CN117606619A - Enhanced detection integrated infrared spectrum chip based on tunable surface plasmon - Google Patents

Abstract

An enhanced detection integrated infrared spectrum chip based on tunable surface plasmons, which from top to bottom is the source and drain stages, graphene/boron nitride heterojunction, nanogap layer, dielectric metasurface, and dielectric layer, infrared detector, substrate. Among them, there is a nanogap layer between the dielectric metasurface and the graphene/boron nitride heterojunction. The dielectric metasurface serves as the gate electrode. The source and drain stages are evaporated on the surface of the graphene/boron nitride heterojunction to form a tunable Surface plasmon waveguide resonators. The infrared detector is vertically integrated with the tunable surface plasmon waveguide resonator through a dielectric layer for infrared spectrum signal detection. Under the irradiation of infrared light waves, the low-loss surface plasmon mode is excited, and the resonant peak is controlled by an external electric field to achieve a wide-band wavelength scan. Infrared spectrum signals are obtained sequentially in a time sequence. Through processing, the infrared spectrum absorption signal of the molecule can be obtained. Finally, Realize the integrated infrared spectrum chip of "spectrum enhancement" and "spectrum detection". The invention has the advantages of high sensitivity, wide range of detection material types, small size and high integration level.

Description

Enhanced detection integrated infrared spectroscopy chip based on tunable surface plasmons

Technical field

The invention relates to the technical field of infrared spectroscopy, and in particular to an infrared spectrum detection chip integrating spectrum enhancement and spectrum detection.

Background technique

Infrared spectroscopy technology can directly detect molecular vibration modes. It has unique advantages such as high "fingerprint" characteristics, no need for sample labeling, non-destructive in-situ detection, and qualitative and quantitative analysis. It is a highly potential on-site rapid spectral detection technology and is widely used in Biomedicine, environmental monitoring, food safety testing, chemical composition analysis, explosive detection and other important fields related to the national economy and people's livelihood and the lifeline of the national economy. However, traditional infrared spectroscopy technology suffers from the problem of low sensitivity and its inability to detect low concentrations of biomolecules. The main reason is that the wavelength of mid-infrared light (6~16 μm) is three orders of magnitude larger than the size of molecules (<10 nm), resulting in extremely weak interaction between light waves and molecules, making it extremely difficult to detect infrared spectrum signals.

In recent years, surface-enhanced infrared spectroscopy technology developed based on the surface plasmon effect can excite highly localized electromagnetic resonance modes around molecules, confining light waves in nanometer space, thereby greatly enhancing the interaction between light waves and molecules. This technology provides a new idea to solve the problem of extremely weak interaction between light waves and molecules, and breaks through the technical bottleneck of low detection sensitivity of infrared spectroscopy systems. It has rapidly developed into a cutting-edge interdisciplinary field such as micro-nano optics, nanotechnology, and life sciences. Research hotspots. Currently, studying the excitation mechanism of high-intensity localized electromagnetic modes and their interaction with molecular vibration modes in order to greatly enhance the molecular infrared absorption spectrum signal is the primary problem that this technology needs to solve. Based on the current research status at home and abroad, there are currently two main solutions:

The first idea is based on the metal surface plasmon effect, using a metal surface plasmon device combined with a Fourier transform infrared spectrometer to achieve spectral signal detection. By designing various metal nanostructures to generate high-intensity localized electromagnetic patterns around molecules, high-precision detection of specific types of trace molecules can be achieved. However, the resonant frequency of metal surface plasmons is located in the ultraviolet and visible light bands. The energy loss of metal surface plasmons in the infrared band is serious. The loss and bandwidth limitation of metal materials are determined by the inherent characteristics of metal free electron gas, resulting in The resonant frequency cannot be dynamically tuned, and the infrared spectrum enhancement band is narrow.

