition

LiMn₂O₄ thin films were deposited by reactive pulsed laser deposition technique and studied the microstructural and electrical properties of the films. The LiMn₂O₄ thin films deposited in an oxygen partial pressure of 100 mTorr and at a substrate temperature of 573 K from a lithium rich target were found to be nearly stoichiometric. The films exhibited predominantly (111) orientation representing the cubic spinel structure with Fd3m symmetry. The intensity of (111) peak increased and a slight shift in the peak position was observed with the increase of substrate temperature. The lattice parameter increased from 8.117 to 8.2417 Å with the increase of substrate temperature from 573 to 873 K. The electrical conductivity of the films is observed to be a strong function of temperature. The evaluated activation energy for the films deposited at 873 K is 0.64 eV.     

Ferroelectric properties of bilayer structured Pb(Zr0.52Ti0.48)O3/SrBi2Ta2O9 (PZT/SBT) thin films on Pt/TiO2/SiO2/Si substrates

Pb(Zr_0.52Ti_0.48)O₃ (PZT) thin films with large remanent polarization and SrBi₂Ta₂O₉ (SBT) thin films with excellent fatigue-resisting characteristic have been widely studied for non-volatile random access memories, respectively. To combine these two advantages_, bilayered Pb(Zr_0.52Ti_0.48)O₃/SrBi₂Ta₂O₉ (PZT/SBT) thin films were fabricated on Pt/TiO₂/SiO₂/Si substrates by chemical solution deposition method. X-ray diffraction patterns revealed that the diffraction peaks of PZT/SBT thin films were completely composed of PZT and SBT, and no other secondary phase was observed. The electrical properties of the bilayered structure PZT/SBT films have been investigated in comparison with pure PZT and SBT films. PZT/SBT bilayered thin films showed larger remanent polarization (2P_r) of 18.37 μC/cm² than pure SBT and less polarization fatigue up to 1 × 10⁹ switching cycles than pure PZT. These results indicated that this bilayered structure of PZT/SBT is a promising material combination for ferroelectric memory applications.     

Effects of strontium on the characteristics of Pb(Zr1/2Ti1/2)O3--Pb(Zn1/3Nb2/3)O3 ceramics

The dielectric and piezoelectric properties of pyrochlore-free lead zirconate titanate-lead zinc niobate ceramics were investigated systematically as a function of Sr doping. The powders of Pb_{(1? x )}Sr _x [0.7(Zr_{1 / 2}Ti_{1 / 2})–0.3(Zn_{1 / 3}Nb_{2 / 3})]O₃, where x?=?0–0.06 were prepared using the columbite-(wolframite) precursor method. The ceramic materials were characterized using X-ray diffraction, dielectric spectra, hysteresis and electromechanical measurements. The phase-pure perovskite phase of Sr-doped PZN--PZT ceramics was obtained over a wide compositional range. The results showed that the optimized electrical properties were also achieved at composition x?=?0.0, which were K _P?=?0.69, d ₃₃?=?670?pC?N^?1, P _r?=?31.9?µC?cm^?2 and ε_rmax?=?18600. Maximum dielectric constant values of the systems decreased rapidly with increasing Sr concentration. Moreover, with increasing Sr concentration dielectric constant versus temperature curves become gradually broader. The diffuseness parameter increased significantly with Sr doping. Furthermore, Sr doping has been shown to produce a linear reduction in the transition temperature (T _m)?=?294.1–12.7x°C with concentration (x). Sr shifts the transition temperature of this system at a rate of 12.7°C?mol^?1%.     

