Nanoscale patterned electrodeposition of metals on flat substrates has become a topic of great interest both scientifically and technologically in recent years. Here, we demonstrate the self-organized growth of extended arrays of parallel nanoscale copper wires on flat glass chips from an ultra-thin aqueous electrolyte layer. Regular, periodic patterns of copper nanowires with diameters in the range of 40 nm-400 nm were grown, forming parallel arrays of alternating lines of copper and cuprous oxide at periodicities down to approx. 80 nm, depending on the deposition parameters such as voltage and pH. The resulting multiline films are investigated with respect to their structure and electrical properties using Electrical Force Microscopy, Scanning Electron Microscopy and Scanning Auger Electron Spectroscopy. The results of the experiments show a strongly anisotropic behavior of the electrical properties of multiline nanostructures corresponding to their strongly anisotropic geometry.

Sheng Zhong;Patrik Dupeyrat;Roland Gröger;牧 王;Thomas Koch;Thomas Schimmel

Journal of Nanoscience and Nanotechnology

2010-9

Hierarchically self-assembled hydroxyapatite (HAP) and organic composite resembling tooth enamel has potential biological and surgery applications. Controlled fabrication remains a great challenge. In this work, large-scale translucent hydroxyapatite (HAP) and chondroitin sulfate (ChS) composite films are fabricated by a unique solution-air interface method. The products excellently represent the characteristic hierarchical "prism" structure of tooth enamel. We demonstrate that the films are formed by evaporation-induced nucleation at the interface and subsequent self-confined spherulitic growth. The supersaturation at the interface increases upon solution evaporation, and the local high supersaturation triggers preferred nucleation there. The spherulitic growth is regulated by ChS and limited by the interfaces between the spherulites as well as the solution and air. Consequently, HAP/ChS films with the hierarchically self-assembled prism structure are produced. We emphasize that the mechanism can excellently explain the unique prism structure formation in tooth enamel and in self-assembled nanorod arrays. The findings provide insight into the fundamentals of hierarchical assembly in nature (e.g., assembly of tooth enamel). Moreover, the approach could be expanded to design and grow other sophisticated functional structures.

Yifei Xu;Guobin Ma;Xiyan Wang;牧 王

Crystal Growth and Design

2012-7-3

We report a hydrodynamic instability related to the periodic growth of needle-like crystals observed in thin aqueous-solution films of Ba(NO3)2 with the free surface in isothermal conditions. The oscillation of the aqueous-solution film, in which the solution film separates, and re-contacts with the needle-like crystal periodically, has been investigated using in situ observations with interference-contrast microscopy. Our experiments indicate that this phenomenon derives from the interplay of the Marangoni effect and the wetting effect.

牧 王;Nai Ben Ming

Physical Review A

1991

Magnetic structures with controlled domain wall pattern may be applied as potential building blocks for three-dimensional magnetic memory and logic devices. Using a unique electrochemical self-assembly method, we achieve regular single-crystalline cobalt filament arrays with specific geometric profile and crystallographic orientation, and the magnetic domain configuration can be conveniently tailored. We report the transition of periodic antiparallel magnetic domains to compressed vortex magnetic domains depending on the ratio of height to width of the wires. A "phase diagram" is obtained to describe the dependence of the type of magnetic domain and the geometrical profiles of the wires. Magnetoresistance of the filaments demonstrates that the contribution of a series of 180 domain walls is over 0.15% of the zero-field resistance ρ(H=0). These self-assembled magnetic nanofilaments, with controlled periodic domain patterns, offer an interesting platform to explore domain-wall-based memory and logic devices.

Fei Chen;Fan Wang;Fei Jia;Jingning Li;Kai Liu;Sunxiang Huang;Zhongzhi Luan;Di Wu;Yanbin Chen;Jianmin Zhu;茹雯 彭;牧 王

Physical Review B

2016-2-3

Traditional microlens focuses the beam with spherical convex surface, which achieves high transmission by restraining the scattering loss yet brings spherical aberration and chromatic aberration. While recently-developed metalens, which relies on phase modulation by elaborately designing local resonators, has realized diffraction-limited focusing. Yet, the issues of scattering loss of nanoresonators and chromatic aberration remain serious. Here, the design strategies of both metalens and traditional microlens are combined by introducing accurate phase modulation for the wavefront into microlens designing; and a broadband, polarization-independent, and achromatic microlens with high efficiency is realized. With concentric-circular polymer (phenolic resin) terrace as basic building blocks, a precise thickness profile is constructed and a high-index polymer microlens is formed by electron-beam grayscale lithography. The diffraction-limited focusing possesses less than 5% change of focal length when the wavelength varies from 425 to 700 nm, showing the full-color imaging and detection with a focusing efficiency of 80% (at 700 nm wavelength). Moreover, the rotation symmetry of the microstructures of microlens makes it work for arbitrary polarization. The achromatic imaging capability of the microlens is verified by whitelight imaging. It is expected that this high-efficiency polarization-independent broadband achromatic polymer microlens may have wide applications in high-efficient imaging and sensing.

