Ag Sputtering Research Articles

Fabrication of Ag–ZnO NRs SERS substrates for abamectin detection: the effect of Ag sputtering times and ZnO sol concentrations in seed layer preparation on SERS performance

Fabrication of Ag–ZnO NRs SERS substrates for abamectin detection: the effect of Ag sputtering times and ZnO sol concentrations in seed layer preparation on SERS performance

Facile fabrication of PS/Cu2S/Ag sandwich structure as SERS substrate for ultra-sensitive detection

In this work, a serials of PS(polystyrene)/Cu2S/Ag sandwich substrates were successfully constructed using the magnetic sputtering method by adjusting the Ag sputtering time (0 min, 2 min, 4 min, 6 min, 8 min and 10 min) and used as the surface-enhanced Raman scattering (SERS) substrates. When the Ag sputtering time was 6 min, the strongest SERS signal was observed. The optimized SERS substrate has strong SERS activity on 4-mercaptobenzoic acid (4-MBA), the minimum detection limit was 10−13 M and the enhancement factor was as high as 4.7 × 107. In addition, the SERS signals were highly reproducible with small standard deviation. The SERS enhancement mechanism of the PS/Cu2S/Ag system was attributed to the synergistic effect of the chemical mechanism and the electromagnetic enhancement mechanism. This strategy has find a new way for manufacturing SERS activity sensor with high sensitivity and reproducibility.

Preparation of CuO/Ag rough nanostructures as SERS-active substrates

In this paper, CuO nanostructures with nanometer roughness were firstly prepared by electrochemical anodic oxidation method, and then CuO/Ag composite nanostructures were prepared by magnetron sputtering method on the surface of CuO substrate. The successful deposition of Ag films on CuO was confirmed by XRD, UV-Vis and SEM. In addition, the effects of different Ag sputtering time on substrate morphology and SERS properties were studied. Due to the many gaps between the rough CuO/Ag nanomorphology, the substrate has many “hot spots” and adsorption sites, which can effectively improve the SERS performance of the substrate. We selected R6G dye molecule as the probe molecule to evaluate the SERS performance of the substrate. The final experimental results show that the preparation method of CuO/Ag rough nanostructure is simple, and it has significant SERS performance improvement. The substrate’s detection limit for R6G can even reach 10-11M.

Sputtering of Mo and Ag with xenon ions from a radio-frequency ion thruster.

The goal of this work is to set up an electric propulsion (EP) sputtering test section as a feasibility study for ground-based sputter testing of spacecraft materials with a radio-frequency ion thruster. Such experiments deliver valuable data, which are scarce but highly desired to model EP-based space missions, for example, with the Spacecraft Plasma Interaction System in order to predict the performance and lifetime of spacecraft components. This study assessed if sufficient testing conditions can be met to produce reliable experimental material data in the future. Therefore, the thruster was operated at ion energies of 1.5 and 1.8 keV, and a quartz crystal microbalance (QCM) was installed to detect sputter deposition rates. Molybdenum (Mo) and silver (Ag) were chosen as sputter targets. Wafer substrates served as a passive sampling method to characterize the composition of sputtered material by Rutherford backscattering spectrometry. Additionally, sputtering simulations matching the experimental conditions were performed with the software SDTrimSP. We obtained comparable experimental and computational data, as measured sputter deposition rates lie within the simulated order of magnitude and to some extent show the predicted angular dependence. Analysis of the deposited sputter material revealed the formation of metal oxides, which requires a future adaption of the material specific QCM settings. Furthermore, the cooling system of the QCM sensor head was not sufficient, limiting the comparability of results.

Preparation and property optimization of silver-embedded FTO transparent conductive thin films by laser etching and coating AZO layer

