Surface Of Metal Film Research Articles

Tuning SERS performance through the laser-induced morphology changes of gold nanostructures

Differently shaped periodic gold nanostructures on the surface of a thin metal film are fabricated utilizing the direct laser writing technique. The variations in the energy of single femtosecond pulses lead to the formation of morphologically distinct hollow nanostructures. The arrays that excite hybridized plasmonic modes are characterized by electron microscopy and assessed for surface-enhanced Raman spectroscopy (SERS). Plasmonic properties are investigated through SERS using the adsorbed 4-mercaptobenzoic acid (4-MBA) molecules. The development of sharp tips in the nanostructures is initiated by the higher-energy laser pulses, while the structure formation principle itself is altered by the thickening of the film. The change in the structure shape and gold layer thickness tune the SERS signal and the enhancement factor (EF), leading to an EF of 107. Such a factor enables the future prospects of the arrays to be applied for single-molecule detection.

EDDY CURRENT METHOD FOR STUDYING INHOMOGENEITIES AND DEFECTS IN THIN METAL FILMS

The variety of structure and specific properties associated with the small thickness of thin metal films lead to the fact that their physical characteristics differ significantly from the characteristics of the same materials in the bulk state. To determine the characteristics of thin metal films, the development of new non-destructive research methods is relevant. The article substantiates the advantages of the eddy current testing method for studying the surface of thin metal films of various metals. The design of a subminiature eddy current transducer designed to study the electrical conductivity, thickness and degree of damage of thin metal films is presented, and a hardware and software complex is designed that allows the control of the developed transducer. The study of metal films made it possible to show the inhomogeneity of the distribution of the substance over the surface of the substrate. The dependence of the signal amplitude of the developed transducer on the film thicknesswas also determined. To verify the results obtained, studies of the light transmittance of the films were carried out using the photometric method. Comparison of the measurement results obtained by the two methods showed a high degree of agreement betweenthe two developed methods for studying films.

Regularities of the Formation of Fractal Structures on the Surface of Metallic Films of Different Thicknesses

Regularities of the Formation of Fractal Structures on the Surface of Metallic Films of Different Thicknesses

On regularities of the formation of fractal structure on the surface of metal films of different thickness

The surface morphology of nanosized copper and nickel films on mica is studied using a scanning tunneling microscope. Altitude parameters and fractal dimension are determined for copper and nickel films of different thicknesses. The characteristic sizes of structural agglomerates for copper and nickel films are indicated depending on the thickness. The choice of the film thickness and the conditions for its production makes it possible to formulate recommendations for the development of the technology of “growing” structures with a given surface morphology.

Dissolving Diamond: Kinetics of the Dissolution of (100) and (110) Single Crystals in Nickel and Cobalt Films

We report a study of the kinetics of dissolution of (100) and (110) single-crystal diamond plates (“D(100)” and “D(110)”) in thin films of nickel (Ni) and cobalt (Co). This dissolution occurs at the metal–D(100) or metal–D(110) interface and was studied in the presence and also in the absence of water vapor at temperatures near 1000 °C. The single-crystal D(100) dissolves in Ni, and also in Co, in the temperature range 900–1050 °C. The dissolution is too slow to measure below 900 °C. In an argon (Ar) atmosphere (under an Ar(g) flow at 1000 sccm and 1 atm pressure, with no water vapor present in the reaction chamber) and at any temperature in the range 900–1050 °C, the metal film is rapidly saturated with dissolved carbon (C), thin graphite films form on the free metal surface and at the metal–D interface during heating at or above 650 °C, and the dissolution of the diamond then stops. For addition of water vapor, its partial pressure was controlled by using a water bubbler immersed in a constant temperature bath and Ar(g) was used as the carrier gas. We discovered two different regimes (I and II) for the kinetics of dissolution of D(100) and D(110), in which the rate-determining step was the removal of carbon atoms on the open metal surface (regime I, lower partial pressure of water vapor) or dissolution of diamond at the metal–diamond interface (regime II, higher partial pressure of water vapor) that yielded different Arrhenius parameters. Time-of-flight-secondary ion mass spectrometry depth profiles show the concentration gradient of C from a certain depth into the metal film surface down to the M–D(100) interface, and residual gas analyzer measurements show that the gas products formed in the presence of water vapor on the metal surface are CO and H2. It was found that the rate of dissolution of diamond in Co was higher than that in Ni for both D(100) and D(110) and for both regimes I and II, and possible reasons are suggested. We also found that D(111) could not be dissolved at the Ni/D(111) and Co/D(111) interface in the presence of water vapor (over the same range of sample temperatures). The reaction paths for dissolution of C at the M–D(100) or M–D(110) interface and for removal of C from the free surfaces of Ni and Co were assessed through density functional theory modeling at 1273 K.

