铁电态-顺电态双层薄膜的高介电调谐

基于Landau-Devonshire自由能理论建立了热力学模型,对生长在(001)SrTiO3衬底上的PbZr0.4Ti0.6O3(PZT)/SrTiO3(STO)双层异质外延结构铁电薄膜以及不受约束的双层薄膜的介电响应与调谐率进行了研究。结果表明,在两层薄膜为无约束的自由薄膜情况下,STO厚度占双层薄膜总厚度的百分比为30%时,相对介电响应达到最大值约3.3×105,当两薄膜为异质外延结构时,其百分比为51%时,相对介电响应达到最大值约4×105。同时,调谐率还随外加电场的增大而增大,在临界百分比时,调谐率可达到约99%。     

Bi_(1.5)Zn_(1.0)Nb_(1.5)O_7/Ba_(0.5)Sr_(0.5)TiO_3复合薄膜介电性能的频率特性研究

采用射频磁控溅射法在蓝宝石基片上制备了Bi1.5Zn1.0Nb1.5O7(BZN)/Ba0.5Sr0.5TiO3(BST)双层复合薄膜,并研究了该薄膜在100 kHz~6 GHz频率范围内的介电性能。研究结果表明,BZN/BST复合薄膜的介电性能具有良好的频率稳定性。该复合薄膜的介电常数在研究的频率范围内基本与频率无关;其介电损耗在频率低于1 GHz时与频率无关,在频率高于1 GHz时随频率的上升而略微增大;薄膜在研究的频率范围内具有稳定的介电调谐率。     

液体介质三维光子晶体禁带可调性能研究

研究了宽频折射率可调液体介质在三维光子晶体上的应用。设计了完美结构的液体光子晶体,采用 平面波展开法和有限时域差分法研究了液体介质的介电常数对光子晶体带隙的影响规律;采用光固化快速成型技 术制造了完美结构光子晶体模型,通过灌注不同介电常数的液体介质,发现液体光子晶体的电磁带隙频率随液体媒 介介电常数的升高而向低频移动,其禁带相比于传统液晶可调光子晶体有所拓宽。     

面向全光信号处理的三角形光脉冲产生技术

三角形光脉冲在时域范围内具有前后沿恒定变化特性,使得其在全光信息处理领域获得了广泛应用。主要针对目前国内外提出的两类三角形光脉冲产生方法：（1）电光法;（2）全光法,简单介绍了几种具体的获得稳定三角形光脉冲串的方法,从所产生三角形脉冲的重复频率、脉冲宽度以及系统稳定性、实验优缺点等方面进行分类比较,并重点介绍了一种利用连续波光调制结合色散所致功率衰落的脉冲生成方法。     

Preparation and dielectric properties of compositionally graded （Ba, Sr）TiO3 thin film by sol-gel technique

Compositional graded BaxSr1-xTiO3 （x=0.6, 0.7, 0.8, 0.9, 1.0） （BST） thin films （less than 400 nm） were fabricated on Si and Pt/Ti/SiO2/Si substrates by sol-gel technique. A special heating treatment was employed to form the uniform composition gradients at 700 ℃. The microstructures of the films were studied by means of X-ray diffraction, atomic force microscope and field emission scanning electron microscopy. The results show that the films have uniform and crack-free surface morphology with perovskite structure phase. The small signal dielectric constant （εr） and dielectric loss （tanδ） are found to be 335 and 0.045 at room temperature and 200 kHz. The dielectric properties change significantly with applied dc bias, and the graded thin film show high tunability of 42.3% at an applied field of 250 kV/cm. All the results indicate that the graded BST thin films prepared by sol-gel technique have a promising candidate for microelectronic device.     

Tunable mid-infrared patch antennas based on VO2 phase transition

The metal-insulator phase transition in vanadium oxide makes it an attractive material for developing reconfigurable infrared optoelectronic components. In this paper, we present a tunable mid-infrared plasmonic patch antenna array based on vanadium oxide. The antennas consist of a circular gold patch array separated from a metallic ground plane by a film of vanadium dioxide. As the insulator-to-metal phase transition is thermally triggered, the resonances of the antenna array redshift with reduced absorbance before they are eventually switched off. The measured tuning range is about 10% of the resonant frequency, and the modulation depth in reflection is as high as 50%. A hysteresis loop in the tuning behavior is also observed. The XRD and XPS characterizations reveal a polycrystalline and multi-phase vanadium oxide. Our demonstrated tunable patch antennas hold promise for optical switching and modulating in mid-infrared applications.     

