Optical properties of metal nanoparticles synthesized in a polymer by ion implantation: A review

Polymer composite layers irradiated by 30-keV Ag⁺ ions with doses from 3.1×10¹⁵ to 7.5×10¹⁶ cm^?2 and an ion current of 4 µA/cm² are investigated. The composites were examined using Rutherford backscattering (RBS), transmission electron microscopy (TEM), and optical spectroscopy. As follows from electron microscopy and electron microdiffraction data, ion implantation is a promising tool for synthesizing silver nanoparticles in the surface region. The optical density spectra taken of these composites demonstrate that the silver nanoparticles exhibit unusually weak plasma resonance. The formation of silver nanoparticles in layers carbonized by ion implantation is considered. Based on the Mie theory, optical extinction spectra for silver particles in the polymer and carbon matrices are simulated and optical spectra for complex silver core-carbon sheath nanoparticles are calculated. The physics behind the experimental optical spectra of the composite is discussed.     

Ag离子注入非晶SiO2的光学吸收、拉曼谱和透射电镜研究

能量为200keV的Ag离子，以1×10¹⁶，5×10¹⁶，1×10¹⁷ cm^-2的剂量分别注入到非晶SiO₂玻璃，光学吸收谱显示：注入剂量为1×10¹⁶ cm^-2的样品的光吸收谱为洛伦兹曲线，与Mie理论模拟的曲线形状一致；注入剂量较大的5×10¹⁶，1×10¹⁷ cm^-2的谱线共振吸收增强，峰位红移并出现伴峰. 透射电镜观察分析表明，注入剂量不同的样品中形成的纳米颗粒的大小、形状、分布都不同，注入剂量较大的还会产生明显的表面溅射效应，这些因素都会影响共振吸收的峰形、峰位和峰强. 当注入剂量达到1×10¹⁷ cm^-2时，Ag纳米颗粒内部可能还形成了杂质团簇. 关键词： 离子注入 纳米颗粒 共振吸收 红移     

Formation of silver nanoparticles during deposition onto viscous-fluid epoxy resin

A new method is proposed for synthesizing metallic nanoparticles in a polymer matrix. These nanoparticles are synthesized during thermal vacuum evaporation of a metal (4.8 × 10⁻⁶ g/cm²) onto the surface of viscousfluid epoxy resin (at a viscosity of 20–120 Pa s) having room temperature, which is well below the glass transition temperature of the polymer. As a result, epoxy resin layers containing silver nanoparticles in their volume form; these nanoparticles are studied by transmission electron microscopy and optical absorption spectroscopy. Various types of disperse structures formed by metallic nanoparticles in the polymer are detected. The morphology of the composite material is found to be controlled by the polymer viscosity and the metal deposition time.     

Interaction of high-power laser pulses with glasses containing implanted metallic nanoparticles

Sodium calcium silicate glasses with Ag⁺ implanted ions are studied. The ion implantation conditions are as follows: the energy is 60 keV, the dose is 7×10¹⁶ cm⁻², and the ion current density is 10 μA/cm². Ion implantation provides the formation of a composite layer that incorporates silver nanoparticles in the surface region of glass. The size distribution of nanoparticles over the depth in the composite layer is strongly nonuniform. The effect of a high-power pulsed excimer laser on the composite layer is investigated. It is found that, under laser irradiation, the size of silver nanoparticles in the implanted layer decreases but the size distribution of nanoparticles over the depth remains nonuniform, even though it becomes slightly narrower compared to that observed prior to irradiation. The experimental results are interpreted in terms of the effects of the melting of glass and metallic particles on a nanosecond scale. __________ Translated from Fizika Tverdogo Tela, Vol. 43, No. 11, 2001, pp. 2100–2106. Original Russian Text Copyright ? 2001 by Stepanov, Popok, Hole, Bukharaev.     

CEMS study on aluminium implanted iron

Up to now a great deal of investigations in ion beam mixing of iron-aluminium layers are known. However, the easier way to produce such layers by direct implantation of aluminium ions in iron is less studied. In the present work aluminium implanted iron layers are studied. Iron samples were implanted with aluminium ions at 50, 100, and 200 keV, respectively, with doses between 5×10¹⁶ and 5×10¹⁷ cm⁻². Independent of energy, at doses up to 2×10¹⁷ cm⁻², besides alpha iron further magnetic fractions with a Fe₃Al-like structure are formed while at a dose of 5×10¹⁷ cm⁻² amorphous nonmagnetic components are formed.     

