Spin resonance transport properties of a single Au atom in S–Au–S junction and Au–Au–Au junction

The spin transport properties of S–Au–S junction and Au–Au–Au junction between Au nanowires are investigated with density functional theory and the non-equilibrium Green's function. We mainly focus on the spin resonance transport properties of the center Au atom. The breaking of chemical bonds between anchor atoms and center Au atom significantly influences their spin transmission characteristics. We find the 0.8 eV orbital energy shift between anchor S atoms and the center Au atom can well protect the spin state stored in the S–Au–S junction and efficiently extract its spin state to the current by spin resonance mechanism, while the spin interaction of itinerant electrons and the valence electron of the center Au atom in the Au–Au–Au junction can extract the current spin information into the center Au atom. Fermi energy drift and bias-dependent spin filtering properties of the Au–Au–Au junction may transform information between distance, bias,and electron spin. Those unique properties make them potential candidates for a logical nanocircuit.     

Electrostatic assembles and optical properties of Au–CdTe QDs and Ag/Au–CdTe QDs

Au–CdTe and Ag/Au–CdTe assembles were firstly investigated through the static interaction between positively charged cysteamine-stabilized CdTe quantum dots (QDs) and negatively charged Au or core/shell Ag/Au nano-particles (NCs). The CdTe QDs synthesized in aqueous solution were capped with cysteamine which endowed them positive charges on the surface. Both Au and Ag/Au NCs were prepared through reducing precursors with gallic acid obtained from the hydrolysis of natural plant poly-phenols and favored negative charges on the surface of NCs. The fluorescence spectra of CdTe QDs exhibited strong quenching with the increase of added Au or Ag/Au NCs. Railey resonance scattering spectra of Au or Ag/Au NCs increased firstly and decreased latter with the concentration of CdTe QDs, accompanied with the solution color changing from red to purple and colorless at last. Experimental results on the effects of gallic acid, chloroauric acid tetrahydrate and other reagents demonstrated the static interaction occurred between QDs and NCs. This finding reveals the possibilities to design and control optical process and electromagnetic coupling in hybrid structures.     

Effect of annealing temperature on the electrical properties of Au/Ta2O5/n-GaN metal–insulator–semiconductor (MIS) structure

We report on the effect of an annealing temperature on the electrical properties of Au/Ta₂O₅/n-GaN metal–insulator–semiconductor (MIS) structure by current–voltage (I–V) and capacitance–voltage (C–V) measurements. The measured Schottky barrier height (Φ _bo) and ideality factor n values of the as-deposited Au/Ta₂O₅/n-GaN MIS structure are 0.93 eV (I–V) and 1.19. The barrier height (BH) increases to 1.03 eV and ideality factor decreases to 1.13 upon annealing at 500 ^°C for 1 min under nitrogen ambient. When the contact is annealed at 600 ^°C, the barrier height decreases and the ideality factor increases to 0.99 eV and 1.15. The barrier heights obtained from the C–V measurements are higher than those obtained from I–V measurements, and this indicates the existence of spatial inhomogeneity at the interface. Cheung’s functions are also used to calculate the barrier height (Φ _bo), ideality factor (n), and series resistance (R _s ) of the Au/Ta₂O₅/n-GaN MIS structure. Investigations reveal that the Schottky emission is the dominant mechanism and the Poole–Frenkel emission occurs only in the high voltage region. The energy distribution of interface states is determined from the forward bias I–V characteristics by taking into account the bias dependence of the effective barrier height. It is observed that the density value of interface states for the annealed samples with interfacial layer is lower than that of the density value of interface states of the as-deposited sample.     