Curvature‐Controlled Wrinkling Surfaces for Friction

Topographical patterns endow material surfaces with unique and intriguing physical and chemical properties. Spontaneously formed wrinkling has been harnessed to generate surface topography for various functionalities. Despite promising applications in biomedical devices and robot engineering, the friction behavior of wrinkling on curved surfaces remains unclear. Herein, wrinkled surfaces are induced by sputtering metals on soft polymer microspheres. The wrinkle morphologies and length scales can be controlled precisely by tailoring the microsphere radius (substrate curvature) and film thickness. The wrinkled surfaces exhibit controlled friction property, depending on the wrinkling patterns and length scales. An increase in friction force with increasing surface roughness is generally found for dimple patterns and labyrinth patterns. The dimple patterns show the lowest friction due to strong curvature constraint. The herringbone patterns exhibit apparent friction anisotropy with respect to topographic orientation. These results will guide future design of wrinkled surfaces for friction by harnessing substrate curvature.     

Energy storage density and tunable dielectric properties of BaTi0.85Sn0.15O3/MgO composite ceramics prepared by SPS

(100-x) wt.% BaTi_0.85Sn_0.15O₃–x wt.% MgO (BTS/MgO) composite ceramics were prepared by spark plasma sintering (SPS) technology. Phase constitution, microstructure, dielectric and electrical energy storage properties of BTS/MgO composite ceramics were investigated. The samples prepared by SPS had smaller grain size and presented layer-plate substructure. Dielectric permittivity and dielectric loss of BTS/MgO composite ceramics decreased significantly with the content of MgO increasing, and dielectric tunability maintained a relatively high value (>45%). Meanwhile, the dielectric breakdown strength was improved when addition of MgO in BTS matrix, which resulted in a significant improvement of energy storage density. The high dielectric breakdown strength of 190 kV/cm, energy storage density of 0.5107 J/cm³ and energy storage efficiency of 92.11% were obtained in 90 wt.% BaTi_0.85Sn_0.15O₃–10 wt.% MgO composite ceramics. Therefore, BTS/MgO composites with good tunable dielectric properties and electrical energy storage properties could be exploited for energy storage and phase shifter device applications.     

ZASP玻璃荧光体的激发波长依赖性及Dy3＋掺杂的荧光色彩调谐

采用熔融法制备了锌铝锑磷酸盐(ZASP)玻璃荧光 体,研究了其荧光色彩对激发波长的依赖性和Dy³⁺掺杂的色彩调谐作用。短波紫外(U VC)和中波紫外(UVB)激发下,ZASP基质玻璃 呈现Sb³⁺的宽谱带发射,色彩位于蓝白光和蓝光区域。差异性光谱行为表明,玻璃中 存在异质 性的Sb³⁺发光中心,导致玻璃荧光对激发波长产生依赖行为。Dy³⁺引入ZASP玻 璃后,产生归属 于Dy³⁺的约484nm波长窄带发 射,其在UVC和UVB激发下的发光有效性相当程度上归因于Sb ³⁺到Dy³⁺的能量传递。Dy³⁺的暖色成分使ZASP玻璃荧光总体上从蓝白区 向白光区移动,同时 也对荧光的激发波长依赖趋势产生显著影响,丰富了荧光发射色彩的多样性,为高质量荧光 器件的研发提供了可能。     

Tunable Optical Mode Ferromagnetic Resonance in FeCoB/Ru/FeCoB Synthetic Antiferromagnetic Trilayers under Uniaxial Magnetic Anisotropy

Ferromagnetic resonance (FMR) is one of the most important characteristics of soft magnetic materials, which practically sets the maximum operation speed of these materials. There are two FMR modes in exchange coupled ferromagnet/nonmagnet/ferromagnet sandwich films. The acoustic mode has relatively lower frequency and is widely used in radio‐frequency/microwave devices, while the optical mode is largely neglected due to its tiny permeability even though it supports much higher frequency. Here, a realistic method is reported to enhance the permeability in the optical mode to an applicable level. FeCoB/Ru/FeCoB trilayers are carefully engineered with both uniaxial magnetic anisotropy and antiferromagnetic interlayer exchange coupling. This special magnetic structure exhibits a high optical mode frequency up to 11.28 GHz and a maximum permeability of 200 at resonance. An abnormally low inverse switch field (<200 Oe, less than 1/5 of the single layer) is observed which can effectively switch the system from optical mode with higher frequency into acoustic mode with lower frequency. The optical mode frequency and inverse switch field can be controlled by tailoring the interlayer coupling strengths and the uniaxial anisotropy fields, respectively. The tunable optical mode resonance thus can increase operation frequency while reduce operation field overhead in FMR based devices.