The second idea is to enhance the infrared absorption spectrum signal of molecules based on the graphene surface plasmon effect, and use a surface plasmon device combined with a Fourier transform infrared spectrometer to achieve spectral signal detection. The two-dimensional material graphene is a new two-dimensional crystal material composed of carbon atoms. It can support the surface plasmon intrinsic localized electromagnetic mode in the infrared band. This mode has extremely low loss, large local enhancement, and resonance. Frequency tunable and other features. By adjusting the external voltage to change the plasmon frequency of the graphene nanostructure, the infrared vibration information of biomolecules such as proteins can be detected with high precision.

However, graphene surface plasmon devices still have common problems such as large plasmon resonance peak linewidth and low quality factor, which leads to the existing graphene surface plasmon enhanced infrared spectroscopy technology having enhancement multiples and spectral The problem of low resolution makes it usually necessary to combine it with a Fourier transform infrared spectrometer to obtain the infrared absorption spectrum signal of molecules. Due to the shortcomings of traditional Fourier transform infrared spectrometers such as large size, heavy weight, and high price, this spectral detection method relies heavily on infrared spectrometers, which seriously hinders the rapid on-site detection application of this technology.

Contents of the invention

In order to overcome the shortcomings of the existing technology, the present invention proposes an enhanced detection integrated infrared spectrum chip based on tunable surface plasmons, which uses graphene/boron nitride heterojunction and dielectric metasurface composite to design a tunable surface The plasmon waveguide resonator excites low-loss surface plasmon modes to achieve narrow-band filtering and molecular infrared absorption spectrum enhancement; the tunable surface plasmon waveguide resonator and the infrared detector are monolithically integrated, and the external The electric field regulates the resonant peak to achieve wide-band wavelength scanning, and obtains infrared spectrum signals in a time sequence, ultimately realizing the enhancement and detection of molecular infrared absorption spectrum signals. It is easy to use, has high sensitivity and high integration, and can realize a variety of unknown trace molecules. Realizing advantages such as detection, it can be used in fields such as biomedicine, environmental monitoring, and food safety.

In order to solve the technical problems of the present invention, the technical solutions adopted are:

An enhanced detection integrated infrared spectrum chip based on tunable surface plasmons. The chip is provided with source and drain stages, graphene/boron nitride heterojunction, nanogap layer, and dielectric metasurface from top to bottom. , dielectric layer, infrared detector and substrate.

The dielectric metasurface is obtained by depositing a silicon layer on the surface of the dielectric layer, and further processing the silicon layer to form the structural outline of the metasurface, thereby obtaining the dielectric metasurface structure, which is used to realize the surface plasmon mode and the wave vector of free space light. match. The dielectric metasurface also serves as a back electrode to achieve electrical control of graphene. Compared with using metal metasurfaces, using dielectric metasurfaces can effectively reduce losses and improve the quality factor (Q value) of the spectrum.

The graphene/boron nitride heterojunction is a composite of a boron nitride film and a graphene film, which is used to reduce the influence of the substrate on the graphene material properties to obtain a low-loss surface plasmon mode.

There is a nanogap layer between the dielectric metasurface and the graphene/boron nitride heterojunction. The nanogap layer serves as a gate dielectric layer. The graphene/boron nitride heterojunction and the dielectric metasurface Forming a structure similar to a parallel plate capacitor.

The source electrode and the drain electrode are deposited on the graphene/boron nitride heterojunction, and the source electrode and the drain electrode are connected through the graphene.

The dielectric layer is located between the infrared detector die and the dielectric metasurface, that is, it is located on the infrared detector as a protective layer to protect the surface of the infrared detector die and avoid subsequent micro-nano processing of infrared detection. causing damage to the device die.

The infrared detector is located on the substrate, and a tunable surface plasmon waveguide resonator is formed by a dielectric layer, the graphene/boron nitride heterojunction, the nanogap layer and the dielectric metasurface. Vertical monolithic integration is used for infrared spectrum signal detection. The detection integrated signal is denoised and demodulated through the spectral reconstruction algorithm to obtain the infrared spectrum absorption signal of the molecule. The detection of trace molecules is realized based on the obtained spectral information.

