Correlated optical measurements and plasmon mapping of silver nanorods

Plasmonics is a rapidly growing field, yet imaging of the plasmonic modes in complex nanoscale architectures is extremely challenging. Here we obtain spatial maps of the localized surface plasmon modes of high-aspect-ratio silver nanorods using electron energy loss spectroscopy (EELS) and correlate to optical data and classical electrodynamics calculations from the exact same particles. EELS mapping is thus demonstrated to be an invaluable technique for elucidating complex and overlapping plasmon modes.     

光学薄膜及其发展现状

介绍了传统光学薄膜的原理,并对反光膜、增透膜、纳米光学薄膜等传统光学薄膜的研究现状及应用情况,以及几种新型光学薄膜如高强度激光器、金刚石及类金刚石膜、软X射线多层膜、光电通信用光学薄膜的研究现状及应用进行了详细分析;最后对光学薄膜的发展前景进行了展望。     

Electroforming of a carbon thin film device with a silver film

To elucidate the process by which a voltage-controlled negative resistance is generated and enhanced in the carbon thin film devices, the transient current-voltage characteristics during the process were measured. A number of areas with a low secondary electron emission yield under the scanning electron beam of an electron microscope were found in the formed region. X-ray microanalyses showed that those areas included the contact material silver.     

Polyelectrolyte assisted silver nanoparticles synthesis and thin film formation

Silver nanoparticles were prepared by the reduction of silver salts with sodium borohydride and capped with a copolymer of styrene sulfonate and maleic monomers. The synthesized nanoparticles were then deposited on a glass substrate using the layer-by-layer deposition technique in alternance with polycationic poly(diallyl-dimethylammonium chloride) PDADMAC. The synthesis of the silver nanoparticles as well as the layer-by-layer deposition with PDADMAC was easily monitored by UV–Vis spectroscopy due to the strong plasmon absorbance at 400 nm of the silver nanoparticles. Our study shows that increasing the concentration ration between the co-polyelectrolyte and silver nitrate has a negative effect on the size distribution of the resulting silver nanoparticles. For the layer-by-layer assembly, the PSS-co-Maleic was found to be a good capping agent since it allows later the formation of uniform thin films when deposited with PDADMAC. A linear increase in absorbance as a function of the number of deposited layers was observed.     

Microstructural transitions and dielectric properties of boron-doped amorphous alumina thin film

Dielectric Al_2?x B _x O_Y thin films were deposited onto Pt (100)/Ti/SiO₂/Si substrates via sol–gel and spin-coating technology. The microstructural transition occurred at ~500 °C due to boron loading was confirmed by DSC and XRD. FTIR, ²⁷Al MAS NMR and XPS measurements were employed to investigate the microstructural transition caused by different boron concentrations. The results revealed that Al–O–B bonds and [AlO₄] tetrahedrons were produced resulting in the reinforcement of structure with relatively low boron concentrations. With the increase of boron concentration, [BO₃] chains and new surfaces crossing over the internal structure gradually produced and disrupted the structural stability. Meanwhile, hydroxyl groups were accumulated in the internal structure owing to the hydrophilic property of boron. According to the reinforced structure with low boron concentrations, the current density decreased and the breakdown strength was enhanced. Typically, the current density was decreased two orders of magnitude at 100 MV m^?1 and the breakdown strength of the 0.5 mol% B-doped alumina thin film was increased by 59% (from 293 to 465 MV m^?1) in comparison with that of the undoped alumina thin film, whereas the dielectric properties gradually become poor due to the weak structure with the increase of boron concentration. Moreover, the dielectric constant increased owing to hydroxyl groups when the boron doping increased. This work may provide a general strategy for enhancing dielectric properties of the alumina thin film.     

