Discontinuous metal film with tunneling effect, tunneling electrode chip and preparation method thereof

Abstract

The invention provides a discontinuous metal film with a tunneling effect, a tunneling electrode chip and a preparation method of the tunneling electrode chip. A large-area uniform discontinuous metal film grows in situ on a glass substrate through a magnetron sputtering deposition method, and a charge tunneling structure with a random nano array is constructed. The discontinuous metal thin film comprises a substrate and a nano gap thin film arranged on the substrate, the nano gap thin film comprises a plurality of nano islands and a plurality of nano gaps which are randomly distributed, and a nano gap is formed between any two adjacent nano islands and a nano gap lt; 10 nm; the thickness of the nano-gap film is lt; the wavelength is 100 nm. According to the tunneling electrode chip, atomic-scale thickness control is achieved through high-precision thin film deposition, the uniformity of multi-batch devices is remarkably improved, the yield is improved by 50% or above compared with a traditional method, the limitation of high cost of micro-nano machining faced by a traditional tunneling device is broken through, and the tunneling electrode chip has the sensitive response capacity for different small molecule media and is suitable for large-scale popularization and application. Molecular information can be presented in the form of transient conductance information.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic devices, and particularly to a discontinuous metal thin film with tunneling effect, a tunneling electrode chip and a preparation method thereof. Background Art

[0002] A tunneling electrode refers to an electrode with an electrode gap below 10 nm, which has advantages such as good mechanical properties, adjustable size, easy modification and easy integration, and has been widely used in research fields such as DNA sequencing, protein conformation analysis, biomolecular interaction, enzyme kinetics, and single molecule sensing. For a long time, the efficient and controllable fabrication of sub-10 nm gap electrodes has been a bottleneck problem in the fields of micro-nano processing and even single molecule sensing. So far, traditional tunneling electrode preparation methods include: break junction technology, electromigration and lithography technology, etc. However, all these technologies also have many problems, such as cumbersome processing steps, high processing costs, limited controllability of gap size, etc. This results in poor repeatability of electrode preparation and is not conducive to large-scale production.

[0003] In the prior art, the preparation of traditional micro-needle type tunneling electrodes usually relies on relatively complex process chains such as glass tube drawing, carbon burning forming, chemical etching, vacuum gold plating and feedback adjustment, resulting in low consistency and success rate of device preparation. In addition, interface contamination is easily introduced during multi-step wet etching and metal deposition processes, significantly reducing the quantum transport efficiency of the tunneling junction, which seriously restricts the large-scale production and application expansion of devices.

[0004] At the same time, existing tunneling electrodes usually only construct a single electron tunneling path in the structural design, and detect and analyze trace molecules in a sample solution by detecting the current change in this path. This tunneling electrode structure is usually used in the field of sensing detection, but its functional limitations make it difficult to meet the requirements of multifunctional integrated devices such as optical detection, molecular sensing and nonlinear optical response. Because these fields usually require a tunneling path array with high density to achieve synchronous detection and response to the tunneling effect in a large number of tunneling paths.

[0005] Therefore, there is an urgent need to develop a new type of integrated tunneling electrode chip. An ideal solution should have the following characteristics: (1) integrating a high-density electron tunneling path array; (2) maintaining the size of a miniaturized device; (3) having a controllable preparation process and low-cost advantages; (4) being able to generate a stable and measurable tunneling effect; (5) achieving precise detection and response to the multi-path tunneling effect. This breakthrough chip design will provide key basic device support for cutting-edge fields such as optoelectronic integration devices and multifunctional sensors. Summary of the Invention

[0006] Aiming at the problems existing in the prior art, the present invention provides a discontinuous metal thin film with tunneling effect, a tunneling electrode chip and a preparation method thereof. By means of magnetron sputtering deposition method, a large-area uniform discontinuous metal thin film is in-situ grown on a glass substrate, and a charge tunneling structure with a random nanoarray is constructed. The discontinuous metal thin film includes a substrate and a nano-gap thin film disposed on the substrate. The nano-gap thin film includes a plurality of randomly distributed nano-islands and a plurality of nano-gaps. A nano-gap is formed between any two adjacent nano-islands, and the nano-gap < 10 nm; the thickness of the nano-gap thin film < 100 nm. The tunneling electrode chip realizes atomic-level thickness control through high-precision thin film deposition, significantly improves the uniformity of multi-batch devices, and the yield rate is increased by more than 50% compared with the traditional method. It breaks through the expensive cost limitation of micro-nano processing faced by traditional tunneling devices, has a sensitive response ability to different small molecule media, and can present molecular information in the form of transient conductance information.

[0007] On the one hand, the present invention provides a discontinuous metal thin film with tunneling effect, including a substrate, and further including a nano-gap thin film disposed on the substrate; the nano-gap thin film includes randomly distributed nano-islands, and a nano-gap is formed between any two adjacent nano-islands; the number of the nano-islands and the nano-gaps is more than one.

[0008] The tunneling effect is a peculiar phenomenon in quantum mechanics, referring to the phenomenon that microscopic particles (such as electrons) can pass through an energy potential barrier that is considered insurmountable in classical physics, which is a direct manifestation of the wave-particle duality of quantum mechanics. By detecting the tunneling current generated by the tunneling effect, it can be applied to many fields such as surface atomic-level imaging, nanoelectronic devices, semiconductor industry, quantum computing, chemical and biological sensing, and basic physical research. The detection of tunneling current not only promotes the development of nanotechnology and quantum information, but also plays an irreplaceable role in industrial storage, biomedicine and other fields.

[0009] The discontinuous metal thin film with tunneling effect provided by the present invention is different from the existing tunneling electrodes that only contain a single electron tunneling path, but has countless nano-gaps in the thin film. Therefore, multiple electron tunneling paths can be formed to construct a high-density integrated tunneling junction array.

[0010] In some ways, based on the discontinuous metal thin film provided by the present invention, the comprehensive tunneling effect generated by each electron tunneling path can be macroscopically detected through an electrode, so as to obtain a macroscopic judgment on the sample to be measured, which can be used for real-time monitoring of interface reactions such as gas-liquid or solid-liquid, such as identification, redox reaction, catalysis, etc.

[0011] The nano-island refers to a metal material discontinuously distributed in the metal thin film. Since its shape is like an isolated island, it is named a nano-island, and the nano-gap between each nano-island is the electron tunneling path.

[0012] In some ways, there are countless nano-islands distributed in the discontinuous metal thin film, and nano-gaps are provided between each nano-island.