In the above structure of the present invention, the graphene/boron nitride heterojunction, the nanogap layer and the dielectric metasurface form a tunable surface plasmon waveguide resonator that can be generated under infrared light wave excitation. Surface plasmons can be tuned to generate strong local electric fields on the graphene surface. Further, by applying an external voltage between the graphene/boron nitride heterojunction and the dielectric metasurface, the surface conductivity of the graphene is adjusted, thereby dynamically adjusting the surface plasmon resonance peak and achieving narrow-band filtering. . At the same time, when the surface plasmon resonance frequency is tuned to be consistent with the molecular vibration frequency of the substance to be detected, the electromagnetic field intensity in the unit space around the molecule to be detected reaches its strongest, greatly enhancing the infrared spectrum signal of the molecule to be detected.

Preferably, the external voltage applied between the graphene/boron nitride heterojunction and the dielectric metasurface ranges from -2 to 2 V, and the graphene surface plasmon resonance peak is achieved in the infrared range of 5 to 16 μm. Dynamic adjustment.

Using the above-mentioned structural device of the present invention, electrical signals are detected under different voltage conditions, and the detected signals are formed into corresponding sets. A numerical calculation model is constructed and converted into a linear model. The parameters to be solved are obtained through an optimization algorithm, and based on the optimal The value of excellence reconstructs spectral information to denoise and demodulate the integrated detection signal output by the infrared detector to obtain the infrared spectrum absorption signal of the molecule. The detection of trace molecules is achieved based on the obtained spectral information.

Furthermore, the metasurface structure of the dielectric metasurface adopts a periodic array structure, and has different structural shapes such as rectangle, circle, bowtie shape, double bowtie shape, concentric ring shape or cross shape in the transverse direction of the chip. It is obtained through photolithography technologies such as electron beam exposure, focused ion beam etching, ultraviolet lithography, and laser direct writing, combined with methods such as electron beam evaporation, magnetron sputtering, and thermal evaporation. The size and period range of the metasurface structure is 0.1μm~1μm, and the thickness of the metasurface structure ranges from 20~100nm.

Further, the graphene/boron nitride heterojunction is a multi-layer stack of boron nitride films and graphene films in the vertical direction. The number of stacked layers is 1 to 5, and boron nitride is located at the bottom layer of the heterojunction. In contact with the nanogap layer, graphene is located on the top layer of the heterojunction and is in contact with the source and drain. It can be prepared through a mechanical peeling process or a chemical vapor deposition method. The number of layers of the heterojunction film can be transferred through multiple transfers. way to achieve.

Further, the nanogap layer located between the graphene/boron nitride heterojunction and the dielectric metasurface has a thickness range of 2-20nm, and the material is an infrared transparent material selected from: Al ₂ O ₃ , KBr, MgF ₂ , CaF ₂ , BaF ₂ , AgCl, ZnSe, SiO ₂ .

Further, the thickness of the dielectric layer on the infrared detector ranges from 100 to 500 nm, which is used to protect the infrared detector bare chip. The material of the dielectric layer is an infrared transparent material, selected from: Al ₂ O ₃ , KBr, MgF ₂ , CaF 2 , BaF ₂ , AgCl, ZnSe, SiO ₂ .

Compared with the existing technology, the present invention has the following advantages:

First, graphene is a two-dimensional electron gas material composed of a single layer of carbon atoms. It supports the propagation of surface plasmons in the infrared band. By adjusting its resonant wavelength to be consistent with the vibration frequency of the molecule to be measured, the trace can be greatly increased. The interaction of light molecules with light. At the same time, graphene has a large specific surface area and good biocompatibility, and can effectively adsorb biomolecules on the surface of graphene.

