A heterojunction terahertz metamaterial sensor and its fabrication method

Abstract

This invention provides a heterojunction terahertz metamaterial sensor and its fabrication method. The sensor comprises: a silicon dioxide substrate, and a polyimide flexible dielectric layer, a metal array layer, a graphene layer, and a carbon nitride layer sequentially located on the silicon dioxide substrate; wherein the metal array layer has multiple metal periodic structural units; the metal periodic structural units are used to resonate with terahertz waves. By setting metal periodic structural units that resonate with terahertz waves in the metal array layer, this invention can change the surface dielectric environment of the metal array layer, thereby altering the resonant frequency and transmission amplitude involved in the terahertz band, and thus achieving ultrasensitive, multi-dimensional detection of proteins.

Description

Technical Field

[0001] This invention relates to the field of terahertz metamaterial sensor technology, and in particular to a heterojunction terahertz metamaterial sensor and its fabrication method. Background Technology

[0002] Terahertz waves (0.1THz-10THz) possess irreplaceable advantages such as wide bandwidth, strong coherence, and high signal-to-noise ratio, showing broad application prospects in fields such as 6G broadband communication, military radar, national security, medical imaging, and biological detection. Due to their low scattering characteristics, the photon energy (4.1 meV) of terahertz waves is much lower than that of X-ray photons (0.12–120 keV) and far lower than the bond energies of various chemical bonds between biomolecules, causing no harmful ionization or chemical damage to biological tissues. Therefore, terahertz waves are an ideal light source for biological detection and have great application potential in the biomedical field. However, many substances in nature respond weakly to terahertz waves, hindering highly sensitive detection of biomolecules. The emergence of metamaterials has solved this bottleneck. Metamaterials are composed of periodically arranged artificial microstructures with subwavelength dimensions, possessing unique electromagnetic properties not found in natural materials.

[0003] Proteins play a crucial role in human metabolism, growth, development, and aging. When the body experiences severe disease or even cancer, certain proteins exhibit significant functional abnormalities. Therefore, developing novel, ultrasensitive analytical methods for detecting proteins closely related to major diseases such as cancer is of significant academic and practical value for early diagnosis, targeted treatment, and drug development and screening. However, achieving highly sensitive, multi-dimensional, and rapid detection of target proteins from diverse, complex, and low-content biological samples remains a significant technical challenge. Existing technologies combining terahertz metamaterials can detect protein molecules, but achieving ultra-high sensitivity and flexible multi-dimensional detection is still difficult. Therefore, there is an urgent need to develop new materials and technologies combined with terahertz metamaterials to provide novel sensing technologies for protein molecule detection. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the purpose of this invention is to provide a heterojunction terahertz metamaterial sensor and its preparation method.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] A heterojunction terahertz metamaterial sensor, comprising:

[0007] A silicon dioxide substrate, and a polyimide flexible dielectric layer, a metal array layer, a graphene layer and a carbon nitride layer sequentially located on the silicon dioxide substrate; wherein the metal array layer has multiple metal periodic structural units; the metal periodic structural units are used to resonate with terahertz waves.

[0008] Preferably, the metal periodic structure unit on the metal array layer is composed of a combination of "D"-shaped and "C"-shaped resonant rings.

[0009] Preferably, the silicon dioxide substrate has a thickness of 300 μm and a size of 1.5 cm × 1.5 cm.

[0010] Preferably, the thickness of the polyimide flexible dielectric layer is 2 μm.

[0011] Preferably, the thickness of the metal array layer is 2 μm.

[0012] Preferably, the thickness of the graphene layer is 1 nm.

[0013] Preferably, the thickness of the carbon nitride layer is 10 nm.

[0014] This invention also provides a method for fabricating a heterojunction terahertz metamaterial sensor, comprising:

[0015] A polyimide film is spin-coated onto a silicon dioxide substrate to form a polyimide flexible dielectric layer and a silicon dioxide substrate layer.

[0016] A metal array layer is fabricated on a flexible polyimide dielectric layer using photolithography; wherein the metal array layer has multiple metal periodic structural units; the metal periodic structural units are used to resonate with terahertz waves;

[0017] A graphene film is transferred to the surface of the metal array layer to form a graphene layer;

[0018] A heterojunction terahertz metamaterial sensor was obtained by spin-coating a carbon nitride layer onto the graphene layer.

[0019] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0020] This invention provides a heterojunction terahertz metamaterial sensor and its fabrication method. The sensor comprises a silicon dioxide substrate, and a polyimide flexible dielectric layer, a metal array layer, a graphene layer, and a carbon nitride layer sequentially disposed on the silicon dioxide substrate. The metal array layer has multiple metal periodic structural units, which resonate with terahertz waves. By incorporating metal periodic structural units that resonate with terahertz waves into the metal array layer, this invention alters the surface dielectric environment of the metal array layer, causing changes in the resonant frequency and phase difference within the terahertz band, thereby achieving ultrasensitive, multi-dimensional detection of proteins. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of a heterojunction terahertz metamaterial sensor structure according to the present invention;

[0023] Figure 2 This is a flowchart illustrating the fabrication process of a heterojunction terahertz metamaterial sensor according to the present invention.