Investigation of ultra-thin and flexible Au–Ag–Au transparent conducting electrode

The performance of ultra-thin Au–Ag–Au tri-layer film deposited thermally over a flexible substrate is investigated using structural, optical, mechanical and electrical-transport measurements. The optimum total thickness of the tri-layer for high transparency and conductivity is determined to be around 8 nm using a theoretical model. The Au–Ag–Au tri-layer shows maximum transmittance (≅ 62%) at wavelength 500 nm. XRD pattern shows peak corresponding to (111) plane of Au and/or Ag. Sheet resistance (≅ 10.42 Ω/□) measured at 300 K using four probe technique is stable up to 150 °C. Hall effect measurements show high conductivity (1.34 × 10⁵ (Ω cm)⁻¹), carrier concentration (2.48 × 10²³/cm³), and mobility (3.4 cm²/Vs). Scotch tape test confirms good adhesion of the film onto PET substrate. Bending-twisting tests using an indigenous apparatus indicate high resistance-stability even after 50,000 cycles. These results imply the viability of Au–Ag–Au tri-layer film as a transparent conducting electrode worth exploring for optoelectronic applications.     

Magnetic characteristics of Au–Mn nanowires

The quantum properties of Au–Mn nanowires are analyzed theoretically from first principles. The emergence of magnetic properties in these nanowires, consisting of nonmagnetic elements, is demonstrated. It is shown that the manganese atoms carry fairly large magnetic moments (～4.3 μ_B), although crystalline Mn is a paramagnet. Analysis of the electronic structure of these bimetallic nanowires indicates that the magnetic moments at the Mn atoms arise owing to the formation of a complicated structure of hybrid orbitals. Furthermore, it is found that the antiferromagnetic state in Au–Mn nanowires is stabilized by the occurrence of indirect exchange interaction between Mn atoms.     

Growth and characterization of Au,Ni and Au–Ni nanoclusters on 6H-SiC(0001) carbon nanomesh

The nucleation and thermal stability of Au, Ni, and Au–Ni nanoclusters on 6H-SiC(0001) carbon nanomesh as well as the interaction between Au–Ni bimetallic clusters and reactive gases have been studied by X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM). Both Au and Ni atoms grow as three-dimensional (3D) clusters. Annealing the Au/carbon nanomesh surface up to 1150 °C leads to complete desorption of the Au clusters, while interfacial reaction occurs between Ni clusters and the substrate surface when the Ni clusters are subjected to the same annealing process. The nucleation of Au–Ni clusters depends critically on the deposition sequence. Au atoms preferentially nucleate on the existing Ni clusters, leading to the formation of bimetallic clusters with Au enriched on the surface. If the deposition sequence is reversed, a part of Ni atoms nucleate between the Au clusters. The thermal stability of the Au–Ni clusters resembles that of the Ni/carbon nanomesh surface, irrespective of the deposition sequence. XPS characterization reveals that Ni atoms in Au–Ni bimetallic clusters are oxidized upon exposure to 5.0 × 10^? 7 mbar O₂ for 5 min at room temperature while negligible structure change can be detected when the bimetallic clusters are exposed to CO gas under the similar conditions.     

Methanol-driven structuring of Au–Pt bimetallic nanoclusters on a thin film of Al2O3/NiAl(100)

The adsorption of methanol altered structures of Au–Pt bimetallic nanoclusters on a thin film of Al₂O₃/NiAl(100). Methanol adsorbed on the Au–Pt intermixed bimetallic clusters, of which the surfaces consist of both Au and Pt, induced a segregation of Au from Pt. This segregation state was unstable, as the clusters returned to the initial Au–Pt intermixed state upon desorption or decomposition of adsorbed methanol. Ethanol and cyclohexene were adsorbed on Au–Pt bimetallic clusters for comparisons, indicating that the interaction of the hydroxyl group of methanol with the clusters accounts for the structural modifications.     

Origin of tweed in Au–Cu–Al alloys

The premartensitic tweed in Au–Cu–Al alloys, contrary to previous thought that resort to defects, is confirmed to be associated with the coherent embryos of an intermediate phase (I phase) embedded in parent phase. The parent?→?I phase transformation temperature was measured by differential scanning calorimeter and dynamic mechanical analysers, which shifts from 82.3 to 557.6?°C depending on the alloy composition. X-ray diffraction and transmission electron microscopes (TEM) results show that the parent?→?I phase transformation is a charge density wave transition that cannot be suppressed even by melt-spun method, which shows obvious compositional inhomogeneity between I phase and parent. The results imply that the parent?→?I phase transition is a fast displacive transformation coupled with diffusion. Moreover, accompanying the parent?→?I phase transformation, alloys demonstrate diversified microstructure revealed by TEM observation, from tweed to chessboard nanowires or twins. These findings provide the experimental evidence for that parent?→?I phase transformation in Au–Cu–Al alloys is originated from pseudospinodal decomposition as theoretically predicted.     