Second, the present invention utilizes the composite method of graphene/boron nitride heterojunction and dielectric metasurface to effectively avoid a large number of boundaries and defects introduced by graphene nanopatterning, improve the lifetime of graphene free carriers, and thereby enhance The lifetime of graphene surface plasmons effectively reduces optical losses. As shown in Figure 5, the use of graphene/boron nitride heterojunction can excite a lower and low-loss surface plasmon mode, and obtain a plasmon resonance peak with higher excitation efficiency and narrower line width. It can improve the coupling efficiency between the surface plasmon resonance mode and the molecular vibration mode during application, and improve the detection sensitivity.

Third, the graphene/boron nitride heterojunction, nanogap layer and dielectric metasurface designed in the present invention are combined to form a tunable plasmon waveguide resonator, which can obtain plasmon resonance with a narrower line width. Peak, by applying an external bias voltage to adjust the conductivity of the graphene surface, it is possible to perform wide-band dynamic tuning of the graphene surface plasmon resonance wavelength to achieve narrow-band filtering in the infrared band.

Fourth, existing graphene surface plasmons usually need to be used in conjunction with a Fourier transform infrared spectrometer to obtain the infrared absorption spectrum signal of molecules. Due to the shortcomings of traditional Fourier transform infrared spectrometers, such as large size, heavy weight, and high price, , hindering the technology from moving from laboratory sampling analysis to on-site rapid detection. In order to solve this problem, the present invention proposes a monolithic integrated structure of a tunable surface plasmon waveguide resonator and an infrared detector. It does not rely on traditional optical interference structures, frequency scanning and spectroscopic components to build an enhanced and detected integrated infrared spectrum chip. , greatly enhances the molecular infrared absorption spectrum signal, and achieves "spectral enhancement" and "spectral detection" on the same device. This invention can achieve wavelength scanning by regulating the resonant peak of the resonator through an external electric field, denoise and demodulate the detection integrated signal through a spectrum reconstruction algorithm, and obtain the infrared spectrum absorption signal of the molecule, thereby realizing molecule detection without using traditional Fourier methods. Leaf infrared spectrometer can be used for rapid on-site detection.

It can be seen that the present invention can realize "spectral enhancement" and "spectral detection" of molecular infrared absorption signals at the same time, and has the advantages of high sensitivity, wide band dynamic tunability, small size, easy integration, etc., and has broad application prospects.

Description of drawings

Figure 1 is a schematic diagram of the enhanced detection integrated infrared spectrum chip;

Figure 2(a)-Figure 2(f) are schematic diagrams of antenna arrays of rectangular, circular, bowtie-shaped, double bowtie-shaped, concentric ring-shaped or cross-shaped dielectric metasurfaces;

Figure 3 is an enlarged longitudinal cross-section of the dielectric metasurface;

Figure 4 is a flow chart of the preparation method of the enhanced detection integrated infrared spectrum chip;

Figure 5 shows the infrared absorption spectrum of graphene/boron nitride heterojunction and different graphene electronic relaxation times;

Figure 6 Infrared absorption spectrum of enhanced detection integrated infrared spectrum chip under different voltage conditions;

Figure 7 shows the reconstructed infrared spectrum signal after the enhanced detection integrated infrared spectrum chip adsorbs probe molecules;

Figure 8 shows the molecular infrared absorption spectrum detected by the enhanced detection integrated infrared spectrum chip;

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention more clear, the preferred embodiments of the present invention will be described in further detail below in conjunction with the accompanying drawings, in which the same symbols represent the same or similar components.

