Ni/Au、Pd/Au与p-AlGaN材料的接触特性

在AlGaNpin型日盲紫外探测器结构中的p-AlGaN层上生长了Ni/Au和Pd/Au,并在600～850℃温度下进行快速热退火,测量其退火前后传输线模型中各金属接触间的电学性质。实验发现,Ni/Au与Pd/Au在p-AlGaN上表现出了不同的接触性能。为了更好的说明金属与p-AlGaN材料接触之间在退火后电流的变化,还测量了p-AlGaN材料裸片两点之间I-V曲线在退火前后的变化。实验表明,比起Ni/Au来,Pd/Au在p-AlGaN材料上制备欧姆接触具有一定的优势,并在文中进行了分析。     

The effect of Cr barrier on interfacial reaction of Au/Zn/Au/Cr/Au contacts to p-type InGaAs/InP

Alloy-type metal is widely used to reduce contact resistance in optoelectronic devices. Among the alloy-types, Au/Zn is one of the most common metallization systems. In this paper, we studied the alloy morphology of p-InP/p-InGaAs/Au/Zn/Au/Cr/Au systems. We found that the amount of Au-Zn alloy depended upon the thickness of the Cr layer. When Cr thickness was reduced to 135 Å, both Au-rich and GaAs-rich excessive compound formation started to occur. The Au diffusion punched through the InGaAs layer and penetrated into the InP. Comparison of Au/Zn/Au and Au/Zn/Au/Cr/Au suggested that the top Au layer maybe very influential during the alloy reaction. The Au-Zn alloy was significantly less in the Au/Zn/Au than that in the Au/Zn/Au/Cr/Au.     

Complexes of DNA bases and gold clusters Au3 and Au4 involving nonconventional N-H...Au hydrogen bonding

DNA base-gold interactions are studied theoretically at the DFT level using Au(3) and Au(4) clusters as simple catalytic models for Au particles. The bonding between DNA bases and gold clusters occurs via the anchoring of a Au atom to the N or O atoms of the bases. In the most stable planar base-Au(3) complexes, the Au-N or Au-O anchor bonds are reinforced by N-H...Au bonds. The mechanism of formation of these nonconventional H-bonds is discussed.     

Au agglomerates observed in the out-diffusion process of supersaturated high-temperature substitutional Au in Si

Out-diffusion profiles of supersaturated substitutional Au in Si annealed at 900 °C for 90 h have been measured by SIMS and ICTS methods over a distance of 80 μm from the specimen surface. The tendency of the profile of total Au atoms measured by SIMS and that of electrically active substitutional Au measured by ICTS agrees well, but the very small regions containing high-concentration of Au atoms, 3 × 10²² cm⁻³, are observed sporadically at the distance deeper than 10 μm from the surface by SIMS method. The size of the high-concentration region is estimated to be about 20 nm and its density is about 2 × 10¹⁰ cm⁻³. The small agglomerates contain 10⁵–10⁷ Au atoms and many of them contain about 2 × 10⁵ atoms. The observed agglomerate is a new agglomeration of Au in Si. The state of the agglomeration (namely, precipitates of Au, agglomeration of substitutional Au in Si, or a new state) is not clear by SIMS measurement.     

A.c. electrical properties of Au/CIAIPc/Au device

The a.c. electrical properties of chloro aluminum phthalocyanine (CIAIPc) thin film sandwiched between two gold (Au) electrodes have been studied in the frequency range 10 Hz to 100 kHz and the temperature range 293 K to 400 K. The a.c. conductivity Σ(Ω) was found to vary as Ω ^s , with the index s < 1, indicating that a hopping process of conduction is dominant at low temperatures and higher frequencies. At higher temperatures and lower frequencies a free carrier conduction mechanism is likely to dominate. At low temperatures the capacitance of the Au-CIAIPc-Au device is temperature-insensitive and increases rapidly above 300 K. The capacitance and loss tangent decreased with frequency and increased with temperature. Such characteristics were found to be in good agreement with the devices Au/CuPc/Au and Au/PbPc/Au.     

