CN111620298B

CN111620298B - Method for cutting metal nano structure, assembling nano device and in-situ characterization of nano device

Info

Publication number: CN111620298B
Application number: CN202010465765.8A
Authority: CN
Inventors: 刘泽
Original assignee: Wuhan University WHU
Current assignee: Wuhan University WHU
Priority date: 2020-05-28
Filing date: 2020-05-28
Publication date: 2023-09-15
Anticipated expiration: 2040-05-28
Also published as: CN111620298A

Abstract

The invention discloses a method for cutting a metal nano structure, assembling a nano device and in-situ characterization of the nano device. The method for cutting and assembling the nano device is completed in situ under a scanning electron microscope and comprises the following steps: (1) The conductive probe is connected with the metal nanostructure through a wire in a short circuit manner, and the conductive probe is controlled to be close to and contact with the metal nanostructure; (2) Moving the conductive probe away from the metal nanostructure while breaking the shorting connection; (3) And moving the conductive probe to be close to the metal nanostructure, so that the metal nanostructure is locally melted and partially transferred and attached to the tip of the conductive probe, forming a nano device with the tip attached with the metal nanostructure, and forming a metal nanostructure of a nanosphere at the tip of the metal nanostructure. Methods of in situ characterization are also provided to obtain microstructure-electrical property relationships. The method provided by the invention has great reference value and application potential.

Description

Method for cutting metal nano structure, assembling nano device and in-situ characterization of nano device

Technical Field

The invention belongs to the field of nano manufacturing, and particularly relates to a cutting method of a metal and metal alloy nano structure and a method for assembling and characterizing a nano device.

Background

The shape of the metal nano structure can be modulated to obviously improve the performances of the metal nano structure in the aspects of light, electricity, magnetism, catalysis and the like, so that the metal nano structure has wide application in the aspects of batteries, catalysis, optics, sensing, surface physical chemistry and the like. Conventional modulation of the shape of metal nanostructures and fabrication of devices based on metal nanostructures typically uses advanced photolithographic techniques. Since photolithography is based on planar micromachining processes, there are also significant challenges in preparing more complex three-dimensional nanostructures or nanodevices. Although focused ion beam technology can locally engrave nanostructures, it is based on the bombardment of the nanostructures by energetic particles, which can cause the energetic particles to embed into the surface of the fabricated nanostructures or devices, causing contamination. On The other hand, the electrical characterization of nanodevices to investigate The relationship between microstructure and electrical properties generally requires additional processing of electrodes and The use of a four-probe test method to reduce The effect of contact resistance, see in detail The paper published on 5/18 of 2015, volume 27, pages 1-29, entitled "The 100th anniversary of The four-point probe technique: the role of probe geometries in isotropic and anisotropic systems" on The Journal of Physics Condensed Matter journal. In particular, the characterization of the electrical properties of molten metals depends on complex equipment, see in detail paper titled "Electrical resistivity MEASUREMENT of liquid metals" published on MEASUREMENT SCIENCE AND techenology journal, 16 th edition, pages 417-425.

At present, few literature reports on methods for in situ assembly of nano devices. Such as: the welding of the nanostructure is realized by inputting current, joule heating and melting the Nano-volume solder, and the paper with the page number of 91-96 and the name of "Bottom-up Nanoconstruction by the Welding of Individual Metallic Nanoobjects Using Nanoscale Solder" published on Nano Letters journal in 12 months and 10 days in 2009 is referred to in detail; welding Pt nanowires to the tip of a conductive probe by Joule heating by inputting current, and referring to papers with the page numbers of 953-956 and the title of Welding of Pt nanowires by Joule heating published on journal Scripta Materialia on 8/14 of 2007 in detail; the preparation of nano-heterojunction is achieved by chemical growth, or by electron beam induced carbon deposition welding, or by application of a high electric, optical or thermal field, and is described in detail in volume 2, pages 2521-2529, titled "The creation of nanojunctions" published under the journal of nanoscales, 9/17. Although some nano structures with complex configurations can be prepared by the method, the method generally depends on externally applied voltage/current or high-energy particle irradiation, is not easy to control and is easy to pollute the prepared device.