Referring to Figure 1, the enhanced detection integrated infrared spectrum chip based on tunable surface plasmons designed by the present invention includes a substrate 1, an infrared detector 2, a dielectric layer 3, a dielectric metasurface 4, and a substrate 1 arranged in sequence from bottom to top. Nanogap layer 5, graphene/boron nitride heterojunction 6, source electrode 7 and drain electrode 8. During testing, the molecules 10 to be tested are placed on the chip through spraying, spin coating, drop coating, etc. Among them, the infrared detector 2 is located on the substrate 1, the dielectric layer 3 is located on the infrared detector 2, the dielectric metasurface 4 serves as a gate electrode and is located on the dielectric layer 3, and the graphene/boron nitride heterojunction 6 is located on the nanogap layer 5, the source electrode 7 and the drain electrode 8 are deposited on the graphene/boron nitride heterojunction 6, and the source electrode 7 and the drain electrode 8 are conductive through the graphene/boron nitride heterojunction 6.

In the above structure, the nanogap layer 5 is arranged between the dielectric metasurface 4 and the graphene/boron nitride heterojunction 6 to form a tunable surface plasmon waveguide resonator for exciting surface plasmons in the infrared band. , and at the same time, a structure similar to a parallel plate capacitor is formed. By applying an external voltage through the voltage source 9 between the graphene/boron nitride heterojunction 6 and the dielectric metasurface 4, the Fermi level of graphene is regulated and achieved. Regulation of ionotropic resonance peaks. The thickness of the nanogap layer 5 ranges from 2 to 20 nm, and the material is an infrared transparent material, which can be selected from: Al ₂ O ₃ , KBr, MgF ₂ , CaF ₂ , BaF ₂ , AgCl, ZnSe, and SiO ₂ .

The dielectric layer 3 is located on the infrared detector 2 and is used to block direct contact between the dielectric metasurface 4 and the infrared detector 2 and protect the bare chip of the infrared detector 2. The thickness of the dielectric layer 3 ranges from 100 to 500 nm, and the material is an infrared transparent material, which can be selected from: Al ₂ O ₃ , KBr, MgF ₂ , CaF ₂ , BaF ₂ , AgCl, ZnSe, and SiO ₂ .

The infrared detector 2 is prepared on the substrate 1 through vacuum coating and molecular beam epitaxy. The available detector types include mercury cadmium telluride (HgCdTe) infrared detector, type II superlattice infrared detector, and pyroelectric infrared detection. device, and the metal electrodes are prepared by vacuum thermal evaporation method. Connect the infrared detector to the external circuit through metal electrodes and leads. In this way, the infrared detector 2 is vertically integrated with the tunable surface plasmon waveguide resonator through the dielectric layer 3 for infrared spectrum signal detection. The detection integrated signal is denoised and demodulated through the spectrum reconstruction algorithm to obtain the molecular information. The infrared spectrum absorbs the signal and realizes the detection of trace molecules based on the obtained spectral information.

Referring to Figures 2 and 3, the structural shape of the dielectric metasurface 4 can adopt a variety of shapes, including Figure 2 (a) rectangle, 2 (b) circle, 2 (c) bow tie shape, 2 (d) double bow tie shape, 2(e) concentric ring type or 2(f) cross type, etc. The size and period of these antenna structures range from 0.1μm to 1μm, and the thickness ranges from 20 to 100nm. They can be processed by electron beam exposure, focused ion beam etching, ultraviolet It is prepared using lithography technologies such as photolithography and laser direct writing, combined with methods such as electron beam evaporation, magnetron sputtering, and thermal evaporation.

In the present invention, a nanogap layer 5 is sandwiched between the graphene/boron nitride heterojunction 6 and the dielectric metasurface 4, and surface plasmons are excited in the graphene/boron nitride heterojunction 6 through the dielectric metasurface 4, so that In the graphene/boron nitride heterojunction 6, a strong local electric field is generated on the graphene surface, and the strong local electric field is coupled with the molecular vibration mode, greatly enhancing the infrared absorption signal of the molecules to be measured 10 on the chip surface.

Figure 4 is a detailed processing flow chart for preparing an integrated infrared spectrum chip for enhanced detection:

Step S1, prepare an infrared detector: use vacuum coating, molecular beam epitaxy and vacuum thermal evaporation methods to prepare an infrared sensitive material film on the substrate 1 to prepare an infrared detector 2.

