Humidity sensor based on polarization effect of water molecules and preparation method thereof

Abstract

The application relates to the humidity detection field and particularly provides a humidity sensor based on a water molecule polarization effect and a preparation method thereof. The sensor comprises a substrate, a conductive film layer and electrodes, the conductive film layer is arranged on the substrate, the electrodes are arranged on the conductive film layer and at two ends of the conductive film layer, the sensor further comprises a polarization material layer, the polarization material layer is arranged on a side of the conductive film layer away from the substrate, and the polarization material layer is arranged between the two electrodes. The preparation method comprises the following steps: step one, depositing the conductive film layer on the substrate; step two, using a sputtering technology to make the deposition electrodes at the two ends of the conductive film layer; and step three, preparing the polarization material layer on the conductive film layer. The humidity sensor couples the interface electric field change caused by the water molecule orientation polarization to the conductive film layer through the polarization material layer, realizes the non-direct contact type conversion from the humidity change to the electrical signal change, and improves the detection sensitivity while giving consideration to the pollution resistance.

Description

Technical Field

[0001] This application relates to the field of humidity detection, and more specifically, to a humidity sensor based on the polarization effect of water molecules and its preparation method. Background Technology

[0002] Humidity detection is widely used in environmental monitoring, industrial production, electronics and semiconductor manufacturing, food storage, and medicine. Generally, humidity detection utilizes moisture-sensitive materials. When these materials absorb water molecules, their electrical resistance changes. Higher humidity levels result in more water absorption, typically increasing conductivity and decreasing resistance; this change in resistance is used to detect humidity. Therefore, the moisture-sensitive material needs to be in full contact with the environment being monitored. However, pollutants in the air, such as dust, acidic or alkaline gases, can also come into contact with the moisture-sensitive material, affecting the sensitivity of humidity detection.

[0003] Especially in the semiconductor and precision electronics manufacturing fields, humidity monitoring needs to be carried out in highly controlled but chemically complex environments. Examples include overall humidity monitoring in wafer fab cleanrooms, localized humidity monitoring inside photolithography, etching, and thin-film deposition equipment, and humidity monitoring in packaging cavities or vacuum chambers during the vacuuming and ventilation recovery phases. In these scenarios, the air contains photoresist and its solvent volatiles, residual acidic or alkaline process gases, and nanoscale particles. If these particles directly contact the conductive film, they can adsorb, contaminate, or chemically corrode its surface, causing abnormal changes in carrier concentration, resistance baseline drift, or even localized conductive channel failure, resulting in distorted humidity signals and decreased sensitivity. While using flexible materials for direct packaging can avoid these problems, the packaging material blocks water molecules from contacting the humidity-sensitive material, significantly reducing detection sensitivity.

[0004] In summary, existing humidity sensors rely on direct contact between the measured environment and the conductive film, which cannot meet the needs of the semiconductor and precision electronics manufacturing industries for non-contact and highly sensitive humidity sensors. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of the prior art by providing a humidity sensor based on the water molecule polarization effect and its preparation method. This solves the problem that existing humidity sensors rely on direct contact between the measured environment and the conductive film, which cannot meet the needs of the semiconductor and precision electronics manufacturing industries for non-contact and highly sensitive humidity sensors.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] This application provides a humidity sensor based on the water molecule polarization effect. The sensor includes a substrate, a conductive thin film layer, and electrodes. The conductive thin film layer is disposed on the substrate, and the electrodes are disposed on the conductive thin film layer at both ends of the conductive thin film layer. The sensor also includes a polarizing material layer disposed on the side of the conductive thin film layer away from the substrate and between the two electrodes.

[0008] In use, water molecules in the ambient air first come into contact with and are adsorbed onto the surface of the polarized material layer. Water molecules are polar molecules with permanent dipole moments. The polarized material layer possesses stable dielectric properties, low free carrier density, and a dielectric environment capable of maintaining the interfacial potential difference, causing the water molecules adsorbed on its surface to undergo orientation bias under the influence of a local electric field. As the degree of water molecule orientation polarization changes, the interfacial electric field distribution within the polarized material layer and between it and the underlying conductive thin film layer changes accordingly. The conductive thin film layer is highly sensitive to changes in the interfacial electric field and surface charge distribution, especially when the conductive thin film layer is a surface-state dominant conductive material. Even small changes in the interfacial electric field can significantly modulate its surface carrier concentration and migration behavior, resulting in changes in the resistance of the conductive thin film layer. Electrodes are placed at both ends of the conductive thin film layer. By detecting changes in its resistance or current through an external measurement circuit, the change in the interfacial electric field can be converted into an electrical signal output, enabling the detection of changes in ambient humidity.

