Spectrometer based on graphene photocurrent response, measurement method and preparation method thereof

Abstract

The present application belongs to the technical field of computing reconstruction spectrum, and particularly relates to a spectrometer based on graphene photocurrent response, a measuring method and a preparation method thereof. The present application carries out electrical doping on graphene by using field effect, that is, by adjusting the gate voltage to adjust the chemical potential mu of single-layer graphene, so that the photons with energy less than 2|mu| in the incident light cannot be absorbed by graphene through interband transition to form photocurrent and affect the intensity of graphene photocurrent response, thereby reconstructing the spectrum of the incident light and realizing high-precision spectrum detection. The method of the present application can break through the millimeter level size limit of traditional spectrometers and realize spectrum detection in micrometer level graphene, thereby providing a completely different technical route for the miniaturization of high-performance spectrometers.

Description

Technical Field

[0001] This invention relates to the field of computational reconstruction spectroscopy, and in particular to an ultra-miniature spectrometer based on graphene photocurrent response, its preparation method, and measurement method. Background Technology

[0002] In fields such as petrochemicals, medicine and health, military reconnaissance, and space exploration, spectrometers have become indispensable instruments. Spectrometers can measure the light reflected from the surface of objects, allowing for the observation, analysis, and processing of the structure and composition of substances. They offer advantages such as high analytical accuracy, a large measurement range, high speed, and small sample volume. Traditional grating spectrometers use gratings or dispersive elements to separate the electromagnetic radiation from a radiation source into the desired wavelengths or wavelength regions, and then measure the intensity at the selected wavelength (or by scanning a certain band). However, to achieve high accuracy and resolution, traditional spectrometers employ complex photodetector arrays, filter arrays, and other complex dispersive structures and components. Their complex optical path design and dispersed optical components pose significant challenges to the miniaturization of spectrometers, making them unable to meet the demands of rapidly evolving portable devices and large-scale on-chip photonic integrated systems.

[0003] Currently, common miniature spectrometers utilize advanced micro- and nanofabrication techniques to replace the functions of bulky dispersive optical elements with smaller components, such as photonic crystals, metasurfaces, and microinterferometers. Traditional spectrometer miniaturization techniques, by sacrificing some performance, have achieved spectrometer sizes down to the millimeter scale. However, further miniaturizing spectrometers to the micrometer scale remains a significant challenge. Recent research, however, indicates that computational reconstruction spectroscopy has been successfully applied to spectrometer miniaturization. Through pre-calibration and based on measurement data characteristics, unknown spectra can be reconstructed using computational reconstruction algorithms. The accuracy and resolution of the reconstructed spectrum depend on the sensitivity of the device's spectral response to changes in gate voltage. Because the band structure of a single material is fixed, its spectral response variation is limited, and the adjustable range is constrained by the material's bandwidth, which is the main reason for the performance limitations of such spectrometers.

[0004] Currently proposed and implemented miniature spectrometers still require a photodetector array to achieve their displayed resolution, limiting further miniaturization of current systems. Single-detector spectrometers, on the other hand, suffer from performance limitations due to insufficient tunability of their spectral response. An effective miniaturization technology for spectrometers remains lacking.

[0005] Chinese patent CN113625475A discloses a miniature spectroscopic device and spectral analysis method combining graphene and optical waveguide. This method solves multiple sets of photocurrent equations for the n graphene absorption layers under different electrical tuning environments based on the photocurrent values ​​of n graphene layers. Finally, it uses a reference function to calculate the photocurrent and obtain the target spectrum. However, the components used include a grating coupler, an optical waveguide, and multiple graphene layers, leaving room for further miniaturization. Furthermore, the spectral measurement range and resolution of this method depend on the number of graphene layers (n), making it difficult to flexibly adjust the spectrometer's spectral measurement range and resolution. Summary of the Invention