Preparation and property optimization of silver (Ag)-embedded fluorine-doped tin oxide (FTO) films were achieved based on laser etching, sputtering Ag layers, furnace annealing, sputtering aluminum-doped zinc oxide (AZO) layers and laser annealing. Specifically, a nanosecond pulsed laser (λ = 532 nm) was used to etch grooves on FTO films before sputtering 5-nm-thick Ag layers, with an aim for enabling the Ag nanoparticles from the furnace-annealed Ag layers to be intensively embedded in the grooves under the thermal-induced dewetting effect. The optimal laser fluence for laser etching and temperature for furnace annealing were found to be 0.4 J/cm2 and 300 °C, respectively. The as-obtained Ag-embedded FTO film exhibited significantly improved optical and electrical properties, being attributed mainly to the decreased coverage area of the Ag nanoparticles on the FTO film surface and the furnace annealing effect. The subsequently sputtered 10-nm-thick AZO layer suppressed the internal light reflection from the Ag nanoparticles, and laser annealing further facilitated grain growth in the film. Therefore, the resulting film had the best comprehensive property with the highest figure of merit of 20.94 × 10–3 Ω–1, which was much higher than that of the original FTO film (7.65 × 10–3 Ω–1). This work may provide a new combined processing method for high-performance transparent conductive films.

Preparation and growth mechanism of a gold-coloured Ag@AAO composite film with no angular dependence

Ag-coated anodic aluminium oxide film with a golden colour was successfully synthesized by an ultrahigh vacuum magnetron sputtering system. Free-standing Ag films were obtained by a mechanical stripping process. The results indicate that the Ag films have an ordered close-packed hexagonal pattern similar to that of the anodic aluminium oxide template. The structural colour of the sample is not derived from thin-film interference. UV–Vis reflectance spectra measurements show that the blue purple-spectrum area has a relatively strong absorption. The absorption peak indicates that the golden colour comes from localized surface plasmons. We think the reason, for the gold-coloured Ag@AAO composite film, is the periodic arrangement of Ag particles. This is also the reason why the golden colour does not change with the viewing angle. Further research shows that the Ag atoms initially grew preferentially on the hexagonal vertices of the anodic aluminium oxide template, and then Ag islands grew on the top of the anodic aluminium oxide surface, finally forming narrow Ag nanoholes on top of the wider pores of the template below, with increasing Ag sputtering time. These films show the promise of application in many areas, including decoration, display and anti-counterfeiting.

Sputtering of Ag (111) nanotwinned films on Si (100) wafers for backside metallization of power devices

For improving the performance of backside metallization for power electronic devices, an innovative Ag film with ultra-high twin density is proposed in this study. Experimentally, nanotwinned Ag films with thicknesses ranging from 2 to 8 µm and a strong (111) preferred orientation were sputtered on Si (100) wafers with and without a Ti thin film. The results indicated that the coincident Σ3 twin and Σ9 near-twin boundaries in proportion to the total grain boundaries in this Ag nanotwinned film on Ti pre-coated Si (100) wafer were 50.8 % and 13.5 %, respectively. These Ag nanotwins had spacing of 2 to 50 nm, with an average spacing of about 12 nm, and were contained in columnar Ag grains grown normal to the Si wafer. The employment of a Ti interlayer of 0.1 µm thickness clearly improved the adhesion at the Ag/Si interface under peeling tests, resulting in a bonding strength of 1.7 MPa and a maximal indentation hardness of 2 GPa.

Improve optical properties by modifying Ag nanoparticles on a razor clam SERS substrate.

Irregular substrates are inappropriate for enhancing surface enhanced Raman scattering (SERS) due to their poor performances in terms of uniformity, enhancement performance, and polarization characteristics. However, in this work, we purposely employed a natural biological razor clam material with messy and irregular structures to improve the SERS. The rough surface was achieved by magnetron sputtering Ag nanoislands on the prism layer of the razor clams, and the Ag nanoparticles were treated using the method of oil-water interface self-assembly to form relatively uniform structures. Compared to the substrate without Ag nanoparticles, the presented substrate has better reproducibility, polarization-independence, and higher SERS intensity, and the detect limitation of R6G can be decreased from 10-12 M to 10-18 M. The ultrasensitive detection of thiram gives our structures potential for high sensitivity biosensors.

