© 2017 American Physical Society. Oxygen partial pressure during vapor phase growth plays a critical role in determining the microstructure and other properties of oxides. However, it remains unclear how it affects the growth mechanism on the atomic scale. In this article, we take ZnO(0001) surface as a model case and demonstrate the influence of oxygen partial pressure on surface adsorption and diffusion of intrinsic adatoms by first-principles calculations. Two typical reconstructions of ZnO(0001) surface, denoted as (2×2)-O and n3, are utilized to model the oxygen-rich condition and oxygen-poor condition, respectively. The (2×2)-O refers to the surface with an oxygen adatom in a (2×2) supercell, while the n3 stands for the surface with triangular pits of edge length n=3. We find that under the oxygen-rich condition in which (2×2)-O forms, adsorption of the O adatom is always more energetically favorable than the Zn adatom. Under oxygen-poor condition in which n3 forms, however, the preferential adsorbate changes from O adatom to Zn adatom as the oxygen partial pressure decreases. The O adatom is less diffusive than the Zn adatom on both reconstructed surfaces. The diffusion barriers of both Zn and O on n3 are higher than their counterparts on (2×2)-O. Insufficient surface diffusion leads to a high nucleation rate; therefore, a second-layer nucleus may form before the completion of the first-layer on n3. It suggests that ZnO growth under oxygen-poor condition, in comparison with the oxygen-rich condition, is more likely to proceed with the three-dimensional island growth mode and result in a rougher surface.

Ruan Qiyuan;Ye Jingchen;Shu Da-Jun;Wang Mu

Physical Review B

2017

© The Royal Society of Chemistry 2017. Exploring new initiation functionalities is critical for the design of efficient photoinitiators applied in two-photon polymerization. In this paper, we present a facile and effective synthesis strategy to construct silyl-based two-photon initiators (2PIs) containing nitro groups as electron acceptors, alkylamines as electron donors and double bonds as conjugation bridges. Steady-state absorption, time-resolved fluorescence, and ns-transient absorption were employed to quantitatively investigate the photo-physics and -chemistry of the 2PIs. The results showed that the photophysical and photochemical behavior of these 2PIs is marginally affected by the introduction of a silyl group, but strongly depends on solvent polarity. The nonlinear absorption spectra over a broad spectral range were determined via two-photon-induced fluorescence, revealing maximum two-photon cross sections of ∼90 GM. In two-photon polymerization structuring tests, the 2PIs can be employed to build fine 3D microstructures with a resolution of ∼280 nm. The acrylate formulations containing novel 2PIs exhibit a comparable threshold energy and ideal processing windows as commercial photoresists IP-L, which have been specifically designed for Nanoscribe's laser lithography systems.

Li Zhiquan;Hu Peng;Zhu Guigang;Liu Xiaoya;Liu Ren;Rosspeintner Arnulf;Hu Yuansheng;Xiong Xiang;Peng Ruwen;Wang Mu

Polymer Chemistry

2017

© 2018 Optical Society of America. The efficiency of photoluminescence (PL) of transition-metal dichalcogenides (TMDCs) significantly influences their practical applications in optoelectronic devices. In this work, we study multiple coupling among excitons, surface plasmons, and optical modes, and their effects on PL of monolayer MoS 2 atop plasmonic nanohole arrays. Under the illumination of visible light, strong intensity enhancement of PL from monolayer MoS 2 is observed in the system. We further demonstrate that there exist excitons induced from MoS 2 , localized and propagating surface plasmons excited from nanoholes, and optical modes related to the incident laser. And hybrid coupling of those modes significantly improves the PL signals and also lightens the PL images of monolayer MoS 2 . This work provides a unique way to improve the emission of monolayer TMDCs. The atomically thin TMDCs coupled to plasmonic metamaterials are also promising for advanced applications such as ultrathin integrated light-emission diodes, photodetection, and nanolasers.

Shi Wen-Bo;Zhang Lei;Zhang Rui-Li;Zhu Yingying;Zhang Li-Heng;Peng Ruwen;Fan Ren-Hao;Wang Mu;Wang Di;Bao Wenzhong

Optics Letters

2018

The morphology of iron electrodeposit is shown to relate closely to the pH of the electrolyte solution. Macroscopically, depending on the strength of the interbranch convection, which is associated with the concentration of [Formula Presented] in the electrolyte, the deposit morphology varies from treelike pattern to meshlike pattern and dense-branching morphology. Microscopically the deposit is ramified and dense-branching at lower concentration of [Formula Presented] while it becomes relatively smooth and stringy at higher [Formula Presented] concentration. The symmetry of the convective vortices on the two sides of the growing tip is observed to decide the growth behavior of the tip. We suggest that [Formula Presented] influences the pattern formation and pattern selection in the electrodeposition of iron from [Formula Presented] solution by either initiating interbranch convection or changing the effective interfacial energy of the deposit and the electrolyte.

克勤 张;牧 王;Sheng Zhong;Guo Xin Chen;Nai ben Ming

Physical Review E

2000

[Figure Presented] Periodic magnetic domains on cobalt filaments can be stabilized by nanoscale corrugations on the surface, which are spontaneously generated by a unique electrodeposition method. The type of magnetic domains varies from anti-parallel single domains to vortex domains depending on the ratio of the spatial periodicity of the corrugations and the filament width (see figure), and can be experimentally tuned.