[0006] To overcome the difficulties of existing spectrometer miniaturization technologies and break through the size limits of traditional spectrometers, the present invention aims to provide a practical and feasible spectrometer miniaturization technology based on the photocurrent response of monolayer graphene. The objective of this invention can be achieved through the following technical solutions:

[0007] As a first aspect of the present invention, a spectrometer based on graphene photocurrent response is provided for measuring the spectrum of unknown incident light, the spectrometer comprising:

[0008] A graphene device includes a single layer of graphene, a substrate material, a source electrode, a drain electrode, and a back gate electrode; the single layer of graphene is disposed on one side of the substrate material to receive unknown incident light and excite photocurrent; the source electrode and the drain electrode are disposed on the single layer of graphene and the substrate material by evaporation and gold plating; the back gate electrode is disposed on the other side of the substrate material, and the back gate electrode material includes, but is not limited to, silicon, gold, etc.

[0009] An electrical control and measurement device is used to apply a gate voltage and simultaneously measure the gate voltage-dependent photocurrent response intensity of graphene, and reconstruct the incident light spectrum based on the change in photocurrent response intensity.

[0010] As a second aspect of the present invention, a spectroscopic measurement method based on graphene photocurrent response is provided. The method uses a spectrometer based on graphene photocurrent response as described above for measurement and includes the following steps:

[0011] Electrochemical doping of monolayer graphene is performed using the field effect, and the chemical potential of monolayer graphene is adjusted by regulating the gate voltage.

[0012] By adjusting the chemical potential of monolayer graphene to near the electrical neutral point of graphene, light absorption and light forbidden effects are made in the graphene.

[0013] By adjusting the chemical potential of monolayer graphene, the intensity of the graphene photocurrent response is affected. Based on the ratio of the decrease in the intensity of the graphene photocurrent response to the light band that cannot be excited to pass through the interband transition under the corresponding chemical potential, the relative intensity of the forbidden band of light to the total incident light is calculated.

[0014] Furthermore, the spectral measurement method adjusts the measurement range and resolution of the spectrum by changing the range and step size of the graphene chemical potential.

[0015] As a third aspect of the present invention, a method for preparing a graphene photocurrent response-based spectrometer as described above is provided, comprising the following steps:

[0016] Monolayer graphene is prepared on a substrate material, and the preparation methods include, but are not limited to, mechanical exfoliation, chemical vapor deposition, two-dimensional material transfer, etc. The substrate material includes, but is not limited to, silicon oxide, boron nitride, etc.

[0017] The electrode is a single-layer graphene electrode deposited with gold, and metal wires are used as electrode leads.

[0018] The graphene device is wired to an electrical control and measurement device, which is used to provide the gate voltage required by the graphene device and to detect the source and drain current of the graphene device in real time.

[0019] A voltage is applied between the source and drain, and the gate voltage is adjusted. Based on the measured source and drain currents, a graph showing the relationship between resistance and gate voltage is plotted to determine the gate voltage at the graphene chemical potential at the graphene electrical neutral point, which is the gate voltage at the point where the resistance is maximum.

[0020] By adjusting the gate voltage, the chemical potential of monolayer graphene was adjusted to be close to the electrical neutral point of graphene, so that graphene exhibited light absorption and light forbidden effects, and the photocurrent response intensity change of monolayer graphene under unknown incident light was measured.

[0021] The relative intensity spectrum of unknown incident light can be reconstructed based on the dependence of the light band that cannot be excited by electrons through interband transitions under the corresponding chemical potential and the intensity of graphene photocurrent response. By modulating the unknown incident light or gate voltage and combining it with phase-locked loop technology, the signal-to-noise ratio of spectral measurement can be further improved.

