Nanometer needle tip preparation device and method for scanning tunneling microscope

Abstract

The invention relates to the technical field of nano needle tip preparation, and discloses a nano needle tip preparation device and method for a scanning tunneling microscope, and the preparation device comprises a needle tip automatic power-off etching device and a silver wire which is connected to the positive electrode of an output port of the needle tip automatic power-off etching device. The device comprises a platinum ring electrode, an etching container, an etching liquid lifting table and a silver wire lifting table, and the silver wire lifting table and the etching liquid lifting table are used for achieving automatic lifting of the etching container in the working process. According to the preparation method, the lowest predetermined etching current is set, and the height of the bottom of the silver wire immersed in the etching container is always a fixed value. According to the nano needle tip preparation device and the preparation method thereof, the high-precision, rapid and efficient preparation process of the tail end of the nano needle tip is successfully realized through an electrochemical etching and automatic power-off control technology, the shape of the nano needle tip can be accurately controlled, the surface quality of the nano needle tip is improved, and the preparation efficiency is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of nano-needle tip preparation, in particular to a device and method for preparing a nano-needle tip for a scanning tunneling microscope. Background Art

[0002] The statements in this section merely provide background art related to the present disclosure and do not necessarily constitute prior art.

[0003] Tip-Enhanced Raman Spectroscopy (TERS) is a highly sensitive surface analysis method that combines scanning probe microscopy (SPM) and Raman spectroscopy. TERS utilizes a nanoscale metal tip to generate a localized enhanced electric field on the sample surface, significantly increasing the intensity of the Raman scattering signal and enabling chemical analysis at the molecular scale.

[0004] Through high-resolution imaging of nanoscale surfaces and monolayers, TERS can provide in-depth chemical, physical, and structural information for surface molecules and is widely used in materials science, environmental monitoring, molecular detection, biomedicine, and other fields.

[0005] In TERS technology, the morphology and surface properties of the metal tip directly determine the signal enhancement effect. Fabricating a metal tip with extremely high sharpness and fine structure is crucial for obtaining high-quality Raman signals.

[0006] However, existing STM tip preparation methods still face many technical challenges, especially in terms of tip morphology control, surface quality, and preparation efficiency. Existing preparation technologies mainly include the following methods: Mechanical processing: Mechanical processing is a traditional method for needle tip preparation, but its precision is limited, making it difficult to achieve nanoscale morphological control. The surface quality of the needle tip often fails to achieve the smoothness and fineness required by TERS technology, thus affecting the signal enhancement effect.

[0007] Electrochemical etching: Electrochemical etching is a technique commonly used to fabricate STM tips. It involves applying an electric current to an electrolyte solution, which causes an electrochemical reaction to etch the tip onto a metal wire. Although this method is simple to operate and inexpensive, it still suffers from issues such as unstable morphology control, poor environmental stability, and low fabrication efficiency in practical applications.

[0008] Although existing technologies can meet the basic requirements of STM tips to a certain extent, in TERS applications, unstable electrolytic environment or unqualified tip morphology caused by control and device reasons, excessive etching and low current resulting in unstable nanotip appearance and surface shape still exist. The tip diameter of the tip and the repeatability and stability of the preparation are still difficult problems that need to be solved urgently. Summary of the Invention

[0009] In order to overcome the shortcomings of the above-mentioned prior art, the present invention provides a method for successfully achieving a high-precision, fast and efficient preparation process through electrochemical etching and automatic power-off control technology. The formed silver needle tip has a sharp end and its morphology meets the requirements of tip-enhanced Raman (TERS) technology. The etching process can be carried out at room temperature, with simple operation, high safety, and flexible control conditions to ensure a stable etching process and a clear end point. The etching time is about 1 minute, which significantly improves the preparation efficiency. When observed under a scanning electron microscope (SEM), the prepared silver needle tip has a tip curvature radius of less than 100 nm, achieving nanometer-level precision, which can significantly enhance the Raman signal and improve the imaging quality of the scanning tunneling microscope (STM). This technology has high stability and good reproducibility, and has a broad application prospect for a nanotip preparation device for scanning tunneling microscopes.