Synthesis of Ag metallic nanoparticles by 120 keV Ag− ion implantation in TiO2 matrix

TiO₂ thin film synthesized by the RF sputtering method has been implanted by 120 keV Ag^? ion with different doses (3?×?10¹⁴, 1?×?10¹⁵, 3?×?10¹⁵, 1?×?10¹⁶ and 3?×?10¹⁶ ions/cm²). Further, these were characterized by Rutherford back Scattering, XRD, X-ray photoelectron spectroscopy (XPS), UV–visible and fluorescence spectroscopy. Here we reported that after implantation, localized surface Plasmon resonance has been observed for the fluence 3?×?10¹⁶ ions/cm², which was due to the formation of silver nanoparticles. Ag is in metallic form in the matrix of TiO₂, which is very interestingly as oxidation of Ag was reported after implantation. Also, we have observed the interaction between nanoparticles of Ag and TiO₂, which results in an increasing intensity in lower charge states (Ti³⁺) of Ti. This interaction is supported by XPS and fluorescence spectroscopy, which can help improve photo catalysis and antibacterial properties.     

Electrical characteristics of etched ion-tracks in polyimide filled with silver nanoparticles

Silicon ions, of energy 150?MeV and fluence ～10¹²?ions/cm², were used to register latent tracks in 40?µm thick polyimide samples. Different sizes of tracks were obtained by etching the ion irradiated polyimide samples, in chemical solutions, by varying the temperature and etching period. Silver nanoparticles were diffused into the etched tracks by immersing the polyimide samples in silver solution and then irradiating with 6.5?MeV electrons at different fluences varying from 1?×?10¹⁵ to 5?×?10¹⁵?cm^?2. Results of morphological and elemental analysis, carried out by Scanning Electron Microscopy and Energy Dispersive X-ray. Analysis revealed that the conical tracks could be fully filled with silver nanoparticles at electron fluence of 5?×?10¹⁵?cm^?2. The minimum d. c. resistance of an array of tracks, filled with silver nanoparticles and measured across the polyimide film, was orders of magnitude higher as compared to that of silver wires of equivalent sizes connected in parallel. In addition, these silver nanoparticles filled tracks exhibited rectifying I–V behavior and frequency dependent a. c. resistance, characteristic of metal–polymer nano-composites. Possible mechanisms have been discussed, which can justify the asymmetric current–voltage characteristics in such nano-composites.     

Structural and Chemical Modification in a Polymer by Metal Ion Implantation

Physical and chemical properties changes in a polymer have been studied for polycarbonate (PC) implanted with 100 keV Ni⁺ ions with varying fluence from 1 × 10¹⁴ to 1 × 10¹⁶ ions/cm². The changes in the surface morphology and composition have been observed with atomic force microscopy (AFM) and X-ray diffraction (XRD). The ions implanted induce changes in topography of PC and indicate that the roughness increases dramatically with ion fluence. Implanted metal ions shows direct evidence of compound formation on the surface. The chemical changes in the surface region have been carried out by Raman Spectroscopy and UV-VIS spectroscopy. UV-VIS absorption analysis indicates a drastic decline in optical band gap from 5.46 eV to 1.76 eV at an implanted dose of 1 × 10¹⁶ ions/cm². It could be shown that the partial destruction of chemical bonding under ion implantation leads to the creation of new amorphous and graphite-like structures, which is confirmed by Raman spectroscopy.     

Nonlinear optical properties of nanometer-size silver composite azobenzene containing polydiacetylene film

Diacetylene monomer containing p-nitrophenyl azobenzene moiety (NADA) was synthesized. Silver nanoparticles with different concentrations were adulterated in the above polymerized NADA (PNADA) films and the third-order nonlinear optical properties were investigated in detail. UV–vis spectra and transmission electron microscopy were used to confirm the formation of PNADA/Ag nanocomposite films. The silver nanoparticles (average size of 10 nm) were well dispersed in the polymer films. The value of the nonlinear refractive index n ₂ for PNADA films (8.48×10⁻¹⁵ cm²/W) was much higher than that of pure polydiacetylene films. Further, the introduction of silver nanoparticles into the PNADA polymer films led to the further enhancement of nonlinear optical properties. The maximum value of n ₂ for PNADA/Ag nanocomposite films could be 11.6×10⁻¹⁵ cm²/W. This enhancement should be ascribed to the surface plasmon resonance of silver nanoparticles.     

Optical reflection from dielectric layers containing metal particles formed by ion implantation

Dielectric layers with silver nanoparticles, which are synthesized in a soda-silicate glass by implantation of 60-keV ions with a dose of 7.0×10¹⁶ Ag⁺/cm² at an ion current density of 10 μmA/cm², are analyzed. The depth of silver distribution was measured by Rutherford backscattering. Data on optical characteristics of composite layers were obtained from the transmission spectra and from the reflection, which were measured both from the side of an implanted glass surface and from the unimplanted side. To calculate reflection spectra, a multilayer plane-parallel film structure was considered, which was modeled on the basis of the matrix method using complex Fresnel coefficients. Dielectric functions of separate layers were determined using the Maxwell-Garnet theory of an effective medium. A qualitative agreement between the experimental and the model optical spectra was obtained taking into account a nonuniform depth distribution of metal nanoparticles in a composite material.     

