Atomic force microscope probe with Raman signal enhancement capability and preparation method thereof
By covering the silicon tip with a metal layer and etching a groove structure, the problem of insufficient Raman spectral signal of the TERS probe was solved, and the effect of efficiently enhancing the Raman signal on any substrate was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- XIAMEN UNIV
- Filing Date
- 2026-03-19
- Publication Date
- 2026-05-01
AI Technical Summary
Existing TERS probes have insufficient Raman spectral signal enhancement capabilities and rely on gold or silver substrates, which limits the research subjects and alters sample properties.
Design an atomic force microscope probe with a silicon tip. The tip is covered with a metal layer and has a groove structure on the second side. The groove is used to confine the excitation light to excite local surface plasmon resonance and enhance the Raman spectral signal.
It achieves significant enhancement of Raman spectral signals without relying on gold or silver substrates, is applicable to any material substrate, and does not change the sample properties.
Smart Images
Figure CN121955455A_ABST
Abstract
Description
An atomic force microscope probe with Raman signal enhancement capability and its preparation method Technical Field
[0001] This invention belongs to the field of physical chemistry and analytical chemistry research technology, and specifically relates to an atomic force microscope probe with Raman signal enhancement capability. Background Technology
[0002] Tip-enhanced Raman spectroscopy (TERS), by combining scanning probe microscopy and plasmon-enhanced Raman spectroscopy, can overcome the diffraction limit under ambient temperature, pressure, and atmospheric conditions, obtaining Raman spectra with nanometer resolution and a million-fold enhancement. It can simultaneously acquire sample surface morphology and chemical fingerprint information at the nanoscale. Therefore, TERS technology has attracted widespread attention in both basic science and industrial applications.
[0003] The basic principle of TERS is as follows: A nanoscale, sharp probe is brought close to the sample under test using scanning probe microscopy, with the distance between the probe and the sample within 1 nm. Then, surface plasmon resonances at the probe tip are excited by excitation light of a suitable wavelength and polarization, thereby generating a nanoscale confined enhanced photoelectric field below the probe tip. This photoelectric field acts as a nanoscale Raman signal "amplifier," amplifying the Raman spectral signal of the sample located within this enhanced photoelectric field by a million times, thus obtaining a Raman spectrum with nanometer resolution.
[0004] It is clear from the above working principle that the core of TERS technology is a probe with Raman spectral signal enhancement capabilities. However, for over 20 years of TERS technology development, the high reproducibility of high-performance probe fabrication has been one of the core bottlenecks limiting the widespread application of this technology. Currently, various probes with Raman spectral signal enhancement capabilities have been reported internationally. Taking TERS technology based on atomic force microscopy as an example, common TERS probes are silicon probes with a gold (or silver) coating. However, relying solely on these gold or silver-coated probes often results in insufficient Raman spectral signal enhancement capabilities, making it difficult to meet the needs of TERS experiments. To overcome this problem, existing solutions typically involve loading the sample to be characterized onto a gold (or silver) substrate, generating high enhancement through electromagnetic field coupling between the gold (or silver) probe and the gold (or silver) substrate. However, this approach has two major drawbacks: first, the distance between the probe and the substrate must be within 5 nm, severely limiting the research objects of TERS; second, when the sample is loaded onto a gold (or silver) substrate, its properties are affected by the substrate, resulting in significant differences from the intrinsic properties of the sample. Summary of the Invention
[0005] The purpose of this invention is to overcome at least one of the shortcomings of the prior art and to provide an atomic force microscope probe with Raman spectral signal enhancement capability, so as to solve the problem that the probe's Raman spectral signal enhancement capability is insufficient in the above-mentioned background art and therefore needs to rely on a gold or silver substrate.
[0006] The technical solution adopted by this invention to solve its technical problem is: an atomic force microscope probe with Raman spectral signal enhancement capability, the tip of which is made of silicon and is cone-shaped or pyramidal; the tip has a first side and a second side opposite to the first side; the first side is covered with a metal layer, the metal layer extending to cover the tip of the probe; a groove structure is formed on the second side. The groove structure acts as a light-limiting nanocavity, confining the excitation light within the silicon layer, thereby efficiently exciting the local surface plasmon resonance of the metal tip and enhancing the Raman spectral signal of the sample below.