Bo Xiong;Jia Nan Wang;茹雯 彭;Hao Jing;Ren Hao Fan;Dong Xiang Qi;Fei Chen;牧 王

Advanced Optical Materials

2020

Polycrystalline ferroelectric SrBi₄Ti₄O₁₅ thin films were prepared on Pt-coated silicon substrates by pulsed laser deposition. Structures of the films were analyzed by x-ray diffraction, atomic force microscopy (AFM) and scanning electron microscopy. At an applied field of 275 kV/cm, the films showed good hysteresis loops with remnant polarization (P_r), saturated polarization (P_s) and coercive field (E_c) of 3.11 μC/cm², 7.81 μC/cm² and 68 kV/cm, respectively. At 120 kV/cm switching pulse field, fatigue tests were carried out systematically by varying the switching pulsewidth with a fixed duty cycle and with a fixed switching period, respectively. A gradual increase followed by an abrupt increase of the fatigue rate was observed with the increase of the switching pulsewidth. Field-induced defect diffusion was used to explain the results.

善涛 张;Bin Yang;Yan Feng Chen;Zhi Guo Liu;Xiao Bo Yin;Yuan Wang;牧 王;Nai Ben Ming

Journal of Applied Physics

2002-2-15

Straight copper wire arrays are electrochemically deposited on a silicon substrate without utilizing additives or templates. To suppress the influence of the factors which arouse the ramification of the copper electrodeposit, an ultrathin electrochemical deposition system and an initially homogeneous electric field are used. The width of the copper wires may vary from about 200 nm to about 1.5 μm depending on the control parameters. The microstructure of the copper wires and their electric resistance after vacuum-annealing at 200°C are studied. We suggest that this self-organized copper electrodeposition is helpful in gaining an understanding of the formation of dense-branching morphology. It also implies the potential application in microelectronics.

Sheng Zhong;牧 王;Xiao Bo Yin;Jian Ming Zhu;茹雯 彭;Yuan Wang;Nai Ben Ming

Journal of the Physical Society of Japan

2001-6

In an assembly of double-layered metallic U-shaped resonators with two resonant frequencies ωH and ωL, the effective induced electric and magnetic dipoles, which originate from the specific distribution of induced surface electric current upon the illumination of incident light, are collinear at the same frequency. Consequently, for left circularly polarized incident light, negative refractive index occurs at ωH, whereas for right circularly polarized incident light it occurs at ωL. We suggest that this design provides a new example to apply chiral structures to tune the electromagnetic properties, and could be enlightening in exploring chiral metamaterials.

Xiang Xiong;Wei Hua Sun;Yong Jun Bao;牧 王;茹雯 彭;Cheng Sun;Xiang Lu;Jun Shao;志锋 李;Nai Ben Ming

Physical Review B - Condensed Matter and Materials Physics

2010-2-23

In this work, we demonstrate broadband integrated polarization rotator (IPR) with a series of three-layer rotating metallic grating structures. This transmissive optical IPR can conveniently rotate the polarization of linearly polarized light to any desired directions at different spatial locations with high conversion efficiency, which is nearly constant for different rotation angles. The linear polarization rotation originates from multi-wave interference in the three-layer grating structure. We anticipate that this type of IPR will find wide applications in analytical chemistry, biology, communication technology, imaging, etc.

Ren Hao Fan;Dong Liu;茹雯 彭;Wen Bo Shi;Hao Jing;Xian Rong Huang;牧 王

Optics Express

2018-1-8

Metamaterials constructed with chiral units can be either optically active or nonactive depending on the spatial configuration of the building blocks. For a class of chiral units, their effective induced electric and magnetic dipoles, which originate from the induced surface electric current upon illumination of incident light, can be collinear at the resonant frequency. This feature provides significant advantage in designing metamaterials. In this paper we concentrate on several examples. In one scenario, chiral units with opposite chiralities are used to construct the optically nonactive metamaterial structure. It turns out that with linearly polarized incident light, the pure electric or magnetic resonance (and accordingly negative permittivity or negative permeability) can be selectively realized by tuning the polarization of incident light for 90°. Alternatively, units with the same chirality can be assembled as a chiral metamaterial by taking the advantage of the collinear induced electric and magnetic dipoles. It follows that for the circularly polarized incident light, negative refractive index can be realized. These examples demonstrate the unique approach to achieve certain optical properties by assembling chiral building blocks, which could be enlightening in designing metamaterials.

Xiang Xiong;Shang Chi Jiang;Yu Hui Hu;Jun Ming Zhao;Yi Jun Feng;茹雯 彭;牧 王

AIP Advances

2012