Surface Of Metal Film Research Articles

Sensitivity Enhancement in Surface Plasmon Resonance Biochemical Sensor Based on Transition Metal Dichalcogenides/Graphene Heterostructure.

In this work, a surface plasmon resonance (SPR) biosensor based on two-dimensional transition metal dichalcogenides (TMDCs) is proposed to improve the biosensor’s sensitivity. In this sensor, different kinds of two-dimensional TMDCs are coated on both surfaces of metal film. By optimizing the structural parameters, the angular sensitivity can reach as high as 315.5 Deg/RIU with 7-layers WS2 and 36 nm Al thin film, which is 3.3 times of the conventional structure based on single Al thin film. We also obtain maximum phase sensitivity (3.85 × 106 Deg/RIU) with bilayer WS2 and 35 nm Al thin film. The phase sensitivity can be further improved by employing Ag and removing air layer. The proposed configuration is of great potential for biochemical sensing.

Combined pulsed laser deposition and non-contact atomic force microscopy system for studies of insulator metal oxide thin films.

We have designed and developed a combined system of pulsed laser deposition (PLD) and non-contact atomic force microscopy (NC-AFM) for observations of insulator metal oxide surfaces. With this system, the long-period iterations of sputtering and annealing used in conventional methods for preparing a metal oxide film surface are not required. The performance of the combined system is demonstrated for the preparation and high-resolution NC-AFM imaging of atomically flat thin films of anatase TiO2(001) and LaAlO3(100).

Radially polarized plasmonic vector vortex generated by a metasurface spiral in gold film.

Vector vortices with spatially varying polarization are interesting phenomena and have motivated many recent studies. A vector vortex in the wavefield of a surface plasmon polariton (SPP) may be extended to the sub-wavelength scale, which would be more significant. However, the formation of vector vortices requires the polarization state to possess components parallel to the surface of metal films. In this study, we generated radially polarized vector plasmonic vortices using the metasurface spiral of orthogonal nanoslit pairs. We theoretically derived the x and y component expressions in the central point area of the spiral and obtained a doughnut-shaped intensity distribution with radial polarization. The Jones matrix of the metasurface spiral was generated to describe the polarization characteristics. The results were validated by performing finite-difference time-domain simulations. In addition, we used a Mach-Zehnder interferometer system to extract the intensity and phase distributions of different components of the SPP field. The experimental doughnut-shaped radially polarized vector vortex was consistent with the theoretical and simulated results.

Surface plasmon dispersion relation at an interface between thin metal film and dielectric using a quantum hydrodynamic model

The plasmon excited at the surface of a thin metal film covering on a semi-infinite dielectric substrate is investigated in detailed. The surface plasmon dispersion relation is derived and presented by using the quantum hydrodynamic theory with taking into the quantum statistical and quantum diffraction effects. The effects of the thin metal film character rs and the dielectric constant ε1 on the dispersion relations are shown and discussed, i.e., without and with quantum effects. The results show that increasing rs weakens the quantum effects while increasing ε1 can enhance the quantum effects. In addition, the plasmon dispersion relation with quantum effects is also compared to a classical model. This simple structure proposed in the paper with quantum hydrodynamic theory can be used for yielding meaningful results for studying more complex systems related to surface plasmons.

Real Time Monitoring of Biomolecular Interactions Using Lab-Built Surface Plasmon Resonance (SPR) Instrument

Surface Plasmon Resonance based sensors have found appreciable application in the biochemical and biological research due to its capability of real time monitoring of biomolecular interactions. In this study, we report the label free detection of low weight biological analytes in real time using a lab-built surface plasmon resonance based instrument. Real time binding of biotin to streptavidin attached on sensor chip was monitored in terms of variation in reflected light intensity. Mixed self-assembled monolayer of 1-Octanethiol and 1,10-Decanedithiol was explored as a linker layer for streptavidin attachment on metal film surface. The result shows that developed surface plasmon resonance based instrument has greater potential for detection of the low weight biological analytes as well as monitoring the biomolecular interactions in real time applications.In future this device can be used to investigate about the binding kinetics of bimolecular interactions to resolve the kinetic constants.

