CN-121978370-A - Microwave impedance microscope

CN121978370ACN 121978370 ACN121978370 ACN 121978370ACN-121978370-A

Abstract

The invention discloses a microwave impedance microscope, which relates to the technical field of scanning probe microscopes, wherein the microwave impedance microscope comprises an antenna module, a probe module, a scanning tube and a displacement module. The probe module adopts an STM probe, and an insulating layer and a metal coating are sequentially arranged on the outer side of a tungsten tip of the STM probe to form a coaxial structure so as to localize signals. The antenna module is arranged on the periphery of the STM probe, and can maintain relatively stable output power in a preset frequency band. Through the cooperative work of the broadband antenna and the STM probe, broadband measurement can be realized without repeated hardware matching, the consistency of data references with different frequencies is ensured, and quantitative comparison and analysis are supported. The STM probe structure effectively eliminates parasitic capacitance of the traditional AFM cantilever, so that the signal height is localized to the needle point, and the spatial resolution and the measurement accuracy are remarkably improved.

Inventors

CHEN YI
YANG XINHAO

Assignees

北京大学

Dates

Publication Date: 20260505
Application Date: 20260121

Claims (10)

1.A microwave impedance microscope, comprising: The antenna module and the probe module comprise STM probes, the antenna module is positioned on the periphery of the STM probes, and the antenna module maintains relatively stable output power in a preset frequency band range; The STM probe comprises a tungsten needle point, wherein an insulating layer and a metal coating are sequentially arranged outwards of the tungsten needle point, and the insulating layer is used for isolating the tungsten needle point and the metal coating; The probe module is fixedly connected with the scanning tube; and the displacement module is used for adjusting the position of the STM probe relative to the sample.
2. The microwave impedance microscope of claim 1, wherein the antenna module comprises a substrate, a feed port, a feed line, and a plurality of antenna elements; The feed source port is used for connecting a coaxial cable; The antenna elements are arranged on the substrate according to a planarization logarithmic period rule, and the feeder lines are used for signal transmission and impedance matching between the antenna elements and the feed source port.
3. The microwave impedance microscope of claim 1, wherein the probe module further comprises a PCB board, a tip holder, and a connection portion; the PCB is electrically connected with the STM probe and the antenna module, and the needle tip holder is used for installing the STM probe and the PCB; the needle point is fixedly connected with the connecting part, and the needle point is fixedly connected with the scanning tube through the connecting part.
4. The microwave impedance microscope of claim 1, further comprising a sample tray and a scan head tray, the sample tray and the scan head tray being fixedly connected; The displacement module comprises a Z-direction adjusting assembly, an X-direction adjusting assembly and a Y-direction adjusting assembly; The displacement module is fixedly connected with the scanning head tray, and the scanning tube is connected with the Z-direction adjusting assembly so as to drive the scanning tube to adjust in the Z direction; The Y-direction adjusting component is fixedly connected with a sample table, the Y-direction adjusting component is fixedly connected with the X-direction adjusting component, and the X-direction adjusting component is fixedly connected with the sample tray so as to drive the sample table to adjust in the X-direction and the Y-direction.
5. The microwave impedance microscope of claim 4, wherein the X-direction adjustment assembly comprises a first base, a first glide table, and a first stack of piezoceramics; The first base is fixedly connected with the sample tray, and the first sliding table is connected with the first base through the first piezoelectric ceramic stack so as to drive the first sliding table to move along the X direction relative to the first base; the Y-direction adjusting component comprises a second base, a second sliding table and a second piezoelectric ceramic stack; The second base is fixedly connected with the first sliding table, the second sliding table is connected with the first base through the second piezoelectric ceramic stack so as to drive the second sliding table to move along the Y direction relative to the second base, and the sample table is fixedly connected with the second sliding table.
6. The microwave impedance microscope of claim 5, wherein the X-direction adjustment assembly further comprises a first adjustment portion, the first adjustment portion and the first piezoceramic stack collectively clamping the first slip table; The first adjusting part is fixedly connected with the first base through a first connecting piece, and the first connecting piece is adjusted to enable the first adjusting part to be close to or far away from the first piezoelectric ceramic stack so as to adjust the pretightening force of the first sliding table on the first piezoelectric ceramic stack; The Y-direction adjusting assembly further comprises a second adjusting part, and the second adjusting part and the second piezoelectric ceramic stack jointly clamp the second sliding table; The second adjusting part is fixedly connected with the second base through a second connecting piece, and the second adjusting part can be made to be close to or far away from the second piezoelectric ceramic stack by adjusting the second connecting piece, so that the pretightening force of the second sliding table on the second piezoelectric ceramic stack is adjusted.
7. The microwave impedance microscope of claim 5, wherein the first base is provided with two first supporting surfaces which are inclined to each other, and the two first piezoelectric ceramic stacks are respectively and vertically arranged on the two first supporting surfaces; Wherein, the two first supporting surfaces are parallel to the X direction so as to prevent the first sliding table from moving along the Y direction; The second base is provided with two second supporting surfaces which are inclined with each other, and the two second piezoelectric ceramic stacks are respectively and vertically arranged on the two second supporting surfaces; the two second supporting surfaces are parallel to the Y direction so as to prevent the first sliding table from moving along the X direction.
8. The microwave impedance microscope of claim 4, wherein the Z-direction adjustment assembly comprises a support housing and a third stack of piezoceramics; the support shell is fixedly connected with the scanning head tray, the scanning tube is positioned in the support shell, and a plurality of third piezoelectric ceramic stacks are arranged on the periphery of the scanning tube at intervals so as to clamp and fix the scanning tube; The third piezoelectric ceramic stack is fixedly connected with the support shell so as to drive the scanning tube to move along the Z direction.
9. The microwave impedance microscope of claim 8, wherein the Z-direction adjustment assembly further comprises a third adjustment portion through which at least one of the third piezoceramic stacks is fixedly connected with the support housing; The third adjusting part is used for adjusting the pretightening force of the scanning tube to the third piezoelectric ceramic stack.
10. The microwave impedance microscope according to claim 4, wherein a plurality of copper pieces and magnets are arranged at intervals on the periphery of the sample tray, and the copper pieces and the magnets are matched to realize magnetic damping and shock absorption; The scanning head tray is fixedly connected with a plurality of damping springs, and is used for hanging the scanning head tray, so that external vibration conduction is reduced.