[0013] On the substrate of the discontinuous metal thin film of the present invention, a number of sub-10nm gap structures are distributed in a large area and uniformly. There is a certain probability that electrons can cross the gap to form a tunneling current. The relationship between the tunneling current and the voltage no longer satisfies Ohm's law. Therefore, its IV curve exhibits typical non-linear characteristics, which is related to the electron transport characteristics of its tunneling mechanism. When a pair of electrodes is turned on, electrons are transported through a continuous conductor, and its characteristics satisfy Ohm's law, and the iv response is an inclined straight line. Therefore, the discontinuous metal thin film provided by the present invention can effectively excite the local surface plasmon resonance effect (LSPR) and the quantum tunneling effect, thus presenting excellent optical and electrical characteristics, laying an experimental foundation for the development of multifunctional integrated devices with functions such as optical detection, molecular sensing, and non-linear optical response.

[0014] Further, the distance of the nano-gap is sub-10nm; and / or the thickness of the nano-gap thin film does not exceed 100 nm.

[0015] In order to generate the tunneling effect, the discontinuous metal thin film cannot be fully conductive or non-conductive, because if it is fully conductive, it is equivalent to the entire discontinuous metal thin film being completely conductive, and its IV curve is linear, and the tunneling current cannot be detected; if it is non-conductive, the current cannot be detected either.

[0016] The discontinuous metal thin film prepared by the present invention can maintain the nano-gap between each nano-island at a specific value, such as within the sub-10nm range, so as to meet the requirements for quantum tunneling detection, such as 3-10nm, 5-10nm, 3-30nm, or 5-20nm, etc. It is also possible to control the nano-gap within a more precise size range through precise control of the preparation method.

[0017] The nano-gap for quantum tunneling detection is theoretically the smaller the better, but too small a gap will limit the adjustment range. If the gap is too small, it may even cause the entire thin film to be fully conductive, and the tunneling current cannot be detected. It may also cause surface atom migration or oxidation, affecting the device life. Of course, the nano-gap cannot be too large either, as too large a gap may directly cause the entire thin film to be non-conductive and the tunneling current cannot be detected. Therefore, the nano-gap needs to balance the tunneling probability, current conduction, signal-to-noise ratio, stability, and process feasibility. The nano-gap of the discontinuous metal thin film prepared by the present invention is preferably controlled within the range of 3-10nm.

[0018] In order to enable the discontinuous metal thin film to meet the requirements of tunneling detection, it is also necessary to maintain the thickness of the discontinuous metal thin film within a specific range. If the thickness of the discontinuous metal thin film is too thin or too thick, not only will the production difficulty increase, but there may even be a situation where the thickness of the nano-islands is uneven; moreover, if the thickness is too thin, it may also cause the nano-gap to be too thin, resulting in an open circuit state for the electrodes, and electrically manifested as no current signal generation. Therefore, the thickness of the discontinuous metal thin film needs to be sub-100 nm to maintain a better tunneling effect, while also maintaining low cost and high yield in the preparation process.

[0019] In some ways, the preferred thickness of the discontinuous metal thin film can be 3 - 20 nm, more preferably 5 - 10 nm, can be 3 - 30 nm, or can also be 5 - 8 nm. The most preferred thickness of the discontinuous metal thin film is 5 - 6 nm.

[0020] In some ways, based on the area of the substrate, the total coverage rate of the nano-gaps in the discontinuous metal thin film is 26.64 - 46.45 %. The coverage rate of the nano-gaps in the present invention refers to: analyzing the SEM image of the discontinuous thin film through ImageJ software and obtaining the ratio of the area of the nano-gaps to the area of the substrate by calculation. When the coverage rate of the nano-gaps is too high, it means that the gap area is larger, the energy barrier that electrons need to cross is higher, and it is more difficult to generate a tunneling current. Therefore, the preferred coverage rate of the nano-gaps is 26.64 - 46.45 %, and the tunneling effect can be detected.

[0021] In some ways, the size of the nano-islands is 100 - 500 nm.

[0022] Furthermore, the material of the substrate is selected from one or more of silicon dioxide, glass, silicon, silicon nitride, and sapphire; and / or, the material of the nano-gap thin film is selected from one or more of gold, silver, aluminum, and copper.

[0023] It can be understood that silicon dioxide, glass, silicon, silicon nitride, and sapphire can all be used to prepare the substrate, and gold, silver, aluminum, and copper can all be used to prepare the nano-gap thin film, so that the discontinuous metal thin film can be prepared by any combination.

[0024] In some ways, the material of the substrate is preferably glass. Because glass has high light transmittance, excellent light transmittance in the visible light range (usually > 90%), it will not interfere with the optical properties of the metal thin film; moreover, it has high surface flatness and smoothness, and good chemical stability, thermal stability, and mechanical strength.

[0025] In some ways, the material of the nano-gap thin film is selected from gold. When the material is gold, due to the characteristics of gold having chemical inertness, high reduction potential, and stable electron structure, the formed discontinuous metal film can maintain structural stability and antioxidant properties at room temperature for a long time.

[0026] Furthermore, an adhesion layer is provided between the nano-gap thin film and the substrate. The adhesion layer can make the adhesion between the thin film and the substrate firmer and the performance more stable.

[0027] Furthermore, the material of the adhesion layer is selected from one or more of chromium, titanium, and titanium tungsten.

[0028] It can be understood that chromium, titanium, and titanium tungsten can all be used to prepare the adhesion layer, thereby enhancing the firmness between the discontinuous metal thin film and the substrate.

[0029] In some embodiments, the material of the adhesion layer is preferably chromium because chromium has good adhesion, film-forming property, and stability. The prepared adhesion layer has a better adhesion effect, can effectively prevent the discontinuous metal thin film from diffusing to the substrate, and avoid interface deterioration. At the same time, it also has appropriate electrical conductivity, which helps to improve the detection accuracy and stability when used for tunneling detection.

[0030] In some embodiments, the thickness of the adhesion layer is 0.8 - 1.2 nm.

[0031] In order to better and more accurately detect the tunneling effect, the conductivity of the discontinuous metal thin film prepared by the present invention must be maintained within a suitable range. If the conductivity is too high, it will lead to full conduction, and if it is too low, it may directly result in non-conduction. Neither full conduction nor non-conduction can be used for tunneling effect detection.

[0032] In some embodiments, the conductivity of the discontinuous metal thin film is 0.1 - 1000 nS, which can be used to respond to the tunneling effect.

[0033] When used in the field of optical detection, the discontinuous metal thin film also needs to have good transmittance. For example, the transmittance must be maintained above 60% and so on. Of course, specifically, the appropriate transmittance can be selected according to the different requirements of the discontinuous metal thin film in different fields of application. The transmittance of the discontinuous metal thin film prepared by the present invention is 66.33 - 70.25%, which meets the requirements of the optical detection field.

[0034] In addition, the discontinuous metal thin film of the present invention has good stability and can be stably stored in a dry environment at room temperature. The loss of conductivity after storage is very small, meeting the requirements of the micro-nano photon device field.

[0035] On the other hand, the present invention provides a method for preparing a discontinuous metal thin film with a tunneling effect. The method includes the following steps: depositing a nano-gap thin film on the surface of a substrate by magnetron sputtering to obtain the discontinuous metal thin film.