Radiation defects introduced by MeV electrons in argon implanted MOS structures

The influence of MeV electron irradiation on the interface states of argon implanted thin oxide MOS samples has been studied by the thermally stimulated current (TSC) method. The oxide thickness of the structures is 18 nm. Two groups of n-type MOS structures non-implanted and implanted with 20 keV Ar⁺ ions and a dose of 5×10¹² cm⁻² are examined. Both groups are simultaneously irradiated by 23 MeV electrons with doses of 1.2×10¹⁶, 2.4×10¹⁶ or 6.0×10¹⁶ el/cm². The energy position and density of the interface states (generated by electron irradiation, ion implantation or both treatments of the samples) are determined. It is shown that MeV electron irradiation decreases the concentration of interface states (like an oxygen-vacancy and di-vacancy) slightly and creates additional interface states (like an impurity-vacancy) at the Si–SiO₂ interface of argon implanted MOS structures.     

Optical properties of ZnO and Al2O3 implanted with silver ions

ZnO and Al₂O₃ samples implanted with 30-keV silver ions with fluences in the interval (0.25–1.00) × 10¹⁷ ions/cm² are studied by the method of optical photometry in the visible part of the spectrum. The optical transmission spectra of the implanted samples exhibit a selective band associated with surface plasmon resonance absorption of silver nanoparticles. The intensity of this band nonmonotonically depends on the implantation fluence. The silver ion depth distribution in the samples is calculated. It is shown that the non-monotonicity observed in experiments is due to an increase in the substrate sputtering ratio with increasing implantation fluence. It is found that vacuum thermal annealing of the implanted Al₂O₃ layers up to 700°C causes a considerable narrowing of the plasmon absorption bandwidth without a tangible change in its intensity. At higher annealing temperatures, the plasmon absorption band broadens and its intensity drops. Annealing of the ZnO films under such conditions causes their complete vaporization.     

Magnetic and transport properties of transition-metal implanted ZnO single crystals

ZnO single crystals were implanted with Mn, Co and Ni with fluences between 1 × 10¹⁶ cm^-2 and 1 × 10¹⁷ cm^-2 and energy of 200 keV. Results indicate that aggregation of transition metal ions in the as implanted state occurs only in the case of Ni. After an annealing stage to recover the ZnO structure aggregation occurs for the higher fluences of all implanted species. For lower concentrations paramagnetic behaviour with magnetic moments close to those of individual ions is observed. No polarised impurity band is formed as a result of the presence of transition metal ions and all samples show electrical conduction by carriers in extended states of ZnO. Significant values of magnetoresistance are measured at low temperatures, where electrical transport is described by hopping mechanisms between localized states. The sign of the magnetoresistance is dependent of the doping ion and is correlated with the observed aggregation.     

Fluence dependant formation of <Emphasis Type="Italic">β</Emphasis>-SiC by ion implantation and thermal annealing

The β-SiC nanocrystals were synthesized by the implantation of carbon ions (C⁻) into silicon followed by high-temperature annealing. The carbon fluences of 1×10¹⁷, 2×10¹⁷, 5×10¹⁷, and 8×10¹⁷ atoms/cm² were implanted at an ion energy of 65 keV. It was observed that the average size of β-SiC crystals decreased and the amount of β-SiC crystals increased with the increase in the implanted fluences when the samples were annealed at 1100 °C for 1 h. However, it was observed that the amount of β-SiC linearly increased with the implanted fluences up to 5×10¹⁷ atoms/cm². Above this fluence the amount of β-SiC appears to saturate. The Fourier Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy, and X-ray diffraction (XRD) techniques were used to characterize the samples.     

钴离子注入对二氧化钛晶体的结构和光学性能的影响

采用离子注入法制备了钴离子掺杂的金红石相TiO₂样品;离子注入能量、注量分别为40 keV(1×10¹⁶cm^-2),80 keV(5×10¹⁵,1×10¹⁶,5×10¹⁶,1×10¹⁷cm^-2),120 keV(1×10¹⁶cm^-2). 通过XRD,XPS和UV-Vis等手段对掺杂前后样品的结构和光学性能进行了表征,分析了掺杂元素在金红石TiO₂中的存在形式. XRD测试表明随着注入能量的增加晶体的损伤程度增加. UV-Vis测试表明掺杂后所有样品在可见光区的吸收增强; 并且随着注量的增加,注量为5×10¹⁵cm^-2到5×10¹⁶cm^-2范围内注入样品的光学带隙逐渐变小. 关键词： 钴 二氧化钛 离子注入 掺杂     