Step S2, prepare a dielectric layer: use electron beam evaporation, atomic deposition or molecular beam epitaxial growth to prepare a dielectric as dielectric layer 3 on the surface of the infrared detector, which is used as a protective layer.

Step S3, prepare the dielectric metasurface 4: deposit a silicon layer on the surface of the dielectric layer 3 using magnetron sputtering, electron beam evaporation, atomic deposition, etc., and use electron beam exposure or focused ion beam etching to deposit the silicon layer on the surface of the dielectric layer 3 The structural outline of the metasurface is written on the silicon layer, and the electron beam exposed structure is dry-etched to obtain the dielectric metasurface structure 4, and the dielectric metasurface is used as a gate electrode.

Step S4, prepare the nanogap layer: use magnetron sputtering, electron beam evaporation, and atomic deposition to prepare a dielectric as the nanogap layer 5 on the dielectric metasurface to achieve surface plasmon excitation and gate voltage regulation.

Step S5, prepare a boron nitride film: use a mechanical peeling process or a chemical vapor deposition method to prepare a boron nitride film;

Step S6, prepare a graphene film: prepare a graphene film using a mechanical peeling process or a chemical vapor deposition method;

Step S7, transfer the graphene/boron nitride heterojunction film: the prepared boron nitride film and the graphene film are alternately stacked and transferred to the substrate prepared above. During the transfer, the boron nitride is located at the bottom layer of the heterojunction. In contact with the nanogap layer, graphene is located on the top layer of the heterojunction and is in contact with the source and drain electrodes. The number of layers of the graphene/boron nitride heterojunction film 6 is 1 to 5, and the multi-layer structure can be realized through multiple transfers.

Step S8, prepare the source and drain electrodes: use ultraviolet lithography, laser direct writing, and electron beam evaporation to prepare metal contact ohmic electrodes, namely the source electrode 7 and the drain electrode 8, on the graphene/boron nitride heterojunction film 6 .

The tunable surface plasmon waveguide resonator composed of the dielectric metasurface 4, nanogap layer 5, and graphene/boron nitride heterojunction 6 can generate surface plasmons under infrared light wave excitation, thereby The infrared region produces strong absorption, as shown in Figure 3, thereby generating a strong local electric field on the graphene surface; further by applying an external voltage 9 between the dielectric metasurface 4 and the graphene/boron nitride heterojunction 6 , to adjust the surface conductivity of graphene. The external voltage 9 ranges from -2 to 2V, and dynamically adjusts the surface plasmon resonance peak of the graphene/boron nitride heterojunction 6 in the infrared range of 5 to 16 μm.

As shown in Figure 8, as the external voltage increases from -0.5V to -2V, the corresponding enhanced resonance peak undergoes a blue shift; when the excited graphene surface plasmon resonance frequency is tuned to be consistent with the molecular vibration of the molecule to be detected 10 When the frequencies are consistent, the electromagnetic field intensity in the unit space around the molecule to be measured reaches the strongest, thereby enhancing the infrared spectrum signal of the molecule to be measured 10 .

The spectral signal is further detected by the infrared detector 2, and electrical signals detected under different voltage conditions are obtained. The spectral reconstruction algorithm is used to denoise and demodulate the detection integrated signal output by the infrared detector. Figure 6 and Figure 7 show the reconstructed infrared spectrum signal before and after adsorption of the probe molecule respectively. Finally, the infrared spectrum of the molecule to be measured 10 is obtained. The absorption signal is used to detect trace molecules based on the obtained spectral information.

The implementation principles and expected effects of the present invention will be further described below with reference to embodiments. However, the present invention is not limited to the exemplary embodiments disclosed below, and those skilled in the relevant art can implement it in different forms. The essence of the description is only to help those skilled in the relevant fields comprehensively understand the specific details of the present invention.