Synthesis and enhanced light absorption of alumina matrix nanocomposites containing multilayer oxide nanorods and silver nanoparticles

In this paper, multilayer oxide nanorods were deposited in the nanopores of anodic aluminum oxide (AAO) via solution infiltration followed by heat treatment. The nanorods have a core–shell structure. First, the shell (nanotube) with the thickness of about 40 nm was made of TiO₂ through the hydrolysis of (NH₄)₂TiF₆. Second, silver nanoparticles with the diameter of about 3 nm were added into the TiO₂ layer through thermal decomposition of AgNO₃ at elevated temperatures. Then, cylindrical cores (nanorods) of CoO and ZnO with 200 nm diameter were prepared, respectively. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the structure and composition of the nanorods. UV–vis light absorption measurements in the wavelength range from 350 to 1000 nm were performed to study the effect of nanorod and nanoparticle addition on the light absorption property of the alumina nanocomposites. It is found that CoO nanorods increase the light absorption of the alumina matrix composite in the wavelength range from 500 nm to 800 nm, but the TiO₂ shell does not increase the light absorption much. The ZnO nanorods do not change the light absorption either. However, the addition of silver nanoparticles significantly enhances light absorption of both AAO/TiO₂/Ag/CoO and AAO/TiO₂/Ag/ZnO nanocomposites. This increase in the visible light absorption reveals that there exists surface plasmon around the fine silver nanoparticles in the nanorods.     

Formation of silver nanoparticles by through thin film ablation

Well dispersed Ag nanoparticles have been formed by a process denoted Through Thin Film Ablation. The nanoparticles were deposited on room temperature substrates, had a most probable size of 1 nm, and were not agglomerated. The nanoparticle deposit produced by this process showed no evidence of the larger particles commonly observed from conventional pulsed laser ablation that uses a bulk target. Synthesis of nanoparticles by Through Thin Film Ablation should be possible for any material that can be made as a thin film target and may enable the unique properties of isolated, non-agglomerated nanoparticles to be exploited more fully.     

Optical and electrical properties of new organic thin film

This paper describes a new organic thin film (OTF) (50 nm) which was deposited by spin coated at room temperature. OTF has been constructed from chemically synthesized poly(pentachlorophenyl methacrylate-co-glycidyl methacrylate). Optical properties of the obtained poly(pentachlorophenyl methacrylate-co-glycidyl methacrylate) in solution were tested by ultraviolet–visible absorption spectroscopy. The analysis of the optical absorption data revealed an existence of a direct and indirect transition optical band gap (E_g). The electrical properties of ITO/PEDOT:PSS/OTF/Al heterojunction structure has been investigated by forward and reverse bias current–voltage (I–V) measurements at room temperature. The main electrical parameters such as barrier height (Φ_Bo), ideality factor (n) and reverse saturation current (I_o) have been calculated by applying thermionic emission theory as 0.80 eV, 3.69, 1.86 × 10^?8 A respectively. Additionally, series resistance (R_s), Φ_Bo and n were calculated from the forward bias I–V data using the methods of Cheung and Cheung with Norde and showed that these methods can be applied successfully for this structure.     

Optical and electrical properties of electrodeposited silver based thin films

The electrodeposited superionic conductor Ag₆I₄WO₄ was doped with various concentrations of [CrO₄]^2– to form the quarternary compound Ag₆I₄WO_4(1–xCrO_4(x). The doping level,x, was varied from 0 to 0.6 and the optimum compound was used for further analysis. X-ray diffraction (XRD) analysis indicated major peaks occurring atd values of 3.75,2.29,1.96 and 3.96 in the order of decreasing intensity. The energy dispersive analysis of X-rays (EDAX) technique verified quantitatively the ratio of the components in the solid electrolyte. From the fringes seen in the interference pattern of the transmission spectrum, the refractive index and thickness of the film was calculated. The absorption spectrum indicated the characteristic chromate peak at 310 nm when the dopant was present. An open circuit voltage (OCV) of 670 mV was observed for the fabricated cells with optimum performance at a doping level ofx=0.1, where the best discharge characteristics were observed. The subsequent conductivity was calculated to be of the order 10^–3–1 cm^–1 from the Cole-Cole plot.     