Formation of (Co-=SUB=-40-=/SUB=-Fe-=SUB=-40-=/SUB=-B-=SUB=-20-=/SUB=-)-=SUB=-x-=/SUB=-(LiNbO-=SUB=-3-=/SUB=-)-=SUB=-100-x-=/SUB=- composite film on a metallic substrate

The topological features of the formation of (Co40Fe40B20)15(LiNbO3)85 composite films deposited by ion-beam method on a metal electrode Cr/Cu/Cr has been investigated. The presence of a dielectric layer between the upper Cr layer and the CoFe-LiNbO3 film with a thickness of dox~ 15 nm has been established. The difference in the size of granules near the amorphous layer and in the volume of the film has been shown. A model of the formation of (Co40Fe40B20)x(LiNbO3)100-x nanocomposite film at the initial stage of growth has been proposed. It has been shown that the formation of α-LiNbO3 layer on the chrome metal film surface is possible with the realization of island and layer-by-layer growth mechanisms for various phases of the composite. Keywords: nanocomposite, growth mechanisms, self-organization, structure.

Формирование пленки композитов (Co-=SUB=-40-=/SUB=-Fe-=SUB=-40-=/SUB=-B-=SUB=-20-=/SUB=-)-=SUB=-x-=/SUB=-(LiNbO-=SUB=-3-=/SUB=-)-=SUB=-100-x-=/SUB=- на металлической подложке

The topological features of the formation of (Co40Fe40B20)15(LiNbO3)85 composite films deposited by ion-beam method on a metal electrode Cr/Cu/Cr has been investigated. The presence of a dielectric layer between the upper Cr layer and the CoFe–LiNbO3 film with a thickness of dox ~ 15 nm has been established. The difference in the size of granules near the amorphous layer and in the volume of the film has been shown. A model of the formation of (Co40Fe40B20)x(LiNbO3)100–x nanocomposite film at the initial stage of growth has been proposed. It has been shown that the formation of α–LiNbO3 layer on the chrome metal film surface is possible with the realization of island and layer-by-layer growth mechanisms for various phases of the composite.

Thermal Isotropic Atomic Layer Etching of Metallic Molybdenum

In high aspect ratio structures such as 3D NAND stacks, high-k oxides or certain metals need to be removed from sidewalls and even non-line-of-site locations where access via reactive ion etching would be challenging or impossible. To achieve etching in these locations, thermal processes need to be applied that lack any intrinsic directionality and are therefore isotropic. Thermal Atomic Layer Etching is one option to facilitate this kind of process. Therefore, it has gathered significant attention recently and is now being explored in academia and industry.In this work, we demonstrate isotropic Atomic Layer Etching on metallic molybdenum using a three-step process that involves oxygenation of the metal surface, a conversion reaction using boron-trichloride followed by a hydrogen-fluoride clean step. We measured the etch rate per cycle to be around 10 Å with low temperature dependence in the range between 150°C and 250°C.Furthermore, we examined the effectiveness of various oxygenation methods on the surface of metallic molybdenum films. These methods included thermal oxygenation as a function of temperature, oxygenation by a remote plasma and in-situ plasma fluorination. We established that an oxygenation level of more than 70% as measured with XPS is needed in order for the ALE process to work. Levels in this range could be achieved via in-situ plasma oxygenation as well as with a remote plasma. Thermal oxygenation, on the other hand, required substrate temperatures in access of 400°C to oxygenate at the 70% level.In this study we also show an example of molybdenum ALE in an application that involved the removal of this metal from a 50:1 aspect ratio 3D NAND structure. We measured etch rates on vertical and horizontal surfaces as well as the depth dependence in removal rate of molybdenum.

Surface Plasmon Resonance for Human Bone Marrow Cells Imaging

Surface plasmon resonance imaging (SPRI) detects the changes in refractive index in close proximity to the surface of a thin metal film as variations in light intensity reflected from the back of the film and thus does not require labeling for visualization of the structures under investigation. While traditionally, the wave vector scanning is performed via angular rotations, the wave vector can also be scanned though tuning of the wavelength. Here we demonstrate that a combination of a non-monochromatic electrically tunable bandpass filter in conjunction with highly chromatically corrected imaging objectives can yield subcellular resolution for imaging of the interior refractive index of human mesenchymal stem cells.