[0036] The tunneling electrode device prepared by the present invention proposes an innovative solution for the limitations of the traditional tunneling electrode preparation process, and provides an integrated tunneling junction array device. Through the innovation of the planar device architecture, a magnetron sputtering technique is used to directly deposit an ultrathin gold film on the surface of a glass substrate, and a nanoscale patterning process is combined to construct a large-area distributed sub-10nm gap array.

[0037] By replacing the traditional micro-needle three-dimensional forming method with a planar sputtering process, atomic-level thickness control is achieved through high-precision thin film deposition, effectively eliminating the structural errors caused by mechanical deformation; in addition, the all-dry process avoids the batch fluctuations of chemical etching, significantly improving the uniformity of single-batch devices, and the yield rate is increased by more than 50% compared with the traditional method; moreover, centimeter-scale planar electrodes can realize the integration of high-density tunneling junction arrays, broadening the application range of planar tunneling electrodes. This innovative preparation strategy not only greatly reduces the process complexity and production cost, but also lays a reliable manufacturing foundation for the large-scale application of quantum tunneling devices in the fields of biosensing, nanoelectronics, etc.

[0038] The magnetron sputtering method is a physical vapor deposition (PVD) technology. Its core principle is that high-energy ions bombard the surface of the target material, causing the target atoms to escape and deposit on the substrate to form a thin film. The present invention compares the preparation of ultrathin nanogap films by different methods and finds that when the magnetron sputtering method is used, the size and coverage of the tunneling nanogaps, as well as the thickness of the discontinuous metal film, can be more precisely controlled. The yield rate of the prepared finished products is higher and the cost is lower.

[0039] The present invention deposits a large-area uniform ultrathin nanogap film on the substrate at one time by the magnetron sputtering method. Its preparation steps are simple and the cost is low, breaking through the technical bottlenecks of the high cost and cumbersome operation of traditional metal nanogap processing.

[0040] Furthermore, in the magnetron sputtering method, the deposition time is 10 - 30 s. The deposition time of magnetron sputtering cannot be too long or too short. If it is too long, the film will be connected into a sheet and show full conduction in electrical characteristics. If it is too short, the film will be too thin and the gap will be too large, showing disconnection in electrical characteristics. In both cases, it cannot be used for the detection of tunneling effects.

[0041] In some cases, the deposition rate of magnetron sputtering is 1.74 Å / s. The deposition rate is an important parameter affecting the performance of discontinuous films.

[0042] In some ways, the starting power of magnetron sputtering is 40 - 60 Ws, and the atmosphere environment is as follows: the nitrogen pressure is 0.05 - 0.09 mPa, the argon is 0.03 - 0.07 mPa, and the air is 0.30 - 0.8 mPa. Specifically, the starting power is 50 W, and the atmosphere environment is: the nitrogen pressure is 0.07 mPa, the argon is 0.05 mPa, and the air is 0.55 mPa.

[0043] In some ways, before magnetron sputtering, the substrate needs to be pre - treated first. The pre - treatment is washing, such as ultrasonic washing, and the organic or inorganic substances on the substrate surface are removed through pre - treatments such as washing. The solvent used for washing is selected from one or more of acetone, isopropanol, and ethanol. After washing, it needs to be dried before being used for magnetron sputtering to prepare a discontinuous metal thin film with tunneling effect.

[0044] In some ways, the adhesion layer is also deposited by magnetron sputtering method.

[0045] In some ways, magnetron sputtering includes the following steps: placing the target in the cavity of the magnetron sputtering equipment, evacuating, ionizing the inert gas (argon) by applying an electric field, generating ions to bombard the target, and the plasma plume bombarded out is deposited on the substrate.

[0046] In some ways, during deposition, the pressure is 1.6E - 6 MPa, the starting power is 40 - 60 W, the deposition time is set to 10 - 30 s, and the turntable rotation speed is set to 10 - 30 rmp; the atmosphere environment is: the nitrogen pressure is 0.05 - 0.09 mPa, the argon is 0.03 - 0.07 mPa, and the air is 0.30 - 0.8 mPa. Specifically, the pressure is 1.6E - 6 MPa, the starting power is 50 W, the deposition time is set to 20 s, and the turntable rotation speed is set to 20 rmp; the atmosphere environment is: the nitrogen pressure = 0.07 mPa, the argon = 0.05 mPa, and the air = 0.55 mPa.

[0047] On the other hand, the present invention provides a tunneling electrode chip, which includes the discontinuous metal thin film as described above; it also includes a continuous conductive layer provided on the discontinuous metal thin film, and an electrode pair provided on the continuous conductive layer.

[0048] Furthermore, the material of the continuous conductive layer is selected from one or more of gold, silver, aluminum, and copper; and / or, the material of the electrode pair is selected from one or more of gold, silver, aluminum, and copper.

[0049] In some ways, the thickness of the conductive layer is 80 - 100 nm.

[0050] In some ways, the method for preparing the electrode chip is as follows: a mask plate is set on a discontinuous metal thin film and obtained by magnetron sputtering deposition. The mask plate is usually in a lattice shape with hollowed-out middle parts, so that a conductive layer is formed on the discontinuous metal thin film at the hollowed-out parts in each lattice, while the parts separated by the partitions formed by the mask plate cannot form a conductive layer.

[0051] Due to the use of the mask plate, the conductive layer is in a discontinuous state, and the connected conductive layers are separated by the mask plate. Therefore, the discontinuous metal thin film cannot be completely conducted through the conductive layer, and thus can be used for the detection or response of the tunneling effect. The positions of the electrode pairs are respectively set on both sides of the partition of the mask plate, and the distance by which the conductive layer is separated is equivalent to the distance between the electrode pairs, so that the discontinuous metal thin film is not completely conducted. That is to say, the distance between the electrode pairs described in the present invention refers to the distance that cannot be conducted and is separated by the mask plate between two pairs of electrode pairs.

[0052] In some ways, the distance between the electrode pairs is 30 - 100 μm. The present invention explores the influence law of the distance between the electrode pairs on the electrical characteristics of the device, and finds that when the electrode distance is within the range of 30 - 100 μm, it can be used to detect the tunneling effect generated by the discontinuous metal thin film; when the distance between the electrode pairs is greater than 100 μm, the prepared electrode chip cannot conduct electricity and thus cannot be used for tunneling effect detection; when the distance between the electrode pairs is less than 30 μm, due to the too-close conductive layers, the discontinuous metal thin film is completely conducted, and only a linear IV curve can be detected, and it also cannot be used for tunneling effect detection. That is to say, the width of the partition in the mask plate needs to be within the range of 30 - 100 μm.

[0053] The magnetron sputtering method includes the following steps: placing the target in the cavity of the magnetron sputtering device, evacuating, ionizing the inert gas (argon) by applying an electric field, and the generated ions bombard the target, and the bombarded plasma plume is deposited on the substrate.