The existing method for modulating the shape of the metal nanostructure and preparing a device based on the metal nanostructure has the problems of overhigh equipment threshold, high process control difficulty, easiness in pollution and the like.

Disclosure of Invention

In order to solve the technical problems, the invention provides a novel convenient, high-precision and controllable nano preparation technology by providing a method for cutting a metal nano structure and assembling a nano device and in-situ characterizing the assembled nano device in a plurality of embodiments.

Unlike available method of assembling nanometer device via input current or voltage welding, the present invention has quantum tunneling effect and can realize the cutting of nanometer metal structure shape under the irradiation of incident electron of low energy, as small as 1 kilo electron volt, even without needing external input voltage or current. The principle is based on the following experimental findings: when the distance between two metal nano structures is as small as 1 nanometer or less, the potential difference generated by electron irradiation can induce electron field emission, so that the metal nano structures are locally melted and transfer and welding of materials occur. Based on the above experimental findings, the invention provides a method for in-situ cutting of metal nano structures and assembling of nano devices, and simultaneously provides a simple and convenient 2-probe method for characterizing the electrical properties of the nano devices without the influence of contact resistance.

The technical scheme provided by the invention is as follows:

one of the purposes of the present invention is to provide a method for cutting and assembling a metal nanostructure into a nano device, which is completed in situ under a scanning electron microscope, and comprises the following steps:

(1) The conductive probe is connected with the metal nanostructure through a wire in a short circuit manner, and the conductive probe is controlled to be close to and contact with the metal nanostructure;

(2) Moving the conductive probe away from the metal nanostructure while breaking the shorting connection;

(3) And moving the conductive probe to be close to the metal nanostructure, so that the metal nanostructure is locally melted and partially transferred and attached to the tip of the conductive probe, forming a nano device with the tip attached with the metal nanostructure, and forming a metal nanostructure of a nanosphere at the tip of the metal nanostructure.

Further, the accelerating voltage of the scanning electron microscope is more than or equal to 1 kiloelectron volt.

Further, the material of the conductive probe comprises W, ag and Au.

Further, the shape of the metal nanostructure in the step (1) includes a rod-like, columnar, cone-like or wire-like configuration, and the material includes a metal of Au, cu, pt, ag, in, sn, bi, pb, zn, al, pd, ti, ni, co, fe or an alloy thereof.

Further, the nanodevices include nanotip probes, nanosphere probes, nanopillar probes, heterojunctions, and combinations thereof.

Further, the step (3) moves the conductive probe so as to be close to the metal nanostructure in a range of 0.1nm to 1000 nm.

Further, the conductive probe is moved by the driving device, the shape of the nano device is modulated by controlling the moving speed of the driving device in the step (2), and the faster the moving speed of the conductive probe is, the sharper the shape of the nano device is obtained at the tip of the conductive probe and the tip of the metal nano structure. Preferably, the driving device is a nanomachining arm.

Further, the method for cutting and assembling the metal nano structure into the nano device can be repeatedly implemented, namely, the prepared nano device is used as a new conductive probe, and the steps of the method for cutting the metal nano structure and assembling the nano device in claim 1 are repeated to form the nano device with the metal nano structure attached to the tip of the nano device again.

Further, the conductive probe can apply a potential difference U between the conductive probe and the metal nanostructure in the contact process or the approach process of the conductive probe and the metal nanostructure, wherein the potential difference U is more than or equal to 0 and less than or equal to 100 volts.

The method for cutting and assembling the metal nano structure into the nano device is as shown in fig. 1 (a):

1) Fixing a metal substrate 5 with a metal nano structure 4 on the surface on a sample stage of a scanning electron microscope 1, fixing a conductive probe 3 on a driving device arranged in a scanning electron microscope chamber, and then short-circuiting the conductive probe 3 with the metal substrate (closing switches 6 and 7), and driving the conductive probe to be close to and contact with the metal nano structure 4 in situ under the state that a scanning electron beam 2 is opened;

2) Moving the conductive probe 3 a distance away from the metal nanostructure 4 and then opening the switch 7 (the switch 6 may also be opened);

3) The conductive probe 3 is moved close to the metal nanostructure 4 such that the metal nanostructure 4 is locally melted and partially transferred, attached to the tip of the conductive probe 3, forming a nano device 9 with the tip attached to the metal nanostructure, and a metal nanostructure forming a nanosphere at the tip of the metal nanostructure 4.