[0010] The technical solution adopted by the present invention is: a nano-needle tip preparation device for a scanning tunneling microscope, including a needle tip automatic power-off etching device, and a silver wire connected to the positive electrode of the output port of the needle tip automatic power-off etching device. The nano-needle tip preparation device also includes: a platinum ring electrode connected to the negative electrode of the needle tip automatic power-off etching device; and an etching container for immersing the silver wire for electrochemical etching; and an etching liquid lifting platform for supporting and lifting the etching container; and a silver wire lifting platform for supporting and lifting the silver wire. The silver wire lifting platform and the etching liquid lifting platform are used to realize the lifting and lowering of the etching container during operation.

[0011] In the present technical solution, the nano-needle tip preparation device further comprises a platinum electrode fixture for supporting the platinum ring electrode on the top of the etching container.

[0012] In this technical solution, the needle tip automatic power-off etching device includes etching lamp 1 and etching lamp 2 connected in parallel between the positive pole and the negative pole, and also includes a needle tip etching switch connected in series between etching lamp 2 and the positive pole or negative pole of the needle tip automatic power-off etching device.

[0013] In the present technical solution, a voltage regulating device and a voltage regulating button are further connected between the two ends of the power supply of the needle tip automatic power-off etching device.

[0014] In this technical solution, the current value of the etching circuit of the needle tip automatic power-off etching device is preset to 10mA. When the current value is lower than 10mA, the needle tip automatic power-off etching device is cut off and etching stops.

[0015] In this technical solution, the etching container is a beaker.

[0016] A method for preparing a nanotip for a scanning tunneling microscope uses the above-mentioned nanotip preparation device for a scanning tunneling microscope, and during the nanotip preparation process, the output voltage value is changed between 6V and 15V by using a voltage adjustment knob to ensure that the output voltage is always a fixed value in the nanotip preparation working state.

[0017] In this technical solution, the electrochemical etching solution in the etching container is ethanol and perchloric acid mixed in a volume ratio of 3:1.

[0018] In this technical solution, the purity of the silver wire is 99.9985%.

[0019] In this technical solution, after the nano-needle tip is completely etched, it is removed from the silver wire lifting platform and rinsed with ethanol and deionized water to remove residual chemicals on the surface.

[0020] Compared with the prior art, the present invention has the following beneficial effects: 1. The platinum ring electrode is stably fixed by a cantilever-supported platinum electrode fixture, which improves its etching stability and accuracy and ensures that the etched nano-needle tip has a smooth and stable appearance.

[0021] 2. A minimum automatic circuit-breaking current is preset. When the current value is lower than 10 mA, the needle tip automatic power-off etching device 4 is cut off and etching is stopped. The needle tip etching device 4 of the present invention automatically interrupts the current, thereby avoiding excessive etching or incomplete etching caused by too low current, and further ensuring that the etched nano-needle tip has a smooth, stable appearance and higher precision.

[0022] 3. Use etching lamp 1 and etching lamp 2 to accurately indicate the working status of etching, improve the etching operation accuracy and reaction speed, and further improve the nano-needle tip etching accuracy.

[0023] 4. The etching process of the preparation method can be carried out at room temperature, with simple operation, high safety, and flexible control conditions, ensuring a stable etching process and a clear end point. The etching time is approximately 1 minute, which significantly improves the preparation efficiency.

[0024] 5. Observation under a scanning electron microscope (SEM) showed that the prepared nanotip had a tip curvature radius of less than 100 nm, achieving nanometer-level precision, which can significantly enhance the Raman signal and improve the imaging quality of the scanning tunneling microscope (STM).