脉冲激光沉积温度及氧压对Bi2Sr2Co2Oy热电薄膜晶体结构与电输运性能的影响

利用脉冲激光沉积技术在c-Al₂O₃单晶基片上制备了Bi₂Sr₂Co₂O_y热电薄膜并研究了沉积温度和氧压对薄膜晶体结构及电输运性能的影响.在最佳沉积条件下制备的单相、c轴取向的Bi₂Sr₂Co₂O_y薄膜的室温电阻率ρ和塞贝克系数S分别为2.9mΩ/cm和110μupV/K,其功率因子S²/ρ好于在单晶样品上得到的值.此外,该薄膜在低温下表现出较强的负磁阻效应,在2K,9T时达到了40%.     

Pulsed laser deposition of Bi2Te3 thermoelectric films

Bi₂Te₃ is one of the most used materials for thermoelectric applications at ambient temperature. An improvement of thermoelectric performances through a suitable modification of electron and phonon transport mechanisms is predicted for low dimensional or nanostructured systems, but this requires a control of the material structure down to the nanoscale. We show that pulsed laser deposition provides control on film composition, phase and structure, necessary for a comprehension of the relationship between structure and thermoelectric properties. We have explored the role of deposition temperature, background inert gas type and pressure, laser fluence and target-to-substrate distance and we found the experimental condition ranges to obtain crystalline films containing the Bi₂Te₃ phase only, by comparing energy dispersive X-ray spectroscopy, Raman spectroscopy and X-ray diffraction analysis. Variations of substrate temperature and deposition gas pressure prove to be crucial also for the control of film morphology and crystallinity. Substrate type has no influence on film stoichiometry and crystallinity, but highly oriented growth can be achieved on mica due to van der Waals epitaxy.     

Shock-wave- and hydrostatic-pressure-induced depolarization of Pb(Zr,Sn,Ti)O3 for pulse power applications

Research on quasi-static pressure-induced depolarization illustrates that Pb(Zr,Sn,Ti)O₃ ceramic may be useful in the technology of pulse power. However, lack of knowledge on the shock-induced depolarization hinders this application. To fill this gap, we investigated the shock-wave- and hydrostatic-pressure-induced depolarization of Pb_0.99Nb_0.02[(Zr_0.90Sn_0.10)_0.96Ti_0.04]_0.98O₃ ceramic. In the hydrostatic experiment, complete and sudden depolarization took place at 140 MPa. Shock wave experiments in the normal and axial modes were conducted in the pressure range from 0.81 to 4.50 GPa. At 2.50 GPa, the phase transition occurred completely and the short-circuit current reached 32 A in the normal mode. We obtained 31.0 kV voltage, 0.96 MW and 0.92 J cm^?3 high-voltage pulse with 1000 Ω load. In the axial mode, the shape of the current pulse and its time integral were found to be strongly shock pressure dependent. Our work lays the foundation for the application of Pb(Zr,Sn,Ti)O₃ in the single-use power supply.     

冲击波加载下孔隙率对Pb_(0.99)(Zr_(0.95)Ti_(0.05))_(0.98)Nb_(0.02)O_3铁电陶瓷去极化性能的影响

制备了四种不同孔隙率的Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3铁电陶瓷,并研究了冲击波作用下孔隙率对陶瓷去极化性能的影响.研究表明:短路负载条件下陶瓷的放电波形不随孔隙的加入而改变,均为方波.多孔陶瓷的放电脉冲幅度较低,脉冲宽度较长.释放的电荷量随着孔隙率的增加而减小,与静态电滞回线测试结果一致.多孔陶瓷具有较低的冲击阻抗,改善了与封装介质的阻抗匹配.用Lysne模型拟合了材料在高电阻负载条件下的放电行为,并指出高电阻负载条件下材料的介电常数是静态介电常数的4—5倍,而且材料的介电常数随孔隙率的增加而减小.冲击波通过样品以后,电路的放电时间常数随着孔隙率的增大而增大.随着电阻的增大,样品负载电压增高,材料铁电-反铁电相变受到抑制,电流上升沿变缓,致密陶瓷出现了击穿现象.     