[0054] In some ways, during deposition, the pressure is 1.6E - 6 MPa, the starting power is 40 - 60 W, the deposition time is set to 10 - 30 s, and the turntable rotation speed is set to 10 - 30 rmp; the atmosphere environment is: the nitrogen pressure is 0.05 - 0.09 mPa, the argon is 0.03 - 0.07 mPa, and the air is 0.30 - 0.8 mPa. Preferably, during deposition, the pressure is 1.6E - 6 MPa, the starting power is 50 W, the deposition time is set to 20 s, and the turntable rotation speed is set to 20 rmp; the atmosphere environment is: the nitrogen pressure is 0.07 mPa, the argon is 0.05 mPa, and the air is 0.55 mPa.

[0055] In another aspect, the present invention provides a method for molecular medium sensing and detection, which uses the discontinuous metal thin film or the tunneling electrode chip as described above for detection; the detection method includes: dropping a solution onto the surface of the discontinuous metal thin film or the tunneling electrode chip, and being captured by the nano-gap under the drive of an electrostatic field, and detecting the IV curve.

[0056] Existing tunneling electrodes usually only have a single electron tunneling path between the electrodes, and can analyze small molecule substances in a sample solution by detecting the current change generated in this electron tunneling path. However, in the field of identification and detection of solid-liquid, gas-liquid interface reactions, catalysis and diffusion effects, traditional micro-needle devices may be difficult to effectively capture interface reactions due to structural limitations and small contact areas, while planar large-area contacts can cover the interface more comprehensively, improving detection sensitivity and accuracy.

[0057] The present invention expands the traditional micro-needle single-point tunneling device to a multi-point tunneling chip on a plane, which has more tunneling arrays and active sites, facilitating the improvement of tunneling efficiency. In addition, this tunneling chip also has the advantages of specific application scenarios, being easy to integrate with a microfluidic system or other analysis technologies, and suitable for real-time monitoring of complex reaction environments.

[0058] For samples with a large number of unknown small molecule media, especially the detection of small molecule media at the solid-liquid interface, using the detection device provided by the present invention, which integrates multiple electron tunneling paths and can accurately detect the comprehensive tunneling effect generated by passing through each electron tunneling path through the electrodes at the same time, can achieve a sensitive response to small molecule media as a whole.

[0059] It should be explained that when detecting through the discontinuous metal thin film or the tunneling electrode chip provided by the present invention, a non-linear IV curve is obtained instead of a linear straight line. This is because the tunneling effect occurs, resulting in the relationship between current and voltage no longer conforming to Ohm's law, thus making the IV curve a non-linear curve. Without the tunneling effect, in the case of normal conduction, the IV curve detected by the electrode is just a linear straight line because the conductivity remains unchanged without the tunneling effect.

[0060] Due to the differences in tunneling barriers caused by different molecular media, the conductivity changes. When different molecular media are filled into the nano-gap, due to their different dielectric constants, the barriers that electrons need to overcome to cross the gap are different, resulting in changes in conductivity. Therefore, when detecting different samples, different non-linear IV curves will be obtained. Therefore, according to the shapes of the non-linear IV curves of different samples, different tunneling effects occurring between the nano-gaps of the discontinuous metal thin film can be judged, so as to be used to judge the overall situation of the molecular media in the sample.

[0061] In some ways, the molecules for detection are one or more of molecules such as n-hexane, carbon tetrachloride, formamide, dimethyl sulfoxide, etc.

[0062] On the other hand, the present invention provides the use of the discontinuous thin film or the tunneling electrode chip as described above in optoelectronic detection devices, molecular sensor devices or light-responsive devices.

[0063] In some ways, the optoelectronic detection device includes imaging, single electron transistors, photoconductive antennas, terahertz wave emitters and detectors.

[0064] In some ways, the molecular sensor device includes ultrasensitive interfacial catalysis, biomolecule detection, and stress sensing of wearable devices.

[0065] In some ways, the light-responsive device includes highly efficient catalytic electrodes, supercapacitors.

[0066] The present invention has the following beneficial effects:

[0067] 1) A brand-new device with a tunneling effect is provided. The device has the shape of a thin film or a chip, includes randomly distributed nanoislands, two adjacent nanoislands and the nano-gap therebetween, realizing a large-area uniformly distributed nano-gap structure. This structure can effectively excite the localized surface plasmon resonance effect (LSPR) and the quantum tunneling effect, thus presenting excellent optical and electrical properties.

[0068] 2) A brand-new preparation method is provided, which can form a discontinuous metal thin film with multiple tunneling nano-gaps on a substrate. Through high-precision thin film deposition, atomic-level thickness control is achieved, significantly improving the uniformity of multi-batch devices, and the yield rate is increased by more than 50% compared with traditional methods.

[0069] 3) Compared with the traditional chemical solvent growth method, by controlling experimental parameters such as the atmosphere, deposition rate, pressure, power, etc. during the deposition process, a discontinuous metal thin film with a large area, high uniformity, controllable nano-gap size and thin film thickness is deposited on the substrate by magnetron sputtering deposition method, constructing a charge tunneling structure with an integrated nanoarray.

[0070] 4) The preparation method of the discontinuous metal thin film of the present invention is conducive to batch preparation, simpler and lower in cost, breaking through the technical bottlenecks such as high processing cost and cumbersome operation of traditional nano-gap electrodes to a certain extent.

[0071] 5) When the discontinuous metal thin film of the present invention is used for molecular medium detection, its IV curve presents typical non-linear characteristics. The cyclic voltammetry method is used to test the IV curve, which is in good agreement with the fitting result of the classical tunneling model.

[0072] 6) The discontinuous metal thin film with tunneling effect prepared maintains a stable structure for a long time under room temperature drying conditions and has excellent antioxidant performance.

[0073] 7) It has important application values in the fields of electronic devices, nanotechnology, biomarker analysis, etc. Description of the Drawings

[0074] Figure 1 It is the physical diagram and SEM diagram of the discontinuous metal thin film with tunneling effect in Example 1.

[0075] Figure 2 It is the structural schematic diagram of the tunneling electrode chip in Example 2.

[0076] Figure 3 It is the physical diagram of the tunneling electrode chip in Example 2 for masking, deposition, laser cutting, and wire bonding; among them, (1) is the physical diagram after masking; (2) is the physical diagram after sputter deposition of the conductive layer; (3) is the physical diagram of the single tunneling electrode chip after laser cutting; (4) is the microscopic photo of the wire-bonded electrode chip.

[0077] Figure 4 It is the IV curve of the tunneling electrode chip in Example 3 in air.

[0078] Figure 5 It is the IV curve of the tunneling electrode chip in Example 3 for different media responses.

[0079] Figure 6 It is the SEM diagram of the discontinuous metal thin film prepared by the chemical solvent growth method (hydrothermal synthesis method) in Example 4.

