Effect of bias treatment in the CVD diamond growth on Ir(001)

The effect of bias treatment (BT) on direct-current plasma CVD diamond growth has been studied in situ by X-ray photoelectron diffraction (XPD) together with LEED and XPS. It was found that C 1s XPD patterns from the sample after BT are similar to those of diamond (001). Coverage of carbon after BT is several tens of ML when BT is very successful. However, LEED shows no diamond (001) spots for the sample after BT. These apparently contradictory findings are explained by the sizes of the diamond (001) crystallites, which, after BT, are large enough to produce C 1s XPD patterns of diamond, but too small to have coherent interference spots in LEED. It is concluded from this and other information that BT in a DC plasma creates hetero-epitaxial diamond crystallites a few nm or less. These diamond crystallites may be related to the atomically abrupt diamond/Ir interfaces of DC plasma CVD-grown samples revealed by TEM [A. Sawabe, H. Fukuda, T. Suzuki, Y. Ikuhara, T. Suzuki, Surf. Sci. 467 (2000) L845].     

GaN在Si(001)上的ECR等离子体增强MOCVD直接生长研究

研究了用电子回旋共振(ECR)等离子体增强金属有机物化学气相沉积(PEMOCVD)技术在Si(001)衬底上,低温(620～720℃)下GaN薄膜的直接外延生长及晶相结构.高分辨透射电镜(HRTEM)和X射线衍射(XRD)结果表明:在Si(001)衬底上外延出了高度c轴取向纤锌矿结构的GaN膜,但在GaN/Si(001)界面处自然形成了一层非晶层,其两个表面平坦而陡峭,厚度均匀(≈2nm).分析认为,在初始成核阶段N与Si之间反应所产生的这层SixNy非晶层使GaN的β相没有形成.XRD和原子力显微镜(AFM)结果表明,衬底表面的原位氢等离子体清洗,GaN初始成核及后续生长条件对GaN膜的晶体质量非常重要.     

RI-R6C-001A集成电路的原理与应用

RI-R6C-001A芯片是Texas Instruments公司生产的RF收发器，可实现ISO15693协议电子标签的阅读。该芯片内含接收、发射和控制接口三部分。文中介绍了RI-R6C-001A的结构、原理和特性，并给出了典型应用电路。     

A combined tuned damper and an optimal design method for wind‐induced vibration control for super tall buildings

The wind‐induced vibrations of super tall buildings become excessive due to strong wind loads, super building height and high flexibility. Tuned mass dampers (TMDs) and tuned liquid column dampers (TLCDs) have been widely used to control vibrations for actual super tall buildings for decades. To fully use both the economic advantage of the TLCD system and the high efficiency of the TMD system, an innovative supplemental damping system including both TLCD and TMD and called combined tuned damper (CTD), which can substantially decrease the cost of the damper, was proposed to control the wind‐induced vibrations of tall buildings. The governing equations are generated for the motion of both the primary structure and the CTD and solved to anticipate the dynamic response of the CTD‐structure system. Moreover, an optimal design method of human comfort performance is proposed, in which the life cycle cost of the damper‐structure system is considered as the quantitative index of the performance. The life cycle cost includes the initial cost, the maintenance cost and the failure cost. The failure cost can be calculated using the vibration‐sensation rate model, which is based on the Japanese code AIJES‐V001‐2004. Copyright © 2016 John Wiley & Sons, Ltd.     

Bonding Character and Formation Energy of Point Defects of He and Vacancy on （001） Surface of bcc Iron by First Principle Calculations

The structure and energy of He impurities and vacancy on (001) surface of bcc iron are investigated by an ab initio method. Three cases for stabilities of a He atom at the surface are found: some of He atoms at surface atomic layers (SAL) relax into vacuum gap; some of surface He atoms at octahedral interstitial site relax into more stable tetrahedral interstitial site; some of surface He atoms still stay at tetrahedral interstitial site. The un-stability of the He atom at the surface system can be explained by deformation mechanism of charge densities and electronic densities of states. It is found that formation energy of the point defects from the topmost SAL to bulk-like atomic layer increase gradually, for example, the formation energies of a monovacancy at the first five topmost SALs are equal to 0.33, 1.56, 2.04, 2.02 and 2.11 eV, respectively. The magnetic moments of Fe atoms in the surface atomic layers are also calculated.     

近距爆破源振动采集系统

本文根据工程爆破测试的需要,提出了一种近爆点的振动信号采集节点的设计方案。该节点中使用一种新型的MEMS拾振器,采用Altera公司FPGA作为主控制器芯片,其中集成控制逻辑单元与NiosII软核嵌入式处理器,二者结合成为单芯片控制器方案。控制器运用多路FIFO进行数据缓冲,顺序传输数据至外部存储器,实现了多路数据的同步采集。拾振器与数据记录仪结合成为一体化的信号采集节点。该节点采样频带宽,体积小。适合近爆区域恶劣环境地震波信号的采集,节点可以灵活布置组成不同测试方案。     

Heterojunction of SrTiO3/TiO2 nanotubes with dominant (001) facets: Synthesis,formation mechanism and photoelectrochemical properties

