Gold Ion Implantation Research Articles

Structure-dependent optical properties of Au/Ag irradiated TiN thin films

Titanium nitride (TiN) is an attractive alternative for modern and future photonic applications, as its optical properties can be engineered over a wide spectral range. In this study, we have used sequential implantation of gold and silver ions with varying ion fluence, as well as subsequent annealing, in order to modify the optical and plasmonic properties of TiN thin films and correlated this to their structural properties. Our investigations show that the columnar structure of the TiN films is partially destroyed upon implantation, but metallic Au and Ag nanoparticles are formed. The irradiation further induces a reduction of the lattice constant as well as changes the TiN stoichiometry and grain size. From the optical point of view, the implanted films possess less metallicity with increasing Ag fluence and losses several times lower than the as-deposited film, which can be correlated with the deficiency of nitrogen and additional defects. Subsequent annealing partially recovered the destroyed columnar structure, and the films become more metallic where the optical losses are much smaller in comparison to the as-implanted situation, being comparable to those of pure Au and Ag. In this way, by varying the implantation fluence of silver ions properly while keeping the gold fluence constant, we were able to optimize experimental parameters in such a way to ensure the formation of TiN with desirable optical performances.

The structural and optical response of the Au nanoparticles embedded in YSZ modified using high-energetic ion irradiation

Gold nanoparticles (Au NPs) were synthesized in single-crystalline yttria-stabilized zirconia (YSZ) using a high-energetic gold ion implantation with the intention of subsequent modification by silicon ion irradiation. (100)-oriented YSZ samples were implanted with 1 MeV Au+ ions at room temperature and fluences of 1.5×1016 cm−2, 5.0×1016 cm−2 and 7.5×1016 cm−2 and subsequently annealed for 1 h at 1100 °C in air. Gold NPs modification was realized with irradiation by 10 MeV Si3+ with the fluence of 5.0×1014 cm−2. Au NPs distribution and subsequent YSZ structure modification were studied. YSZ samples as-implanted with Au ions, annealed and subsequently irradiated with Si ions were characterized using Rutherford backscattering spectrometry (RBS) and RBS in channelling mode (RBS-C). The RBS spectra show that the implanted Auions concentrate in the YSZ sub-surface layer in the depth of about 50-250 nm and shift to greater depth with increasing ion fluence. The Si3+ ions irradiation slightly increased Zr sub-lattice disorder. Optical absorbance shows an increase of absorption band at 550 nm after Au implantation only for the two highest ion fluences. After annealing and Si irradiation, optical absorbance increased at 530-580 nm with connection to ion implantation fluence of Au+ ions.

Self-assembled Au and Pt nanoparticles in Poly(methyl methacrylate).

Nanocomposites formed by metal nanoparticles self-assembled in an insulator matrix are of great technological importance. Applications include surface enhanced Raman spectroscopy based biosensors, optical devices, photovoltaic cells, and more. Self-assembling of nanocomposites using low energy ion implantation offers a fast and low cost process. We report here on our work on nanocomposites formed by very low energy ion implantation of gold and platinum nanoparticles into Poly(methyl methacrylate) (PMMA), with description of the nanoparticle evolution as a function of implantation dose. The Au-PMMA and Pt-PMMA nanocomposites were characterized by transmission electron microscopy, thus determining the nanoparticle density, their size distribution, and the distance between particles as a function of implantation dose. A comparison between Au-PMMA and Pt-PMMA reveals substantial differences in the formation processes of the nanoparticles. The results provide insight into basic nanoparticle formation processes, as well as crucial information important for design applications. In addition, the tunneling decay length ξ and the electron affinity ε of the implantation-modified PMMA were obtained using a new and simple approach.

Creation of Gold Nanoparticles in ZnO by Ion Implantation-DFT and Experimental Studies.