Xiao Ping Huang;Zi Liang Shi;牧 王;Makoto Konoto;豪慎 周;Guo Bin Ma;Di Wu;茹雯 彭;Nai Ben Ming

Advanced Materials

2010-6-25

We studied the photonic localization of one-dimensional (Formula presented)-component Fibonacci structures (KCFS’s), in which (Formula presented) different intervals are ordered according to a substitution rule. By using a transfer-matrix method, the optical transmission through KCFS’s is obtained. It is demonstrated that the transmission coefficient has a rich structure, which depends on the wavelength of light and the number of different incommensurate intervals (Formula presented). For the KCFS’s with an identical (Formula presented), by increasing the layer number of the sequences, more and more transmission dips develop and some of them approach zero transmission, which may finally make a one-dimensional photonic band gap. For a series of finite KCFS’s, by increasing the number of different incommensurate intervals (Formula presented), the total transmission over the spectral region of interest decreases gradually and the width of photonic band gap becomes larger. This property may be useful in the design of the high-performance optical and electronic devices. As for the infinite KCFS’s, the transmission coefficient is singularly continuous and multifractal analysis is employed to characterize the transmission spectra. A dimensional spectrum of singularities associated with the transmission spectrum (Formula presented) demonstrates that the light propagation in the KCFS’s presents scaling properties and hence shows a genuine multifractality.

茹雯 彭;牧 王;A. Hu;S. Jiang;G. Jin;D. Feng

Physical Review B - Condensed Matter and Materials Physics

1998

In this review, we present our recent work on making structured metals transparent for broadband electromagnetic waves and acoustic waves via excitation of surface waves. First, we theoretically show that one-dimensional metallic gratings can become transparent and completely antireflective for extremely broadband electromagnetic waves by relying on surface plasmons or spoof surface plasmons. Second, we experimentally demonstrate that metallic gratings with narrow slits are highly transparent for broadband terahertz waves at oblique incidence and high transmission efficiency is insensitive to the metal thickness. Further, we significantly develop oblique metal gratings transparent for broadband electromagnetic waves (including optical waves and terahertz ones) under normal incidence. In the third, we find the principles of broadband transparency for structured metals can be extended from one-dimensional metallic gratings to two-dimensional cases. Moreover, similar phenomena are found in sonic artificially metallic structures, which present the transparency for broadband acoustic waves. These investigations provide guidelines to develop many novel materials and devices, such as transparent conducting panels, antireflective solar cells, and other broadband metamaterials and stealth technologies.

Ren Hao Fan;茹雯 彭;Xian Rong Huang;牧 王

Annals of Physics

2015-7-1

SrBi₂Ta₂O₉(SBT) films were prepared by metalorganic decomposition technique. The films were obtained by spin-on pyrolysis of the precursor solutions on various substrates and then annealed at 550-850°C in dry oxygen, wet oxygen, or Ar. Effects of precursor solution concentration, anneal temperature, anneal atmosphere, substrate and Ar ion sputtering on the microstructure, morphology and electrical properties were investigated by means of x-ray diffraction, scanning electron microscope, atomic force microscope, x-ray photoelectron spectroscopy, and electrical measurements. The results indicated the grain size, and the remnant polarization (Pr) increased with increasing the anneal temperature up to 800°C and the significant hysteresis loop could be obtained only after anneal above 700°C. At 850°C, the pyrochlore phase and other secondary phases were observed along with the SBT phase, leading to the decreasing Pr and dielectric constant. In addition, the development of crystalline phase and electrical properties were affected by anneal atmosphere. When annealed in Ar at 750°C, the layered SBT structure was destroyed with evident Bi loss. As though the original structure could be restored basically by subsequent adequate O₂ anneal, the electrical properties were deteriorated seriously due to the shorted capacitor. Wet oxygen anneal evidently deformed the morphology and the hysteresis loop. This was attributed to the effect of possible produced slight H₂ due to the reaction between H₂O and residual carbonaceous in films under Pt catalyst. Substrates also played an important role on film crystallinity. The films deposited on Si, SrTiO₃, and crystal quartz at 750°C had a layered perovskite polycrystalline structure while the films on fused quartz exhibited poor crystalline nature even after 800°C anneal and films on NaCl showed (200)-predominant orientation of SBT phase with some pyrochlore. In addition, Ar ion sputtering might lead to the severe Bi and oxygen deficiency in the surface of the sputtered film.

Aidong Li;镝 吴;Huiqin Ling;涛 于;牧 王;Xiaobo Yin;Zhiguo Liu;Naiben Ming

Journal of Applied Physics

2000-7-15

Interfacial growth from vapor has been extensively studied. However, a straightforward picture of the growth mode under different growth conditions is still lacking. In this paper, we develop a comprehensive interfacial growth theory based on the stochastic approach. Using a critical interisland separation, we construct a general phase diagram of the growth modes. It has been revealed that if the Ehrlich-Schwoebel barrier EES is smaller than a critical value, the interfacial growth proceeds in a layer-by-layer (LBL) mode at any deposition rate. However, if EES is larger than the critical value, LBL growth occurs only at very small or very large deposition rates relative to the intralayer hopping rate, and multilayer (ML) growth occurs at a moderate deposition rate. Experiments with zinc oxide growth by chemical vapor deposition have been designed to qualitatively demonstrate the theoretical model. By changing the flux of the carrier gas (nitrogen gas) in chemical vapor deposition, we realize LBL, ML, and then reentrance of LBL homoepitaxial growth of ZnO successively. Moreover, we find that surface kinetics of ZnO is suppressed by decreasing oxygen partial pressure by comparing the experimental observations and theoretical models, which is supported by our recent first-principles calculations. Since the influence of the substrate and the growth species on growth can approximately be represented by binding energy and surface kinetics, we suggest that the phase diagram is essential for interfacial growth of different materials by vapor deposition.

大军 舒;Xiang Xiong;Ming Liu;牧 王

Physical Review B

2017-9-7

Guipeng Luo;Haiming Wu;牧 王;世宁 祝;延青 陆;Zhiguo Liu;Yu Wei;Naiben Ming

Chinese Science Bulletin

1997