Characteristics of secondary electron emission and multipactor from a nested microtrap structure surface

It is known that an appropriate surface structure can suppress the secondary electron emission as a result of the receded multipactor in a spacecraft microwave component. On the other hand, the multiplier effect caused by electron re-entrance in ordinary surface structures can degrade the suppression of secondary electron emission. The present paper concerns our proposition of a new type of two-level nested microtrap structure surface able to effectively inhibit the generation of the secondary electrons inside the trap structure to achieve better suppression of the total secondary electron emission on the surface. The surface of a two-level nested microtrap array structure was obtained by lithography, stripping, dry etching, and Ag sputtering. Experimental tests were conducted on the two proposed nested structures with different sizes. The test results show that inhibition effects of the two structures have been improved by 100% and 144% compared with those of the traditional single-hole trap structure. The secondary electron yield on the bottom surface of the rough nested trap due to Ag sputtering is higher than that of the ideal regular structure simulated by Monte Carlo. In addition, the larger depth-to-width ratio of the nested trap can inhibit the multi-generation multiplication of electrons in the trap more effectively and further improve the inhibition effect on secondary electrons. For an impedance transformer, the proposed two size nested structure surface can increase the multipactor power threshold by about 346% and 386%. This method plus the nested microtrap structure can achieve a better secondary electron emission suppression effect and further improve the multipactor threshold of space microwave components.

Angular Distributions during Magnetron Sputtering of Polycrystalline Mg, Al, Si, Ti, Cr, Cu, Zn, Ge, Zr, Nb, Mo, Ag, In, Sn, W, Pt, Au, and Bi Targets

The results of experimental investigations of the angular distributions during magnetron sputtering of Mg, Al, Si, Ti, Cr, Cu, Zn, Ge, Zr, Nb, Mo, Ag, In, Sn, W, Pt, Au, and Bi targets in argon at a constant current are presented. The operating conditions during the experiments corresponded to the values typical of industrial sputtering equipment. The angular distribution of the material flow was calculated based on the measured thickness of the coating deposited on two flexible ribbon substrates. These substrates were fixed in place on a substrate holder in the form of two crossed half-rings that were equidistant from the center of the magnetron target (the curvature radius was 100 mm). The influence of the magnitude and shape of the magnetic field near the surface of the sputtered cathode on the angular distribution was also investigated. The results can be used as the source data for calculating the profile of the coating during magnetron sputtering.

Monolayer ZnS@Ag Nanospheres SERS Substrate for Highly Sensitive Dye Molecules Detection

Surface-enhanced Raman scattering (SERS) substrates with low cost, high sensitivity and good reproducibility are still challenging in practical application. Herein, we propose a facile method to prepare monolayer ZnS@Ag nanospheres (NSs) by sputtering Ag nanoparticles (NPs) on the surfaces of the monolayer ZnS NSs produced by self-assembly. The monolayer ZnS@Ag NSs have rough surface and nanoscale gaps, which can produce large SERS effect. The dye molecules, Rhodamine 6G (R6G) and Rhodamine B (RhB), were used as probe to evaluate the SERS performance on the monolayer ZnS@Ag NSs. It was found that the monolayer ZnS@Ag NSs showed the high SERS sensitivity in the detection of R6G and RhB, the limit of detection (LOD) down to 9.12×10−13 M and 8.55×10−11 M, respectively. The corresponding enhancement factors (EF) are 3.01×108 and 8.2×106, respectively. Furthermore, the ordered structure makes the monolayer ZnS@Ag NSs substrate with high signal reproducibility and stability, and the relative standard deviation (RSD) values are less than 15%. Therefore, the monolayer ZnS@Ag NSs is a candidate for detecting organic dyes in the environment.

The Effect of Charged Ag Nanoparticles on Thin Film Growth during DC Magnetron Sputtering

The possibility that charged nanoparticles (CNPs) are generated in the gas phase during direct current (DC) magnetron sputtering of Ag is studied. Sputtered Ag particles could be captured on an ultrathin amorphous carbon membrane for transmission electron microscopy (TEM) observation. It is confirmed that the average particle size and the total area of deposition under the condition of the positive bias applied to the substrate are bigger than those under the condition of the negative bias applied to the substrate. The results indicate that some of the sputtered Ag particles are negatively charged. To evaluate the contribution of negatively-charged particles to the film growth, Ag thin films were deposited for 30 min on the Si substrate with the substrate biases of −300, 0 and +300 V and analyzed by field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and four-point probe. When +300 V was applied to the substrate, the film growth rate was highest with the film thickness of 85.0 nm, the crystallinity was best with the smallest full width at half maximum (FWHM) value of 0.44 and the resistivity was smallest with 3.67 μΩ·cm. In contrast, when −300 V was applied to the substrate, the film growth rate was lowest with the film thickness of 68.9 nm, the crystallinity was worst with the largest FWHM value of 0.53 and the resistivity was largest with 8.87 μΩ·cm. This result indicates that the charge plays an important role in film growth and can be a new process parameter in sputtering.