Three different crystallographic orientations of the wurtzite ZnO structure (labeled as c-plane, a-plane and m-plane) were implanted with Au+ ions using various energies and fluences to form gold nanoparticles (GNPs). The ion implantation process was followed by annealing at 600 °C in an oxygen atmosphere to decrease the number of unwanted defects and improve luminescence properties. With regard to our previous publications, the paper provides a summary of theoretical and experimental results, i.e., both DFT and FLUX simulations, as well as experimental results from TEM, HRTEM, RBS, RBS/C, Raman spectroscopy and photoluminescence. From the results, it follows that in the ZnO structure, implanted gold atoms are located in random interstitial positions —experimentally, the amount of interstitial gold atoms increased with increasing ion implantation fluence. During ion implantation and subsequent annealing, the metal clusters and nanoparticles with sizes from 2 to 20 nm were formed. The crystal structure of the resulting gold was not cubic (confirmed by diffraction patterns), but it had a hexagonal close-packed (hcp) arrangement. The ion implantation of gold leads to the creation of Zn and O interstitial defects and extended defects with distinct character in various crystallographic cuts of ZnO, where significant O-sublattice disordering occurred in m-plane ZnO.

Substrate for Surface-Enhanced Raman Spectroscopy Formed by Gold Nanoparticles Buried in Poly(methyl methacrylate).

In this work, we present some properties and use of a nanocomposite formed by gold nanoparticles (NPs) into poly(methyl methacrylate) (PMMA) and its application as substrates for surface-enhanced Raman spectroscopy (SERS). The nanocomposite was formed using low-energy (49 eV) ion implantation of gold in PMMA using a cathodic arc plasma gun. The gold NPs are formed spontaneously from the implanted ions and they remain isolated from each other by the polymer medium surrounding them, ensuring a spacing between the NPs of less than 10 nm (hot spot places). The NPs form below the surface, protected from the environment, guaranteeing the stability of the composite layer. Moreover, here, we present an interesting approach to concentrate analyte molecules closer to the metal surface using the swelling effect in PMMA. Using absorption of the analyte, the molecules stay in the gaps between NPs, which is a good solution for one of the biggest challenges in SERS, that is, to guide molecules to the hot spot places.

Reversing an S-kink effect caused by interface degradation in organic solar cells through gold ion implantation in the PEDOT:PSS layer

In this work, we performed a study on the recovery of the photovoltaic performance of an ITO/PEDOT:PSS/P3HT:PCBM/Ca/Al solar cell after the hole transport layer (PEDOT:PSS) had been degraded by contact with the environment. A device that was fully built in an inert environment exhibited a fill factor (FF) of 0.64, while the device whose hole transport layer was exposed to air presented a FF equal to 0.2. In addition, the J-V characteristic curve of the degraded device did not follow the photovoltaic pattern exhibiting the degenerate S shape. However, the elimination of the deleterious effect was achieved by bombarding gold ions on the contaminated surface of PEDOT:PSS by means of the Metal Plasma Immersion Ion Implantation technique. Due to the low energy of the ionic beam of gold, the implanted gold atoms were located at few nanometers off the surface, forming nanometric clusters, that is, gold nanoparticles. Most probably, the degradation of the J-V photovoltaic curve, represented by the S-kink effect, was caused by the appearance of a potential barrier at PEDOT:PSS/P3HT:PCBM interface, which was demolished by the gold nanoparticles that have work function close to HOMO of P3HT. This S-kink effect was also simulated by using an equivalent circuit model constituted by a two-diode circuit, one of which plays the role of the undesirable potential barrier formed at the PEDOT:PSS/P3HT:PCBM interface. Our analysis shows that deposition of gold nanoparticles next to the interface recovers the good hole injection condition from the PEDOT:PSS into the active layer, restoring the fill factor and the device efficiency.

Plasmonic nanoparticles embedded in single crystals synthesized by gold ion implantation for enhanced optical nonlinearity and efficient Q-switched lasing

We report on the synthesis of embedded gold (Au) nanoparticles (NPs) in Nd:YAG single crystals using ion implantation and subsequent thermal annealing. Both linear and nonlinear absorption of the Nd:YAG crystals have been enhanced significantly due to the embedded Au NPs, which is induced by the surface plasmon resonance (SPR) effect in the visible light wavelength band. Particularly, through a typical Z-scan system excited by a femtosecond laser at 515 nm within the SPR band, the nonlinear absorption coefficients of crystals with Au NPs have been observed to be nearly 5 orders of magnitude larger than that without Au NPs. This giant enhancement of nonlinear absorption properties is correlated with the saturable absorption (SA) effect, which is the basis of passive Q-switching or mode-locking for pulsed laser generation. In addition, the linear and nonlinear absorption enhancement could be tailored by varying the fluence of implanted Au+ ions, corresponding to the NP size and concentration modulation. Finally, the Nd:YAG wafer with embedded Au NPs has been applied as a saturable absorber in a Pr:LuLiF4 crystal laser cavity, and efficient pulsed laser generation at 639 nm has been realized, which presents superior performance to the MoS2 saturable absorber based system. This work opens an avenue to enhance and modulate the nonlinearities of dielectrics by embedding plasmonic Au NPs for efficient pulsed laser operation.