Microplasma Source Circuit Using Microring Space–Time Distortion Control

In this work, a microring circuit using space–time distortion control is proposed for plasma source applications. The microring circuit consists of a center microring with two small rings at its sides. The center microring circuit is embedded by a metallic film. The space–time control is applied to the circuit, where the minimum space–time distortion is achieved by the resonant optical path difference of the two-side rings. The whispering gallery mode (WGM) is established by the matching of the space–time distortion in terms of the optical path difference. The coupling between the WGM and electrons on the metallic film surface introduces the trapped electron cloud oscillation. The plasma frequency of the electron cloud is generated by the plasmonic wave oscillation, in which the plasma force can be calculated and obtained. The plasmaforce generated by selected metallic films is investigated for dried spray, force sensor, and electron cloud speed applications. By using the practical device parameters, the simulation results obtained have shown that the plasma frequencies of $1.93\times1016$ , $1.91\times1016$ , and $1.88\times 1016\,\,{\mathrm {rad}} \mathord {\left /{ {\vphantom {{\mathrm {rad}} s}} }\right. } s$ are obtained for gold, silver, and copper films, respectively. The force sensor sensitivity and electron cloud plasma speed are calculated.

Precursor-surface interactions revealed during plasma-enhanced atomic layer deposition of metal oxide thin films by in-situ spectroscopic ellipsometry

We find that a five-phase (substrate, mixed native oxide and roughness interface layer, metal oxide thin film layer, surface ligand layer, ambient) model with two-dynamic (metal oxide thin film layer thickness and surface ligand layer void fraction) parameters (dynamic dual box model) is sufficient to explain in-situ spectroscopic ellipsometry data measured within and across multiple cycles during plasma-enhanced atomic layer deposition of metal oxide thin films. We demonstrate our dynamic dual box model for analysis of in-situ spectroscopic ellipsometry data in the photon energy range of 0.7–3.4 eV measured with time resolution of few seconds over large numbers of cycles during the growth of titanium oxide (TiO2) and tungsten oxide (WO3) thin films, as examples. We observe cyclic surface roughening with fast kinetics and subsequent roughness reduction with slow kinetics, upon cyclic exposure to precursor materials, leading to oscillations of the metal thin film thickness with small but positive growth per cycle. We explain the cyclic surface roughening by precursor-surface interactions leading to defect creation, and subsequent surface restructuring. Atomic force microscopic images before and after growth, x-ray photoelectron spectroscopy, and x-ray diffraction investigations confirm structural and chemical properties of our thin films. Our proposed dynamic dual box model may be generally applicable to monitor and control metal oxide growth in atomic layer deposition, and we include data for SiO2 and Al2O3 as further examples.

Hybrid Plasmonic Fiber-Optic Sensors.

With the increasing demand of achieving comprehensive perception in every aspect of life, optical fibers have shown great potential in various applications due to their highly-sensitive, highly-integrated, flexible and real-time sensing capabilities. Among various sensing mechanisms, plasmonics based fiber-optic sensors provide remarkable sensitivity benefiting from their outstanding plasmon–matter interaction. Therefore, surface plasmon resonance (SPR) and localized SPR (LSPR)-based hybrid fiber-optic sensors have captured intensive research attention. Conventionally, SPR- or LSPR-based hybrid fiber-optic sensors rely on the resonant electron oscillations of thin metallic films or metallic nanoparticles functionalized on fiber surfaces. Coupled with the new advances in functional nanomaterials as well as fiber structure design and fabrication in recent years, new solutions continue to emerge to further improve the fiber-optic plasmonic sensors’ performances in terms of sensitivity, specificity and biocompatibility. For instance, 2D materials like graphene can enhance the surface plasmon intensity at the metallic film surface due to the plasmon–matter interaction. Two-dimensional (2D) morphology of transition metal oxides can be doped with abundant free electrons to facilitate intrinsic plasmonics in visible or near-infrared frequencies, realizing exceptional field confinement and high sensitivity detection of analyte molecules. Gold nanoparticles capped with macrocyclic supramolecules show excellent selectivity to target biomolecules and ultralow limits of detection. Moreover, specially designed microstructured optical fibers are able to achieve high birefringence that can suppress the output inaccuracy induced by polarization crosstalk and meanwhile deliver promising sensitivity. This review aims to reveal and explore the frontiers of such hybrid plasmonic fiber-optic platforms in various sensing applications.

Growth of Thin Graphite Films on a Dielectric Substrate using Heteroepitaxial Synthesis

A technique for growing thin graphite films on a dielectric substrate by annealing the Al2O3(0001)/Ni(111)/ta-C structure has been optimized. This technique is based on catalytic decomposition of hydrocarbons on the surface of a single-crystal catalyst metal film on a dielectric substrate and subsequent diffusion and crystallization of carbon between the metal film and the substrate. A thin graphite film with a low density of crystal-structure defects is obtained on the dielectric substrate after chemical etching of the metal film.