Another object of the present invention is to provide a method for in situ characterization of the above nano device, comprising the steps of:

(1) Connecting the prepared nano device with a metal electrode through a wire in a short circuit manner, and moving the nano device to be close to and in contact with the metal electrode;

(2) Disconnecting the short-circuit connection and applying a potential difference between the nano device and the metal electrode;

(3) And moving the nano device under the condition that the nano device and the metal electrode are kept in contact, so that the contact state between the nano device and the metal electrode is changed, and simultaneously monitoring a voltage-current curve to obtain the microstructure-electrical property relationship of the nano device.

The method of in situ characterization is shown in FIG. 1 (b):

1) Shorting the fabricated nano-device 9 to the metal substrate 5 (closing switch 7), moving the nano-device 9 closer to and in contact with the metal substrate 5;

2) Applying a potential difference between the nano-device 9 and the metal substrate 5 (opening switch 7), joule heating causing a localized melting of the contact area of the nano-device 9 with the metal substrate 5 to form a liquid bridge;

3) The nano device 9 is driven to move, so that the size (contact state) of a liquid bridge between the nano device 9 and the metal substrate 5 is changed, and meanwhile, a voltage-current curve is monitored, so that the microstructure-electrical property relation of the metal nano structure at the tip of the nano device 9 is obtained.

If the switch 7 is closed after step 2), the formed liquid bridge will solidify, and if the nano-device 9 is driven away from the metal substrate 5, the solidified liquid bridge will neck and deform until it opens, thereby forming sharp nano-tips on the surfaces of the nano-device 9 and the metal substrate 5.

The principle of the invention is as follows:

the principle of cutting the metal nano structure and assembling the nano device is as follows: the scanning electron in the scanning electron microscope can form weak potential difference on the surfaces of two mutually adjacent metal electrodes which are disconnected, when the distance between the two electrodes is as small as 1 nanometer, the quantum tunneling effect can lead to field emission electrons, and the field emission electrons carry energy which is compared with the fermi level and the joule heating effect caused by the field emission current determine the local melting position of the metal nano structure. In general, the emission current density of the surface field of the metal electrode (J, unit: A/cm ² ) From Fowler-Nordheim theory

Wherein E (unit: V/cm) is the electric field intensity at the surface of the metal electrode,(unit: eV) is the work function of the metal electrode. t is t ² (y)≈1.1，v(y)≈0.95-y ² ，/>Typically for Pt metal, the following is true>We drive the tungsten probe close to a Pt nanopillar (fig. 2 (a)) and gradually increase the input voltage, we measured a field emission voltage of about 2.3 volts and a field emission current density of about 1.1×10 ⁴ A/cm ² (FIG. 2 (b)). This means that the current density required to melt the Pt nanopillars in fig. 2 (a) is 10 ⁴ A/cm ² Magnitude. However, we have found experimentally that even with an external input voltage as small as 1mV, the Pt nanopillar tip melts during driving of the tungsten probe close to a Pt nanopillar of similar dimensions to FIG. 2 (a), 10 according to equation (1) ⁴ A/cm ² The current density between the metal electrodes is required to be 10 ⁷ V/cm magnitude, which means metal electrode spacing +.>This value is smaller than the lattice constant-! The field emission current we have found experimentally is not derived from the Fowler-Nordheim mechanism. It is noted that quantum tunneling effects can result in the transfer of charge (Q, unit: C) when the metal electrode spacing is as small as within 1 nanometer

Q＝σ(d)·E·S·t (2)

Wherein E, S, t respectively represent the electric field strength between the metal electrodes, the relative area of the metal electrodes, and the time. σ (d) is the conductivity of the tunneling junction formed by the metal electrode, which is obviously a function of the electrode spacing d. Under the conditions of low voltage and assuming plane electrodes, there are

Wherein the method comprises the steps ofIs the wavelength of the tunneled electron, m is the mass of the electron, ">h is the Planck constant. Substituting formula (3) into (2), we have

Substituting typical electrode spacing d-0.3 nm for quantum tunneling, applied voltage 1mV and work function of Pt, the current density is J=3.0×10 ⁴ A/cm ² Is consistent with the experimentally measured current density values required to locally melt Pt nanopillars (fig. 2).