[0022] The standard spectrum of the unknown incident light is measured using standard spectral testing equipment; by comparing the reconstructed spectrum and the standard spectrum, the conversion ratio between the relative intensity and intensity of the reconstructed spectrum is obtained, thereby achieving independent and accurate measurement of the spectrum of the unknown incident light.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1) The ultra-miniature spectrometer based on the photocurrent response of monolayer graphene provided by this invention utilizes only one graphene layer. By adjusting the gate voltage to change the chemical potential of the graphene, the target spectrum is calculated and reconstructed based on the dependence of the graphene absorption of incident light bands and the change in photocurrent response intensity. Compared with existing technologies, it eliminates the need for grating couplers, optical waveguides, and multiple graphene layers, achieving micrometer-scale miniaturization of the spectrometer.

[0025] 2) The ultra-miniature spectrometer provided by this invention can be miniaturized without sacrificing performance. By changing the adjustment range and step size of the graphene chemical potential, the spectral measurement range and the resolution of the reconstructed spectrum for different bands of incident light can be adjusted more flexibly, thus enabling the measurement range and resolution of the spectrometer.

[0026] 3) The gate voltage-dependent photocurrent response reconstructs the unknown incident light spectrum provided by this invention. By comparing it with the standard spectrum measured by a standard spectral testing device, the accuracy of the micro spectrometer based on graphene photocurrent is demonstrated. Furthermore, for the calibration of the reconstructed spectrum, the relative intensity of different bands of the reconstructed spectrum can be quantified into intensity spectra of different bands. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the monolayer graphene electrical control device and its gate voltage-dependent photocurrent response intensity measurement in this invention.

[0028] Figure 2 This is a schematic diagram illustrating how the chemical potential of monolayer graphene is adjusted by regulating the gate voltage to induce light absorption in this invention.

[0029] Figure 3 This is a schematic diagram illustrating how the chemical potential of monolayer graphene is adjusted by regulating the gate voltage to induce a photoforbidden effect in this invention.

[0030] Figure 4 This is a schematic diagram illustrating the process of calculating the unknown incident light spectrometer based on the voltage-dependent photocurrent response intensity of a single-layer graphene gate in this invention. Detailed Implementation

[0031] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0032] Example

[0033] The ultra-miniature spectrometer based on graphene photocurrent response proposed in this invention utilizes the field effect to electrically dope graphene. Specifically, by adjusting the gate voltage, the chemical potential (μ) of monolayer graphene is adjusted so that photons with energy less than 2|μ| in the incident light cannot be absorbed by graphene through interband transitions to form a photocurrent, and the intensity of the graphene photocurrent response is affected, thereby reconstructing the incident light spectrum and achieving high-precision spectral detection.

[0034] The physical principle of this invention is as follows: Monolayer graphene possesses a unique linear band structure and zero bandgap characteristics. Due to the Pauli exclusion principle, the minimum incident light energy required to excite graphene electrons to undergo interband transitions varies under different chemical potentials. Since the photocurrent response of graphene is related to the interband transitions of electrons excited by incident light, when the chemical potential of graphene is adjusted using electrical doping, if some of the incident light-excited interband transition processes are chemically forbidden, the intensity of the photocurrent response will change significantly.

[0035] Specifically, as one embodiment of the present invention, such as Figure 1 As shown, this embodiment provides an ultra-miniature spectrometer based on graphene photocurrent response, including a graphene device, unknown incident light, and electrical control and measurement devices, such as... Figure 1 As shown, the graphene device includes a monolayer graphene 1, a substrate material 2, a source electrode 3, a drain electrode 4, and a back gate electrode 5. The monolayer graphene 1 is disposed on one side of the substrate material 2, and unknown incident light excites the photocurrent of the monolayer graphene 1. The electrical control and measurement device is used to apply a gate voltage and simultaneously measure the gate voltage-dependent photocurrent response intensity of the graphene.

[0036] In the aforementioned graphene device, the source electrode 3 and drain electrode 4 are prepared by vapor deposition onto the monolayer graphene 1 sample and the substrate material 2. The substrate material 2 includes, but is not limited to, silicon oxide and boron nitride. The back gate electrode 5 is disposed on the side of the substrate material 2 opposite to the monolayer graphene 1. The material of the back gate electrode 5 includes, but is not limited to, silicon and gold.