The effects of Au surface diffusion to formation of Au droplets/clusters and nanowire growth on GaAs substrate using VLS method

Using VLS method with the separated 220 nm thick Au catalyst circles/stripes configurations sputtered onto GaAs substrate surface, this paper investigated the effects of the Au droplets/clusters formation as well as the nanowires growth process inside and outside the Au circles/stripes configurations. The Au surface outward diffusion from the Au layer edge up to several tens of micrometers has strongly dominated. The effects of Au surface diffusion to formation of Au droplets/cluster and to the nanowires growth on GaAs semiconductor substrate in the region outside the Au layers have been shown. The mechanism of the droplets/clusters formation outside the Au layer could explained by the surface cluster diffusion, meanwhile the nanowires have grown simultaneously during the Au outward diffusion. The growth could explain by the diffusion of Ga and As atoms into the diffusing Au droplets/clusters via dissociative mechanism to form nanowire seeds inside for nanowires growth. The Au droplets/clusters formation and nanowires growth on GaAs substrate outside Au layer could be applied for making nanodevices blocks outside the Au layer. Unfortunately if this Au surface diffusion phenomenon is occurring on the GaAs semiconductor containing the Au stripes interconnections in micro/nanocircuits this could also cause the short-circuits phenomenon, even at thin Au layer.     

亲油性金纳米粒子的合成

利用相转移法成功地合成了粒径在2～7nm的硫醇表面修饰Au纳米粒子.采用透射电子显微镜、纳米粒度分布仪、红外光谱分析仪等现代测试技术对所合成的Au纳米粒子进行了表征.结果表明,表面为硫醇所修饰的Au纳米粒子,在有机溶剂中具有很好的分散性,表面修饰层的存在不仅有效地阻止Au纳米粒子的团聚,而且使得纳米粒子粒径分布窄,粒径可控.     

Electrical conduction through self-assembled monolayers in molecular junctions: Au/molecules/Au versus Au/molecule/PEDOT:PSS/Au

We fabricated and characterized a large number of octanedithiol (denoted as DC8) molecular devices as vertical metal–molecule–metal structure with or without using an intermediate conducting polymer layer of poly (3,4-ethylenedioxythiophene) stabilized with poly(4-styenesulfonic acid) (called as PEDOT:PSS). The electronic transport properties of DC8 molecular devices with and without PEDOT:PSS layer were statistically compared in terms of current density and device yield. The yields of the working molecular devices were found to be ~ 1.75% (84 out of 4800 devices) for Au/DC8/Au junctions and ~ 58% (74 out of 128 devices) for Au–DC8/PEDOT:PSS/Au junctions. The tunneling decay constants were obtained with the Simmons tunneling model and a multibarrier tunneling model for two kinds of molecular devices with and without PEDOT:PSS layer.     

Micro-patterned nanoscale Au films on PMMA: fabrication and effect of PMMA dewetting on Au patterning

Patterned metallic thin films have attracted a lot of attention, in recent years, due to their wide technological applications. On the basis of this fact, in the present work, we illustrate a simple, versatile, and low-cost methodology to prepare surface micro-patterns in nanoscale deposited Au films. The methodology is based on the following steps: (a) to perform nanoscale Au film depositions assisted by micrometric templates to obtain the deposited Au film micrometric patterned in specific and desired ways (micrometric squares, hexagons, …), and (b) by low-temperature thermal processes (<300 °C) to induce a dewetting process of the PMMA to guide specific patterning effects in the top nanoscale Au film. In this approach, the Au surface pattern order is established by the template confined deposition on a micrometric scale while the realization and control of the Au surface pattern is given by the control of the dewetting process of the underlaying substrate, without invoking high temperature thermal processes.     

Enhanced middle-infrared light transmission through Au/SiO(x)N(y)/Au aperture arrays