Development of a Surface Plasmon Resonance and Plasmon-Waveguide Resonance Combined Chip for Studying the Transport Behaviors of Cell Membrane Transporters

Surface plasmon resonance (SPR) is a powerful label-free and contact-free technique for chemical and biological sensing experiments. However, the traditional use of SPR instruments is for molecular interactions on the surface of metallic film. In order to extend the application of SPR, we integrated the concept of plasmon-waveguide resonance (PWR) and proposed the idea of PWR/SPR combined chip in order to measure the transport behaviors of cell membrane transport proteins. The PWR/SPR combined chip is composed of a silica layer with sub-micron sized pores on a thin gold film. The geometry allows us to use SPR to detect the refractive index change in the pore region, which is correlated to the target species concentration inside the pore, and PWR to simultaneously monitor the change of refractive index at the top silica surface. We deposited the giant plasma membrane vesicles (GPMV) derived from cells onto the PWR/SPR combined chip to construct the lipid membrane with native membrane proteins suspending over the sub-micron sized pores. Consequently, the detection area can be divided into two regions including the space inside the pores and the region above the grating structure. By using COMSOL simulation, we confirmed that this system allows us to simultaneously measure the change of refractive indices in the two regions across the lipid membrane. We experimentally demonstrated how the platform can be used to study the glucose transport through the corresponding membrane transport proteins (Glut 1, Glut2). In the future, we plan to use these platforms to monitor how various inhibitors or ligands could influence the transport dynamics of interested membrane transport proteins.

Surface plasmon resonance refractive index sensor based on ultraviolet bleached polymer waveguide

In this paper, a compact refractive index (RI) sensor based on the resonant interaction between surface plasmon polaritons (SPP) mode and polymer waveguide mode is demonstrated. The hybrid plasmonic waveguide consists of ultraviolet (UV) sensitive SU-8 polymer and thin gold film on a silica layer. The SPP mode field is theoretically confirmed to be sensitive to the RI of analyte on the metal film surface. UV light bleaching method is adopted to fabricate the channel waveguide, which is covered by a 35 nm-thick gold layer. Microfluidic channel is used to flow organic solutions with RI of 1.52–1.60 through the sensing area. The experimental result indicates that the device has a sensitivity of 1023dB/RIU, corresponding to a resolution of 1×10−6 refractive index units (RIU) at 1550nm. The advantages of inherent feature and simple fabrication promise its potential for a portable, compact, and easily-produced refractometer.

Analytical inversion solutions for temperature dependent surface absorptivity of metal film irradiated by laser

In this paper, the analytical inversion algorithm for temperature dependent absorptivity during the metal film surface irradiated by laser is studied. Firstly, the heat conduction modeling of laser irradiated metal thin film is presented, and the analytical solutions of temperature are obtained by using Laplace transformation. Then, the inversion algorithm of temperature dependent absorptivity is established based on the conjugate gradient method, and the sensitivity analysis of the inversion parameters is carried out. Finally, accuracy and efficiency of the inversion algorithm for temperature dependent absorptivity are tested by the specific examples. The presented algorithm can be used to optimize the parameters of laser processing, and can also provide a theoretical basis for the design of anti laser materials, which has a certain theoretical significance and application value.

Blistering of film from substrate after action of ultrashort laser pulse

The goal of the paper is to explain experimental results concerning film blistering. Tightly focused diffraction limited ultrashort optical laser pulse illuminates a small spot at a surface of a thin metal film mounted upon a dielectric or semiconductor support (substrate). Film mechanically separates from substrate and form a cupola like bump in a rather narrow range of absorbed fluences. Below this range deformations inside the spot are negligible. While above the range the hole remains in a film in the irradiated spot. The paper presents physical model starting from absorption and two-temperature state and including, first, description of conductive redistribution of absorbed heat, melting, hydrodynamics of strong three-dimensional deformations of a moving film, and, second, freezing of molten metal.