[0025] In summary, the nanotip preparation device and preparation method for scanning tunneling microscope of the present invention realize the rapid, stable and efficient preparation of nanotips through electrochemical etching and automatic power-off control technology, realize a high-precision, rapid and efficient preparation process, can accurately control the morphology of nanotips and improve the surface quality of nanotips. The formed nanotip has a sharp end and its morphology meets the requirements of tip-enhanced Raman spectroscopy (TERS) technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the structure of an embodiment of the present invention; FIG2 is an optical microscope morphology image of the needle tip made in an embodiment of the present invention, wherein: part a and part b are morphology images under 20x and 100x objective lenses, respectively; Figure 3 This is a scanning electron microscope image of the needle tip made in an embodiment of the present invention; Figure 4 This is a comparison of the enhancement effects of the needle tip prepared by the present invention and the needle tip prepared without current control, where the abscissa is the Raman shift and the ordinate is the intensity; Figure 5 This is an atomic resolution image of highly oriented pyrolytic graphite (HOPG) prepared using the tip disclosed in an embodiment of the present invention; Among them: 1-etching lamp, 2-needle tip etching lamp, 3-needle tip etching switch, 4-needle tip automatic power-off etching device, 5-platinum ring electrode, 6-silver wire, 7-silver wire lifting platform, 8-etching container, 9-etching liquid lifting platform, 10-platinum electrode clamp, 11-silver wire clamp, 12-voltage regulating device and voltage regulating knob. DETAILED DESCRIPTION

[0027] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0028] In the description of the present invention, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right" and the like indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the combination or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as limiting the present invention. In addition, in the description of the embodiments of the present invention, the device positional relationships such as "up", "down", "front", "back", "left", "right" and the like in all the drawings are based on the directions or positional relationships shown in the accompanying drawings. Figure 1 As standard.

[0029] like Figure 1 As shown, a nano-needle tip preparation device for a scanning tunneling microscope includes a needle tip automatic power-off etching device 4, and a silver wire 6 connected to the positive electrode of the output port of the needle tip automatic power-off etching device 4. The nano-needle tip preparation device also includes: a platinum ring electrode 5 connected to the negative electrode of the needle tip automatic power-off etching device 4; and an etching container 8 for immersing the silver wire 6 therein for electrochemical etching; and an etching liquid lifting platform 9 for supporting and lifting the etching container 8; and a silver wire lifting platform 7 for supporting and lifting the silver wire 6. The silver wire lifting platform 7 and the etching liquid lifting platform 9 are used to realize the lifting and lowering of the etching container 8 during work. When the silver wire 6 is etched in the etching container 8, as the lower part of the silver wire 6 gradually sinks, it finally falls to the bottom of the etching container 8, thereby realizing automatic electrochemical etching of the silver wire 6 during etching.

[0030] In at least one embodiment, the nano-tip preparation device further comprises a platinum electrode fixture 10 for supporting the platinum ring electrode 5 on the top of the etching container 8, thereby stably arranging the platinum ring electrode 5 at the top position of the etching container. Figure 1 It can be seen from the figure that the platinum electrode fixture 10 is a cantilever support, which can maintain the stability of the platinum ring electrode 5 during etching.

[0031] In at least one embodiment, the current value of the etching circuit of the needle tip automatic power-off etching device 4 is preset to 10mA. When the current value is lower than 10mA, the needle tip automatic power-off etching device 4 is cut off and etching is stopped. The needle tip etching device 4 of the present invention automatically interrupts the current, thereby avoiding excessive etching or incomplete etching caused by too low current, ensuring that the etched nano-needle tip has a smooth, stable appearance and higher precision.

[0032] In at least one embodiment, the etching container 8 is a beaker.