Surface modified graphene oxide nanosheets by gold ion implantation as a substrate for surface enhanced Raman scattering

Graphene oxide (GO) nanosheets are the nanoscale building blocks for stabilization of metal nanoparticles with new hybrid nanocomposite properties. Here, we report on GO nanosheets implanted with low energy gold (Au) ion induced reactive sites for nucleation and intercalation of Au particles in a few layers of GO nanosheets. The nucleation and intercalation mechanisms were dependent on the doses of implanted Au ions in GO nanosheets. Atomic force microscopy (AFM) and Raman analysis of Au ion implanted GO nanostructure showed surface roughening and altered surface chemical states in GO nanostructure. We also observed that Au ion implantation induced reduction of GO surface as confirmed by X-ray diffraction (XRD) analysis and enhanced current-voltage (I-V) characteristics. Our study also indicated that the Au implanted-GO nanocomposites exhibited excellent surface enhanced Raman scattering (SERS) effects which can be used as an excellent SERS substrate.

Density functional theory modeling of C-Au chemical bond formation in gold implanted polyethylene.

We have studied processes of gold ion implantation in polyethylene (PE) by theoretical chemistry methods. Car-Parrinello molecular dynamics (CPMD) simulations of collisions and following chemical kinetics considerations lead to the conclusion that chemical bonds between gold atoms and PE chains are formed. We have identified and characterized by a DFT method various stable structures with C-Au, C-Au-C, C-Au-H and C-AuH2 types of chemical bonds. The binding energies (BE) of C-Au bonds are as high as 227 kJ mol-1 and the bond analysis reveals a covalent bonding character. For the experimental detection of these structures in gold implanted PE, we predicted characteristic infra-red (IR) frequencies. The C-Au stretching vibrational modes lie around 500 cm-1. Other characteristic frequencies lie in a band between 730 cm-1 and 1500 cm-1.

Gold-decorated highly ordered self-organized grating-like nanostructures on Ge surface: Kelvin probe force microscopy and conductive atomic force microscopy studies

Nanoarchitecture by atomic manipulation is considered to be one of the emerging trends in advanced functional materials. It has a gamut of applications to offer in nanoelectronics, chemical sensing, and nanobiological science. In particular, highly ordered one-dimensional semiconductor nanostructures fabricated by self-organization methods are in high demand for their high aspect ratios and large number of applications. An efficient way of fabricating semiconductor nanostructures is by molecular beam epitaxy, where atoms are added to a crystalline surface at an elevated temperature during growth, yielding the desired structures in a self-assembled manner. In this article, we offer a room temperature process, in which atoms are sputtered away by ion impacts. Using gold ion implantation, the present study reports on the formation of highly ordered self-organized long grating-like nanostructures, with grooves between them, on a germanium surface. The ridges of the patterns are shown to have flower-like protruding nanostructures, which are mostly decorated by gold atoms. By employing local probe microscopic techniques like Kelvin probe force microscopy and conductive atomic force microscopy, we observe a spatial variation in the work function and different nanoscale electrical conductivity on the ridges of the patterns and the grooves between them, which can be attributed to gold atom decorated ridges. Thus, the architecture presented offers the advantage of using the patterned germanium substrates as periodic arrays of conducting ridges and poorly conducting grooves between them.