Interplay of quantum size effect, anisotropy and surface stress shapes the instability of thin metal films

Morphological instability of a planar surface ([111], [011], or [001]) of an ultra-thin metal film is studied in a parameter space formed by three major effects (the quantum size effect, the surface energy anisotropy and the surface stress) that influence a film dewetting. The analysis is based on the extended Mullins equation, where the effects are cast as functions of the film thickness. The formulation of the quantum size effect (Z. Zhang et al., PRL 80, 5381 (1998)) includes the oscillation of the surface energy with thickness caused by electrons confinement. By systematically comparing the effects, their contributions into the overall stability (or instability) is highlighted.

Towards a high performing UV-A sensor based on Silicon Carbide and hydrogenated Silicon Nitride absorbing layers

Exposure to ultraviolet (UV) radiation is a major risk factor for most skin cancers. The sun is our primary natural source of UV radiation. The strength of the sun's ultraviolet radiation is expressed as Solar UV Index (UVI). UV-A (320–400 nm) and UV-B (290–320 nm) rays mostly contribute to UVI. UV-B is typically the most destructive form of UV radiation because it has enough energy to cause photochemical damage to cellular DNA. Also overexposure to UV-A rays, although these are less energetic than UV-B photons, has been associated with toughening of the skin, suppression of the immune system, and cataract formation. The use of preventive measures to decrease sunlight UV radiation absorption is fundamental to reduce acute and irreversible health diseases to skin, eyes and immune system. In this perspective UV sensors able to monitor in a monolithic and compact chip the UV Index and relative UV-A and UV-B components of solar spectrum can play a relevant role for prevention, especially in view of the integration of these detectors in close at hand portable devices. Here we present the preliminary results obtained on our UV-A sensor technology based on the use of hydrogenated Silicon Nitride (SiN:H) thin passivating layers deposited on the surface of thin continuous metal film Ni2Si/4H-SiC Schottky detectors, already used for UV-Index monitoring. The first UV-A detector prototypes exhibit a very low leakage current density of about 0.2 pA/mm2 and a peak responsivity value of 0.027 A/W at 330 nm, both measured at 0V bias.

Bottom-Up Fabrication of Hybrid Plasmonic Sensors: Gold-Capped Hydrogel Microspheres Embedded in Periodic Metal Hole Arrays.

The high potential of bottom-up fabrication strategies for realizing sophisticated optical sensors combining the high sensitivity of a surface plasmon resonance with the exceptional properties of stimuli-responsive hydrogel is demonstrated. The sensor is composed of a periodic hole array in a gold film whose holes are filled with gold-capped poly(N-isoproyl-acrylamide) (polyNIPAM) microspheres. The production of this sensor relies on a pure chemical approach enabling simple, time-efficient, and cost-efficient preparation of sensor platforms covering areas of cm2. The transmission spectrum of this plasmonic sensor shows a strong interaction between propagating surface plasmon polaritons at the metal film surface and localized surface plasmon resonance of the gold cap on top of the polyNIPAM microspheres. Computer simulations support this experimental observation. These interactions lead to distinct changes in the transmission spectrum, which allow for the simultaneous, sensitive optical detection of refractive index changes in the surrounding medium and the swelling state of the embedded polyNIPAM microsphere under the gold cap. The volume of the polyNIPAM microsphere located underneath the gold cap can be changed by certain stimuli such as temperature, pH, ionic strength, and distinct molecules bound to the hydrogel matrix facilitating the detection of analytes which do not change the refractive index of the surrounding medium significantly.