Description

Microwave impedance microscope Technical Field The invention relates to the technical field of scanning probe microscopes, in particular to a microwave impedance microscope. Background MIM (Microwave Impedance Microscopy ) is a critical scanning probe technology capable of characterizing electrical properties of materials on the nanometer scale, and is widely used in modern materials research. Typical MIM systems couple microwave signals to a sample through a metallized probe and detect the amplitude and phase of their reflected signals, thereby generating a two-dimensional image corresponding to the resistive and capacitive properties of the sample. Existing systems are typically optimized for a particular frequency bin, resulting in limited effective operating bandwidth. When broadband measurement is carried out, impedance matching needs to be carried out again for different frequency points, the process is complicated, the efficiency is low, and the data under different frequencies are difficult to directly carry out quantitative comparison. And the existing MIM system generally adopts an AFM (atomic force microscope ) probe as a carrier of microwave signals, and the spatial resolution of the MIM system has inherent limitations. The metallized tapered tip of the AFM probe and its cantilever structure can introduce significant parasitic capacitance, and these non-localized electromagnetic couplings can "drown" the localized signals from the very tip region of the tip, resulting in reduced spatial resolution of the final image. Disclosure of Invention The invention mainly aims to provide a microwave impedance microscope, which aims to improve resolution and adapt to a frequency range. In order to achieve the above object, the microwave impedance microscope according to the present invention includes: The antenna module and the probe module comprise STM probes, the antenna module is positioned on the periphery of the STM probes, and the antenna module maintains relatively stable output power in a preset frequency band range; The STM probe comprises a tungsten needle point, wherein an insulating layer and a metal coating are sequentially arranged outwards of the tungsten needle point, and the insulating layer is used for isolating the tungsten needle point and the metal coating; The probe module is fixedly connected with the scanning tube; and the displacement module is used for adjusting the position of the STM probe relative to the sample. In one embodiment, the antenna module includes a substrate, a feed port, a feed line, and a plurality of antenna elements; The feed source port is used for connecting a coaxial cable; The antenna elements are arranged on the substrate according to a planarization logarithmic period rule, and the feeder lines are used for signal transmission and impedance matching between the antenna elements and the feed source port. In one embodiment, the probe module further comprises a PCB board, a tip holder, and a connection portion; the PCB is electrically connected with the STM probe and the antenna module, and the needle tip holder is used for installing the STM probe and the PCB; the needle point is fixedly connected with the connecting part, and the needle point is fixedly connected with the scanning tube through the connecting part. In one embodiment, the microwave impedance microscope further comprises a sample tray and a scanning head tray, wherein the sample tray and the scanning head tray are fixedly connected; The displacement module comprises a Z-direction adjusting assembly, an X-direction adjusting assembly and a Y-direction adjusting assembly; The displacement module is fixedly connected with the scanning head tray, and the scanning tube is connected with the Z-direction adjusting assembly so as to drive the scanning tube to adjust in the Z direction; The Y-direction adjusting component is fixedly connected with a sample table, the Y-direction adjusting component is fixedly connected with the X-direction adjusting component, and the X-direction adjusting component is fixedly connected with the sample tray so as to drive the sample table to adjust in the X-direction and the Y-direction. In one embodiment, the X-direction adjustment assembly includes a first base, a first skid, and a first piezoceramic stack; The first base is fixedly connected with the sample tray, and the first sliding table is connected with the first base through the first piezoelectric ceramic stack so as to drive the first sliding table to move along the X direction relative to the first base; the Y-direction adjusting component comprises a second base, a second sliding table and a second piezoelectric ceramic stack; The second base is fixedly connected with the first sliding table, the second sliding table is connected with the first base through the second piezoelectric ceramic stack so as to drive the second sliding table to move along the Y direction relative to the second base, and the sample