CN110618478B

CN110618478B - Fano resonance structure based on single metal silver nanoparticle-metal silver film and preparation method thereof

Info

Publication number: CN110618478B
Application number: CN201910908748.4A
Authority: CN
Inventors: 李芳�; 姚付强; 韩晓博; 刘帅; 许立图; 刘亚辉
Original assignee: Wuhan Institute of Technology
Current assignee: Wuhan Institute of Technology
Priority date: 2019-09-25
Filing date: 2019-09-25
Publication date: 2021-12-24
Anticipated expiration: 2039-09-25
Also published as: CN110618478A

Abstract

The invention discloses a Fano resonance structure based on a single metal silver nanoparticle-metal silver film and a preparation method thereof. The preparation method of the resonance structure comprises the following steps: (1) plating a metal film on the insulating substrate by an electron beam evaporation method; (2) depositing a layer of transparent dielectric film on the metal film by using an atomic layer deposition method; (3) and dispersing the metal nano particles on the transparent dielectric film by a drop coating method. The resonance structure can realize and regulate Fano resonance by adjusting the size of the metal nano particles, when the medium environment around the metal nano particles changes, the resonance peak position of the Fano resonance changes, the energy locality of the resonance structure can improve the sensitivity of the resonance structure to the environmental change, and the preparation method is simple and easy to operate, has good repeatability and is convenient to apply.

Description

Fano resonance structure based on single metal silver nanoparticle-metal silver film and preparation method thereof

Technical Field

The invention relates to a metal plasmon resonance structure and a preparation method thereof, in particular to a Fano resonance structure based on a single metal silver nanoparticle-metal silver film and a preparation method thereof.

Background

Metal surface plasmon is a physical optical phenomenon in which light irradiates on a metal interface to excite collective oscillation of electrons on the surface of the metal. The optical properties of metallic nanostructures originate from Localized Surface Plasmon Resonance (LSPR). Localized surface plasmon resonances are highly sensitive to the material, size and shape of the nanostructure as well as the surrounding dielectric environment. Because of the sensitive characteristic, the LSPR attracts people's attention, and has very wide application in the fields of biosensing, Surface Enhanced Raman Scattering (SERS), slow light transmission, nano-antenna, nonlinear enhancement, sensing and the like. In addition, through coupling between surface plasmons, one observes a Fano resonance effect in a surface plasmon system.

The Fano resonance is caused by destructive interference of a weak radiation dark mode and an ultra-radiation bright mode in the metal nano structure, can effectively inhibit radiation attenuation and form a fine spectral line, has high quality factors and large local field enhancement, and has resonance characteristics which are very sensitive to the surrounding environment of the nano structure, so that the Fano resonance is very suitable for preparing a high-sensitivity biochemical sensor. In recent years, with the development of the nanostructure fabrication process, the Fano resonance of the nanostructure has attracted much attention. By breaking the symmetry of nanostructures, a wide variety of metal nanostructures have been designed to achieve Fano resonance, such as nanoring-nanodisc resonant cavities, heterodimers, nanoshells, asymmetric nanoparticle dimers, nanodiscs incorporating gaps, nanoparticle-substrate coupled systems, and the like. However, most structures are complex to manufacture.

Disclosure of Invention

The invention aims to provide a Fano resonance structure based on a single metal silver nanoparticle-metal silver film, which is simple and easy to operate and can realize and regulate Fano resonance. Meanwhile, the invention also provides a preparation method of the Fano resonance structure, and the preparation method is simple and easy to operate, good in repeatability and convenient to apply.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows: a Fano resonance structure based on a single metal silver nanoparticle-metal silver film comprises metal nanoparticles, a transparent dielectric film and a metal film which are sequentially arranged from top to bottom.

In a specific embodiment of the present invention, the diameter of the metal nanoparticles in the metal nanoparticles is on the order of nanometers.

Further, the metal nanoparticles are Ag nanocubes with an average diameter of 75nm and different chamfer sizes.

In one embodiment of the present invention, the thickness of the metal thin film is less than 100 nm.

Further, the metal thin film is a silver film.

Further, the silver film thickness was 80 nm.

In one embodiment of the present invention, the thickness of the transparent dielectric film is 2 nm.

Further, the transparent dielectric film is Al₂O₃A film.

A preparation method of a Fano resonance structure based on a single metal silver nanoparticle-metal silver film comprises the following steps:

(1) plating a metal film on the insulating substrate by an electron beam evaporation method;

(2) depositing a layer of transparent dielectric film on the metal film by using an atomic layer deposition method;

(3) and dispersing the metal nano particles on the transparent dielectric film by a drop coating method.

Further, the insulating substrate in the step (1) is a silicon wafer.

Compared with the prior art, the invention has the beneficial effects that:

(1) the single metal nanoparticle can excite local plasma resonance (LSPR), the metal nanoparticle and a mirror light field excited by a bottom metal film are mutually coupled by introducing the transparent dielectric film to form Fano resonance, and meanwhile, the position and the coupling strength of a resonance peak can be conveniently adjusted by adjusting the diameter and the chamfer size of an Ag cube and the thickness of the transparent dielectric film.