[0033] In at least one embodiment, the needle tip automatic power-off etching device 4 includes an etching lamp 1 and an etching lamp 2 connected in parallel between the positive electrode and the negative electrode, and also includes a needle tip etching switch 3 connected in series between the etching lamp 2 2 and the positive electrode or the negative electrode of the needle tip automatic power-off etching device 4, wherein the etching lamp 1 is used to indicate whether the power of the needle tip automatic power-off etching device 4 is on or off, and the etching lamp 2 2 is used to control whether it is working through the needle tip etching switch 3, thereby realizing the indication of whether the needle tip automatic power-off etching device 4 is working. Its working principle is according to Figure 1 As shown in the circuit diagram. Figure 1As shown, a voltage regulator and a voltage adjustment button 12 are connected between the two ends of the power supply of the automatic needle tip power-off etching device 4. The voltage adjustment button 12 is used to adjust the terminal voltage of the automatic needle tip power-off etching device 4 in real time. The output voltage can be adjusted from 6 to 15V. The output voltage is adjusted according to the required experimental conditions and the actual effect will be the basis. In the specific implementation process, the voltage regulator is generally an LM3478 chip to achieve true 6-24V full range regulation. Alternatively, a digital potentiometer (such as the MCP4131) can be used to achieve voltage step adjustment through single-chip microcomputer programming. The method for preparing a nanotip for a scanning tunneling microscope uses the aforementioned nanotip preparation device for a scanning tunneling microscope. During the nanotip preparation process, the output voltage can be adjusted between 6V and 15V using the voltage adjustment knob 12. During operation, the output voltage remains fixed within an adjustable range of 6 to 15V. The output voltage is adjusted based on the desired experimental conditions, with the actual results being the most important factor. The etching process can be performed at room temperature, is simple to operate, highly safe, and has flexible control conditions, ensuring a stable etching process and a clear endpoint. The etching time is approximately 1 minute, significantly improving preparation efficiency.

[0034] In at least one embodiment, the electrochemical etching solution in the etching container 8 is a mixture of ethanol and perchloric acid in a volume ratio of 3:1.

[0035] In at least one embodiment, the purity of the silver wire 6 is 99.9985%, and the diameter of the silver wire 6 is about 0.25 mm.

[0036] In at least one embodiment, after the nano-needle tip is completely etched, it is removed from the silver wire lifting platform 7 and rinsed with ethanol and deionized water to remove residual chemicals on the surface.

[0037] In some embodiments, the following materials are used in the preparation of nano-needle tips (i.e., silver tips): S1. Select silver wire 6 with a diameter of 0.25 mm and a purity of 99.9985% as the raw material of the nanotip.

[0038] Prepare an etching solution by mixing ethanol and perchloric acid in a volume ratio of 3:1 as an electrochemical etching solution.

[0039] S2. Use a platinum ring electrode 5 with an inner diameter of about 13 mm and a diameter of 0.5 mm, fix it with a platinum electrode fixture 10, turn the knob of the etching liquid lifting platform 9 to lift the etching container 8 until the platinum electrode 5 is immersed in the etching liquid. The immersion depth of the platinum ring electrode 5 is maintained at 1 mm for etching.

[0040] S3. Prepare a silver wire 6 about 20 mm long, secure it with the clamp 11, and rotate the knob of the silver wire lifting platform 7 to immerse the silver wire 6 about 2 mm into the electrolyte.

[0041] S4. Connect the positive electrode of the output port of the needle tip automatic power-off etching device 4 to a silver wire, and the negative electrode to a platinum ring electrode 5.

[0042] S5. Apply 24V voltage to the needle tip automatic power-off etching device 4, the light 1 lights up, and adjust the voltage regulating knob 12 to adjust the output voltage to 8V.

[0043] S6. Turn on the needle tip etching switch 3 of the needle tip automatic power-off etching device 4, the etching lamp 2 lights up, and the circuit starts to be energized.

[0044] S7. The current is maintained above 10 mA to ensure the etching reaction proceeds. As the etching proceeds, the lower portion of the silver wire 6 gradually sinks and eventually falls to the bottom of the beaker / etching container 8.

[0045] S8. When the current gradually drops to a preset value (10 mA), the current is interrupted by the needle tip automatic power-off etching device 4 of the present invention, thereby avoiding excessive etching or incomplete etching caused by too low current.

[0046] S9. During the etching process, the shape of the needle tip will gradually form according to the change of the current until the current drops below 10 mA. At this time, the needle tip automatic power-off etching device 4 will cut off the current.

[0047] S10. After etching is complete, carefully turn the knob on the silver wire lifter 7 to lift the silver needle tip from the electrolyte surface. Remove the silver needle tip and rinse it with ethanol and deionized water to remove any residual chemicals on the surface and ensure that the tip surface is free of impurities.