[0009] Because water molecules possess a large permanent dipole moment, the orientation polarization occurring on the surface of the polarized material layer generates a significant electric field modulation effect at the interface. Changes in the electric field are effectively coupled to the surface of the conductive thin film layer through the polarized material layer, allowing a change in humidity of the same magnitude to induce a larger change in surface charge carriers, resulting in a more significant change in resistance and improving the sensitivity of humidity detection. Simultaneously, the polarized material layer exhibits good chemical inertness, electrical insulation, and corrosion resistance, forming a continuous and stable coating layer in complex environments. This prevents airborne pollutants, corrosive gases, and particulate matter from directly contacting the conductive thin film layer, reducing electrical performance drift caused by pollution and corrosion. The adsorption of water molecules by the polarized material layer is primarily physical adsorption, with a fast kinetic process and good reversibility. This facilitates the rapid establishment and release of orientation polarization states by water molecules on the surface, resulting in a shorter response time and less hysteresis for the sensor. The electrical insulation properties also suppress external electrical interference, ensuring that changes in the resistance of the conductive thin film layer are mainly dominated by changes in the interfacial electric field caused by water molecule polarization, thereby improving the accuracy of humidity detection.

[0010] Furthermore, the conductive thin film layer is made of a topological insulator. Topological insulators possess the electronic structure characteristics of bulk insulation and surface conductivity. Their conductivity is mainly contributed by surface state carriers, while the concentration of bulk carriers is low, causing the conductivity to concentrate in the material surface region. When water molecules in the polarized material layer undergo orientation polarization, causing a change in the interfacial electric field distribution, this change in electric field can directly act on the surface state carriers of the topological insulator, and is not easily shielded by the bulk charge, thereby amplifying the modulation effect of humidity changes on the electrical signal. The surface state electrons of topological insulators typically have high mobility and low scattering probability, resulting in a fast response to external electric field disturbances. Even weak interfacial electric field changes caused by water molecule polarization can be converted into measurable resistance changes in a short time, thus achieving high-sensitivity and fast-response humidity detection. In addition, since the conductive channel is mainly confined to the surface state, topological insulators are less dependent on temperature fluctuations, bulk defects, and changes in bulk carriers, which helps suppress background noise and signal drift, ensuring good reliability of the sensor under different operating conditions.

[0011] Furthermore, the polarization layer is made of polytetrafluoroethylene (PTFE). PTFE exhibits strong chemical inertness and excellent resistance to acids, alkalis, organic solvents, and various process gases. It is not easily corroded in complex environments, thus providing stable protection for the underlying conductive film layer during long-term use, improving the reliability and lifespan of the humidity sensor. The CF bonds in the PTFE molecular structure have strong polarity, and the molecular chain orientation in the film exhibits microscopic asymmetry, providing a stable dielectric environment for water molecule orientation polarization and enhancing the modulation of the interfacial electric field by water molecule polarization. PTFE is a high-resistivity, low-dielectric-loss dielectric material, maintaining a stable potential distribution at the interface formed with air and the conductive film layer, and is not easily shielded by free carriers. When the ambient humidity changes, water molecules adsorbed on the PTFE surface undergo orientation bias on its surface and near-surface layer. The local electric field change caused by this orientation polarization can be coupled through PTFE and transmitted to the interface below, stably and repeatedly converting the water molecule polarization effect into changes in the interfacial electric field.

[0012] Furthermore, a semiconductor layer is disposed between the conductive thin film layer and the substrate. The presence of a semiconductor material layer between the conductive thin film layer and the substrate amplifies the interface electric field modulation effect caused by humidity changes, thereby improving the sensitivity of humidity detection. Semiconductor materials possess carrier concentration and dielectric properties intermediate between conductors and insulators, and can form a significant space charge distribution and band bending under the influence of an external electric field. A heterogeneous interface is formed between the topological insulator conductive thin film layer and the semiconductor material layer. This interface typically exhibits a high density of interface states and band discontinuities, which are highly sensitive to changes in the local electric field. When water molecules adsorbed on the surface of the polarized material layer undergo orientation polarization, causing a change in the interface electric field, this change simultaneously passes through the semiconductor material layer. The redistribution of carriers in the semiconductor material layer amplifies the potential change at the interface, increasing the equivalent electric field strength and the magnitude of the potential change near the conductive thin film layer.

[0013] Furthermore, the semiconductor layer is made of one of zinc oxide, titanium dioxide, or gallium nitride. These materials have large band gaps and low intrinsic carrier concentrations, and under the influence of an external electric field, they easily form significant space charge regions and band bending, which is beneficial for amplifying the interfacial electric field changes caused by water molecule polarization. These materials readily form stable and repeatable heterojunctions with the topological insulator thin film, and their interface states are highly sensitive to electric field disturbances. This facilitates the further amplification and transfer of the potential changes caused by the orientation polarization of water molecules in the polarized material layer to the conductive thin film layer, thereby improving the sensitivity of humidity detection.