This embodiment takes the graphene plasmon enhanced detection integrated chip based on HgCdTe detector as an example. First, vacuum coating and molecular epitaxy are used to grow a layer of HgCdTe material on the substrate to prepare an infrared detector, and then Connect to an external circuit; secondly, use electron beam evaporation to deposit an aluminum oxide film with a thickness of about 200 nm on the surface of the infrared detector as a dielectric layer to protect the infrared detector; then deposit it on the dielectric layer through a magnetron sputtering process A layer of silicon with a thickness of about 30 nm is used as a gate material to control the Fermi level and carrier concentration of graphene, and is also used as a dielectric metasurface material; the focused ion beam etching process is then used to prepare the dielectric metasurface structure. , the shape of the dielectric metasurface structure is a bow tie, the period is 300nm, the gap is 80 nm, and the overall size of the metasurface is 100 μm × 100 μm; then the atomic layer deposition method is used to deposit a thickness of about 10 nm on the dielectric metasurface structure A thin layer of aluminum oxide was used to prepare a nanogap layer; chemical vapor deposition (CVD) was further used to grow a single layer of boron nitride (0.1 nm) and a single layer of graphene (0.34nm) films on the copper foil, and poly(methane) was used. Using methyl acrylate (PMMA) as a transfer reagent, the boron nitride film and the graphene film are sequentially superimposed and transferred to a thin layer of alumina; finally, ultraviolet photolithography and electron beam evaporation are used to coat the graphene/boron nitride heterogeneous Gold source and drain electrodes were prepared on the junction.

Since lattice defects, mechanical damage and impurity contamination on the surface of the detector may introduce energy levels in the forbidden band, the surface trap charge density increases, resulting in more surface recombination, and more injected carriers recombine and disappear on the surface. , seriously affecting device performance. Therefore, the difficulty of the infrared detector integration process is how to optimize the device surface passivation process. By depositing or growing a suitable passivation film on the semiconductor surface, it can bind the dangling bonds on the semiconductor surface, reduce the surface state density, and reduce the surface The recombination rate effectively reduces device dark current and improves detection performance.

In the embodiment, biomolecules are used as probe molecules, and an 8 nm thick biomolecule film is spin-coated on the detection chip. Figure 8 shows the infrared absorption enhancement curves of the chip for biomolecules under different voltage conditions. It can be seen from the figure that the vibration modes of biomolecules at 6.235μm and 6.355μm are greatly enhanced on the graphene nanoprobe. By controlling the external voltage to increase from -0.5V to -2V to blue-shift the infrared resonance frequency of the graphene nanoprobe, the vibration mode of biomolecules can be selectively enhanced. It can be seen from the figure that the coupling of the biomolecule vibration mode and the graphene surface plasmon resonance mode causes a concave peak, whose frequency corresponds to the resonance frequency of each vibration mode of the biomolecule. When the external voltage is -0.5V and -2V, the resonance mode of the graphene nanoprobe is closest to the vibration frequency of biomolecules, and the enhancement effect of the molecular vibration mode is greatest at this time. It is calculated that the chip can enhance the infrared spectrum signal of biomolecules by up to 100 times.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail through the above embodiments, those skilled in the art should understand that the illustrations and examples are only considered to be are illustrative and may be variously changed in form and detail. The true scope and spirit of the invention are defined by the claims.