The 2-probe method for carrying out electrical property characterization on the prepared nano device without the influence of contact resistance has the following principle: when a liquid bridge is formed between the nano device and the metal substrate, the resistance in the circuit is as follows:

R＝R ₀ +R _n (5)

wherein the constant resistance R ₀ Represents the loop resistance outside the liquid bridge region, R _n Representing the resistance of the liquid bridge, the value of which depends on the size L of the liquid bridge

Wherein ρ is _m Is the resistance of the liquid bridge. When the nano-device is driven to move so that the size of the liquid bridge is changed, the loop resistance outside the liquid bridge region can be regarded as constant, and thus the measured change in the circuit resistance is merely due to the change in the liquid bridge resistance. By continuously changing the size of the liquid bridge, experimental data of the circuit resistance and the size of the liquid bridge can be obtained, and the resistivity of the liquid bridge can be conveniently measured by combining the theoretical formula (6).

The invention has the beneficial effects that:

the invention uses quantum tunneling effect, and can realize cutting and assembling of the shape of the metal nano structure under the irradiation of incident electrons with lower energy (which can be as small as 1 kiloelectron volt) even without external input voltage or current. The method has the advantages of low equipment threshold requirement, simple process, convenient operation and no pollution in the preparation process.

The invention also provides a method for controllably tailoring the shape of the metal nanostructure by controlling the movement speed of the probe. The faster the movement speed of the conductive probe, the sharper the shape of the nano device obtained at the tip of the conductive probe and the tip of the metal nano structure, facilitating the customization of different shapes.

The invention also provides a simple and convenient 2-probe method for characterizing the electrical property of the nano device without being influenced by contact resistance.

The invention opens up a new idea for tailoring and assembling the shape of the metal nano structure and characterizing the electrical property, and has great reference value and application potential.

Drawings

Exemplary embodiments of the invention will become more fully understood from the detailed description and the accompanying drawings, wherein:

FIG. 1 provides a schematic illustration of a solution; in the figure, 1 is a scanning electron microscope, 2 is a scanning electron beam, 3 is a conductive probe, 4 is a metal nano structure, 5 is a metal substrate, 6 and 7 are switches, and 8 is a source meter; FIG. 1 (a) is a schematic diagram of in-situ tailoring of metal nanostructures, i.e., assembling of nano-devices, and FIG. 1 (b) is a schematic diagram of in-situ characterization of electrical properties of metal nanostructures;

fig. 2 illustrates the field emission effect measured when a tungsten tip is near a Pt nanopillar under external source conditions. FIG. 2 (a) shows the change in morphology of Pt nano-pillars before and after field emission during tungsten tip approach; FIG. 2 (b) field emission voltage-current curve recorded by source table;

FIG. 3 is an exemplary illustration of a tungsten tip-Au nanosphere device prepared by electron beam irradiation induced field emission during the approach of the tungsten tip to the Au nanorods with both the tungsten tip and the Au nanorods in an open state from the outside;

fig. 4 illustrates the results of transmission electron microscope characterization of one prepared tungsten tip-Pt nanosphere device. FIG. 4 (a) illustrates the transfer of a prepared tungsten tip-Pt nanosphere device onto a Mo mesh; FIG. 4 (b) is a topography of a tungsten tip-Pt nanosphere device; FIGS. 4 (c) - (d) are eds mapping diagrams; FIG. 4 (e) is a graph of component content at positions (i) and (ii); FIG. 4 (f) is a high resolution transmission electron microscope image of the tungsten tip-Pt nanosphere weld interface;