Controllable growth of anatase TiO₂ with dominant high reactive crystal facets has attracted intense interest in the past few years due to their unique structure-dependent properties. In this work, SrTiO₃/TiO₂ heterostructure nanotubes (SrT) arrays films with high reactive dominant (001) facets of anatase TiO₂ were successfully prepared through the part conversion of TiO₂ by a hydrothermal method. Various characterizations were used to investigate the morphologies, crystal phases and chemical compositions of the prepared samples. Structure analyses using X-ray diffraction and a high-resolution transmission electron microscope revealed that, the treatment sequence of hydrothermal reaction and annealing was a crucial influence factor on controlling the growth of preferred orientation of (001) facets of TiO₂ in SrTiO₃/TiO₂ heterojunction, whereas the inverse treatment sequence yielded randomly oriented facets. The formation mechanism of dominant (001) facets of TiO₂ in the heterojunction was related to crystal structures of TiO₂ and SrTiO₃. The heteroepitaxial growth on (001) plane of SrTiO₃ led to dominant (001) facets of anatase TiO₂ attributing to their excellent surface lattices match. The photoelectric performances of pure TiO₂ nanotubes and SrT were investigated by photoluminescence, UV–visible diffuse reflectance, photocurrent and current–voltage response. The semiconductor characteristics of them were studied by electrochemical impedance spectroscopy and Mott–Schottky analysis in detail. The results demonstrated that the heterostructure of SrT not only increased light absorption, but also effectively shifted the Fermi level and promoted charge transfer. Among all the samples, the SrTiO₃/TiO₂ heterojunction prepared by 1 h hydrothermal treatment (1SrT) exhibited the best photoelectrochemical performances due to the synergetic contributions of the high active (001) facets of anatase TiO₂ and the charge transport properties of the heterostructure.     

Ab initio studies of single-height Si(001) steps

We have studied the Si(001) surface with single-height steps by ab initio molecular dynamics simulations. Surface dimers were found to be unstable with respect to buckling for all geometries considered. However, the ground state reconstruction depends on the type of step. For the SA step, the c(2 × 4) geometry is induced by the step edge, while, for the SB step, the p(2 × 2) reconstruction is more stable. The binding sites and diffusion barriers for a single Si adatom were investigated via the adiabatic trajectory method. In agreement with other studies of the flat surface, fast diffusion takes place along the dimer rows. The local changes to buckling induced by the adatom are sizable and lead to changes in the activation barriers for diffusion, in particular for the path perpendicular to the dimer rows. We also investigated the diffusion of the adatom over the rebonded SB step. The calculations show that there is no additional barrier for the arrival of the adatom at the edge from the upper terrace, while a barrier of at least 1 eV exists for the arrival of the adatom from the lower edge. In step flow growth involving the rebonded SB step, most of the adatoms will thus arrive from the upper terrace.     

Quasi-freestanding,striped WS2 monolayer with an invariable band gap on Au(001)

Revealing the structural/electronic features and interfacial interactions of monolayer MoS2 and WS2 on metals is essential to evaluating the performance of related devices.In this study,we focused on the atomic-scale features of monolayer WS2 on Au(001) synthesized via chemical vapor deposition.Scanning tunneling microscopy and spectroscopy reveal that the WS2/Au(001) system exhibits a striped superstructure similar to that of MoS2/Au(001) but weaker interfacial interactions,as evidenced by experimental and theoretical investigations.Specifically,the WS2/Au(001) band gap exhibits a relatively intrinsic value of ～ 2.0 eV.However,the band gap can gradually decrease to ～ 1.5 eV when the sample annealing temperature increases from ～370 to 720 ℃.In addition,the doping level (or Fermi energy) of monolayer WS2/Au(001) varies little over the valley and ridge regions of the striped patterns because of the homogenous distributions of point defects introduced by annealing.Briefly,this work provides an in-depth investigation into the interfacial interactions and electronic properties of monolayer MX2 on metal substrates.     

Mesocrystalline TiO<Subscript>2</Subscript> nanosheet arrays with exposed {001} facets: Synthesis via topotactic transformation and applications in dye-sensitized solar cells

A facile,fluorine-free approach for synthesizing vertically aligned arrays of mesocrystalline anatase TiO2 nanosheets with highly exposed {001} facets was developed through topotactic transformation.Unique mesocrystalline {001}-faceted TiO2 nanosheet arrays vertically aligned on conductive fluorine-doped tin oxide glass were realized through topotactic conversion from single-crystalline precursor nanosheet arrays based on lattice matching between the precursor and the anatase crystals.The morphology and microstructure of the {001}-faceted TiO2 nanosheets could be readily modulated by changing the reactant concentration and annealing temperature.Owing to enhanced dye adsorption,reduced charge recombination,and enhanced light scattering arising from the exposed {001} facets,in addition to the advantageous features of low-dimensional structure arrays (e.g.,fast electron transport and efficient charge collection),the obtained TiO2 nanosheet arrays exhibited superior performance when they were used as anodes for dye-sensitized solar cells (DSSCs).Particularly,{001}-faceted TiO2 nanosheet arrays ～15 μm long annealed at 500 ℃ showed a power conversion efficiency of 7.51％.Furthermore,a remarkable efficiency of 8.85％ was achieved for a DSSC based on double-layered TiO2 nanosheet arrays ～35 μm long,which were prepared by conversion from the precursor nanoarrays produced via secondary hydrothermal growth.