A high-sensitivity ion sensor based on schottky heterojunction and a preparation method thereof

Abstract

The application provides a high-sensitivity ion sensor based on a Schottky heterojunction and a preparation method, and mainly solves the problems of a complex structure, many layers, poor inspection sensitivity and a difficult preparation process of an existing sensor. The scheme of the application includes a platinum / silicon Schottky heterojunction, a functionalized sensitive layer and a double-terminal working electrode. A platinum film is deposited on a silicon substrate by magnetron sputtering to form the platinum / silicon Schottky heterojunction; the functionalized sensitive layer contains an ion probe which can selectively bind heavy metal ions; and the current signal of the sensor chip is read by the working electrode at both ends of the platinum / silicon Schottky heterojunction. The sensor has the characteristics of simple structure, convenient manufacturing process and specific and rapid identification of heavy metal ions, and avoids the problem of the influence of the use of a reference electrode on the sensing performance.

Description

Technical Field

[0001] This invention belongs to the field of sensors and mainly relates to a highly sensitive ion sensor based on a Schottky heterojunction. Background Technology

[0002] Semiconductor biochemical sensors based on the field-effect principle are developing rapidly due to their high compatibility with existing microelectronic processes and their advantages such as low cost and high sensitivity, making them widely used for the detection of heavy metal ions. In traditional field-effect biochemical sensors, the gate voltage needs to be applied to the electrolyte through a reference electrode during detection. How to simplify the sensor structure, avoid the influence of the reference electrode on sensor stability, and reduce the sensor size are urgent problems to be solved.

[0003] Reference 1, "Performance of Pt / Ga2O3 / GaN Schottky-diode ammonia sensor covered with thermally evaporated Pt nanoparticles," discloses an ammonia sensor based on a Pt / Ga2O3 / GaN Schottky heterojunction structure. The Schottky heterojunction ammonia sensor described in Reference 1 is formed by sequentially bonding an aluminum nitride layer, a gallium nitride layer, another gallium nitride layer, and platinum metal onto a silicon substrate, with a gallium oxide layer with a wide bandgap inserted between the upper gallium nitride layer and the platinum metal. The platinum nanoparticles thermally evaporated on the platinum metal layer significantly reduce the height of the metal semiconductor Schottky barrier when detecting ammonia, improving surface roughness and the sensing surface area-to-volume ratio, thereby improving ammonia adsorption efficiency. Reference 2, "Rapid-Response and Portable Lead Ion Sensor Using Co / Pt / Si Schottky Heterojunction Without Reference Electrode," discloses a lead ion sensor based on a Co / Pt / Si Schottky heterojunction structure. The Schottky heterojunction lead ion sensor described in Reference 2 is formed by sequentially bonding a platinum film, a cobalt film, a ruthenium film, and a gold film onto a silicon substrate via magnetron sputtering.

[0004] The Schottky heterojunction ammonia sensor described in Reference 1 exhibits performance significantly affected by ambient temperature. While it performs well at high temperatures, its performance deteriorates at low temperatures, limiting its application scenarios and hindering widespread adoption. Furthermore, the sensor, designed for molecular measurements in gaseous environments, is ill-suited for monitoring heavy metal ions in water. Additionally, the eight-layer sensor in Reference 1 has a complex structure and requires cumbersome fabrication steps. The Schottky heterojunction lead ion sensor described in Reference 2 has a six-layer structure, making it complex and requiring cumbersome fabrication. Moreover, its detection sensitivity is poor as it relies on altering the sensor's DC characteristics. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies and solve the problems of complex structure, large number of layers, poor detection sensitivity, and difficult preparation process of existing sensors, this invention provides a high-sensitivity ion sensor based on Schottky heterojunction and its preparation method.