[0007] In this invention, the material of the metal layer includes gold, silver, copper, or a composite layer or alloy of any two or three of gold, silver, and copper.
[0008] In this invention, the thickness of the metal layer is 20-200 nm.
[0009] In this invention, the distance between the groove and the tip of the needle is 100-800 nm, the length of the groove structure along the needle tip axis is 100-1000 nm, and the depth is 50-300 nm.
[0010] Furthermore, the atomic force microscope probe of the present invention also includes a substrate and a cantilever.
[0011] Another object of the present invention is to provide a method for preparing the atomic force microscope probe, comprising the following steps:
[0012] S1: Provide an atomic force microscope probe substrate with a silicon tip;
[0013] S2: A groove structure is machined on the second side surface of the needle tip;
[0014] S3: Deposit a metal layer on the first side of the needle tip and make the metal layer cover the tip of the needle tip.
[0015] Furthermore, in step S2, the groove structure is etched on the second side of the needle tip using micro-nano fabrication techniques such as focused ion beam technology.
[0016] Furthermore, in step S3, a metal layer is deposited on the first side of the needle tip using physical vapor deposition or electrochemical deposition.
[0017] Furthermore, the physical vapor deposition technique includes, but is not limited to, electron beam evaporation, thermal resistance evaporation, magnetron sputtering, or pulsed laser deposition.
[0018] The present invention also provides the application of the atomic force microscope probe in tip-enhanced Raman spectroscopy (TERS) technology, which enables simultaneous characterization of chemical fingerprint information and surface morphology information of samples located on any material substrate at nanometer resolution without relying on gold or silver substrates.
[0019] The atomic force microscope probe structure proposed in this technical solution is simple and suitable for TERS instruments based on atomic force microscopy. Compared with the prior art, it has the following advantages:
[0020] 1. The tip described in this scheme has high Raman enhancement activity and can carry out TERS experiments without relying on a gold (or silver) substrate.
[0021] 2. The probe structure described in this scheme is simple, does not require the use of a transmission-type TERS instrument, and has no special requirements for the sample being studied. Attached Figure Description
[0022] Figure 1 is a schematic diagram of the structure of Example 1.
[0023] Figure 2 is a scanning electron microscope image of Example 1.
[0024] Figure 3 is a comparison of the probes used in Example 1 and Comparative Example 1 for Raman signal detection of two-dimensional material samples on silicon surfaces. Detailed Implementation
[0025] As shown in Figure 1, the present invention provides an atomic force microscope probe with Raman spectral signal enhancement capability, comprising a substrate, a cantilever, and a tip located on the cantilever.
[0026] The substrate can be any substrate used in existing atomic force microscopes, as long as it meets the substrate requirements of atomic force microscopes. The cantilever can also be any cantilever used in existing atomic force microscopes, as long as it meets the tip connection requirements of atomic force microscopes.
[0027] The needle tip of the present invention is made of silicon and is in the shape of a cone or pyramid; or similar to a cone or pyramid; the height of the cone or pyramid is 10-15 μm; the angle between the side of the cone or pyramid and the central axis can be 10 degrees to 75 degrees; and the diameter of the tip is 10-200 nm.
[0028] A cone includes a regular cone or an oblique cone, and a prism includes a regular prism or an oblique prism.
[0029] The needle tip has a first side and a second side opposite to the first side; the first side is covered with a metal layer that extends to cover the tip of the needle; a groove structure is formed on the second side; the groove structure serves as a light-limiting nanocavity, confining the excitation light within the silicon layer, exciting the local surface plasmon resonance of the metal tip, and enhancing the Raman spectral signal of the sample below.