Optical properties of NAEC-PMMA nonlinear polymeric thin film

Novel guest nonlinear optical (NLO) chromophore molecules (4-nitrobenzene)-3-azo-9-ethylcarbazole (NAEC) were doped in poly (methyl methacrylate) (PMMA) host with a concentration of approximately 15% by weight. For a useful macroscopic electro-optic (EO) effect, these NLO molecules NAEC were arranged in a noncentrosymmetric structure in the host polymer by corona-onset poling at elevated temperature (COPET). For applying NAEC-PMMA polymer in optical devices such as EO switch, its optical properties have been investigated. The UV/Visible absorption spectra for the unpoled and poled polymer film were determined. The refractive index of the film was also determined from measurements of the coupling angles with the reflective intensity at 632.8 nm wavelength. Using the simple reflection technique, the EO coefficient ₃₃ value was measured as 60 pm/V at 632.8 nm wavelength. The second-order nonlinear coefficient d ₃₃ was characterized by the second-harmonic-generation (SHG) experimental setup and the calculated d ₃₃ value reached 18.4 pm/V at 1064 nm wavelength. The relation between the second-order nonlinear coefficients d ₃₃ and d ₁₃ for the poled polymer film was also discussed in detail and the ratio d ₃₃/d ₁₃ value was obtained as 3.3.     

Deposition and characterization of a novel integrated ZnO nanorods/thin film structure

One-dimensional (1-D) ZnO (zinc oxide) nanostructures have received a lot of attention due to their superior properties. Various techniques have been developed to synthesize ZnO nanorods at high-temperature process using vapor–liquid–solid (VLS) mechanism. In this paper, we report a novel process to synthesize integrated ZnO nanorods/thin film structures using an RF magnetron sputter deposition under different deposition parameters and substrate conditions. The substrate used was glass plated with electroless Cu prepared using various conditions. The resulting specimens are analyzed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The effect of the copper surface roughness was found to be significant. ZnO nanorods were found only when the copper layer is rough enough. The roughness of the copper in general increases with the plating time and/or the ratio of V_HCHO/V_Cu used in the plating bath. Post-plating annealing of the copper was also found to increase the surface roughness of the copper.     

Electrical transport properties of thin film of a-Se87Te13 nanorods

We have studied the electrical transport properties of thin film of a-S₈₇Te₁₃ nanorods. Initially, the glassy alloy of S₈₇Te₁₃ is prepared by melt-quenching technique. The amorphous nature of this alloy is verified by using X-ray diffraction technique. The nanorods of a-S₈₇Te₁₃ are synthesised on a glass substrate under an ambient gas (Ar) atmosphere using physical vapour condensation system. The morphology and microstructure of these nanorods are studied using scanning electron microscopy and transmission electron microscopy. The temperature dependence of dc conductivity for these nanorods is also studied over a temperature range of 500–100?K. On the basis of the temperature dependence of dc conductivity, the conduction mechanism in these nanorods is investigated. The results reveal that the thermally activated process is responsible for the transport of carriers in the temperature range 500–300?K. While the conduction takes place via variable range hopping (VRH) for temperature region 300–100?K. It is therefore, suggested that three-dimensional Mott's variable range hopping (3D VRH) is the conduction mechanism responsible for the transport of charge carriers in the temperature region 300–100?K. Various Mott's parameters such as density of states, degree of disorder, hopping distance and hopping energy are estimated on the basis of best fitting to our experimental data for Mott's 3D VRH model.     

Self-assembly of silver nanoparticles: Formation of a thin silver film in a polymer matrix

A synthetic route is presented for the preparation of a silver film in presence of UV-radiation. Methoxy polyethylene glycol, a water-soluble polymer, was used as the reducing agent of the silver ions in the presence of an ultraviolet source to produce silver nanoparticles. During solution stirring, a centrifugal force was generated at the center of the solution. At this point on the surface of the solution, the nanoparticles coalesced to form a self-assembly of small subunits that ultimately develops into a film-like network.     

SnS_2纳米薄膜的制备及结构和光学特性

采用真空热蒸发法,在玻璃衬底上制备纳米SnS2薄膜。研究不同Sn和S配比及不同热处理条件对薄膜性能的影响。实验给出采用Sn∶S=1∶1.5摩尔比混合粉末制备的薄膜,经T=430℃,t=40min氮气保护热处理可获得性能良好的SnS2纳米多晶薄膜。薄膜呈n型、表面结构较致密,平均晶粒尺寸为77nm,直接光学带隙约为2.02eV。     

Breakdown conduction in carbon thin film devices with silver film contacts on glass substrates

The process in which a device changes irreversibly from a low to a high conducting state was followed by observing transient current-voltage (I_f−V_f) characteristics. The locus enveloped by a group of the I_f−V_f characteristics represented the current-controlled negative resistance (CCNR). It is shown that these events can be explained by a thermal activation mechanism.