Some electrical and structural properties of Cd/CdS/n–Si/Au–Sb sandwich structure

In view of CdS growth is very impotent for technological importance especially solar applications; synthesis of this material remains a topic of great interest for researchers by means of an economically and technically viable method. In the present paper, Cd/CdS/n–Si/Au–Sb sandwich structure has been grown by Successive Ionic Layer Adsorption and Reaction (SILAR) technique. For investigating the structural properties, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX) measurements have been performed and it has been seen that films exhibit polycrystalline behavior. The capacitance–voltage (C–V) and conductance/w-voltage (G/w–V) characteristics of Cd/CdS/n–Si/Au–Sb structure have been investigated by considering series resistance and interface states effects. These measurements have been done in the −4 V, 4 V voltage range and in the frequency range of 10 kHz–3 MHz at room temperature. It is seen that, the series resistance (R_s) and interface state density have been strongly depend on frequency. The barrier height, donor concentration, diffusion potential parameters have been determined from the linear C⁻²–V plot. The barrier height values are obtained between 0.495 and 0.796 eV and doping density values have been ranged from 1.455 × 10¹⁴ to 1.999 × 10¹⁴ cm⁻³respectively. The capacitance–frequency (C–f) and conductance/w-frequency (G/w–f) characteristics of Cd/CdS/n–Si/Au–Sb structures have been measured at the various biases 0.00–0.14 V at room temperature. The energy distribution of the interface states (N_ss) and their relaxation time (τ) have been determined from the forward bias capacitance–frequency characteristics. The N_ss and τ values have ranged from 2.01 × 10¹² cm⁻² eV⁻¹and 9.68 × 10⁻⁴ s in (Ec-0.45) eV–2.86 × 10¹³ cm⁻² eV⁻¹ and 3.81 × 10⁻⁴ s in (Ec-0.75) eV, respectively.     

Au–Cu nanoparticles produced by laser ablation of mixtures of Au and Cu microparticles

In this study we investigate the possibility of producing alloy nanoparticles (NP) from mixtures of elemental microparticle (MP) powders using the laser ablation of microparticle (LAM) process. Mixtures of Au and Cu particles with a diameter of 1.5–2.0 m were fed in aerosol form into a laser ablation cell and ablated using a pulsed laser. The resulting NP were collected electrostatically and characterized using TEM. The NP were spherical and crystalline with a size that depended on the collection location but ranged from 2 to 15 nm. Using TEM/SAD, it was determined that the NP had a face-centered cubic (fcc) crystal structure and, with EDS, it was found that individual NP consisted of both Au and Cu. These experimental results confirm previous numerical models that suggested that it might be possible to form alloy NP from mixtures of elemental MP using the LAM process.     

Properties of the πh_(9/2)  νi_(13/2) band in odd-odd ~(188)Au

A new rotational band has been identified and assigned to 188Au for the first time using the 173Yb(19F,4nγ) reaction at the beam energies of 86 and 90 MeV. This band is proposed to be built on the πh9/2  νi13/2 configuration by comparing the band properties with known bands in neighboring nuclei. The prolate-to-oblate shape transition through triaxial shape has been proposed to occur around 188Au for the πh9/2  νi13/2 bands in odd-odd Au isotopes on the basis of total Routhian surface (TRS) calculations.     

Current–voltage and capacitance–voltage studies of nanocrystalline CdSe/Au Schottky junction interface

Journal of Nanoparticle Research - CdSe nanocrystalline thin films have been synthesized on indium tin oxide (ITO) substrates by an electrodeposition technique. A Schottky junction device in the...     