Multienergy gold ion implantation for enhancing the field electron emission characteristics of heterogranular structured diamond films grown on Au-coated Si substrates

Multienergy Au-ion implantation enhanced the electrical conductivity of heterogranular structured diamond films grown on Au-coated Si substrates to a high level of 5076.0 (Ω cm)−1 and improved the field electron emission (FEE) characteristics of the films to low turn-on field of 1.6 V/μm, high current density of 5.4 mA/cm2 (@ 2.65 V/μm), and high lifetime stability of 1825 min. The catalytic induction of nanographitic phases in the films due to Au-ion implantation and the formation of diamond-to-Si eutectic interface layer due to Au-coating on Si together encouraged the efficient conducting channels for electron transport, thereby improved the FEE characteristics of the films.

Preliminary studies of creation of gold nanoparticles on titanium surface towards biomedical applications

This paper is devoted to present the results of creation of gold nanoparticles on titanium surface. We focused on the problem how to create gold nanoparticles on the titanium surface with defined particle size and distribution, which could be interesting for several applications (e.g. providing well-defined substrates for biomedical research, etc.). To do that the sample is affected by the complex physical rout of gold nanoparticles formation: by gold ion implantation, thin Au layer deposition and thermal annealing. The effect of the technology, influence on the surface structure and its parameters were investigated by the X-ray diffraction, Scanning Electron and Atomic Force Microscopy, as well as by Secondary Neutral Mass Spectrometry methods.

Controlling cell morphology on ion beam textured polymeric surfaces

Objectives: Nano and micro sized textures on surfaces are generally useful biomaterials. Although the importance of roughness degree has been reported for cell morphology, texture morphology can be more determining for cell adhesion and proliferation. Biodegradable polymers are extensively used as scaffolds as well as implant materials in the human body. The aim of this study was to investigate the effect of ion beam bombardment on cell morphology. Methods: Gold and carbon ion implantation was made on biodegradable polymers polyglycolic acid, polycaprolactone and polylactic-co-glycolic-acid. Roughness data were obtained from atomic force microscopy. After surface modification with ion beam, B35 neural cells were evaluated on surfaces for cell compatibility. Morphology and cell surface interaction were analyzed with scanning electron microscopy. Results: We observed improved cell adhesion after ion beam surface modification. Cell adhesion was greater on gold implanted surfaces compared to the carbon implanted. Neural cells attached to lamellar wrinkles, spread by taking the shape of the pattern and exhibited high aspect ratios and axon extension. In contrast, cells that attached on the untreated surfaces remained rounded with low spreading. Conclusion: The findings of this study are important for development of ion beam modified cell cultures and scaffold systems to understand texture-based cell adhesion mechanisms. Keywords: cell culture; ion implantation; polylactic-co-glycolic acid; surface treatment; topography; wettability

Formation of Au4Zr nanocrystals in yttria stabilized zirconia in the course of implantation of gold ions

High-resolution transmission microscopy and optical absorption spectroscopy have been used to examine how metallic nanocrystals (NCs) are formed in the course of implantation of Au ions into thin films of yttria stabilized zirconia (YSZ) and subsequent thermal annealing. It was found that, under certain implantation conditions, Au4Zr NCs are formed in addition to Au NCs in the YSZ matrix. The conditions in which Au4Zr NCs are formed in the course of implantation and decompose under the subsequent annealing were determined.

Effect of UV/ozone treatment on the nanoscale surface properties of gold implanted polyethylene

Abstract The effect of ultraviolet (UV) ozone treatment on the surface properties of gold implanted high density polyethylene (HDPE) was investigated at a nanoscale using Atomic Force Microscopy (AFM). HDPE samples were modified by the implantation of gold ions at a dose of 5 × 1015 ions/cm2, using energies of 50, 100, 150, and 200 keV, and subsequently treated with UV/ozone. AFM surface topography images revealed that after UV/ozone treatment, the surface roughness of all Au/HDPE samples increased, while Power Spectral Density function increased only for samples implanted using higher energies, with a maximum for 150 keV. The chemical surface composition was homogenous in all cases, which was evidenced by the appearance of single peaks in the histograms obtained from the phase AFM images. For UV/ozone treated samples, the shift of the peaks positions in the histograms to the higher values of the phase lag with respect to untreated ones indicated the decrease of surface hardness. Besides, a significant change of fractal dimension of surface grains is observed after UV/ozone treatment.