[0048] The morphology of the nano-needle tip prepared using the above device and preparation method is shown in parts a and b of Figure 2. The effect of the nano-needle tip before enhancement is compared with the effect of the nano-needle tip after enhancement and the effect of the tip prepared without current control is shown in Figure 2. Figure 3 As shown in the figure, the formed silver tip has a sharp tip, and its morphology meets the requirements of tip-enhanced Raman spectroscopy (TERS). The enhancement effect is particularly pronounced. Electrochemical etching and automatic power-off control technology successfully achieved a high-precision, fast, and efficient preparation process.

[0049] Observation under a scanning electron microscope (SEM) showed Figure 3 As shown in the figure, the prepared silver needle tip has a tip curvature radius of less than 100 nm, achieving nanometer-level precision, which can significantly enhance the Raman signal and improve the imaging quality of scanning tunneling microscopy (STM). This technology has high stability and good reproducibility and has broad application prospects. Figure 5Atomic resolution image of highly oriented pyrolytic graphite (HOPG) prepared using the tip disclosed in an embodiment of the present invention.

[0050] The embodiments disclosed in the present invention are preferred embodiments, but are not limited thereto. Ordinary technicians in this field can easily understand the spirit of the present invention based on the above embodiments and make different extensions and changes. As long as they do not deviate from the spirit of the present invention, they are all within the scope of protection of the present invention.

Claims

1. A nano-needle tip preparation device for a scanning tunneling microscope, comprising a needle tip automatic power-off etching device (4), and a silver wire (6) connected to the positive electrode of the output port of the needle tip automatic power-off etching device (4), characterized in that: The nano needle tip preparation device also includes: a platinum ring electrode (5) connected to the negative electrode of the needle tip automatic power-off etching device (4); and an etching container (8) for immersing the silver wire (6) therein for electrochemical etching; and An etching liquid lifting platform (9) for supporting and lifting the etching container (8); and A silver wire lifting platform (7) for supporting and lifting the silver wire (6).

2. The device for preparing a nanotip for a scanning tunneling microscope according to claim 1, characterized in that: The nano needle tip preparation device further comprises a platinum electrode fixture (10) for supporting the platinum ring electrode (5) on the top of the etching container (8).

3. The device for preparing a nanotip for a scanning tunneling microscope according to claim 2, characterized in that: The current value of the etching circuit of the needle tip automatic power-off etching device (4) is preset to 10 mA. When the current value is lower than 10 mA, the needle tip automatic power-off etching device (4) is cut off to stop etching.

4. The device for preparing a nano-tip for a scanning tunneling microscope according to claim 3, characterized in that: The needle tip automatic power-off etching device (4) comprises an etching lamp 1 (1) and an etching lamp 2 (2) connected in parallel between a positive electrode and a negative electrode, and also comprises a needle tip etching switch (3) connected in series between the etching lamp 2 (2) and the positive electrode or the negative electrode of the needle tip automatic power-off etching device (4).

5. The device for preparing a nano-tip for a scanning tunneling microscope according to claim 3, characterized in that: A voltage regulating device and a voltage regulating button (12) are also connected between the two ends of the power supply of the needle tip automatic power-off etching device (4).

6. The device for preparing a nanotip for a scanning tunneling microscope according to any one of claims 1 to 5, characterized in that: The etching container (8) is a beaker.

7. A method for preparing a nanotip for a scanning tunneling microscope, characterized in that: The nanotip preparation device for a scanning tunneling microscope according to claim 5 or 6 is used for preparation, and the output voltage value is changed between 6V and 15V by the voltage adjustment knob to ensure that the output voltage is always a fixed value in the working state of the nanotip preparation.

8. The method for preparing a nanotip for a scanning tunneling microscope according to claim 7, wherein: The electrochemical etching solution in the etching container is ethanol and perchloric acid mixed in a volume ratio of 3:

1.

9. The method for preparing a nanotip for a scanning tunneling microscope according to claim 8, wherein: The purity of the silver wire is 99.9985%.

10. The method for preparing a nanotip for a scanning tunneling microscope according to any one of claims 6 to 9, characterized in that: After the nanotip is completely etched, it is removed from the silver wire lifting platform and rinsed with ethanol and deionized water to remove residual chemicals on the surface.

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