[0080] Figure 7 It is the IV curve diagram that is completely conductive and linear formed with a deposition time of 40 s in Example 5.

[0081] Figure 8 It is the physical diagram after the substrate / Au and substrate / Cr / Au are heat-treated respectively and soaked in an ethanol solution overnight; among them, A is substrate / Au (without an adhesion layer), and B is substrate / Cr / Au (with an adhesion layer). Detailed Embodiments

[0082] To describe the present invention more specifically, the technical solutions of the present invention will be described in detail below in conjunction with the drawings and specific embodiments. These descriptions only show how the present invention is implemented and cannot limit the specific scope of the present invention. The scope of the present invention is defined in the claims.

[0083] When the magnetron sputtering method is used for deposition in the following examples, the equipment adopted is the PRO Line PVD 75 multi-functional sputtering, electron beam and thermal evaporation thin film deposition system platform, which is purchased from Kurt J. Lesker Company in the United States; when sputtering deposition is carried out, the turntable speed is 20 rmp and the temperature is room temperature.

[0084] The Cr target in the example has a specification of φ76.2×3 mm (diameter and thickness) and a purity of 99.99%, which is purchased from Zhongnuo New Materials (Beijing) Technology Co., Ltd. The Au target in the example has a specification of φ50.8×3 mm and a purity of 99.999%, which is purchased from Kurt J. Lesker Company in the United States; the Ag target has a specification of φ76.2×3 mm and a purity of 99.999%, which is purchased from Kurt J.Lesker Company in the United States; the Al target has a specification of φ76.2×3 mm and a purity of 99.999%, which is purchased from Kurt J. Lesker Company in the United States. The substrate glass sheet in the example has a specification of φ150×1 mm.

[0085] Example 1: Preparation of discontinuous metal thin film with tunneling effect

[0086] The specific preparation method of the discontinuous metal thin film with tunneling effect provided in this example is as follows:

[0087] 1) Deposit a Cr layer about 1 nm thick as an adhesion layer on the substrate surface through a magnetron sputtering deposition device. The specific operation steps are as follows:

[0088] Sample loading: Place the Cr target (purity 99.999%) in the corresponding cavity of the magnetron sputtering device, fix the substrate on the turntable with tape, and hang it vertically with the front side down on the electron gun in the middle of the cavity.

[0089] Vacuum pumping: Click PC Pump to pump the cavity to a pressure of 1.6E-6 MPa in the cavity.

[0090] Parameter setting: Select the corresponding working end, click Switch to switch, and open the working end cover of the Cr target. The starting power is 50W, the deposition time is set to 5s, and the turntable speed is set to 20 rmp.

[0091] Sputtering deposition: Click Substrate Shutter to start generating dust. Ionize the inert gas (argon) by applying a high-voltage electric field to generate high-energy ions. These ions strike the target, causing Cr target atoms to be sputtered out and deposited on the substrate surface to form a uniform thin film. The atmosphere environment is: nitrogen pressure = 0.07 mPa, argon = 0.05 mPa, air = 0.55 mPa.

[0092] Post-treatment: After the deposition is completed, the substrate with the adhesion layer deposited thereon is taken out of the cavity and subjected to subsequent treatment or processing.

[0093] Among them, the substrate is a glass sheet, and the substrate is pretreated. The pretreatment is as follows: The glass sheet (15 cm * 15 cm) is ultrasonically cleaned with acetone and isopropyl alcohol for 5 minutes respectively to remove the impurities adsorbed on its surface, and then rinsed with deionized water and dried with nitrogen.

[0094] 2) Use a magnetron sputtering deposition device to in-situ deposit a nano-gap thin film on the adhesion layer. The specific operation steps are as follows

[0095] Loading: Place the Au target in the corresponding cavity, fix the substrate after depositing the adhesion layer in step 1) on the turntable with tape, and hang it vertically with the front side down in the middle of the electron gun in the cavity.

[0096] Vacuum pumping: Click PC Pump to pump the cavity to a pressure of 1.6E-6 MPa.

[0097] Parameter setting: Select the corresponding working end, click Switch to switch, and open the working end cover of the Au target. The starting power is 50 W, the deposition time is set to 20 s, and the turntable rotation speed is set to 20 rmp.

[0098] Sputtering deposition: Click Substrate Shutter to start generating dust. Ionize the inert gas (argon) by applying a high-voltage electric field to generate high-energy ions. These ions strike the target, causing the Au target atoms to be sputtered out and deposited on the surface of the adhesion layer to form a nano-gap thin film. The nano-gap thin film contains randomly distributed nano-islands. Two adjacent nano-islands and the nano-gap between them form a pair of tunneling junctions to obtain a discontinuous thin film with tunneling effect. The atmosphere environment is: nitrogen pressure = 0.07 mPa, argon = 0.05 mPa, air = 0.55 mPa.

[0099] Post-treatment: After the deposition is completed, the substrate with the nano-gap thin film deposited thereon is taken out of the cavity to obtain a discontinuous metal thin film.

[0100] Take a physical photo and SEM scan of the obtained discontinuous thin film. See the physical picture and SEM picture in Figure 1 。

[0101] From Figure 1 the left picture in the middle (the prepared discontinuous metal thin film is in a transparent state). It can be seen that the discontinuous thin film is composed of several randomly distributed, independent nano-islands with clear boundaries. There are channels (nano-gaps) between the nano-islands and adjacent nano-islands. Two adjacent nano-islands and the nano-gap between them form a tunneling junction.

[0102] From Figure 1 As can be seen from the SEM images in Figure 1 , the Nano Measurer software was used to analyze the width of the nanogaps between adjacent nanoisland structures in the SEM images. The average nanogap was 5 nm. The Image J software was used to analyze and calculate the coverage rate of the nanogaps in the SEM images, that is, the area of the nanogaps divided by the area of the substrate. The calculated coverage of the nanogaps was 21.69%.

[0103] Example 2. Preparation of the tunneling electrode chip

[0104] The structure of the tunneling electrode chip provided in this example is as Figure 2 shown. The tunneling electrode chip includes, from bottom to top, a substrate 4, an adhesion layer 3, a discontinuous metal thin film 2, and a conductive layer 1. Depositing a continuous conductive layer on the surface of the discontinuous metal thin film obtained in Example 1 and setting electrode pairs on the continuous conductive layer to form the tunneling electrode chip includes the following:

[0105] 1) Mask: The size of the mask plate is 7*7 cm, which contains 105 small structural units (each structural unit is hollowed in the middle to form a conductive layer on the surface of the discontinuous metal thin film, and the non-hollowed positions on the mask plate can play a blocking role and cannot form a conductive layer on the surface of the discontinuous metal thin film at this part). The smallest structural unit is a rectangular structure of 0.3*0.4 cm. The mask plate (the shortest distance between adjacent two rectangular structures (the partition part 5 of the mask plate) is 30 µm) is pasted on the surface of the discontinuous metal thin film obtained in Example 1 through tape, and then the sample is placed in the sputtering cavity. After adhering the mask, see Figure 3 in (1) (the black in the figure is the color of the lower metal turntable, and the thin film is actually transparent).