[0006] A highly sensitive ion sensor based on a Schottky heterojunction includes a platinum / silicon Schottky heterojunction, a functionalized sensitive layer, and a dual-terminal working electrode. The dual-terminal working electrode includes a positive electrode and a negative electrode. The platinum / silicon Schottky heterojunction comprises a silicon (Si) substrate and a Pt film, which are sequentially bonded from bottom to top. The functionalized sensitive layer is functionalized with organic macromolecules, which serve as ion probes. The functionalized sensitive layer is a Pt film bonded to the platinum / silicon Schottky heterojunction via magnetron sputtering. Above; the positive and negative terminals of the dual-terminal working electrode are respectively bonded to a Pt film of a platinum / silicon Schottky heterojunction for voltage signal input and current signal output; the input of the positive terminal of the dual-terminal working electrode is a DC bias signal and an AC excitation signal, which are used as the input of the sensor voltage signal, and the sensor current signal is output from the negative terminal of the dual-terminal working electrode; the negative terminal of the dual-terminal working electrode is connected to a current-to-voltage conversion circuit; the current-to-voltage conversion circuit is used to convert the weak current signal into a detectable voltage signal.

[0007] A method for fabricating a highly sensitive ion sensor based on a Schottky heterojunction is as follows:

[0008] Step S1: Obtain a clean silicon (Si) substrate through photolithography etching;

[0009] Step S2: A Schottky heterojunction is formed between the silicon substrate (Si) and the platinum (Pt) metal on the surface of the silicon substrate by magnetron sputtering;

[0010] Step S3: A functionalized sensitive layer is prepared on the surface of a Schottky heterojunction by magnetron sputtering; organic macromolecules are combined in the functionalized sensitive layer to form an ion probe;

[0011] Step S4: A dual-terminal working electrode positive and a dual-terminal working electrode negative are formed on the surface of the Schottky heterojunction Pt film by magnetron sputtering.

[0012] The advantages of this invention compared to existing technologies are as follows: It uses a platinum / silicon Schottky heterojunction as the sensor's working substrate, which has a simpler structure and is easier to fabricate; it employs a functionalized sensitive layer containing an ion probe to achieve heavy metal ion detection, expanding its application range; it uses a dual-terminal working electrode configuration for direct measurement, eliminating the need for a reference electrode, simplifying the measurement process and improving sensor stability; and it utilizes the detection mechanism of platinum / silicon Schottky heterojunction capacitance sensitive to membrane potential, giving the sensor higher sensitivity. Attached Figure Description

[0013] Appendix Figure 1 This is a basic structural diagram of a high-sensitivity ion sensor based on a Schottky heterojunction.

[0014] Appendix Figure 2 This is a flowchart illustrating the fabrication process of a highly sensitive ion sensor based on a Schottky heterostructure.

[0015] Appendix Figure 3 This is a schematic diagram of the ion sensor detection.

[0016] Appendix Figure 4 This is a schematic diagram of the electrical property testing of a heterojunction structure.

[0017] Appendix Figure 5 This is a schematic diagram of the sensing performance of an ion sensor.

[0018] Figure reference numerals: 1-Platinum / silicon Schottky heterojunction, 2-Silicon substrate, 3-Platinum film, 4-Functionalized sensitive layer, 5-Dual-terminal working electrode, 6-Positive dual-terminal working electrode, 7-Negative dual-terminal working electrode, 8-DC bias input, 9-AC excitation input, 10-Current-voltage conversion circuit, 11-Solution cell containing the heavy metal ions to be measured. Detailed Implementation

[0019] A highly sensitive ion sensor based on a Schottky heterojunction includes a platinum / silicon Schottky heterojunction, a functionalized sensitive layer, and a dual-terminal working electrode. The dual-terminal working electrode includes a positive electrode and a negative electrode. The platinum / silicon Schottky heterojunction comprises a silicon (Si) substrate and a Pt film, which are sequentially bonded from bottom to top. The functionalized sensitive layer is functionalized with organic macromolecules, which serve as ion probes. The functionalized sensitive layer is a Pt film bonded to the platinum / silicon Schottky heterojunction via magnetron sputtering. The above describes a dual-terminal working electrode; the positive and negative electrodes are respectively bonded to a platinum / silicon Schottky heterojunction Pt film for voltage signal input and current signal output. The input to the positive electrode is a DC bias signal and an AC excitation signal, which are used as the input to the sensor voltage signal. The sensor current signal is output from the negative electrode. The negative electrode is connected to a current-to-voltage conversion circuit, which converts a weak current signal into a detectable voltage signal.

[0020] To use, simply connect the solution cell containing the heavy metal ions to be measured to the functionalized sensitive layer to complete the measurement.

