STO/YBCO薄膜的制备及介电性能研究

采用脉冲激光沉积技术,在(100)LaAlO3单晶基片上生长SrTiO3/Y1Ba2Cu3O7-x(STO/YBCO)多层薄膜。XRD分析表明:YBCO薄膜和STO薄膜均为C轴取向,STO(002)/YBCO(006)衍射峰摇摆曲线半高宽为0.73°。AFM分析表明,STO/YBCO多层薄膜表面平整、均匀,在77K,100kHz的测试条件下,STO薄膜介电损耗tgδ<10-2,在53.6kV/cm电场作用下,介电常数的相对变化为38%。     

Simultaneous Fabrication of Very High Aspect Ratio Positive Nano‐ to Milliscale Structures

A simple and inexpensive technique for the simultaneous fabrication of positive (i.e., protruding), very high aspect (>10) ratio nanostructures together with micro‐ or millistructures is developed. The method involves using residual patterns of thin‐film over‐etching (RPTO) to produce sub‐micro‐/nanoscale features. The residual thin‐film nanopattern is used as an etching mask for Si deep reactive ion etching. The etched Si structures are further reduced in size by Si thermal oxidation to produce amorphous SiO₂, which is subsequently etched away by HF. Two arrays of positive Si nanowalls are demonstrated with this combined RPTO‐SiO₂‐HF technique. One array has a feature size of 150 nm and an aspect ratio of 26.7 and another has a feature size of 50 nm and an aspect ratio of 15. No other parallel reduction technique can achieve such a very high aspect ratio for 50‐nm‐wide nanowalls. As a demonstration of the technique to simultaneously achieve nano‐ and milliscale features, a simple Si nanofluidic master mold with positive features with dimensions varying continuously from 1 mm to 200 nm and a highest aspect ratio of 6.75 is fabricated; the narrow 200‐nm section is 4.5 mm long. This Si master mold is then used as a mold for UV embossing. The embossed open channels are then closed by a cover with glue bonding. A high aspect ratio is necessary to produce unblocked closed channels after the cover bonding process of the nanofluidic chip. The combined method of RPTO, Si thermal oxidation, and HF etching can be used to make complex nanofluidic systems and nano‐/micro‐/millistructures for diverse applications.     

Perpendicular exchange bias in IrMn/Pt/[Co/Pt]3 multilayers with cone magnetization

The perpendicular exchange bias and magnetic anisotropy were investigated in IrMn/Pt/[Co/Pt]₃ multilayers through the analysis of in-plane and out-of-plane magnetization hysteresis loops. A phenomenological model was used to simulate the in-plane curves and the effective perpendicular anisotropies were obtained employing the area method. The canted state anisotropy was introduced by taking into account the first and second uniaxial anisotropy terms of the ferromagnet with the corresponding uniaxial anisotropy direction allowed to make a nonzero angle with the film's normal. This angle, obtained from the fittings, was of approximately 15° for IrMn/[Co/Pt]₃ film and decreases with the introduction of Pt in the IrMn/Pt/ [Co/Pt]₃ system, indicating that the Pt interlayer leads to a predominant perpendicular anisotropy. A maximum of the out-of-plane anisotropy was found between 0.5 and 0.6 nm of Pt, whereas a maximum of the perpendicular exchange bias was found at 0.3 nm. These results are very similar to those obtained for IrMn/Cu/[Co/Pt]₃ system; however, the decrease of the exchange bias with the spacer thickness is more abrupt and the enhacement of the perpendicular anisotropy is higher for the case of Cu spacer as compared with that of Pt spacer. The existence of a maximum in the perpendicular exchange bias as a function of the Pt layer thickness was attributed to the predominance of the enhancement of exchange bias due to more perpendicular Co moment orientation over the exponential decrease of the ferromagnetic/antiferromagnetic exchange coupling and, consequently, of the exchange-bias field.     

BST/BZT/BST多层薄膜结构与性能研究

利用脉冲激光沉积法在LaNiO3/LaAlO3(001)基片上生长了Ba0.6Sr0.4TiO3(BST)和Ba(Zr0.2Ti0.8)O3(BZT)单层薄膜,以及Ba(Zr0.2Ti0.8)O3/Ba0.6Sr0.4TiO3/Ba(Zr0.2Ti0.8)O3(BZT/BST/BZT)多层薄膜.X射线衍射(XRD)分析发现,BST、BZT和LNO薄膜都具有高度的(00l)取向.原子力显微镜(AFM)显示三种样品表面光滑无裂纹,晶粒尺寸和表面粗糙度相当.电容测试表明,相对BST、BZT单层薄膜,多层薄膜具有最大的品质因数42.07.表明多层薄膜在微波应用中具有很大的潜力.     

Multifunctional FeCo/TiN Multilayer Thin Films with Combined Magnetic and Protective Properties

Coatings with thicknesses ranging from a few nanometer up to several micrometer produced by physical vapor deposition (PVD) processes have been established in engineering technologies since the early 1980s. In particular, magnetron sputtered wear resistance coatings are industrially established and capable to enhance tool lifetimes significantly. However, in cases where optical inspection of a coating in use is not possible, an intrinsic sensor function of the film would be beneficial. Therefore, the development of wear resistant coatings with an integrated sensor functionality based on the insertion of a magnetoelastic ferromagnetic phase is suggested. In combination with appropriate read‐out electronics such a film system would be ready for online monitoring of the coatings' actual state (e.g., strain, temperature, volume loss). This paper focuses on the development of wear resistance coatings which simultaneously supply beneficial mechanical properties as well as ferromagnetic properties optimized for online non‐contact read‐out applications. Multilayer coatings obtained through alternate stacking of magnetron sputtered TiN and FeCo layers with a nominal total thickness of 1000 nm were produced as a model system meeting the above conditions. The bilayer period was varied down to 2.6 nm while the individual layer thickness ratio t_TiN/t_FeCo was determined by the deposition rates and maintained constant at a value of about 3/1. The films were vacuum annealed ex situ in a static magnetic field subsequent to the deposition. The constitution of the as‐deposited and annealed coatings as well as their mechanical (nanohardness, Young's modulus) and magnetic properties (magnetization hysteresis, frequency‐dependent permeability) are described. Finally, the suitability of the coatings for the use in remote‐interrogable wear sensor applications is briefly discussed.     

Vertical geometry ultraviolet photodetectors with high photosensitivity based on nanocrystalline TiO2 films

Porous and dense nanocrystalline TiO₂ films grown on F:SnO substrates used in vertical geometry ultraviolet photodetectors are investigated. Compared with a detector with a dense nanocrystalline TiO₂ film (D-detector), a detector with a porous nanocrystalline TiO₂ film (P-detector) exhibits one order of magnitude higher responsivity due to a light scattering effect. In addition, the vertical geometry detectors show a fast response time. The rise time and decay time of the P-detector and D-detector are 19 and 136 ns, and 14 and 100 ns, respectively, which are six orders of magnitude faster than those of lateral geometry detectors based on dense nanocrystalline TiO₂ films. It is a result of a decreased mobility fluctuation.     

导波光学技术在测量“夹心”光学薄膜各向异性方面的应用:不同膜堆结构中同类薄膜特性的比较

本文介绍了应用导波光学技术测量“夹心”光学薄膜的特征参数的方法,并研究了比较简单的结构(由二、三层膜组成),检测到了高折射率薄膜的各向异性。从不同结构的膜系中的同类薄膜的比较中发现了单层膜与膜堆中对应的“夹心”膜之间在折射率和各向异性上的差别。