[0106] 2) Sputtering deposition: Subsequently, a continuous gold film about 10 nm thick is deposited on the surface of the mask for 120 s as the conductive layer, and electrode pairs are formed at both ends. The operation method refers to step 2) of the deposition method of the discontinuous thin film in the specific Example 1. After sputtering is completed, the mask is removed, and the obtained physical object is seen Figure 3 in (2).

[0107] 3) Laser cutting: The product obtained in step 2) is cut using a laser cutting system to form individual tunneling electrode chips for subsequent testing. The individual tunneling electrode chips are seen Figure 3 in (3).

[0108] 4) Wire bonding: A 30-µm aluminum wire is welded to both ends of the electrode pair through a wire bonder, and the other end of the aluminum wire is connected to the pcb pad, see Figure 3 in (4), and the working electrode and the reference / counter electrode of the microcurrent instrument are connected through pin headers and DuPont wires.

[0109] Example 3: Performance study of tunneling electrode chip

[0110] This example studies the performance of the tunneling electrode chip prepared in Example 2:

[0111] 1. Consistency study

[0112] The same method as in Example 1 was used to prepare discontinuous metal films from 5 different batches, and tunneling electrode chips were obtained by the same method in steps 1) to 4). The conductivity and transmittance of electrode chips from different batches were studied to study the consistency of the magnetron sputtering method. The results are shown in Table 1.

[0113] The test method of conductivity is: collecting the iv curve by cyclic voltammetry and calculating it by the formula G=ΔI / ΔU.

[0114] Transmittance detection: The tunneling electrode chip (substrate specification is φ150×1 mm) deposited with a continuous conductive layer and an electrode pair was cut into pieces with a specification of 10*10*1 mm. The test was carried out at room temperature using a Thermo Scientific Evolution 220 series UV spectrophotometer. Each sample was scanned three times and the average value was taken.

[0115] Table 1. Statistics of average conductivity and transmittance of 5 different batches

[0116]

[0117] As can be seen from Table 1, the conductivity of the electrode chips of the five batches is within the theoretical tunneling conductivity range (0.1-1000 nS), and the RSD is 25.2% (since 0.1-1000 nS belongs to the range of tunneling conductivity, the RSD is relatively large). The RSD of the transmittance is 2.26%, which is less than 10%, indicating that the electrode chips prepared in this embodiment have good consistency, and the method can achieve good repeatability and can be used for large-scale production of non-continuous films and electrode chips.

[0118] In addition, in order to detect the tunneling effect, the conductivity must be maintained in the range of 0.1-1000nS. The reason is that if the conductivity is too high, the electrodes will be completely conductive, and a linear IV curve will be directly detected, and the tunneling effect cannot be detected. When the conductivity is too low, it will be difficult for the two electrodes to be conductive, and the tunneling effect cannot be detected. Therefore, the tunneling electrode chip prepared in this embodiment can maintain the conductivity in the range of 0.1-1000nS, and can be used to successfully detect the tunneling effect.

[0119] 2. IV performance

[0120] The tunneling electrode chip No. 1 in Table 1 was used to test the IV curve of a single tunneling electrode chip by cyclic voltammetry. The results are shown in Figure 4 . The test condition parameters are as follows: voltage 1V, Scan Rate (V / s) = 0.1.

[0121] From Figure 4 It can be seen that the IV curve of the tunneling electrode chip shows typical non-linear characteristics, indicating that the tunneling electrode chip prepared in this embodiment can produce an obvious tunneling effect and can detect or respond to tunneling current. The research results lay an experimental foundation for the development of multifunctional integrated devices with functions such as optical detection, molecular sensing, and non-linear optical response. The relevant technical parameters (nano-gap size, metal thin film thickness, conductivity, transmittance, etc.) meet the core requirements of the micro-nano photon device field for high sensitivity, wide-spectrum response, and low-power operation.

[0122] 3. Stability study

[0123] The tunneling electrode chip was placed at room temperature for 15 days, and the conductivity was measured every 5 days. After the storage was completed, the loss and ratio were calculated. The loss is: conductivity on the Nth day - conductivity on the 0th day; the ratio is: conductivity on the Nth day ÷ conductivity on the 0th day. Table 2 shows the change in conductivity of the device during 15 days of storage.

[0124] Table 2. Change in conductivity of the sample during 15 days of storage

[0125]

[0126] It can be seen from Table 2 that after 15 days of storage, the loss of conductivity of the electrode chip is 1.8 nS, and the ratio (storage 15 / 0 days) is 40%, which also indicates that the tunneling electrode chip has good repeatability and reliability, which is conducive to large-scale production and commercial application.

[0127] 4. Small molecule medium sensing detection

[0128] The tunneling electrode chip prepared in this embodiment was used to test the IV curves of the sample solution and air respectively. The sample solutions were formamide, dimethyl sulfoxide, n-hexane, and carbon tetrachloride solutions with a mass concentration of 100% respectively. 10 μL of the sample solution was respectively dropped onto the tunneling electrode chip, and a voltage of 6V was applied to the control end of the micro-current instrument, and the signal-to-noise ratio was set to 0.3 rat / s. The IV curves of different media were tested by cyclic voltammetry ( Figure 5 ).

[0129] According to Figure 5It can be seen that due to the differences in the dielectric constants of different small molecules, the potential barriers that electrons need to overcome when traversing the gaps are different, resulting in different changes in conductivity, and the obtained non-linear IV curves are also different. The small molecule medium in the sample solution can be deduced by the obtained different IV curves.

[0130] Example 4. Comparison of discontinuous metal films with tunneling effect prepared by different preparation methods

[0131] In this example, discontinuous metal films were prepared by the following two methods respectively: 1. Magnetron sputtering (according to Example 1); 2. Chemical solvent growth method (hydrothermal synthesis method). In the chemical solvent growth method, sodium citrate was used as both a reducing agent and a stabilizer. The specific steps are as follows: First, 500 mL of HAuCl4 (1 mM) was added to a round-bottom flask (1 L) and heated to boiling under vigorous stirring. Then, 50 mL of sodium citrate (38.8 mM) was immediately added, and the color changed from light yellow to chestnut red at this time. Continue to heat for 10 min, remove the heating jacket and continue to stir for 15 min, and the color changed to purple-red to obtain gold nanoparticles. Finally, the prepared gold nanoparticles were cooled to room temperature and stored at 4 °C for later use. When in use, 500 μL of gold nanoparticles was dropped on the surface of the cleaned glass slide, incubated overnight at room temperature and dried to form a glass slide sample loaded with gold nanoparticles.