Synthesis and optical properties of silver nanoparticles in ORMOCER

Experimental results on synthesis of metal nanoparticles in ORMOCER by ion implantation are presented. Silver ions were implanted into organic/inorganic matrix at an accelerating energy of 30?keV and doses in the range of 0.25?10¹⁷ to 0.75?10¹⁷?ion/cm². The silver ions form metal nanoparticles, which demonstrate surface plasmon absorption at the wavelength of 425?C580?nm. The nonlinear absorption of new composite materials is measured by Z-scan technique using 150?fs laser pulses at 780?nm wavelength. ORMOCER matrix shows two-photon nonlinear absorption, whereas ORMOCER with silver nanoparticles demonstrates saturated absorption. Some optical applications of these composite materials are discussed.     

Changes in Structural and Optical Properties of Polycarbonate Induced by Ag+ Ion Implantation

Transparent polycarbonate samples were implanted with 1 MeV Ag⁺ ions to various doses ranging from 5 × 10¹⁴ to 3 × 10¹⁶ ions cm^?2 with a beam current density of 900 nA cm^?2. Modification in the structure of polycarbonate as a function of the implantation fluence was investigated using micro-Raman spectroscopy, glancing angle X-ray diffraction, and UV-Vis spectroscopy. Raman spectroscopy pointed toward the formation of graphite structures/clusters due to the ion implantation. UV-Vis absorption analysis suggests the formation of a carbonaceous layer and a drastic decrease in optical band gap from 4.12 eV to 0.50 eV at an implanted dose of 3 × 10¹⁶ ions cm^?2. The correlation between the decrease in band gap and the structural changes is discussed.     

Raman scattering in a near-surface n-GaAs layer implanted with boron ions

Structure in the Raman scattering spectra of near-surface n-GaAs layers (n=2×10¹⁸ cm⁻³) implanted with 100 keV B⁺ ions in the dose range 3.1×10¹¹–1.2×10¹⁴ cm⁻² is investigated. The qualitative and quantitative data on the carrier density and mobility and on the degree of amorphization of the crystal lattice and the parameters of the nanocrystalline phase as a result of ion implantation are obtained using a method proposed for analyzing room-temperature Raman spectra. Fiz. Tverd. Tela (St. Petersburg) 41, 1495–1498 (August 1999)     

First order Raman scattering analysis of transition metal ions implanted GaN

Transition Metal (TM) ions V, Cr, Mn and Co were implanted into GaN/sapphire films at fluences 5×10¹⁴, 5×10¹⁵ and 5×10¹⁶ cm⁻². First order Raman Scattering (RS) measurements were carried out to study the effects of ion implantation on the microstructure of the materials, which revealed the appearance of disorder and new phonon modes in the lattice. The variations in characteristic modes 1GaN i.e. E₂(high) and A₁(LO), observed for different implanted samples is discussed in detail. The intensity of nitrogen vacancy related vibrational modes appearing at 363 and 665 cm⁻¹ was observed for samples having different fluences. A gallium vacancy related mode observed at 277/281 cm⁻¹ for TM ions implanted at 5×10¹⁴ cm⁻² disappeared for all samples implanted with rest of fluences. The fluence dependent production of implantation induced disorder and substitution of TM ions on cationic sites is discussed, which is expected to provide necessary information for the potential use of these materials as diluted magnetic semiconductors in future spintronic devices.     

Fast ion beams from intense,femtosecond laser irradiated nanostructured surfaces

We present results on hot electron and energetic ion (keV–MeV) generation from polished and nanostructured metallic surfaces excited by p-polarized, femtosecond laser pulses in the intensity range of 1×10¹⁵–1.5×10¹⁷ W cm^-2. A clear enhancement in the hard X-ray spectrum from nanoparticle-coated surfaces is observed, indicating ‘hotter’ electron production in nanoparticle-produced plasma until the intensity of 2×10¹⁶ W cm^-2 is reached. Contrary to the existing perception, we find that the hotter electrons do not lead to hotter ion emission. The total ion flux and the ion energy integrated over the 4–1400 keV energy range are found to be enhanced by 50% and 16%, respectively, for nanostructured targets in comparison to those from polished targets. 55% enhancement in yield is observed for ions at the lower end of the energy range, while hotter ions are actually found to be suppressed by ∼40%. The surface modulations present on the nanoparticle-coated targets are observed to reduce the maximum energy of the ions and showed an intensity-dependent increase in the divergence of the ion beam. PACS 79.20.Ds; 68.47.De; 61.80.Ba; 61.82.Bg; 42.65.Re