Modification of high density polyethylene by gold implantation using different ion energies

High density polyethylene (HDPE) samples were modified by Au+ ion implantation at a dose of 5 × 1015 ions cm−2, using energies of 50, 100, 150 and 200 keV. The existence of implanted gold in the near-surface region of HDPE samples was confirmed by X-ray diffraction analysis. Surface roughness and Power Spectral Density analyses based on Atomic Force Microscopy (AFM) images of the surface topography revealed that the mechanism of HDPE modification during gold ion implantation depended on the energy of gold ions. Histograms obtained from phase AFM images indicated a qualitative change in the chemical composition of the surface during implantation with gold ions with different energies. Depth profiles obtained experimentally from cross-sectional Force Modulation Microscopy images and ones obtained from a theoretical simulation are in agreement for gold ions energies lower than 100 keV. The deviation that was observed for higher energies of the gold ions is explained by carbon precipitation in the near surface region of the HDPE, which prevented the penetration of gold ions further into the depth of the sample.

Raman Scattering and Backscattering Studies of Silicon Nanocrystals Formed Using Sequential Ion Implantation

Silicon nanocrystals were produced using a two-stage gold ion implantation technique. The first stage implantation using low energy ions led to the formation of an amorphous Si (a-Si) layer. A subsequent high energy Au irradiation in the second stage was found to produce strained Si NCs. An annealing step at a temperature as low as 500 °C was seen to result in strain free NCs. Higher temperature annealing of the samples was found to result in a growth in size from recrystallization of the a-Si matrix. Raman Scattering, X-Ray diffraction and Rutherford Backscattering Spectrometry have been used to study the effect of annealing on the samples and the size of the Si NCs formed. The data can be well explained using a phonon confinement model with an extremely narrow size distribution. The XRD results are in line with the Raman analysis.

Electrical conductivity of gold-implanted alumina nanocomposite

We have carried out ion implantation of gold into alumina ceramic substrates and measured the surface resistivity as a function of implantation dose. The Au ion energy was 40keV and the dose spanned the range 2.7–8.9×1016cm−2. Imaging of the implanted material by transmission electron microscopy revealed that the implanted gold self-assembles into nanoparticles, thus forming a gold-alumina nano-composite. The surface resistivity measurements were compared with the predictions of a model based on percolation theory, in which electron transport through the composite is explained by conduction through a random resistor network formed by the Au nanoparticles. The electrical conductivity of a composite, near the critical conductor–insulator transition, is given by σ≈σ0(x−xc)t, where σ0 is the saturation conductivity for which the material still remains a composite, x is the normalized metal atom concentration of the conducting phase, xc is the critical concentration, or percolation threshold and t is the critical exponent. Excellent agreement was found between the experimental results and the predictions of the theory, and the results are consistent with prior related (but more limited) work. The percolation dose was 4.4×1016cm−2, and the critical exponent obtained was t=1.4±0.1. We conclude that the conductivity process is due to percolation and that the contribution from tunneling conduction is negligible.

Gold ion implantation induced high conductivity and enhanced electron field emission properties in ultrananocrystalline diamond films

We report high conductivity of 185 (Ω cm)−1 and superior electron field emission (EFE) properties, viz. low turn-on field of 4.88 V/μm with high EFE current density of 6.52 mA/cm2 at an applied field of 8.0 V/μm in ultrananocrystalline diamond (UNCD) films due to gold ion implantation. Transmission electron microscopy examinations reveal the presence of Au nanoparticles in films, which result in the induction of nanographitic phases in grain boundaries, forming conduction channels for electron transport. Highly conducting Au ion implanted UNCD films overwhelms that of nitrogen doped ones and will create a remarkable impact to diamond-based electronics.

Electromagnetic characterisation of flexible conductive membranes at millimetre‐waves

Presented is the experimental surface impedance characterisation of stretchable conductors at Ka-band, using a non-contact technique based on two-port rectangular waveguide measurements. Two different types of metallisations are analysed, namely gold ion implantation and corrugated Ag deposition on polydimethylsiloxane membranes. The method allows characterising, in a simple configuration, the surface impedance of any thin metallisation, and is able to reduce the effects of tolerances of substrates and the possible gap between the conductive sheet and the holder waveguide. The obtained surface impedances are discussed in the light of potential applications.