[0024] Figure 3 This is a transmission spectrum of the heterojunction terahertz metamaterial sensor of the present invention; where Frequency represents the frequency in THz; Transmission represents the transmittance of the terahertz wave.

[0025] Figure 4 When different concentrations of casein molecules are added to the top layer of the heterojunction terahertz metamaterial sensor in this invention, the terahertz waves pass through the transmission spectrum of the sensor respectively.

[0026] Figure 5 The phase difference curves of the terahertz waves passing through the sensor are obtained when different concentrations of casein molecules are added to the top layer of the heterojunction terahertz metamaterial sensor in this invention.

[0027] Symbol explanation:

[0028] 1. Carbon nitride layer; 2. Graphene layer; 3. Metal array layer; 4. Polyimide flexible dielectric layer; 5. Silicon dioxide substrate layer. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0031] The terms "first," "second," "third," and "fourth," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, including a series of steps, processes, methods, etc., is not limited to the steps listed, but may optionally include steps not listed, or may optionally include other steps inherent to these processes, methods, products, or devices.

[0032] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] Please see Figure 1 A heterojunction terahertz metamaterial sensor, comprising:

[0034] A silicon dioxide substrate 5, and a polyimide flexible dielectric layer 4, a metal array layer 3, a graphene layer 2 and a carbon nitride layer 1 sequentially located on the silicon dioxide substrate 5; wherein, the metal array layer 3 has a plurality of metal periodic structural units; the metal periodic structural units are used to resonate with terahertz waves.

[0035] Furthermore, in this invention, the periodic metal structural units on the metal array layer 3 are composed of a combination of "D"-shaped and "C"-shaped resonant rings. This dipole resonance is highly sensitive to minute changes in the external medium environment in the terahertz band. Combined with the charge characteristics inherent in protein molecules, different protein concentrations cause changes in the conductivity of the carbon nitride layer 1 and graphene layer 2 in the heterojunction, thereby altering the surface medium environment of the metal array layer 3. This results in changes to the designed resonant frequency and transmission amplitude within the terahertz band, enabling ultrasensitive, multi-dimensional detection of proteins.

[0036] In this embodiment of the invention, the silicon dioxide substrate layer 5 has a thickness of 300 μm and a size of 1.5 cm × 1.5 cm. The polyimide flexible dielectric layer 4 has a thickness of 2 μm. The metal array layer 3 has a thickness of 2 μm. The graphene layer 2 has a thickness of 1 nm. The carbon nitride layer 1 has a thickness of 10 nm.

[0037] This invention also provides a method for fabricating a heterojunction terahertz metamaterial sensor, comprising:

[0038] A polyimide film is spin-coated onto a silicon dioxide substrate to form a polyimide flexible dielectric layer 4 and a silicon dioxide substrate layer 5.

[0039] A metal array layer 3 is fabricated on a polyimide flexible dielectric layer 4 using photolithography; wherein, the metal array layer 3 has multiple metal periodic structural units; the metal periodic structural units are used to resonate with terahertz waves;

[0040] A graphene film is transferred to the surface of the metal array layer 3 to form a graphene layer 2;

[0041] A heterojunction terahertz metamaterial sensor is obtained by spin-coating a carbon nitride layer 1 onto the graphene layer 2.

[0042] The detection principle and effect of the heterojunction terahertz metamaterial sensor of the present invention will be further explained below with reference to specific embodiments:

[0043] Figure 1 The diagram shows the design of the terahertz metamaterial sensor proposed in this invention. It consists of 5 layers from top to bottom: the top layer is a carbon nitride layer 1, followed by a graphene layer 2, a metal array layer 3, a polyimide flexible dielectric layer 4, and the bottom layer is a silicon dioxide substrate layer 5. Figure 2 This paper demonstrates the fabrication process of the terahertz metamaterial sensor designed in this invention. First, a 2 μm thick polyimide film is spin-coated onto a 300 μm thick silicon dioxide substrate (1.5 cm × 1.5 cm). Second, a 2 μm thick aluminum array, measuring 1.5 cm × 1.5 cm, is fabricated on the polyimide film using photolithography. The periodic unit structure is as follows... Figure 1On the left, the metal array contains approximately 10,000 metal periodic structural units. Finally, a monolayer graphene film (1 nm) was transferred to the surface of the metal array layer 3, and then a carbon nitride layer 1 (10 nm) was spin-coated onto the graphene layer 2 to obtain the designed terahertz metamaterial sensor. The biosensing characteristics of the device were experimentally characterized using terahertz time-domain spectroscopy. Casein molecules were selected as probe analytes to verify the performance of the biosensor. This invention prepared suspensions with five different casein concentrations: C1 = 3.54 ng / mL, C2 = 56.09 ng / mL, C3 = 852.6 ng / mL, C4 = 1.99103 ng / mL, and C5 = 1.56106 ng / mL.