[0037] This embodiment also provides a method for measurement using the above-mentioned spectrometer based on graphene photocurrent response, including the following steps:

[0038] Electrical doping of graphene is achieved by utilizing the field effect, i.e., by adjusting the gate voltage to regulate the chemical potential (μ) of monolayer graphene.

[0039] By adjusting the chemical potential of monolayer graphene, its absorption spectrum can be altered. Approaching the graphene's electrical neutral point, its chemical potential induces both light absorption and photoforbidden effects. The light absorption effect occurs when the graphene's chemical potential is near its electrical neutral point, allowing incident light of any wavelength to be absorbed and excited by electrons, generating a photocurrent through interband transitions, resulting in maximum photocurrent intensity. Conversely, the photoforbidden effect occurs when the graphene's chemical potential is far from its electrical neutral point, preventing incident light with energies less than 2|μ| from generating a photocurrent through interband transitions, thus reducing the photocurrent intensity.

[0040] Based on physical principles, by adjusting the chemical potential of monolayer graphene, the intensity of the graphene photocurrent response can be affected. By calculating the ratio of the decrease in the intensity of the graphene photocurrent response to the light band that cannot be excited to pass through interband transitions under the corresponding chemical potential, the relative intensity of the forbidden band to the total incident light can be calculated, thereby reconstructing the incident light spectrum. By modulating the unknown incident light or the gate voltage, combined with phase-locked loop technology, the signal-to-noise ratio of the spectral measurement can be further improved, thus achieving high-precision spectral detection.

[0041] The step size of the graphene chemical potential adjustment determines the resolution of the spectrum. The smaller the step size, the smaller the range of incident light wavelengths that are forbidden, and the higher the resolution of the incident light spectrum obtained from the photocurrent response for different wavelengths. The range of the graphene chemical potential adjustment determines the measurement range of the spectrum. The larger the range of the chemical potential adjustment, the larger the range of photocurrent responses that can be generated, and the larger the measurement range of the spectrum.

[0042] This embodiment also provides a miniaturized fabrication technology for a spectrometer based on graphene photocurrent response, including the following steps:

[0043] (1) A single-layer graphene 1 sample is prepared on substrate material 2. The preparation methods include, but are not limited to, mechanical exfoliation, chemical vapor deposition, two-dimensional material transfer, etc. The substrate material 2 includes, but is not limited to, silicon oxide, boron nitride, etc.

[0044] (2) A gold electrode was prepared for monolayer graphene 1, and metal wires were used as leads for the gold electrode.

[0045] (3) According to Figure 1 The wiring method described above connects the graphene device to the electrical control and measurement device. The electrical control and measurement device is used to provide the gate voltage required by the graphene device and to detect the source and drain current of the graphene device in real time.

[0046] (4) Apply a small voltage between the source and drain, adjust the gate voltage, and draw a graph of the relationship between resistance and gate voltage based on the measured source and drain currents. Determine the gate voltage at the graphene chemical potential at the graphene electrical neutral point, that is, the gate voltage at the point where the resistance is the largest.

[0047] (5) By adjusting the gate voltage, such as Figure 2 and 3 As shown, the chemical potential of monolayer graphene was adjusted to be close to the electrical neutral point of graphene to induce light absorption and light forbidden effects, and the change in photocurrent response intensity of monolayer graphene under unknown incident light was measured.

[0048] (6) Figure 3 As shown, the relative intensity spectrum of unknown incident light is reconstructed based on the dependence of the light band that cannot be excited by electrons under the corresponding chemical potential through interband transitions and the intensity of the graphene photocurrent response.

[0049] (7) Measure the standard spectrum of the unknown incident light using standard spectral testing equipment, including but not limited to a Fourier transform infrared spectrometer. Based on the comparison between the reconstructed spectrum and the standard spectrum, prove the accuracy of the ultra-miniature spectrometer based on the graphene photocurrent response, and after obtaining the conversion ratio between the relative intensity and the intensity of the reconstructed spectrum, the relative intensity spectrum measured by the ultra-miniature spectrometer can be quantized into an intensity spectrum.