入射能量对Au/Au(111)薄膜生长影响的分子动力学模拟

利用分子动力学模拟了Au原子在Au(111)表面低能沉积的动力学过程.采用嵌入原子方法的原子间相互作用势,通过对沉积层原子结构的分析和薄膜表面粗糙度、层覆盖率的计算,研究了沉积粒子能量对薄膜质量的影响及其机制.结果表明:当入射能量Ein25 eV时,沉积层和基体表层均呈现规则的单晶面心立方(111)表面的排列,沉积原子仅注入到基体最表面两层,随着入射能量的增加,薄膜表面粗糙度降低,薄膜越趋于层状生长,入射能量的增加有利于薄膜的成核和致密化;当Ein 25 eV时,沉积层表面原子结构出现了较为明显的晶界,沉积原子注入到基体表面第三层及以下,随着入射能量的增加,薄膜表面粗糙度增加,沉积层和基体表层原子排列越不规则,载能沉积会降低基体内部的稳定性,导致基体和薄膜内部缺陷的产生,降低薄膜质量.此外,当基体内部某层沉积原子数约等于该层总原子数的一半时,沉积原子将能穿过该层进入到基体内部更深层.     

Temperature-Dependent Current–Voltage (I–V) and Capacitance–Voltage (C–V) Characteristics of Ni/Cu/n-InP Schottky Barrier Diodes

The current-voltage (I–V) and capacitance-voltage (C–V) characteristics of Ni/Cu/n-InP Schottky barrier diodes are studied over a wide temperature range, from 210 K to 420 K. The I–V characteristics display anomalous thermal behavior. The apparent barrier height decays, and the ideality factor grows at low temperatures, and the series resistances resulting from Cheung’s and Norde’s procedures are markedly temperature dependent. The nonlinearity of the Richardson plot and the strong temperature dependence of the Schottky-barrier parameters indicate that the interface is spatially inhomogeneous. Plots of the zero-bias barrier height as a function of 1/(2kT) points to a Gaussian distribution of barrier heights with 0.90 eV mean height and 0.014 eV standard deviation. When this distribution is accounted for, a Richardson of 6.5 A/(cm K)² results, relatively close to the 9.4/(cm K)² predicted by theory. We conclude that, combined with a Gaussian distribution of barrier heights, the thermionic-emission mechanism explains the temperature-dependent I–V and C–V characteristics of the studied Schottky-barrier diodes.     

Current–voltage temperature characteristics of Au/n-Ge (1 0 0) Schottky diodes

The variation in electrical characteristics of Au/n-Ge (1 0 0) Schottky contacts have been systematically investigated as a function of temperature using current–voltage (I−V) measurements in the temperature range 140–300 K. The I–V characteristics of the diodes indicate very strong temperature dependence. While the ideality factor n decreases, the zero-bias Schottky barrier height (SBH) (Φ_B) increases with the increasing temperature. The I–V characteristics are analyzed using the thermionic emission (TE) model and the assumption of a Gaussian distribution of the barrier heights due to barrier inhomogeneities at the metal–semiconductor interface. The zero-bias barrier height Φ_B vs. 1/2 kT plot has been used to show the evidence of a Gaussian distribution of barrier heights and values of Φ_B=0.615 eV and standard deviation σ_s0=0.0858 eV for the mean barrier height and zero-bias standard deviation have been obtained from this plot, respectively. The Richardson constant and the mean barrier height from the modified Richardson plot were obtained as 1.37 A cm⁻² K⁻² and 0.639 eV, respectively. This Richardson constant is much smaller than the reported of 50 A cm⁻² K⁻². This may be due to greater inhomogeneities at the interface.     

Neutron irradiation effects on I–V characteristics of Au/n-GaAs Schottky diodes

Diodes are one of the most important and widely used components of electronic circuits. These devices can be damaged especially when they are used in radiation fields whose effects depend on radiation type and energy. To investigate these effects, the Au/n-GaAs type Schottky diodes have been irradiated by neutrons emitted from a ²⁵²Cf source which provides neutrons at an average energy of 2.14 MeV. The diode parameters barrier height (Φ_b0), ideality factor (n) and series resistance (R_s) have been obtained from forward current–voltage (I–V) characteristics before and after irradiation and the results are discussed.