Improved Charge Transfer Contribution by Cosputtering Ag and ZnO.

A two-dimensional polystyrene microsphere array cosputtered with Ag and ZnO was designed for evaluating surface-enhanced Raman scattering (SERS) activity. The surface plasmon resonance (SPR) and SERS properties were significantly changed by the introduction of ZnO into the Ag film. By increasing the Ag sputtering power, a redshift of the SPR peak was obtained. Moreover, improved SERS activity occurred because of the electromagnetic (EM) contribution from the increasing Ag content and the charge transfer (CT) contribution from the introduction of ZnO. More importantly, the Hall effect was employed to evaluate the carrier density effect on the SERS contribution of the Ag/ZnO film. The increase in the carrier density as the Ag sputtering power increased indicated an increasing number of free electrons stored in the Ag/ZnO film, which was accompanied by improved EM and CT contributions.

Ag nanoparticles decorated ZnO: Al nanoneedles as a high-performance surface-enhanced Raman scattering substrate

This present study used a simple aqueous chemical growth method to synthesize Al-doped ZnO (ZnO: Al) nanoneedles on ZnO seeds/glass substrates. The surface morphology and length of ZnO: Al nanostructures can suitably control by the concentration of aluminum sulfate. The surface-enhanced Raman scattering (SERS) effect of Ag sputtering durations on the ZnO: Al nanoneedles and the concentration of aluminum sulfate on the ZnO: Al/Ag heterostructures systematically investigated. The ZnO: Al/Ag heterostructures (2 mM aluminum sulfate and 60 s sputtering time) exhibited a more substantial enhancement, a lower detection limit (10−10 M), excellent uniformity, high reusability and stability for the SERS detection of rhodamine 6G molecule. The ZnO: Al/Ag heterostructures can also use to detect the lower concentration of melamine (10−9 M) and 5-fluorouracil (10−7 M). ZnO: Al/Ag heterostructures can provide a low-cost and straightforward manufacturing method with high enhancement, low detection limit, excellent uniformity, and reusability for the SERS applications in areas of chemical and medicine.

Damping resonance and refractive index effect on the layer-by-layer sputtering of Ag and Al2O3 on the polystyrene template

In this study, an ordered metal oxide-metal composite system was designed. By changing the thickness of film of Ag/Al2O3 nanoparticles (NPs), the red and blue shifts of local surface plasma resonance (LSPR) were realized in the proposed system and discussed by damping resonance theory and Mie's scattering theory to demonstrating the relationship between wavelength (λ) and particle diameter (D). With the increasing of sputtering time of Ag, the SPR of Ag was red shifted under the influence of damped vibration, obtaining that square of wavelength (λ2) is proportional to D. The surface plasma resonance (SPR) of Ag/Al2O3 showed an obvious blue shift, and then red shift suddenly, which is affected by the competition between damping resonance and refractive index. When the blue shift occurs, the change of wavelength (∆λ) is exponentially related to the diameter (D). The modulation of LSPR of the proposed composite nano-metal materials will have a potential application in SPR sensor and surface enhanced Raman scattering (SERS).

A novel SERS substrate: Wrinkled ZnS nanobelt film coated with Ag nanoparticle

Wrinkled ZnS nanobelt film was used as a template for Ag sputtering deposition as a surface-enhanced Raman scattering (SERS) substrate. The substrate exhibits excellent SERS performance because of its unique structure and possesses the great potential in trace-detecting persistent organic pollutants in the environment.

Enhancing the thermoelectric performance of ZnO film by sputter-deposition of Ag nanoparticles