The enhanced middle-infrared light transmission through Au/SiO(x)N(y)/Au aperture arrays by changing the refractive index and the thickness of a dielectric layer was studied experimentally. The results indicated that the transmission spectra was highly dependent on the refractive index and the thickness of SiO(x)N(y). We found that the transmission peaks redshifted regularly along with the refractive index from 1.6 to 1.8, owing to the role of surface plasmon polaritons (SPP) coupling in the Au/SiO(x)N(y)/Au cascaded metallic structure. Simultaneously, a higher transmission efficiency and narrower transmission peak was obtained in Au/SiO2.1N0.3/Au cascaded metallic structure with small refractive index (1.6) than in Au/SiO0.6N1/Au cascaded metallic structure with large refractive index (1.8). When the thickness of SiO(x)N(y) changes from 0.2 to 0.4 microm, the shape of transmission spectra exhibits a large change. It was found that a higher transmission efficiency and narrower transmission peak was obtained in Au/SiO(x)N(y)/Au cascaded metallic structure with a thin dielectric film (0.2 microm), with the increase of SiO(x)N(y) film's thickness, the transmission peak gradually widened and disappeared finally. This effect is useful in applications of biochemical sensing and tunable integrated plasmonic devices in the middle-infrared region.     

气体吸附诱导Cu(Au)合金中Au原子的偏聚和富集

合金中的表面成分和相偏析会改变其功能,尤其是在表面结构和化学起着至关重要作用的应用中.例如,合金催化剂的表面状态显著影响其在异相催化和电化学过程中的催化性能.表面成分偏析被认为是由表面能的差异驱动,以减少合金体系的总自由能.然而,目前合金中成分偏析的原子尺度进程还尚不清楚,尤其是对于气体分子诱导的成分偏析,在该过程中可能同时发生结构和化学重排.本文通过像差校正环境TEM从原子尺度研究了固溶态Cu(Au)合金在CO气氛下的表面偏析行为. CO气氛能够诱导Cu(Au)合金表面形成有序结构,在很大程度上改变合金的表面化学性质.高温条件下, CO气氛会进一步促进Au原子通过特定的"原子通道"进行扩散,在合金表面偏聚和富集.富集形成的Au纳米颗粒与合金表面在形貌和结构方面发生了丰富的动力学交互作用.这其中CO气体吸附也起着重要的作用.这些原子尺度的研究结果为双金属合金的表面偏析和去合金化机理提供了直接证据,并突出了气体吸附物在这些表面行为中的作用.     

Au Fixed Point Development at NRC

Two Au fixed points filled using metal of different nominal purities in carbon crucibles have been developed at the National Research Council Canada (NRC). The primary motivation behind this project was to provide the means for direct thermocouple calibrations at the Au freezing point (\(1064.18~^\circ \hbox {C}\)). Using a Au fixed point filled with the metal of maximum available purity [99.9997 % pure according to glow discharge mass spectroscopy (GDMS)], multiple freezing plateaus were measured in a commercial high-temperature furnace. Four Pt/Pd thermocouples constructed and calibrated in-house were used to measure the freezing plateaus. From the calibration at Sn, Zn, Al and Ag fixed points, the linear deviation function from the NIST-IMGC reference function (IEC 62460:2008 Standard) was determined and extrapolated to the freezing temperature of Au. For all the Pt/Pd thermocouples used in this study, the measured EMF values agree with the extrapolated values within expanded uncertainty, thus substantiating the use of 99.9997 % pure Au fixed point cell for thermocouple calibrations at NRC. Using the Au fixed point filled with metal of lower purity (99.99 % pure according to GDMS), the effect of impurities on the Au freezing temperature measured with Pt/Pd thermocouple was further investigated.     

Structural and electrical properties of Au and Ti/Au contacts to n-type GaN

Au and Ti/Au layers were deposited on n-GaN. The samples were annealed at 400, 700 and 900 °C for 10 min in vacuum. The contacts were rectifying up to 700 °C and the highest Schottky barrier height of 1.07 eV was obtained for an Au single layer by current-voltage measurements. A binary phase of Au₂Ga was identified at the interface of the n-GaN/Ti/Au contact after annealing at 900 °C. The formation of Ti₂N and TiN (twin) phases epitaxially grown on GaN was also observed in the same contact as well as some gold diffusion into the topmost region of the GaN epilayer.     