[0014] Furthermore, the surface of the polarization material layer is provided with parallel trenches. This trench structure increases the effective surface area of ​​the polarization material layer in contact with air, allowing for the adsorption and containment of more water molecules per unit projected area, thus enhancing the modulation amplitude of the interfacial electric field by water molecule orientation polarization. The sidewalls and bottom of the trenches form a multi-directional interface, introducing electric field concentration and local enhancement effects, making the electric field disturbance caused by water molecule polarization more spatially concentrated, which is beneficial for more efficiently coupling the polarization effect to the underlying conductive thin film layer. The trenches provide a restricted but continuous diffusion and residence path for water molecules on the surface of the polarization material layer. Compared to a flat surface, water molecules are more easily captured and temporarily retained inside the trenches, thereby increasing the effective contact time and interaction probability between water molecules and the polarization material layer. The restricted diffusion environment helps water molecules quickly establish an orientation bias state on the surface, making the polarization process more complete and improving detection sensitivity.

[0015] Furthermore, a top shell is provided on the upper side of the polarized material layer, with a distance between the top shell and the polarized material layer. The top shell, the supporting shells on both sides, and the polarized material layer form a gas flow channel. An air pump and a blowing port connected to the air pump are provided at the air inlet of the gas flow channel, with the blowing port opposite the air inlet. This facilitates the establishment of an airflow environment on the surface of the polarized material layer, avoiding airflow disturbances and environmental noise caused by the polarized material layer being directly exposed to an open environment. Through active blowing provided by the air pump, the gas to be detected can glide along a predetermined path across the surface of the polarized material layer within the flow channel, achieving continuous transport and renewal of water molecules. Under semi-closed, controlled flow conditions, water molecules in the gas can fully contact the polarized material layer in a stable and repeatable manner, reducing signal fluctuations caused by random diffusion and uneven retention, thus making the water molecule adsorption and orientation polarization process more controllable. The interfacial electric field change caused by water molecule polarization can act on the underlying conductive thin film layer in a more consistent manner, making the resistance response corresponding to humidity changes clearer, with a larger amplitude and lower noise, thereby improving the sensitivity of humidity detection.

[0016] Furthermore, the direction of the gas flow channel is parallel to the direction of the trench. Setting the direction of the gas flow channel parallel to the direction of the trench on the surface of the polarized material layer allows the gas to stably sweep across the surface of the polarized material layer along the trench direction during flow, avoiding lateral eddies and local stagnation zones generated when the airflow is perpendicular to the trench, thus forming a more uniform flow field distribution. Under parallel flow conditions, the trench can guide and constrain the airflow, allowing water molecules to be continuously transported along the trench and fully enter the interior of the trench, forming multi-interface contact with the polarized material on the sidewalls and bottom of the trench, thereby significantly increasing the effective contact area and interaction time between water molecules and the polarized material layer. At the same time, the directional airflow along the trench direction helps to continuously refresh the boundary layer inside the trench, reducing the random aggregation or stagnation of water molecules in local areas, making the adsorption and desorption processes more uniform and controllable, thereby improving the sensitivity of humidity detection.

[0017] Furthermore, the top outer shell is angled, with the distance between the top outer shell and the polarized material layer gradually decreasing from the inlet to the outlet. By positioning the top outer shell to gradually approach the polarized material layer along the gas flow direction, the gas flow channel converges from the inlet to the outlet, gradually increasing the local flow velocity and wall shear strength of the gas on the surface of the polarized material layer. At the same volumetric flow rate, the gradually decreasing channel gap increases the gas velocity near the outlet, effectively thinning the flow boundary layer on the surface of the polarized material layer, shortening the diffusion path of water molecules from the main flow to the surface, and improving the equivalent mass transfer coefficient between the gas and the surface. The adsorption and desorption processes of water molecules on the surface of the polarized material layer are closer to controlled mass transfer conditions, enabling faster achievement of stable coverage and preventing water molecules from remaining on the interface, thus improving the sensitivity of humidity detection. Simultaneously, the convergent flow channel structure effectively suppresses the inlet effect, preventing the formation of a region with insufficient gas renewal downstream due to strong local scouring at the inlet, resulting in a more uniform distribution of water molecules along the flow direction on the surface of the polarized material layer. Uniform water molecule coverage helps reduce the inhomogeneity of interfacial electric field modulation, decrease signal drift, and improve the stability of humidity detection signals. In addition, during purging, the high-velocity region formed at the convergence end can more effectively strip and clean residual adsorbed water molecules, reducing adsorption effects and response hysteresis, and enabling the sensor to maintain good recovery performance when switching between different humidity conditions.

[0018] This application also proposes a method for fabricating a humidity sensor based on the polarization effect of water molecules, which includes the following steps:

[0019] Step 1: Deposit a conductive thin film layer on the substrate;

[0020] Step 2: Using sputtering technology, deposited electrodes are fabricated at both ends of the conductive thin film layer;

[0021] Step 3: Prepare a polarization material layer on the conductive thin film layer.