氧压对SrTiO3和SrNb0.2Ti0.8O3薄膜晶格参数的影响及激光感生热电电压效应

采用脉冲激光沉积技术制备了SrTiO₃和SrNb_0.2Ti_0.8O₃薄膜.X射线衍射分析表明在LaAlO₃(100)单晶平衬底上生长的SrTiO₃及SrNb_0.2Ti_0.8O₃薄膜是沿［001］取向的近外延生长.随着氧压在一定范围内逐渐增大,SrTiO₃薄膜的晶格参数减小,而SrNb_0.2Ti_0.8O₃薄膜的晶格参数先减小后增大.同时摸索出制备具有二维电子气超晶格(SrTiO₃/SrNb_0.2Ti_0.8O₃)_L的最佳氧压为1.0×10^-2Pa.另外在LaAlO₃(100)倾斜衬底上制备的SrNb_0.2Ti_0.8O₃薄膜中观察到激光感生热电电压效应. 关键词： 0.2Ti_0.8O₃薄膜')" href="#">SrNb_0.2Ti_0.8O₃薄膜 晶格参数 激光感生热电电压 脉冲激光沉积     

Microstructure and electrical properties of (Zr, Sn)TiO4 thin film deposited on Si(1 0 0) using a sol-gel process

Polycrystalline zirconium tin titanate (Zr_0.8Sn_0.2TiO₄, ZST) thin films with thickness of 81 nm were deposited successfully along the (1 0 0) on a p-type Si substrate by an improved sol-gel method. The deposited films were crystallized when annealing temperature was up to 450 °C. The thickness and compositions of the interface layer between the ZST films and Si substrate were identified by high-resolution transmission electron microscope (HRTEM). The electrical properties such as leakage current density, flat-band voltage and capacitance of the films were measured and discussed. Furthermore, the mechanism of the leakage current was also investigated.     

低温生长Cu(InGa)Se2薄膜吸收层的掺钠工艺研究

在柔性聚酰亚胺衬底上低温制备Cu(In,Ga)Se₂薄膜太阳能电池, Na的掺入会改善电池特性, 但不同的掺Na工艺对Cu(In,Ga)Se₂薄膜和器件特性的改善机理不同. 本实验通过对比前掺NaF和后掺NaF工艺发现, 在前掺Na工艺下, 由于Na始终存在于Cu(In,Ga)Se₂薄膜生长过程中, Na存在于多晶 Cu(In,Ga)Se₂ 薄膜晶界处, 起到了扩散势垒的作用, 导致晶粒细碎、加剧两相分离, 同时减小了施主缺陷的形成概率; 而在后掺Na工艺下, 掺入的Na对薄膜的结构及生长不产生影响, 仅仅起到了钝化施主缺陷、改善薄膜缺陷态的作用. 同时, 研究表明, 后掺Na工艺中, NaF必须依靠外界能量辅助才能扩散进Cu(In,Ga)Se₂内部, 实验结果证实, 只有衬底温度达到350 ℃以上时, 掺入的NaF才能较好地改善薄膜特性. 最终经掺Na工艺的优化, 得到低温工艺制备的柔性聚酰亚胺衬底器件效率达10.4%.     

High temperature thermoelectric properties of highly c-axis oriented Bi2Sr2Co2Oy thin films fabricated by pulsed laser deposition

High-temperature thermoelectric transport property measurements have been performed on the highly c-axis oriented Bi2Sr2Co20v thin films prepared by pulsed laser deposition on LaA1Oa （001）. Both the electric resistivity p and the seebeck coefficient S of the film exhibit an increasing trend with the temperature from 300 K-1000 K and reach up to 4.8 m. cm and 202 V/K at 980 K, resulting in a power factor of 0.85 mW/mK which are comparable to those of the single crystalline samples. A small polaron hopping conduction can be responsible for the conduction mechanism of the film at high temperature. The results demonstrate that the Bi2Sr2Co2Oy thin film has potential application has high temperature thin film thermoelectric devices,