[0132] The SEM images of the discontinuous metal films prepared by the first method (Example 1) and the second method (hydrothermal synthesis method) are respectively as Figure 1 B in Figure 6 and Figure 6 shown. It can be seen from

[0133] that for the discontinuous metal film prepared by the second method (hydrothermal synthesis method), the aggregation of gold nanoparticles is relatively serious, indicating that the dispersibility and uniformity of the gold film prepared by this method are poor. Moreover, due to the poor uniformity of the discontinuous metal film prepared by the second method, the sizes of the nano-gaps in it are different, some are too small, and some are too large, and the yield rate is extremely low (only about 1.2%), and it is impossible to accurately detect or respond to the tunneling current signal, making it difficult to be applied in the industry. The detection method of the yield rate: A non-linear IV curve is judged to be able to generate a tunneling effect, and the film thickness is less than 100 nm, the nano-gap is 3 - 10 nm, the nano-gap coverage rate is 21.64 - 46.45%, the conductivity is 0.1 - 1000 nS, and the transmittance is 66.33 - 70.25, then it is judged as a good product.

[0134] Example 5. Influence of different deposition times on the preparation of discontinuous metal films

[0135] In this embodiment, the method provided in Embodiment 1 is adopted to prepare the discontinuous metal thin film. When the magnetron sputtering Au target is used, the deposition times are 5, 10, 20, 30, and 40 s respectively, and other conditions are the same as those in Embodiment 1. Thus, 5 kinds of discontinuous metal thin films are prepared, and the nano-gap size, nano-gap coverage rate, thin film thickness, particle morphology, IV characteristics, and yield rate of the two thin films are detected respectively. The detection methods of the nano-gap size and nano-gap coverage rate are as shown in Embodiment 1. The detection method of the thin film thickness is to take pictures of the scribed step method using an atomic force microscope (AFM) and analyze and calculate. The detection method of the particle morphology is to take scanning electron microscope (SEM) pictures. The detection method of the IV characteristics is as shown in Embodiment 3. The detection method of the yield rate is as shown in Embodiment 4. Each is repeated more than three times, and the average value is taken. The specific performance parameter detection results are shown in Table 3.

[0136] Table 3. Influence of different deposition times on the preparation of discontinuous metal thin films

[0137]

[0138] It can be seen from Table 3 that when the magnetron sputtering Au target is used, the change of the deposition time will directly affect the performance of the prepared discontinuous metal thin film. When the deposition time is 5 s, due to the too short deposition time, the prepared discontinuous metal thin film is very thin, the uniformity of the nano-gap size decreases, and the IV curve is parallel, indicating that the thin film cannot conduct and cannot be used for the detection of the tunneling effect, and its yield rate is basically 0%. When the deposition time is 40 s, due to the too long deposition time, the prepared discontinuous metal thin film is thicker, and the nano-islands are intertwined into a wire mesh, and the IV curve is linear (see Figure 7 ), the conductivity is very high, 0.03 S, and the electrical performance shows full conduction corresponding to the ohmic conduction mechanism, indicating that the thin film is completely conductive and the tunneling effect cannot be detected, and its yield rate is also basically 0%. Therefore, the deposition time needs to be controlled within 10 - 30 s, and the prepared discontinuous metal thin film can be used to detect or respond to the tunneling effect. The most preferred is 20 s. At this time, the nano-gap of the prepared discontinuous metal thin film is smaller and the consistency is better, the thin film thickness is moderate, and the yield rate is higher, which can be used to accurately detect or respond to the tunneling effect.

[0139] Embodiment 6. Necessity of the adhesion layer

[0140] In this embodiment, the method provided in Embodiment 1 is used to prepare the discontinuous metal thin film, and the situation without the adhesion layer is compared at the same time, so as to obtain two kinds of discontinuous metal thin films. The nano-gap size, nano-gap coverage rate, film thickness, film uniformity, particle morphology, adhesion firmness, IV characteristics and yield rate of the two films are respectively detected. The detection method is as shown in Embodiment 5. Each is repeated more than three times, and the average value is taken. The specific performance parameter detection results are shown in Table 4.

[0141] Table 4. Influence of the adhesion layer on the preparation of the discontinuous metal thin film

[0142]

[0143] As can be seen from Table 4, when there is no adhesion layer in the prepared discontinuous metal thin film, its adhesion firmness is not good. (Poor adhesion means that in the subsequent application test process, the effect is inconsistent after repeated use, and the gold film is easily corroded after multiple immersions, damaging the microstructure and affecting the stability). Although a non-linear IV curve can also be detected and the tunneling effect can be responded to, the yield rate is low, and it is difficult to obtain a discontinuous metal thin film that fully meets the requirements. Therefore, it is very necessary to set the adhesion layer.

[0144] In this embodiment, the two prepared discontinuous metal thin films are heat-treated at 500 °C for 30 min, and then soaked in an ethanol solution overnight and then photographed. The results are shown in Figure 8 , where A is the case without the adhesion layer and B is the case with the adhesion layer.

[0145] From Figure 8 it can be seen that after the film without the adhesion layer is heat-treated and soaked in the ethanol solution overnight, the film dissolves and fades more seriously, which limits its application performance. On the contrary, the film with the adhesion layer still remains bright purple-red in color. The results show that the Cr layer can inhibit the diffusion of Au atoms and significantly improve the thermal stability and adhesion ability.

[0146] Embodiment 7. Screening of the target material

[0147] In this embodiment, the method provided in Embodiment 1 is used to prepare the discontinuous metal thin film, and the target materials are respectively Au, Ag, and Al, and the other preparation methods are the same as those in Embodiment 1, so as to obtain three kinds of discontinuous metal thin films. The oxidation resistance, corrosion resistance, work function, contact resistance, yield rate, etc. of the three films are respectively detected. Each is repeated more than three times, and the average value is taken. The specific performance parameter detection results are shown in Table 5.

[0148] Table 5. Influence of different target materials on the preparation of the discontinuous metal thin film

[0149]

[0150] As can be seen from Table 5, Au, Ag, and Al target materials can all be used to prepare discontinuous metal films. However, there are certain differences in the preparation effects. Among them, the most preferred one is the Au target material, and the reasons are as follows:

[0151] 1. Au hardly oxidizes at room temperature (inert metal), while for Al and Ag, they oxidize in air at room temperature to form insulating layers of Al2O3 and Ag2S, resulting in fluctuations in surface roughness and an increase in contact resistance, which affects the magnitude of the tunneling current and the device stability.

[0152] 2. The high work function of Au can form a higher tunneling barrier, and the tunneling probability and sensitivity can be optimized by regulating the barrier thickness (discontinuous gap).

[0153] 3. The Au film can be stably stored at room temperature without obvious diffusion or structural changes, while Ag and Al are more sensitive to temperature and humidity and are soluble in acid or alkaline solutions and corroded. Due to the above reasons, the yield rate of using the Au target material is higher.