[0022] Furthermore, after step three, the method also includes using electron beam lithography to create parallel trenches on the surface of the polarization material layer.

[0023] Furthermore, after step three, the method further includes fixing support shells on both sides of the substrate, with the upper ends of the two support shells welded and fixed to the top shell, forming a gas flow channel with open ends together with the polarization material.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] A conductive thin film layer is covered by a polarized material layer and isolated from the external environment. Humidity detection does not rely on direct contact between water molecules and the conductive thin film layer, but rather on non-contact coupling achieved through the polarized material layer. When the ambient humidity changes, water molecules in the air, as polar molecules with permanent dipole moments, are adsorbed onto the surface of the polarized material layer and undergo orientation polarization. This causes a change in the electric field distribution within the polarized material layer and at the interface between it and the conductive thin film layer. This change in the interface electric field further alters the charge distribution and carrier behavior on the surface of the conductive thin film layer, resulting in a change in the resistance of the conductive thin film layer, which is detected by the electrodes at both ends, thus achieving humidity change detection. The polarized material layer mainly exhibits reversible physical adsorption and polarization response to water molecules, while providing physical isolation and blocking for polluting gases and particulate matter in the air, preventing them from directly contacting and contaminating the conductive thin film layer. In other words, while protecting the conductive thin film layer, the polarized material layer can still selectively and effectively couple the electric field changes caused by water molecule polarization to the conductive thin film layer, achieving non-contact humidity detection that combines anti-pollution capability with high sensitivity. The humidity sensor in this application meets the non-contact and highly sensitive detection requirements of the semiconductor and precision electronics manufacturing industries for humidity sensors. Attached Figure Description

[0026] Figure 1 A schematic diagram of a humidity sensor based on the water molecule polarization effect provided by the present invention;

[0027] Figure 2 A schematic diagram of the groove in a humidity sensor based on the polarization effect of water molecules provided by the present invention;

[0028] Figure 3 This is a schematic diagram illustrating a method for fabricating a humidity sensor based on the polarization effect of water molecules, as provided by the present invention.

[0029] Icons: 1-Substrate; 2-Conductive thin film layer; 3-Electrode; 4-Polarization material layer. Detailed Implementation

[0030] To make the implementation process of this invention clearer, a detailed description will be provided below in conjunction with the accompanying drawings.

[0031] Example 1:

[0032] This invention provides a humidity sensor based on the water molecule polarization effect, such as... Figure 1As shown, the sensor includes a substrate 1, a conductive thin film layer 2, an electrode 3, and a polarization material layer 4. The conductive thin film layer 2 is disposed on the substrate 1, which is made of glass, silicon, or silicon oxide with a high surface flatness. The material of the conductive thin film layer 2 is a topological insulator, which can be one of Bi2Se3, Bi2Te3, Sb2Te3, or SnTe. The thickness of the conductive thin film layer 2 is less than 50 nanometers. When the thickness of the conductive thin film layer 2 is less than 50 nanometers, the electronic structure characteristics of bulk insulation and surface conductivity are more prominent. The conductivity is mainly contributed by surface state carriers, while bulk conductivity and bulk charge shielding effects are suppressed. The carrier transport path is strongly confined to the region near the interface, making the conductive thin film layer 2 more sensitive to changes in the interfacial electric field. When the ambient humidity changes, the water molecules adsorbed on the surface of the polarization material layer 4 undergo orientation polarization, causing a slight change in the distribution of the interfacial electric field. Due to the small film thickness, this interfacial electric field can act more effectively on the entire conductive thin film layer 2, resulting in a significant change in the surface carrier concentration and migration behavior, thereby causing a larger change in resistance. Meanwhile, at nanometer thicknesses, the quantum size effect and surface state coupling effect are more pronounced in topological insulators, and the response of charge carriers to external electric field disturbances is stronger, amplifying the conversion efficiency of water molecule polarization effects into electrical signals. Therefore, humidity changes of the same magnitude can induce more significant resistance changes in topological insulator conductive thin film layers 2 with a thickness of less than 50 nanometers, effectively amplifying the interfacial electric field and thus improving the detection sensitivity of humidity sensors to minute humidity changes.

[0033] Electrodes 3 are disposed on the conductive thin film layer 2 at both ends of the conductive thin film layer 2. Electrodes 3 do not directly contact the polarization material layer 4, so that the change in the interfacial electric field caused by humidity mainly modulates the conductivity of the conductive thin film layer 2, thereby reducing parasitic effects and contact resistance instability and improving the accuracy of the humidity detection signal. The two electrodes 3 are used to connect the positive and negative terminals of the external circuit, respectively. The materials of electrodes 3 are gold or copper, which have good conductivity and can play a good role in connecting the circuit for detecting the resistance change of the conductive thin film layer 2; the shape can be strip-shaped, and the thickness is 50-200 nanometers. The polarization material layer 4 is disposed on the conductive thin film layer 2 between the two electrodes 3.