Claims (8)

1. An enhancement detection integrated infrared spectrum chip based on tunable surface plasmons, which is characterized in that: the device comprises a source electrode, a drain electrode, a graphene/boron nitride heterojunction, a nano gap layer, a dielectric super-surface, a dielectric layer, an infrared detector and a substrate from top to bottom;

the dielectric super-surface is formed by depositing a silicon layer on the surface of a dielectric layer and further carrying out micro-nano processing on the silicon layer to form a super-surface structural profile, so as to obtain a dielectric super-surface structure, and the dielectric super-surface structure is used for realizing wave vector matching of a surface plasmon mode and free space light;

the graphene/boron nitride heterojunction is of a composite structure of a boron nitride film and a graphene film and is used for reducing the influence of a substrate on the characteristics of a graphene material so as to obtain a low-loss surface plasmon mode;

a nano gap layer is arranged between the dielectric super surface and the graphene/boron nitride heterojunction to form a tunable surface plasmon waveguide resonator, tunable surface plasmons are generated under the excitation of infrared light waves, so that a strong local electric field is generated on the surface of the graphene, and the surface conductivity of the graphene is further regulated through external voltage applied between the graphene and the dielectric super surface, so that the surface plasmon resonance peak is dynamically regulated, and narrow-band filtering is realized; meanwhile, when the resonance frequency of the surface plasmon is tuned to be consistent with the molecular vibration frequency of the substance to be detected, the infrared spectrum signal of the molecule to be detected is enhanced;

the source electrode and the drain electrode are deposited on the graphene/boron nitride heterojunction, and the source electrode and the drain electrode are conducted through graphene;

the dielectric layer is positioned between the infrared detector bare chip and the dielectric super surface and is used for protecting the surface of the infrared detector bare chip;

the infrared detector bare chip is positioned on the substrate, longitudinally integrated with the tunable surface plasmon waveguide resonator through the dielectric layer and used for infrared spectrum signal detection.

2. The enhanced detection integrated infrared spectrum chip of claim 1, wherein: the super-surface structure of the medium super-surface is rectangular, circular, bow-tie-shaped, double bow-tie-shaped, concentric ring-shaped or cross-shaped in the transverse direction of the chip; the size and the period range of the super surface structure are 0.1-1 mu m, and the thickness range of the super surface structure is 20-100 nm.

3. The enhanced detection integrated infrared spectrum chip according to claim 1 or 2, wherein: the dielectric super-surface is obtained by utilizing photoetching technologies such as electron beam exposure, focused ion beam etching, ultraviolet lithography, laser direct writing and the like and combining methods such as electron beam evaporation, magnetron sputtering, thermal evaporation and the like.

4. The enhanced detection integrated infrared spectrum chip of claim 1, wherein: the graphene/boron nitride heterojunction is characterized in that a boron nitride film and a graphene film are alternately stacked in multiple layers in the vertical direction, the stacking range is 1-5 layers, the boron nitride is located at the bottom layer of the heterojunction and is in contact with the nanometer gap layer, and the graphene is located at the top layer of the heterojunction and is in contact conduction with the source electrode and the drain electrode.

5. The enhanced detection integrated infrared spectrum chip of claim 4, wherein: the graphene/boron nitride heterojunction film is prepared by a mechanical stripping process or a chemical vapor deposition method, and the number of layers of the heterojunction film is realized in a multiple transfer mode.

6. The enhanced detection integrated infrared spectroscopy chip of claim 1, whichIs characterized in that: the thickness of the nano gap layer is 2-20nm, the material is an infrared transparent material, and the nano gap layer is selected from the following materials: al (Al) ₂ O ₃ ，KBr，MgF ₂ ，CaF ₂ ，BaF2，AgCl，ZnSe，SiO ₂ 。

7. The enhanced detection integrated infrared spectrum chip of claim 1, wherein: the thickness of the dielectric layer ranges from 100nm to 500nm, the material is an infrared transparent material, and the material is selected from the following materials: al (Al) ₂ O ₃ ，KBr，MgF ₂ ，CaF ₂ ，BaF2，AgCl，ZnSe，SiO ₂ 。

8. The enhanced detection integrated infrared spectrum chip of claim 1, wherein: the detection wave band range of the infrared detector is 3-10 mu m, and the infrared detector is selected from a tellurium cadmium mercury (HgCdTe) infrared detector, a II-type superlattice infrared detector and a pyroelectric infrared detector.