Owing to the surface plasmon resonance (SPR), noble metal nanoparticles (NPs) have been intensively employed to improve the optical properties of semiconductors. In this work, Ag NPs are deposited on fully c-axis oriented ZnO film with high-crystallinity prepared by radiofrequency magnetron sputtering on glass substrates. After Ag sputtering of 15 s, the ultraviolet light emission intensity of ZnO film significantly is increased by 50% due to the SPR of Ag NPs. Moreover, the conductive behavior changes from n-type semiconductor to metal-like with room-temperature conductivity sharply increasing by nearly three orders of magnitude from 4.8 for pure ZnO film to 3400 S cm−1 for Ag-deposited ZnO film. The change of conductive behavior and the remarkable increase of the conductivity can be ascribed to isolated Ag NPs with high-density electrons which are distributed on the ZnO film, leading to an increase of carrier concentration that exceeds Mott’s critical density (>1019 cm−3). Hall measurements show that after Ag sputtering of 15 s, the mobility increases from about 8 to 40 cm2 V−1s−1 and that the carrier concentration increases from 4 × 1018 to 5 × 1020 cm−3. Owing to the remarkable improvement of the conductivity, the power-factor value at room temperature is enhanced from 11.5 to 49.2 μWm−1K−2.

Material and device properties of Si-based Cu0.5Ag0.5InSe2 thin-film heterojunction diode

Cu0.5Ag0.5InSe2 (CAIS) thin films were deposited on a glass substrate by sequential sputtering of Cu, Ag, and In2Se3-stacked film layers. Structural characterization showed that the deposited CAIS film satisfies nearly the stoichiometric form with uniform and homogeneous surface structure. The single-phase polycrystalline behavior without any secondary-phase formation was observed from the diffraction profile. The optical properties were investigated using temperature-dependent transmission measurements in the wavelength region of 600–1100 nm and in between 10 and 300 K. In the region of interest, the transmission spectra shifted towards the higher wavelengths as a result of an increase in the sample temperature. The analysis of the absorption data based on the transmission spectra resulted in absorption coefficient values of around 105 cm−1 and the presence of direct allowed optical transition. From the Tauc plots, CAIS samples were found to have three distinct direct optical transitions depending on the possible splitting in the valence band. The obtained room temperature uppermost band gap energy value of 1.09 eV was found in the energy limit of ternary analogues (CuInSe2 and AgInSe2), and also in a good agreement with the previous works in the literature. The dependency of the band gap energy on the temperature was analyzed using fundamental relations. In addition, the electrical characteristics of the film layer were discussed in four-contact conductivity measurements, and room temperature conductivity was observed as 0.8 Ω−1 cm−1. Additionally, two activation energy values were found in the temperature-dependent conductivity profile. As a diode application, CAIS/Si heterojunction was fabricated and the main diode parameters were extracted at dark and room temperature conditions.

Enhanced transparency of ultrathin Ag films through wetting layer of phosphomolybdic acid

Phosphomolybdic acid (PMA) was exploited as a cost-efficient material in combined spin-coating/sputtering deposition of PMA/Ag transparent conductive electrode for optoelectronic applications. Sputtering of Ag on glass results in the grainy films which are characterized by low transmittance and poor conductivity. It is demonstrated that the wetting layer composed of spin-coated PMA provides perfect conditions for the formation of ultrathin (7–10 nm) and smooth (root-mean-square < 3 nm) Ag films. By optimizing the thickness of Ag film, the sheet resistance of 17 Ω/sq and the transmittance of 79% at 550 nm is achieved. Further improvement of electrode performance is shown for PMA/Ag/PMA multilayer where the top PMA is applied as a bifunctional layer to boost the transmittance up to 84% and to effectively encapsulate Ag film providing its long-term stability in ambient conditions.

Enhanced antibacterial performance of ultrathin silver/platinum nanopatches by a sacrificial anode mechanism

The development of antibacterial implant surfaces is a challenging task in biomaterial research. We fabricated a highly antibacterial bimetallic platinum (Pt)/silver(Ag) nanopatch surface by short time sputtering of Pt and Ag on titanium. The sputter process led to a patch-like distribution with crystalline areas in the nanometer-size range (1.3–3.9 nm thickness, 3–60 nm extension). Structural analyses of Pt/Ag samples showed Ag- and Pt-rich areas containing nanoparticle-like Pt deposits of 1–2 nm. The adhesion and proliferation properties of S. aureus on the nanopatch samples were analyzed. Consecutively sputtered Ag/Pt nanopatches (Pt followed by Ag) induced enhanced antimicrobial activity compared to co-sputtered Pt/Ag samples or pure Ag patches of similar Ag amounts. The underlying sacrificial anode mechanism was proved by linear sweep voltammetry. The advantages of this nanopatch coating are the enhanced antimicrobial activity despite a reduced total amount of Ag/Pt and a self-limited effect due the rapid Ag dissolution.