[0034] The polarization material layer 4 is made of polytetrafluoroethylene (PTFE), and its thickness is 100-200 nanometers. Within this thickness range, the PTFE film forms a continuous, dense, and electrically insulating dielectric layer with very few free charge carriers, thus avoiding significant shielding of the interface electric field and maintaining the potential change caused by water molecule polarization. Water molecules, as polar molecules with permanent dipole moments, readily undergo orientation bias after adsorption onto the PTFE surface in a stable dielectric environment. This orientation polarization can effectively couple and transfer to the lower PTFE surface within the 100-200 nanometer scale, causing a significant change in the interface electric field distribution between the PTFE layer and the underlying conductive film layer 2. Compared to a thicker PTFE layer, the polarization material layer 4 within this thickness range exhibits less attenuation of the electric field, enabling higher fidelity transmission of the water molecule polarization effect to the interface and improving the sensitivity of humidity detection. Furthermore, compared to an excessively thin PTFE layer, it avoids problems such as discontinuous coverage, localized leakage, or interface instability, ensuring the stability of humidity detection.

[0035] Example 2:

[0036] Based on Example 1, a semiconductor material layer is further disposed between the conductive thin film layer 2 and the substrate 1. The semiconductor material layer is made of materials such as zinc oxide, titanium dioxide, and gallium nitride. The thickness of the semiconductor material layer is 100 nanometers to 1 micrometer; it has sufficient volume to form a significant space charge region and band bending under the influence of an external electric field, while avoiding excessive shielding of electric field disturbances caused by water molecule polarization due to excessive thickness. When water molecules adsorbed on the surface of the polarization material layer 4 undergo orientation polarization and cause a change in the interfacial electric field, the electric field effectively propagates within the 100 nanometers to 1 micrometer thick semiconductor layer and induces carrier redistribution, thereby enhancing the equivalent electric field strength near the topological insulator conductive thin film layer 2 and amplifying the modulation effect of the interfacial potential change on surface state carriers. Compared to an excessively thin semiconductor layer, it avoids the problems of insufficient electric field modulation and a limited number of interfacial states; compared to an excessively thick semiconductor layer, it reduces electric field attenuation and response hysteresis. Therefore, the semiconductor material layer can serve as an electric field modulation and buffering medium, more effectively converting the water molecule polarization effect into a change in the resistance of the conductive thin film layer 2, thereby achieving highly sensitive detection of minute humidity changes.

[0037] Example 3:

[0038] Based on Example 1 or 2, parallel trenches are formed on the surface of the polarization material layer 4. The width of the trenches can be 0.5-10 micrometers, and the spacing can be 1-20 micrometers. The trenches can provide a sufficiently high surface structure density per unit area, increasing the effective interface between the polarization material layer 4 and the air, making it easier for water molecules to enter the trenches and undergo adsorption and orientation polarization on the sidewalls and bottom, thereby enhancing the modulation effect of water molecule polarization on the interface electric field. When the trench width or spacing is too large, the number of trenches per unit area decreases, the water molecule capture and polarization enhancement effect weakens, and the sensitivity improvement effect is not obvious. When the trench width and spacing are too small, the flow resistance of gas in the trenches increases, easily forming stagnant and diffusion-restricted areas, which is not conducive to rapid adsorption and desorption, and also increases the preparation difficulty and introduces structural inhomogeneity. In this way, the trenches can form a stable and controllable wall-attached flow and restricted diffusion environment, and can achieve efficient coupling between water molecule polarization, electric field modulation and the response of the conductive thin film layer 2 without significantly increasing flow resistance and parasitic effects, thereby improving the sensitivity of humidity detection.

[0039] The trenches on the surface of the polarization material layer 4 are periodically and gradually distributed along the gas flow direction. The trench spacing near the inlet is 10-20 micrometers, gradually decreasing to 1-5 micrometers near the outlet, while maintaining a consistent trench depth and cross-sectional shape. At the inlet, the larger trench spacing helps reduce flow resistance and quickly guides gas into the surface region of the polarization material layer 4. As the gas flows downstream, the trenches gradually become denser, significantly increasing the polarization interface per unit area. This makes it easier for water molecules to be captured in the terminal region, resulting in higher local coverage. Simultaneously, due to the higher mass transfer efficiency and thinner boundary layer at the end of the flow channel, the increased trench density, combined with the high mass transfer region, further amplifies the interfacial electric field modulation caused by water molecule orientation polarization in the downstream region. This avoids the flow resistance and noise problems caused by high-density trenches throughout the entire area, while concentrating the amplification of the polarization effect in favorable areas, resulting in a larger amplitude and more uniform spatial distribution of resistance changes corresponding to humidity variations, thereby improving the sensitivity of humidity detection.