(2) Simple structure, easy and simple to handle, good reproducibility easily uses.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments will be briefly described below.

FIG. 1 is a schematic structural diagram of a Fano resonant structure based on a single metal silver nanoparticle-metal silver thin film, wherein the electric field polarization direction of incident light is in an XZ plane;

FIG. 2 is a TEM image of an Ag cube with the inset being a cross-sectional view of the structure of a single Ag cube;

FIG. 3 is a dark field imaging of an Ag cube;

FIG. 4 shows the scattering spectra obtained from experiments with different cubic Ag samples;

FIG. 5 is a scattering spectrogram obtained by theoretical calculation for different sizes of Ag cubes;

FIG. 6 is a scattering spectrogram of experiment obtained when the surrounding environment of Ag cube is air, water and alcohol respectively;

fig. 7 is a linear fit plot of Fano resonance shift as a function of refractive index n.

Detailed Description

Other aspects, features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which form a part of this specification, and which illustrate, by way of example, the principles of the invention. In the referenced drawings, the same or similar components in different drawings are denoted by the same reference numerals.

As shown in fig. 1, the Fano resonant structure based on a single metallic silver nanoparticle-metallic silver thin film according to the embodiment of the present invention includes a metallic nanoparticle, a transparent dielectric film, and a metallic thin film, which are sequentially disposed from top to bottom.

In a specific embodiment of the invention, the metal nanoparticles are Ag cubes with a diameter of 75 nm; the transparent dielectric film is Al₂O₃A thin film having a thickness of 2 nm; the metal thin film was a silver film, and the thickness thereof was 80 nm.

The preparation method of the Fano resonance structure based on the single metal silver nanoparticle-metal silver film comprises the following steps:

(1) the method of electron beam evaporation on insulating silicon wafer by using electron beam evaporation and resistance evaporation coating equipment is at 9 x 10^-4Plating a silver film with the thickness of 80nm under the air pressure of Pa.

(2) Depositing a layer of Al on the silver film by utilizing the atomic layer deposition method for the ALD atomic layer deposition coating equipment at the temperature of 100 ℃ and the gas pressure of 0.004Torr₂O₃And the thickness of the film is 2 nm.

(3) Taking out 5 μ L of Ag cubic solution with pipette at room temperature, and dripping the Ag cubic solution on Al₂O₃On the Ag film, after about 1 minute, distilled water was dropped thereon to dilute the density of the Ag cubic particles, achieving a monodispersed dispersion.

After the structure is prepared, the structure can be used for corresponding tests, and the test results are as follows:

as shown in fig. 2, fig. 2 shows a TEM image of Ag cubes, and it can be seen from fig. 2 that there are some slight differences in the chamfer size and diameter of the Ag cubes. As shown in fig. 3, fig. 3 shows a dark field imaging diagram of Ag cubes, and bright spots with different gray values can be seen from fig. 3, which represents that the scattering wavelength of particles is different because the difference of the chamfer size and diameter of the Ag cubes causes the difference of the plasma resonance peak position of the metal nanocavity. The scattering spectrograms obtained by experiments and theoretical calculation under different sizes of the Ag cube are obtained by changing the size of the Ag cube, and are respectively shown in FIGS. 4 and 5, but the diameters of the Ag cube are different when the chamfer sizes of the Ag cube are different, so that the applicant calculates three chamfer sizes through FDTD software, wherein the chamfer sizes are respectively 9nm, 9nm and 10nm, and the corresponding side lengths are respectively 73nm, 74nm and 75 nm. Finally, the silver nanocubes were placed in different medium environments, and a spectrogram of the experimental spectrum as a function of the refractive index of the surrounding environment was measured, as shown in fig. 6, and a linear fit of the Fano resonance shift as a function of the refractive index n was plotted, as shown in fig. 7, and the FOM value for the Fano resonance was calculated to be 2.57. And a certain reference value is provided for the sensor based on the Fano resonance refractive index sensitivity.

While the foregoing is directed to the preferred embodiment of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

1. A Fano resonance structure based on a single metal silver nanoparticle-metal silver film is characterized by comprising metal nanoparticles, a transparent dielectric film and a metal film which are sequentially arranged from top to bottom;

the metal nano particles are Ag nano cubes, and the average diameter of the metal nano particles is 75 nm;

the metal film is a silver film, and the thickness of the silver film is 80 nm;

the transparent dielectric film is Al₂O₃And the thickness of the film is 2 nm.

2. The method for preparing the Fano resonant structure based on the single metal silver nano-particle-metal silver thin film according to claim 1, comprising the following steps:

3. The method for preparing the Fano resonant structure based on the single metallic silver nano-particle-metallic silver thin film according to claim 2, wherein the insulating substrate in the step (1) is a silicon wafer.