레이저 초음파를 이용한 체적종파의 박막 내 전파특성 연구

본 논문에서는 나노스케일 금속박막 내에서 체적종파가 전파하는 특성을 연구하였다. 실리콘(100) 기판 위에 150 nm 두께의 크로뮴 혹은 알루미늄 박막을 적층하여 시편을 제작하였으며, 펨토초 레이저 시스템으로 구성된 시간영역 열반사율 기법(time-domain theromoreflectance technique)을 이용하여 박막 표면으로부터 여기된 탄성파가 박막과 기판의 계면에서 반향될 때 발생하는 신호를 검출하였다. 체적종파의 거동을 모사하는 열탄성 방정식을 수치해석적으로 풀어 측정값과 곡선맞춤함으로써 박막의 체적종파 속도와 탄성계수를 평가할 수 있었으며, 결과를 문헌값과 비교하여 그 타당성을 검증하였다. 본 연구로부터 확립된 레이저 계측법은 나노재료의 특성평가에 적합함을 보여주며, 이는 기존의 접촉식 파괴식 검사법의 한계를 뛰어넘을 대안을 제시한다. This paper presents the investigation of the propagation behavior of bulk longitudinal waves generated by an ultrafast laser system in thin films. A train of femtosecond laser pulses was focused onto the surface of a 150-nm thick metallic (chromium or aluminum) film on a silicon substrate to excite elastic waves, and the change in thermoreflectance at the spot was monitored to detect the arrival of echoes from the film/substrate interface. The experimental results show that the film material characteristics such as the wave velocity and Young's modulus can be evaluated through curve-fitting in numerical solutions. The material properties of nanoscale thin films are difficult to measure using conventional techniques. Therefore, this research provides an effective method for the nondestructive characterization of nanomaterials.

3D Cross-Point Plasmonic Nanoarchitectures Containing Dense and Regular Hot Spots for Surface-Enhanced Raman Spectroscopy Analysis.

3D stacking of plasmonic nanostructures is achieved using a solvent-assisted nanotransfer printing (S-nTP) technique to provide extremely dense and regular hot spot arrays for highly sensitive surface-enhanced Raman spectroscopy (SERS) analysis. Moreover, hybrid plasmonic nanostructures obtained by printing the nanowires on a continuous metal film or graphene surface show significantly intensified SERS signals due to vertical plasmonic coupling.

Raman Enhancement in Metal-Cladding Waveguide and the Influence of the Metal Film Surface Roughness

Enhanced Raman scattering in a metal cladding waveguide was demonstrated theoretically and experimentally. The thickness of guiding layer of the waveguide sensor was about 0.5–1 mm, the analyte was located in the guiding layer of the sensor, where the electric field intensity is enhanced owing to the ultrahigh order modes excited by a focused laser beam. An enhancement of at least one order of magnitude was got experimentally. As the coupling metal film is only about 30 nm, the effect of surface roughness may not be ignored. The effect of surface roughness of coupling film on Raman scattering was also studied. It was found that roughness of coupling film surface may also make a contribution to Raman enhancement.

An electrochemical study of the nickel hydroxide-gold modified electrode employing the surface resistance technique

Simultaneous cyclic voltammetry (CV) and surface resistance (SR) measurements were employed to study the electrochemical behaviour of the nickel hydroxide-gold modified electrode. To this end, firstly, gold film electrodes of different thicknesses were synthesized, and their CV and SR responses within the potential regions corresponding to hydroxide ion adsorption (OHads) and gold oxide (AuO) formation in alkaline medium were analysed. Then, these gold film electrodes were modified with different nickel hydroxide surface coverages, and their CV and SR responses were compared with those of bare gold films within the same potential regions and electrolyte solution. While cyclic voltammetric responses of the bare gold film electrode and the nickel hydroxide-gold film modified electrode are practically the same within the whole potential range−0.5V<E<0.35V (SCE), SR responses are the same only within the potential range −0.3V<E<0.35V. Strong differences between the SR responses of the bare gold electrode and the nickel hydroxide-gold modified electrode within the potential range comprised between −0.5V and −0.3V are observed. SR data were interpreted in terms of the field effect and size effect theories formulated to study adsorption processes at thin metallic films. With regard to the bare gold film electrode, the field effect theory allows one to conclude that within the potential region corresponding to hydroxide ion adsorption, 77% of the electron density charge of gold is involved in the hydroxide ion–gold interaction. Besides, a linear relation between the surface resistance change (ΔR) and the degree of oxidation (θox) at fixed gold film thickness (ϕm) is obtained within the potential region corresponding to gold oxide formation. In agreement with the size effect theory, the ΔR/θox slope exhibits a linear dependence on ϕm−2. The same SR responses for the nickel hydroxide-gold modified electrode and the bare gold electrode within the potential range −0.3V<E<0.35V indicate that the nickel hydroxide layer does not directly interact with the gold film surface. However, after the reduction of OHads and AuO layers, at potential values more negative than −0.3V (SCE), an increase of the surface resistance is observed for the nickel hydroxide-gold modified electrode, which was attributed to nickel adatoms that directly interact with the gold film surface. On the basis of the electron conduction scattering model employed to describe the interaction of a metal film surface with a foreign atom layer, one can conclude that nickel film growth involves an initial stage in which nickel islands and then, compact structures are formed.