[0040] The direction of the trench is perpendicular to the direction of the line connecting the two electrodes (3), and perpendicular to the plane of the paper. Figure 2As shown, the black area represents the trenches. In the vertical direction, the trenches do not penetrate the polarization material layer 4, but maintain a continuous dielectric path within them. This allows the local electric field changes caused by water molecule polarization to be stably transmitted to the lower interface without the electric field splitting or leakage due to excessive trench depth. With the trench direction perpendicular to the line connecting the two electrodes 3, the airflow can uniformly sweep across the effective sensing area between the electrodes 3 along the trench direction, avoiding stagnation or dead zones near the electrodes 3. This results in a more uniform distribution of water molecules on the surface of the polarization material layer 4. Simultaneously, the trench arrangement perpendicular to the electrode 3 effectively shortens the lateral diffusion path of water molecules within the polarization material layer 4, reducing parasitic resistance and local electric field distortion caused by non-uniform polarization, and making the interface electric field modulation more concentrated and consistent. Therefore, the electric field changes generated during water molecule adsorption and desorption are more linear, resulting in a larger amplitude and lower noise in the electrical response to humidity changes, thus improving the sensitivity of humidity detection. The depth of the trenches is less than half the thickness of the polarization material layer 4. Preferably, the trenches have different depths: the deep trenches are two-thirds the depth of the polarization material layer 4, and the shallow trenches are one-third the depth of the polarization material layer 4. The deep and shallow trenches are arranged alternately. The shallow trenches maintain the dielectric continuity and electric field transmission consistency of the polarization material layer 4 on an overall scale, avoiding electric field splitting, local leakage, or increased noise caused by excessive etching. The deep trenches, due to their greater sidewall curvature and stronger geometric convergence effect, form a local electric field enhancement region at the bottom of the trench, making it easier for water molecules to undergo orientation polarization in this region. The shallow and deep trenches form electric field modulation levels of different intensities in the vertical direction. The strong polarization region generated by the deep trenches can affect the interface electric field distribution of adjacent shallow trench regions through dielectric coupling within the polarization material layer 4, resulting in multiple local electric field hotspots at the interface. In other words, while maintaining low noise and high stability, deep trenches are introduced as polarization-enhancing hotspots, so that the same humidity change can cause a larger perturbation of the interface electric field, thereby improving the sensitivity of humidity detection.

[0041] The trench's cross-sectional shape can be an inverted triangle, wider at the top and narrower at the bottom, with an inlet width of 2-10 micrometers, a bottom width of 0.2-2 micrometers, and a base angle of 30-70°. It can be fabricated using electron beam lithography combined with anisotropic etching. Specifically, a gradient mask pattern is defined on the surface of the polarization material layer 4 using tilted exposure or grayscale electron beam lithography, followed by ion beam etching to create an inverted triangular cross-section with controlled sidewall convergence. This results in a wide-opening, convergent trench inlet, making it easier for the gas to enter the trench, reducing dynamic pressure loss during entry, preventing backflow at the inlet, and improving the efficiency of water molecules entering the trench and contacting the polarization material surface. Simultaneously, the gradually narrowing shape of the trench from top to bottom creates a local velocity and shear intensity gradient during gas flow within the trench, continuously compressing the flow boundary layer near the bottom. This shortens the diffusion path of water molecules from the main flow to the polarization material surface, enhancing the mass transfer efficiency of water molecules to the trench bottom and sidewalls. In terms of electric field distribution, the bottom of the trench exhibits a curvature enhancement effect, which concentrates the local electric field changes caused by water molecule orientation polarization in the trench bottom region. This allows for more effective coupling and transmission to the lower surface of the polarization material layer 4, thereby amplifying the effect of interfacial electric field modulation on the underlying conductive thin film layer 2. During gas flow, the higher local flow velocity and shear force at the bottom of the trench more effectively strip away residual adsorbed water molecules, promoting water molecule desorption and improving the sensitivity of humidity detection.

[0042] Example 4:

[0043] A top outer shell is provided on the upper side of the polarized material layer 4. There is a distance between the top outer shell and the polarized material layer 4. The top outer shell, the two side supporting shells, and the polarized material layer 4 form a gas flow channel, the direction of which is parallel to the direction of the groove. The top outer shell is positioned above the polarized material layer 4, and is spaced from the polarized material layer 4 by the two side supporting shells, thus forming a gas flow channel together with the polarized material layer 4. The top outer shell and supporting shells can be made of chemically inert, low-adsorption, and corrosion-resistant materials, such as PFA-type fluoropolymers or 316L stainless steel. The thickness of the top outer shell is 0.3-1 mm to ensure shape stability and facilitate processing into an inclined surface. The supporting shells can be 0.5-2 mm thick plate-shaped supports to provide reliable lateral restraint and lateral sealing. Furthermore, the top outer shell is inclined, and the distance between the top outer shell and the polarized material layer 4 gradually decreases from the air inlet to the air outlet. The spacing between the top shell and the polarization material layer 4 is designed as a gradually converging structure along the flow direction. The spacing at the inlet can be 0.5-1 cm to reduce the inlet pressure drop and facilitate the rapid entry of the gas to be measured into the flow channel; the spacing at the outlet can be 0.1-0.5 cm. The direction of the gas flow channel is arranged parallel to the direction of the grooves on the surface of the polarization material layer 4, so that the gas flows along the wall along the direction of the grooves. The grooves play a guiding and rectifying role in the flow field, avoiding the formation of transverse eddies, improving the effective transport and uniform distribution of water molecules in the grooves, and thus enhancing the degree to which the orientation polarization of water molecules changes the electric field of the interface below.