[0154] Example 8. Screening of the adhesion layer

[0155] In this example, the method provided in Example 1 was used to prepare the discontinuous metal film, and the adhesion layers were respectively chromium, titanium, and titanium tungsten, and the other preparation methods were the same as those in Example 1, so as to obtain three discontinuous metal films, and their adhesion force, adhesion mechanism, contact resistance, cost, application scenarios and other performances were analyzed and evaluated. Subsequently, the thermal stability and yield rate of the tunneling devices containing different adhesion layers were tested. The detection method was as shown in Example 5, and the detection method for heat treatment stability was as shown in Example 6. Each was repeated more than three times and the average value was taken. The specific performance parameter detection results are shown in Table 6.

[0156] Table 6. Influence of different adhesion layers on the preparation of discontinuous metal films

[0157]

[0158] As can be seen from Table 6, chromium, titanium, and titanium tungsten target materials can all be used to prepare the adhesion layer of the discontinuous metal film, but there are also certain differences in the preparation effects. Among them, the most preferred one is the chromium target material. The reason for the selection is that all three materials have a small contact resistance and good thermal stability. However, the chromium material adheres through a physical mechanism, which largely avoids the interference brought by chemical bonding. In addition, its cost is lower, and it is most suitable for the processing of rigid substrates, and it has good adhesion and a higher processing yield rate, and performs optimally in the processing of this tunneling chip.

[0159] Example 9. Screening of the substrate material

[0160] In this embodiment, the method provided in Embodiment 1 is used to prepare a discontinuous metal thin film. Among them, three substrate materials are compared respectively: 1. quartz wafer, 2. glass wafer, and 3. high-resistance silicon. And the discontinuous metal thin film is prepared through the same magnetron sputtering parameters. By comparing the electrical conductivity, thermal stability, resistivity and cost of the three substrates, and testing the iv curves of the coatings on different substrates and counting the yield rate, it is found that it is optimal to select the glass wafer as the substrate. The detection method is as shown in Embodiment 5. Each is repeated more than three times and the average value is taken. The specific performance parameter detection results are shown in Table 7.

[0161] Table 7. Influence of different substrates on the preparation of discontinuous metal thin films

[0162]

[0163] As can be seen from Table 7, except for high-resistance silicon, quartz and glass can both be used as substrates. However, there are differences in the effects of substrates made of different materials on the preparation of non-linear metal thin films. The most preferred is glass as the substrate. The reasons for the selection are as follows:

[0164] 1. In order to prevent the substrate from interfering with the tunneling current in the gold film, a completely insulating substrate should be selected. Since high-resistance silicon is a semiconductor material with a resistivity significantly higher than that of a conventional doped silicon crystal, its resistance value is in the MΩ level, and the IV curve shows non-linearity and is not completely insulating, so it is excluded.

[0165] 2. Secondly, both quartz and glass have good insulation, high resistivity, good thermal stability, and the IV is a parallel line (no current). However, the price of the quartz wafer is more than 10 times higher than that of the glass wafer, but its yield rate cannot be higher than that of the glass, and the performance of the glass has fully met the process requirements, and the yield rate has reached the level of the quartz wafer, which is more conducive to mass production and commercialization. Therefore, considering from the perspectives of cost and yield rate, it is preferred to use the glass wafer as the substrate material.

[0166] Embodiment 10. Distance between electrode pairs

[0167] In this embodiment, the method provided in Embodiment 2 is used to prepare a tunneling electrode chip. Among them, the distance between electrode pairs, that is, the width of the partition part 5 of the mask plate (see Figure 3 (3) and (4) of )), that is, the shortest distance between adjacent two rectangular structures (that is, the distance between electrode pairs) is 30 µm, 50 µm, 100 µm, 300 µm, 500 µm and 1000 µm respectively, so as to prepare 6 groups of tunneling electrode chips, and their conductivities are detected respectively. See Table 8 for details.

[0168] Table 8. Statistical situation of the spacing of different electrode pairs

[0169]

[0170] As can be seen from Table 8, the study found that when the distance ≤ 100 µm, its conductivity can be maintained in the range of 0.1 - 1000 nS, and a tunneling effect can be formed between subsequent electrode pairs. When the distance is greater than 100 µm, the conductivity is too small, and the electrode pairs cannot be conducted, and the tunneling current cannot be detected. Therefore, the distance between the electrode pairs needs to be controlled within 100 µm. Therefore, the optimal choice is the shortest distance of 30 - 100 µm, and the most preferred is a mask plate of 30 µm for subsequent tests.

[0171] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be subject to the scope defined by the claims.

Claims

1. A discontinuous metal thin film with tunneling effect, comprising a substrate, characterized in that, It further includes a nano-gap thin film disposed on the substrate; the nano-gap thin film includes randomly distributed nano-islands, and a nano-gap is formed between any two adjacent nano-islands; the number of the nano-islands and nano-gaps is more than one.

2. The discontinuous metal thin film according to claim 1, wherein The distance of the nano-gap is sub-10 nm; and / or the thickness of the nano-gap thin film does not exceed 100 nm.

3. The discontinuous metal thin film according to claim 1, wherein The material of the substrate is selected from one or more of silicon dioxide, glass, silicon, silicon nitride, and sapphire; and / or, the material of the nano-gap thin film is selected from one or more of gold, silver, aluminum, and copper.

4. The discontinuous metal thin film according to claim 1, wherein An adhesion layer is provided between the nano-gap thin film and the substrate; the material of the adhesion layer is selected from one or more of chromium, titanium, and titanium tungsten.

5. A method for preparing a discontinuous metal thin film with tunneling effect, characterized in that, It includes the following steps: Using a magnetron sputtering method to deposit a nano-gap thin film on the surface of the substrate to obtain the discontinuous metal thin film.

6. The preparation method according to claim 5, wherein In the magnetron sputtering method, the deposition time is 10 to 30 s.

7. A tunneling electrode chip, characterized in that, It includes the discontinuous metal thin film according to any one of claims 1-4; it further includes a continuous conductive layer disposed on the discontinuous metal thin film, and an electrode pair disposed on the continuous conductive layer.

8. The tunneling electrode chip according to claim 7, characterized in that, The material of the continuous conductive layer is selected from one or more of gold, silver, aluminum, and copper; and / or, the material of the electrode pair is selected from one or more of gold, silver, aluminum, and copper; and / or, the distance between the electrode pairs is 30 to 100 μm.

9. A method for molecular medium sensing and detection, characterized in that, Using the discontinuous metal thin film according to any one of claims 1-4, or the tunneling electrode chip according to claim 7 or 8 for detection; the detection method includes: dropping a solution onto the surface of the discontinuous metal thin film or the tunneling electrode chip, and being captured by the nano-gap under the drive of an electrostatic field, and detecting the IV curve.

10. Use of the discontinuous metal thin film according to any one of claims 1-4 or the tunneling electrode chip according to claim 7 or 8 in optoelectronic detection devices, molecular sensor devices, and light response devices.

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