[0021] A method for fabricating a highly sensitive ion sensor based on a Schottky heterojunction is as follows:

[0022] First, a clean silicon (Si) substrate is obtained through photolithography etching;

[0023] A Schottky heterojunction is formed between the silicon substrate (Si) and the platinum (Pt) metal on the surface of the silicon substrate using magnetron sputtering technology;

[0024] A functionalized sensitive layer was prepared on the surface of a Schottky heterojunction by magnetron sputtering; organic macromolecules were then incorporated into the functionalized sensitive layer to form an ion probe.

[0025] A dual-terminal working electrode positive and a dual-terminal working electrode negative are formed on the surface of a Schottky heterojunction Pt film by magnetron sputtering.

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0027] To address the stability issues of reference electrodes in traditional semiconductor biochemical sensors and the limitations of heavy metal ion detection technology, this invention proposes a highly sensitive ion sensor based on a Schottky heterojunction. The sensor comprises a platinum / silicon Schottky heterojunction 1, a functionalized sensitive layer 4, and a dual-terminal working electrode 5.

[0028] The platinum / silicon Schottky heterojunction 1 is used as the working substrate of the sensor;

[0029] The functionalized sensitive layer 4 contains an ion probe that can selectively bind heavy metal ions;

[0030] The dual-terminal working electrode 5 is coupled to both ends of the platinum / silicon Schottky heterojunction 1 and is used for voltage signal input and current signal output.

[0031] The high-sensitivity ion sensor based on Schottky heterojunction has its input voltage directly applied to the dual-terminal working electrode 5. Without the need for gate voltage control or a reference electrode, the amplitude of the alternating current can be directly read to detect the concentration of the heavy metal ions to be detected.

[0032] The following description of the technical features of the present invention refers to the appendix. Figure 1 Appendix Figure 2 Appendix Figure 3 .

[0033] The solution adopted by the present invention to solve its technical problem is: a high-sensitivity ion sensor based on a Schottky heterojunction, comprising a platinum / silicon Schottky heterojunction 1, a functionalized sensitive layer 4, and a dual-terminal working electrode 5;

[0034] The fabrication process of the high-sensitivity ion sensor based on Schottky heterojunction proposed in this invention is attached. Figure 2 As shown, firstly, the platinum / silicon Schottky heterojunction 1 is formed by bonding metallic platinum 3 to the surface of silicon substrate 2 via magnetron sputtering. The junction capacitance of this heterojunction is highly sensitive to the magnitude of the reverse bias voltage applied across the heterojunction.

[0035] The dual-terminal working electrode 5 is formed by magnetron sputtering at both ends of the platinum / silicon Schottky heterojunction 1, forming a positive electrode 6 and a negative electrode 7. A DC bias 8 and an AC excitation 9 are simultaneously applied to the positive electrode 6 of the dual-terminal working electrode 5 for the input of the sensor voltage signal, and the sensor current signal is output from the negative electrode 7.

[0036] Subsequently, a sensitive layer is prepared on the surface of the platinum / silicon Schottky heterojunction 1, and then the surface of the sensitive layer is functionalized to form the functionalized sensitive layer 4. The surface of the functionalized sensitive layer 4 contains ion probes that can selectively bind heavy metal ions, including but not limited to organic macromolecules, enzymes, and nanoparticles. Different heavy metal ions in the ion solution selectively bind to these ion probes, causing changes in the surface potential of the functionalized sensitive layer 4. This change in potential alters the junction capacitance of the heterojunction.

[0037] The negative electrode 7 of the dual-terminal working electrode 5 is connected to the current-to-voltage conversion circuit 10, which is used to convert weak current signals into detectable voltage signals.

[0038] The basic structure of this invention is shown in the appendix. Figure 1As shown, the high-sensitivity ion sensor based on a Schottky heterojunction consists of a platinum / silicon Schottky heterojunction 1, a functionalized sensitive layer 4, and a dual-terminal working electrode 5. The silicon substrate 2 used to fabricate the platinum / silicon Schottky heterojunction 1 is n-type silicon. A platinum film 3 is deposited on the silicon substrate 2 by DC magnetron sputtering. The ion probe of this invention uses organic macromolecules, enzymes, nanoparticles, etc., to functionalize the functionalized sensitive layer. The dual-terminal working electrode 5 of this invention is bonded to both ends of the platinum / silicon Schottky heterojunction 1 by magnetron sputtering.