[0044] The gas flow channel's inlet is equipped with an air pump and a blow-out port connected to the air pump, with the blow-out port facing the inlet. The air pump and blow-out port are positioned opposite the inlet and towards the flow channel entrance to create a stable directional airflow. The air pump can be a miniature diaphragm pump or other types. Flow control components such as flow-limiting orifices can be installed at the front end of the blow-out port to maintain the flow rate at 20-200 sccm, reducing electrical noise introduced by pump pulsation and improving measurement repeatability. Through the semi-enclosed, controlled flow, and convergent flow channel design, the boundary layer on the surface of the polarized material layer 4 can be continuously refreshed and the interfacial electric field modulation effect caused by humidity changes can be amplified while ensuring that the conductive thin film layer 2 is protected from direct contact with contaminant particles and corrosive gases, thereby improving the sensitivity of humidity detection.

[0045] Example 5:

[0046] This application also proposes a method for fabricating a humidity sensor based on the polarization effect of water molecules, such as... Figure 3 As shown, the method includes the following steps:

[0047] Step 1: Deposit a conductive thin film layer 2 on substrate 1.

[0048] First, substrate 1 was cleaned using isopropanol and acetone via ultrasonic cleaning, each solvent for 10 minutes, to remove organic contaminants from the surface of substrate 1. Finally, the surface of substrate 1 was rinsed with deionized water to remove residual solvent. After cleaning, substrate 1 was dried by nitrogen blowing and set aside for later use. Before depositing the conductive film, substrate 1 was baked in a vacuum environment at approximately 200°C for 1 hour to remove moisture and adsorbed gases. Preparation can be performed using molecular beam epitaxy or radio frequency sputtering. In molecular beam epitaxy, the vacuum level was maintained at 10⁻⁹ Torr. During sputtering, a topological insulator target was used, and the film deposition rate was controlled by radio frequency power. The temperature of substrate 1 was maintained between room temperature and 300°C during deposition. The film thickness was controlled by both the deposition rate and deposition time, ensuring it was less than 50 nm. After film deposition, annealing was performed at a temperature between 250°C and 350°C for 30 minutes to 1 hour to improve the film's crystallinity.

[0049] Step 2: Using sputtering technology, deposited electrodes 3 are fabricated at both ends of the conductive thin film layer 2.

[0050] Electrodes 3 are fabricated at both ends of the conductive thin film to connect to external circuits for signal acquisition. The sample obtained in step one is placed in a sputtering apparatus as a substrate, and metal is sputtered onto its surface. The area where no electrodes 3 are placed in the middle needs to be shielded beforehand to prevent deposition in that area.

[0051] Step 3: Prepare a polarization material layer 4 on the conductive thin film layer 2.

[0052] An active material layer 4 is deposited on the conductive film to enhance humidity response. A polytetrafluoroethylene (PTFE) solution is prepared beforehand. The sample obtained in step two is placed in a spin coater at a speed of 3500-45000 rpm for 20-60 seconds, depending on the specific thickness, which is also related to the solution concentration. Similarly, the surface of the prepared electrode 3 needs to be masked during spin coating. After spin coating, the sample is heated to 350°C-400°C in a heat treatment furnace and annealed for 30 minutes to remove the solvent and improve film quality.

[0053] Optionally, between steps one and two, a semiconductor material layer is deposited on substrate 1. This is prepared using chemical vapor deposition, taking zinc oxide as an example. The reaction gases are oxygen and zinc alkylene, and deposition is carried out at 200°C-400°C for 10-60 minutes; preferably, the temperature is 350°C and the deposition time is 30 minutes. The pressure inside the quartz tube is 10-100 mTorr.

[0054] Optionally, after step three, the process further includes forming parallel trenches on the surface of the polarization material layer 4 using electron beam lithography. A layer of electron beam photoresist, such as PMMA, with a thickness of approximately 200 nm, is spin-coated onto the polarization material layer 4. Using an electron beam exposure device, a trench pattern is defined on the photoresist; for example, the trench width and spacing are in the nanometer to micrometer range. After development, the unexposed portions of the photoresist are removed, exposing the polarization material layer 4.