[0050] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A spectroscopic measurement method based on graphene photocurrent response, characterized in that, The method employs a graphene photocurrent response-based spectrometer to measure the spectrum of unknown incident light. The spectrometer includes a graphene device and an electrical control and measurement device. The graphene device includes a monolayer graphene (1), a substrate material (2), a source electrode (3), a drain electrode (4), and a back gate electrode (5). The monolayer graphene (1) is disposed on one side of the substrate material (2) to receive unknown incident light and excite photocurrent. The source electrode (3) and the drain electrode (4) are disposed on the monolayer graphene (1) and the substrate material (2). The back gate electrode (5) is disposed on the side of the substrate material (2) opposite to the monolayer graphene (1). The electrical control and measurement device is used to apply a gate voltage and simultaneously measure the change in graphene photocurrent response intensity with the gate voltage, and then reconstruct the incident light spectrum based on the change in photocurrent response intensity. The method includes the following steps: Electrochemical doping of monolayer graphene is performed using the field effect, and the chemical potential of monolayer graphene is adjusted by regulating the gate voltage. The absorption spectrum of graphene can be altered by adjusting the chemical potential of monolayer graphene. By adjusting the chemical potential of monolayer graphene, the intensity of the graphene photocurrent response is affected. Based on the ratio of the decrease in the intensity of the graphene photocurrent response to the light band that cannot be excited to pass through the interband transition under the corresponding chemical potential, the relative intensity of the forbidden band of light to the total incident light is calculated. Based on the principle of interband transitions of forbidden electrons by chemical potential, the dependence between the photocurrent response intensity of graphene and chemical potential is extracted, thereby reconstructing the relative intensity spectrum of unknown incident light.

2. The spectral measurement method based on graphene photocurrent response according to claim 1, characterized in that, The aforementioned spectral measurement method adjusts the measurement range and resolution of the spectrum by changing the range and step size of the graphene chemical potential modulation.

3. The spectral measurement method based on graphene photocurrent response according to claim 1, characterized in that, The spectral measurement method further improves the signal-to-noise ratio of spectral measurements by modulating unknown incident light or gate voltage and combining it with phase-locked loop technology.

4. The spectral measurement method based on graphene photocurrent response according to claim 1, characterized in that, The standard spectrum of the unknown incident light was measured using standard spectral testing equipment, and the reconstructed spectrum was calibrated.

5. A method for preparing a spectrometer used in the spectroscopic measurement method based on graphene photocurrent response as described in claim 1, characterized in that, Includes the following steps: Monolayer graphene (1) was prepared on substrate material (2); Electrodes were prepared for monolayer graphene (1), and metal wires were used as electrode leads; The graphene device is wired to an electrical control and measurement device, which is used to provide the gate voltage required by the graphene device and to detect the source and drain current of the graphene device in real time. A voltage is applied between the source and drain, and the gate voltage is adjusted. Based on the measured source and drain currents, a graph showing the relationship between resistance and gate voltage is plotted to determine the gate voltage at the graphene chemical potential at the graphene electrical neutral point, which is the gate voltage at the point where the resistance is maximum. By adjusting the gate voltage, the chemical potential of monolayer graphene was adjusted to be close to the electrical neutral point of graphene, so that graphene exhibited light absorption and light forbidden effects, and the photocurrent response intensity change of monolayer graphene under unknown incident light was measured. The relative intensity spectrum of unknown incident light was reconstructed based on the dependence of the light band and the intensity of the graphene photocurrent response on the light band that cannot be excited by electrons under the corresponding chemical potential through interband transitions. The standard spectrum of the unknown incident light is measured using standard spectral testing equipment; based on the comparison between the reconstructed spectrum and the standard spectrum, the conversion ratio between the relative intensity of the reconstructed spectrum and the true intensity of the incident light is obtained.

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