Noninvasive thickness measurements of metal films through microwave dielectric resonators

Thicknesses of Pt films ranging from 60 to 950 nm are measured noninvasively using a TE011-mode dielectric resonator with the resonant frequency of 8.5 - 9.8 GHz at temperatures of 77 K and 293 K. A cylindrical rutile rod is used as the dielectric, with a high-TC superconductive YBa2Cu3O7−δ film used as the bottom endplate of the resonator for measurements at 77 K. This method is based on two facts: i) Due to the electromagnetic interferences of incoming and reflected waves at the surface of the metal film surface, the effective surface resistance varies with the film thickness, and ii) the intrinsic surface resistance of normal metals is equal to the intrinsic surface reactance in the local limit. The measured thicknesses using the rutile resonator appear to be comparable with those obtained using a profilometer.

Simultaneous Excitation of Surface Plasmon Polaritons on Both Interfaces in an Asymmetric Dielectric-Metal Corrugated Structure

The simultaneous excitation of plasmon polaritons on both surfaces of metal film was studied for asymmetric dielectric-metal-dielectric corrugated structures. Due to the small resonant absorption of the incident light on the transmission side of the structure, we investigated the enhancement of the surface plasmon polaritons on the mentioned side by controlling the structure parameters. When the illuminate light changes from normal incidence to non-normal incidence, the resonant absorption peak splits into a doublet. The simultaneous excitation of surface plasmon polaritons on both surfaces of the metal film can be achieved by controlling the incident angle. Since the wave vector matching condition is not satisfied, there is no coupling between the plasmon polaritons modes on the two surfaces of the corrugated metallic film. The excitation and control of the non-coupled surface plasmon polartions simultaneously propagating on the different interfaces of one metallic film have potential applications for designing novel compact and tunable nano-photonic devices at visible frequency.

凝縮形態へ及ぼす金属薄膜面と微細加工面の影響に関する実験的検討

凝縮形態へ及ぼす金属薄膜面と微細加工面の影響に関する実験的検討

Strong-Field-Enhanced Spectroscopy in Silicon Nanoparticle Electric and Magnetic Dipole Resonance near a Metal Surface

Strong-field-enhanced spectroscopy in a hybrid dipole resonance system composed of a low-loss semiconductor nanoparticle and metal film is proposed and demonstrated. This hybrid Si nanoparticle on silver system is featuring extraordinary near-field enhancement and large field confinement. Extensive numerical calculations are carried out to investigate the influence of the gap size, particle diameter, and metal substrate on the near-field enhancement response in the Si particle–metal gap in order to properly model their hybridization. Our analysis reveals that this near-field enhancement originates from the strong gap magnetic resonance response by the Si nanoparticle dipole interaction with metal mirror image and metal film surface plasmon effects. We further demonstrate the strong enhanced Raman spectroscopy of a single silicon nanoparticle over Ag film with a precisely sized molecular spacer layer between them. These results illustrate the capacity and tunability of the low-loss silicon particle on the ...