[0055] Example 6:

[0056] Based on Example 5, after step three, the method further includes fixing support shells to both sides of the substrate 1. The support shells are made of stainless steel or corrosion-resistant fluoropolymer material and are fixed to the edges of the substrate 1 by welding, laser welding, or high-strength, high-temperature adhesive bonding, thus forming a stable height-limiting structure in the vertical direction. Subsequently, a top shell is placed over the upper ends of the two support shells and welded or sealed to them, forming a gas flow channel between the top shell, the support shells, and the polarization material layer 4. During assembly, by controlling the height of the support shells or setting a predetermined angle on the lower surface of the top shell, the distance between the top shell and the polarization material layer 4 gradually decreases from the inlet end to the outlet end, thereby forming a converging flow channel structure.

[0057] During use, the air pump is connected to the air inlet and started, allowing the gas to be detected to be blown directionally into the gas flow channel. Driven stably by the air pump, the gas flows continuously along the gas flow channel formed by the top shell, support shell, and polarized material layer 4, and sweeps across the surface of polarized material layer 4 in a direction parallel to the grooves on its surface. Throughout the humidity detection process, the gas flow rate is maintained within a preset range by controlling the air pump speed or flow rate adjustment component, thereby establishing a stable and repeatable controlled flow environment within the gas flow channel. Under this controlled flow condition, water molecules in the gas are continuously transported to the surface of the polarized material layer 4 and participate in the adsorption and orientation polarization process. The change in the interfacial electric field is stably coupled to the underlying conductive thin film layer 2. The resistance change of the conductive thin film layer 2 is obtained in real time through the electrodes 3 at both ends, enabling continuous, online detection of ambient humidity.

[0058] It should be noted that under normal environmental conditions, the partial pressure of water molecules in the air is typically around 10. 3 -10 4The concentration of water molecules is on the order of Pa, fluctuating with changes in ambient humidity. Other polar gas molecules, such as volatile organic compounds and ammonia, typically have concentrations in the order of ppm or even ppb. Water molecules are at least 6-9 orders of magnitude higher. Therefore, the interfacial electric field changes caused by polar molecules in the sensor are almost entirely dominated by water molecules. Furthermore, water molecules possess a large permanent dipole moment and strong electrical response, resulting in greater perturbation of the interfacial electric field under the same concentration conditions compared to most other polar gas molecules. The polarized material layer 4 also exhibits rapid, reversible, and stable physical adsorption and polarization response characteristics to water molecules, while showing low adsorption probability, slow kinetics, and instability for most organic or inorganic pollutant molecules, further weakening their contribution to the sensor's output signal. In other words, based on the aforementioned order-of-magnitude advantage, polarization effect advantage, and material adsorption selectivity, the electrical signal changes detected in this application are dominated by changes in water molecule concentration.

[0059] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A humidity sensor based on the water molecule polarization effect, the sensor comprising a substrate, a conductive thin film layer, and electrodes, wherein the conductive thin film layer is disposed on the substrate, and the electrodes are disposed on the conductive thin film layer and at both ends of the conductive thin film layer, characterized in that: The sensor further includes a polarization material layer disposed on the side of the conductive thin film layer away from the substrate and between the two electrodes. The conductive thin film layer is made of a topological insulator, and the polarization material layer is made of polytetrafluoroethylene (PTFE). The thickness of the polarization material layer is 100-200 nanometers. In application, water molecules adsorb onto the PTFE surface, undergo orientation polarization, and are transferred to the lower surface of the PTFE, changing the resistance of the conductive thin film layer and achieving humidity sensing.

2. The humidity sensor based on water molecule polarization effect according to claim 1, characterized in that: A semiconductor layer is further disposed between the conductive thin film layer and the substrate.

3. The humidity sensor based on water molecule polarization effect according to claim 2, characterized in that: The semiconductor layer is made of one of zinc oxide, titanium dioxide, or gallium nitride.

4. The humidity sensor based on water molecule polarization effect according to claim 3, characterized in that: The surface of the polarized material layer is provided with parallel grooves.

5. The humidity sensor based on water molecule polarization effect according to claim 4, characterized in that: A top shell is provided on the upper side of the polarized material layer. There is a distance between the top shell and the polarized material layer. The top shell, the supporting shells on both sides, and the polarized material layer form a gas flow channel. An air pump and an air blowing port connected to the air pump are provided at the air inlet of the gas flow channel. The air blowing port is opposite to the air inlet.

6. The humidity sensor based on water molecule polarization effect according to claim 5, characterized in that: The direction of the gas flow channel is parallel to the direction of the groove.

7. The humidity sensor based on water molecule polarization effect according to claim 6, characterized in that: The top outer shell is inclined, and the distance between the top outer shell and the polarized material layer gradually decreases from the air inlet to the air outlet.

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