Influence of Au underlayer thickness on the electro-optical properties of ITO/Au layered films deposited by magnetron sputtering on unheated polycarbonate substrates

Transparent and conducting tin-doped indium oxide (ITO) and ITO/Au multilayered films were prepared on polycarbonate (PC) substrates by magnetron sputtering without intentional substrate heating. In order to consider the influence of the Au thickness on the optoelectrical properties and structure of ITO/Au films, the thickness of the Au underlayer was varied from 5 to 20 nm. The optoelectrical properties of the films were quite dependent on the Au film thickness. The lowest sheet resistance of 11 Ω/sq. and an optical transmittance of 61% with respect to air was obtained from ITO (95 nm)/Au (5 nm) films. Thin film crystallinity was also affected by the presence of the Au underlayer and varied with the thickness of the Au films. In X-ray diffraction (XRD) spectra, ITO films did not show any characteristic diffraction peak, while ITO/Au films with a 5-nm Au underlayer showed a characteristic diffraction peak. From the figure of merit, it can be concluded that the most effective Au thickness in ITO/Au films is 5 nm.     

低温非晶硅/金圆片键合技术(英文)

本文研究了低温非晶硅/金圆片键合技术.具有不同金硅比的键合片在400℃键合温度和1 MPa键合压力下维持30 min,其键合成功区域均高于94%,平均剪切强度均大于10.1 MPa.键合强度测试结果表明键合成品率与金硅比大小无关,平均剪切强度在10～20 MPa范围内.微观结构分析表明键合后单晶硅颗粒随机分布在键合层内,而金则充满其他区域,形成了一个无空洞的键合层.无空洞键合层确保不同金硅比非晶硅/金键合片均具有较高的键合强度,可实现非晶硅/金键合技术在圆片键合领域的应用.     

Au-CZT与Au/Cr-CZT接触性能比较

本文通过附着力测试,应力模拟和IV特性及多道能谱分析对Au-CZT与Au/Cr-CZT接触进行研究。结果表明采用Au/Cr复合电极可提高电极附着强度和热稳定性。在老化实验中,Au-CZT界面附着力下降了61.98%,而Au/Cr-CZT仅降低28%。Au/Cr电极器件的漏电流较低,241Am射线下能谱响应更佳。分析其原因可能是Au与CZT间的Cr层降低了接触层内的热应力,合金化过程促进了金-半界面的互扩散,使Au和CZT更易形成欧姆接触,综合考虑Au/Cr复合电极能获得比Au电极更理想的接触性能。     

Twisting Ultrathin Au Nanowires into Double Helices

Previously, double helix nanowire was reported by coating Pd/Pt/Au onto Au‐Ag alloy nanowire. Here, straight oleylamine‐stabilized ultrathin Au nanowires with single crystalline fcc lattice are surprisingly converted into double helix helices upon reacting with Ag in tetrahydrofuran (THF). The obtained Au‐Ag helical nanowires contain lattice distinctively different from the fcc lattice and are different in many aspects with the previous system. The discovery may expand the scope of nanoscale double helix formation and the understanding of lattice transformation among ultrafine nanostructures.     

Sub-two nanometer single crystal Au nanowires

Ultrathin single crystal Au nanowires with diameter of approximately 1.6 nm and length of few micrometers were synthesized with high yield by simply mixing HAuCl 4 and oleylamine at room temperature. High resolution transmission electron microscopy studies revealed that all of these nanowires are single crystalline and grew along the [111] direction. The valency evolution of the gold species during the synthesis was studied by X-ray photoelectron spectroscopy, which showed a clear Au (3+) --> Au (+) --> Au stepwise reduction at different reaction stages. Small angle X-ray scattering and small-angle X-ray diffraction suggest mesostructure formation upon HAuCl 4 and oleylamine mixing. The slow in situ reduction of this mesostructure leads to the formation of ultrathin nanowires in solution. This novel nanowire growth mechanism relies on cooperative interaction, organization, and reaction between inorganic precursor salts and oleylamine.     

Nanoparticle formation in Au thin films by electron-beam-induced dewetting

We carried out investigations on electron-beam-induced nanoparticle formation in thin (5-30?nm) Au films on smooth SiO(2)/Si substrates. When the Au films were irradiated with an electron beam, the Au films broke up into nanoparticles through the dewetting process. The dominant wavelengths of the surface (corresponding to the pitch between nanoparticles) were closely related with the thickness of the Au. We then developed a new technique for the formation of periodically arranged Au nanoparticles using a holed substrate. The nanoholes induced heterogeneous nucleation and helped to form ordered nanoparticles between the holes. Two-dimensionally, periodically arranged Au nanoparticles with a pitch of 100?nm were?obtained.