[0030] Example 1
[0031] This embodiment describes an atomic force microscope (AFM) probe with enhanced Raman spectral signal prepared based on a commercially available AFM probe. The commercially available AFM is an ARROW FM probe manufactured by Nanoworld. The probe tip has a first side and a second side opposite to the first side. Based on the commercially available probe, a gold layer with a thickness of approximately 75 nm is deposited on the first side by electron beam evaporation. The gold layer extends to cover the tip of the probe, and the tip diameter is approximately 90 nm. The second side has a groove structure introduced by focused ion beam etching. The groove structure is approximately 500 nm from the tip (see Figure 1 or Figure 2). The length of the groove structure along the probe tip axis is approximately 500 nm, and the depth (left-right direction) is approximately 200 nm. The groove structure extends through the probe in the front-back direction.
[0032] Comparative Example 1
[0033] Comparative Example 1 is a gold-plated atomic force microscope probe without a groove structure, which is also based on the ARROW FM probe manufactured by Nanoworld. It has a first side and a second side opposite to the first side. A gold layer with a thickness of about 75 nm is deposited on the first side by electron beam evaporation. The gold layer extends to cover the tip of the probe, and the tip diameter is about 90 nm.
[0034] Example 1 was compared with Comparative Example 1: a monolayer of molybdenum diselenide loaded on a silicon substrate, prepared by mechanical exfoliation, was used as a standard sample to compare the Raman signal enhancement capabilities of Example 1 and Comparative Example 1. A 632.8 nm laser was focused onto the tip of a needle using an objective lens. The tip was then controlled using an atomic force microscope system. Raman spectra were acquired in contact mode using Example 1, and then, with the laser stationary, the system switched to tapping mode to acquire Raman spectra as the Raman spectra when the tip was far from the sample. After completion, the tip was replaced with that of Comparative Example 1, and the same operation was performed.
[0035] As can be seen from Figure 3, the probe of Comparative Example 1 has almost no Raman signal enhancement capability, while the probe of Example 1 can enhance the Raman signal of the sample to be tested by more than 7 times.
[0036] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. An atomic force microscope probe with Raman spectral signal enhancement capability, characterized in that: The probe tip is made of silicon and is shaped like a cone or pyramid. The tip has a first side and a second side opposite to the first side. The first side is covered with a metal layer that extends to cover the tip of the probe. The second side has at least one groove structure.
2. The atomic force microscope probe with Raman spectral signal enhancement capability according to claim 1, characterized in that: The metal layer is made of gold, silver, copper, or a composite layer or alloy of any two or three of gold, silver, and copper.
3. An atomic force microscope probe with Raman spectral signal enhancement capability according to claim 1, characterized in that: The thickness of the metal layer is 20-200 nm.
4. An atomic force microscope probe with Raman spectral signal enhancement capability according to claim 1, characterized in that: The distance between the groove structure and the tip of the needle is 100-800 nm, the length of the groove structure along the axis of the needle tip is 100-1000 nm, and the depth is 50-300 nm.
5. An atomic force microscope probe with Raman spectral signal enhancement capability according to any one of claims 1 to 4, characterized in that: It also includes the substrate and the cantilever.
6. A method for preparing an atomic force microscope probe according to any one of claims 1 to 4, comprising the following steps: S1: Provide an atomic force microscope probe substrate with a silicon tip; S2: Process a groove structure on the second side of the tip; S3: Deposit a metal layer on the first side of the tip and cover the tip tip with the metal layer.
7. The preparation method according to claim 6, characterized in that, In step S2, the groove structure is etched on the second side of the needle tip using micro-nano fabrication techniques, including focused ion beam technology.
8. The preparation method according to claim 6, characterized in that, In step S3, a metal layer is deposited on the first side of the needle tip using techniques including physical vapor deposition or electrochemical deposition.
9. The preparation method according to claim 8, characterized in that, The physical vapor deposition technique includes at least one of electron beam evaporation, thermal resistance evaporation, magnetron sputtering, or pulsed laser deposition.
10. The application of an atomic force microscope probe according to any one of claims 1 to 4 in tip-enhanced Raman spectroscopy, characterized in that, Simultaneous characterization of chemical fingerprint information and surface morphology information at nanometer resolution for samples located on arbitrary material substrates.