Enhanced sensitivity of bimetallic optical fiber SPR sensor based on MoS2 nanosheets

In this paper, we have fabricated and characterized a bimetallic optical fiber surface plasmon resonance (SPR) sensor, followed by molybdenum disulfide (MoS2) nanosheets have been coated on the surface of metal film. The performance of the sensor is discussed in terms of the sensitivity and the figure of merit (FOM) theoretically and experimentally. The effect of different thickness of Au/Ag film on the performance of the sensor was studied. The results indicate that the FOM of sensor with silver film is much higher than that with gold film, although gold film is conducive to the sensitivity improvement. Two types of sensors are fabricated, which are the sensor with silver layer and the sensor with bimetallic layers of silver and gold. The sensitivity of the sensor with silver film and the sensor with bimetallic layers are 2141 nm/RIU and 2487 nm/RIU, respectively; and the FOM values are 19.44 RIU−1 and 18.47 RIU−1, respectively. Then, it is theoretically confirmed that MoS2 has the potential to promote the sensitivity of SPR sensor, and the sensitivity is tuned by the number of layers of MoS2 nanosheets. MoS2 nanosheets successfully bridged the gold film with the help of chemical bonds. The sensitivity of the sensor with MoS2 nanosheets is 3061 nm/RIU, and its FOM value is 23.29 RIU−1.

High-sensitivity nanostructured aluminium ultrathin film sensors with spectral response from ultraviolet to near-infrared

An aluminum ultrathin film with nanohole arrays arranged in a hexagonal lattice is theoretically explored for the sensor application. Two transmission dips, which exhibit high sensitivity to the refractive index (RI) of the cladding layer or substrate, are presented owing to the excitation of surface plasmons at the top and bottom surfaces of the ultrathin metal film. Numerical results show that a sensitivity of 348 nm/RIU, with a figure of merit of 34.8, are obtained, which are tolerated in the existence of aluminum oxidization. By increasing the RI of the substrate, the related transmission dip is obviously red-shifted, which makes the sensors based on the proposed nanostructure work effectively in a broad spectral range from ultraviolet to near-infrared.

Room temperature sintering of Cu-Ag core-shell nanoparticles conductive inks for printed electronics

The monodisperse Cu-Ag core-shell nanoparticles (Cu@Ag NPs) for electric conductive inks were successfully prepared by a simple two-step process consisting of thermal decomposition and galvanic displacement. It was found that 20 mol.% coverage of Ag enabled Cu@Ag NPs oxidation resisting with air. A new approach to achieve coalescence and sintering of Cu@Ag NPs at room temperature was proposed. 1-amino-2-propanol (MIPA), hydrophilic amine with a short C-chain, was first applied to replace the strong stabilizer, the strong stabilizer oleylamine (OAM) adsorbed on particles, thereby obtained preliminary agglomeration and hydrophobic -to- hydrophilic transition to improve the wetting capability of electrolyte solution on the surface of metal film. Then, the reducing electrolyte NaBH4 solution was used as the destabilizing agent to deeply coalesce particles, and also inhibit the electrochemical corrosion. It takes only a few minutes to achieve sintering in air at room temperature. Due to the effective sintering at room temperature, the conductive patterns could be formed on thermo-sensitive substrates. The eventual resistivity was found to be as low as 36.3 μΩ·cm.

Effect of Thin Metal Film and Micro Structured Surface on Condensation Heat Transfer

Effect of Thin Metal Film and Micro Structured Surface on Condensation Heat Transfer

Effect of Thin Metal Film and Micro Structured Surface on Condensation Heat Transfer

Effect of Thin Metal Film and Micro Structured Surface on Condensation Heat Transfer

Плазмонна спектроскопія поверхні плівок перехідних металів після низькоенергетичного йонного впливу

Плазмонна спектроскопія поверхні плівок перехідних металів після низькоенергетичного йонного впливу

The Effect of Localized Plasmons in Silver and Gold Thin Films on the Optical Properties of Organic Dyes in an Acrylate Polymer Matrix

We present the results of our investigation into the effect of localized surface plasmon resonances of gold and silver nanoparticles on the emissivity of two organic dyes—2-(4-(dimethylamino)styryl)-1-methylpyridinium and rhodamine B—in acrylate-based polymer matrices formed on the surface of island metal films by the UV lithography method. We show that the presence of plasmon resonances significantly enhances both the optical absorption and the fluorescence intensity of these organic dyes in polymer matrices.