[0044] Figure 3 The image shows the transmission spectrum of the terahertz metamaterial sensor. The horizontal axis, labeled Frequency, represents the frequency in THz; the vertical axis, labeled Transmission, represents the transmittance of the terahertz wave. The transmission spectrum shows that the metallic periodic unit cell metamaterial designed in this invention resonates with the terahertz wave at 1.41 THz, and the resonance mode is a dipole resonance mode.

[0045] Figure 4 Different concentrations (C1-C5) of casein molecules were added to the top layer of the sensor, and terahertz waves were observed through the transmission spectrum of the sensor. The horizontal axis represents frequency in THz, and the vertical axis represents the transmittance of the terahertz waves. As shown in the figure, with increasing casein concentration, the resonance valley shifts towards lower frequencies. When the concentration reaches 1.56 × 10⁶ ng / mL, the frequency shift of the resonance valley stops, reaching saturation. At protein concentration C1, the frequency shift of the resonance valley is close to 32 GHz. When the protein concentration increases to C2, the frequency shift is close to 77 GHz. Continuing to increase the protein concentration to C3, the frequency shift increases to 127 GHz. When the protein concentration increases to C4, the frequency shift increases to 194 GHz, reaching a maximum of 251 GHz at protein concentration C5. Since adding casein changes the carrier concentration on the heterojunction surface, thus altering the conductivity, the frequency of the resonance valley changes with the heterojunction conductivity. The sensor successfully detects protein concentrations, with a detection limit as low as 3.54 ng / mL; the maximum offset of the resonance valley reaches 251 GHz, achieving ultra-high sensitivity protein detection.

[0046] Figure 5To illustrate the phase difference curves obtained by adding casein molecules of different concentrations (C1-C5) to the top layer of the sensor, terahertz waves were observed passing through the sensor. The horizontal axis, Frequency, represents the frequency in THz; the vertical axis, Phase Difference, represents the phase difference (the phase difference between protein-containing and protein-free samples), in degrees (°). The graph shows that the phase difference exhibits a near-linear dependence on frequency, gradually increasing with increasing casein concentration. At 1.56 × 10⁶ ng / mL, the phase difference reaches a high of 327°. In conclusion, this sensor enables multi-dimensional detection of protein concentration, identifying and detecting different protein molecules through frequency shift and phase difference.

[0047] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0048] This invention provides a heterojunction terahertz metamaterial sensor, comprising, from top to bottom, a carbon nitride layer, a graphene layer, a metal array layer, a flexible dielectric layer, and a silicon dioxide substrate layer; wherein, the periodic unit structure of the metal array layer is composed of a combination of "D"-shaped and "C"-shaped resonant rings. This dipole resonance is highly sensitive to minute changes in the external dielectric environment in the terahertz band. Combined with the charge characteristics of protein molecules, different protein concentrations cause changes in the conductivity of the carbon nitride and graphene layers in the heterojunction, thereby altering the surface dielectric environment of the metal array layer. This results in changes to the designed resonant frequency and transmission amplitude in the terahertz band, enabling ultrasensitive, multi-dimensional detection of proteins.

[0049] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. Regarding the methods disclosed in the embodiments, since they correspond to the apparatus disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the apparatus description.

[0050] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A heterojunction terahertz metamaterial sensor, characterized in that, include: A silicon dioxide substrate, and a polyimide flexible dielectric layer, a metal array layer, a graphene layer, and a carbon nitride layer sequentially located on the silicon dioxide substrate; wherein the metal array layer has multiple metal periodic structural units; the metal periodic structural units are used to resonate with terahertz waves; The metal periodic structure unit on the metal array layer is composed of a combination of "D"-shaped and "C"-shaped resonant rings.

2. The heterojunction terahertz metamaterial sensor according to claim 1, characterized in that, The silicon dioxide substrate has a thickness of 300 μm and a size of 1.5 cm × 1.5 cm.

3. The heterojunction terahertz metamaterial sensor according to claim 2, characterized in that, The thickness of the polyimide flexible dielectric layer is 2 μm.

4. A heterojunction terahertz metamaterial sensor according to claim 3, characterized in that, The thickness of the metal array layer is 2 μm.

5. A heterojunction terahertz metamaterial sensor according to claim 4, characterized in that, The thickness of the graphene layer is 1 nm.

6. A heterojunction terahertz metamaterial sensor according to claim 5, characterized in that, The thickness of the carbon nitride layer is 10 nm.

7. A method for fabricating a heterojunction terahertz metamaterial sensor as described in claim 1, characterized in that, include: A polyimide film is spin-coated onto a silicon dioxide substrate to form a polyimide flexible dielectric layer and a silicon dioxide substrate layer. A metal array layer is fabricated on a flexible polyimide dielectric layer using photolithography; wherein the metal array layer has multiple metal periodic structural units; the metal periodic structural units are used to resonate with terahertz waves; A graphene film is transferred to the surface of the metal array layer to form a graphene layer; A heterojunction terahertz metamaterial sensor was obtained by spin-coating a carbon nitride layer onto the graphene layer.

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