[0039] The detection mechanism of this invention is:

[0040] When the ion probe on the surface of the functionalized sensitive layer 4 chelates heavy metal ions, a large number of heavy metal ions adhere to the surface of the functionalized sensitive layer 4. Considering the factors affecting the capacitance of the Schottky heterojunction, the metal-semiconductor contact results in surface states at the contact interface. As positively charged heavy metal ions accumulate on the surface of the functionalized sensitive layer 4 away from the platinum / silicon Schottky heterojunction, a faceted distribution of induced positive charge will be generated at the platinum / silicon Schottky heterojunction contact interface. The induced positive charge causes an increase in surface states, which reduces the capacitance of the Schottky heterojunction, and consequently reduces the AC current output of the sensor. Therefore, as the concentration of heavy metal ions increases, the AC current output of the sensor will decrease.

[0041] The embodiments are shown in the appendix. Figure 1 Appendix Figure 3 This invention provides a clearer and more complete description of the specific use of the sensor described herein.

[0042] (1) A schematic diagram of the detection of the ion sensor based on the Schottky heterojunction is attached. Figure 2 A DC bias of -2.6 to 0V 8 and an AC excitation of 120mV amplitude and 15KHz frequency 9 are applied to the sensor through the positive electrode 6 of the dual-terminal working electrode;

[0043] (2) The current-to-voltage conversion circuit 10 is responsible for receiving the weak current signal output through the negative electrode 7 of the dual-terminal working electrode, and after current-to-voltage conversion, obtaining the amplitude component from the output current.

[0044] (4) Add a phosphate buffer solution with a pH of 7.5 dropwise into solution tank 11;

[0045] (5) Subsequently, a low-concentration heavy metal ion solution is slowly added to solution pool 11 containing phosphate buffer solution. After waiting for 5 minutes for the system to reach equilibrium, a set of current signals is collected after processing by current-voltage conversion circuit 10;

[0046] (6) Then, a heavy metal ion solution with gradually increasing concentration is added dropwise. A 5-minute interval is maintained between the continuous application of heavy metal ions with different concentrations to allow the system to reach equilibrium, thereby minimizing the error caused by previous measurements. Similarly, multiple sets of current signals are collected after processing by the current-voltage conversion circuit 10.

[0047] (7) The obtained data is processed to obtain the heavy metal ion measurement results.

Claims

1. An application of a highly sensitive ion sensor based on a Schottky heterojunction in the monitoring of heavy metal particles in liquids, characterized in that: The high-sensitivity ion sensor comprises a platinum / silicon Schottky heterojunction, a functionalized sensitive layer, and a dual-terminal working electrode. The dual-terminal working electrode includes a positive and a negative electrode. The platinum / silicon Schottky heterojunction comprises a silicon (Si) substrate and a Pt film, which are bonded sequentially from bottom to top. The functionalized sensitive layer is modified with organic macromolecules, which serve as ion probes. The functionalized sensitive layer is bonded to the Pt film of the platinum / silicon Schottky heterojunction via magnetron sputtering. The positive and negative dual-terminal working electrodes are respectively bonded to the Pt film of the platinum / silicon Schottky heterojunction and are used for voltage signal input and current signal output. The input to the positive dual-terminal working electrode is a DC bias signal and an AC excitation signal, while the sensor current signal is output from the negative dual-terminal working electrode. The negative dual-terminal working electrode is connected to a current-to-voltage conversion circuit.

2. The application of a high-sensitivity ion sensor based on a Schottky heterojunction according to claim 1 in the monitoring of heavy metal particles in liquid, characterized in that, The method for preparing the high-sensitivity ion sensor includes the following steps: Step S1: Obtain a clean silicon (Si) substrate through photolithography etching; Step S2: A Schottky heterojunction is formed between the silicon substrate (Si) and the platinum (Pt) metal on the surface of the silicon substrate by magnetron sputtering; Step S3: A functionalized sensitive layer is prepared on the surface of a Schottky heterojunction by magnetron sputtering; organic macromolecules are combined in the functionalized sensitive layer to form an ion probe; Step S4: A dual-terminal working electrode positive and a dual-terminal working electrode negative are formed on the surface of the Schottky heterojunction Pt film by magnetron sputtering.

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