FIG. 5 (a) is an exemplary illustration of a tungsten tip-Pt nanorod-Pt nanosphere device prepared by localized melting of the electron beam-induced field emission in the middle of a Pt nanorod during approach of the tungsten tip to a longer Pt nanorod; FIG. 5 (b) schematically illustrates a complex-shaped nano-device prepared by repeating the process of FIG. 5 (a);

FIG. 6 illustrates a tungsten probe-Pt nano-pillar-Ag nano-pillar heterojunction prepared after a tungsten tip is respectively adjacent to a Pt nano-pillar and an Ag nano-pillar; FIGS. 6 (a) - (b) are topographical views; FIGS. 6 (c) - (e) are selective electron diffraction patterns near Pt-Ag heterojunction;

FIG. 7 illustrates a tungsten tip-Pt nanosphere bead (FIG. 7 (a)) prepared by repeatedly approaching a tungsten tip to a Pt nanosphere array (FIG. 7 (b)) and a Pt nanosphere array with nanospheres at the tip;

FIG. 8 illustrates a scanning electron microscope image of shape trimming of Ag (FIG. 8 (a)) and CuZnSn (FIG. 8 (b)) and PtCuNiP (FIG. 8 (c)) alloy nanopillars;

fig. 9 (a) exemplarily shows a process of forming a neck by moving a tungsten tip after welding the tungsten tip and an Ag nano-pillar; fig. 9 (b) exemplarily shows a sharp tungsten tip and an Ag nanopillar tip manufactured by necking down to breaking through the process of fig. 9 (a);

FIG. 10 illustrates a scanning electron microscope image of nanostructures of different sharpness obtained at the tungsten probe tip and the Pt nanostructure tip by controlling the speed of movement of the tungsten probe; fig. 10 (a) and 10 (c) are pictures before moving the tungsten probe, and fig. 10 (b) and 10 (d) are pictures after the tungsten probe moves at different speeds and is separated from the Pt nanostructure in fig. 10 (a) and 10 (c), respectively;

FIG. 11 is an exemplary scanning electron microscope image before and after forming a Pt liquid bridge after a tungsten tip-Pt nanosphere device contacts a Pt nanostructure;

FIG. 12 is a graph (FIG. 12 (a)) illustrating voltage versus current measured by moving a tungsten probe such that the size of a Pt liquid bridge formed between the tungsten probe and the Pt substrate is changed; the data points in fig. 12 (b) are the relationship between the measured resistance and the Pt liquid bridge size, and the solid line is a theoretical curve obtained based on formula (1).

Detailed Description

The presently preferred embodiments and methods of the present invention, which constitute the presently preferred modes of practicing the invention, will be described in more detail below with reference to the accompanying drawings. However, the embodiments disclosed herein are merely examples of the invention and thus the disclosed implementation details merely serve as a representative basis for the invention and are not to be construed as limitations of the invention. The invention may encompass different implementation details and methods. In the examples below, metallic nanostructures were produced by superplastic nano-die casting (see, for details, volume 8, pages 1-7, paper titled "One-step fabrication of crystalline metal nanostructures by direct nanoimprinting below melting temperatures" on journal Nature Communications, 5, 28).

Example 1

1) An Au substrate with an Au nano-pillar array on the surface, which is prepared by superplastic nano-die casting, is fixed on a sample stage of a scanning electron microscope, and a tungsten probe is fixed on a nano manipulator installed in the scanning electron microscope, wherein the nano manipulator has three degrees of freedom and the movement precision can be better than 1 nanometer. Firstly, the tungsten needle point is connected with the Au substrate in a short circuit way through a lead by the output end of the nano manipulator;

2) Under the condition that a scanning electron microscope electron beam is started (generally, the accelerating voltage of the electron beam is set to be more than or equal to 1 kilovolt and less than or equal to 20 kilovolts), a nanomachining arm is driven to move in situ, so that a tungsten needle point is close to and contacts one Au nano column, then, a tungsten probe is retracted to be separated from the Au nano column by a certain distance (generally less than 2 micrometers), and meanwhile, a wire between the tungsten needle point and an Au substrate is disconnected, so that the tungsten needle point and the Au substrate are in an open circuit state;

3) The tungsten probe is driven to approach the Au nano-pillar, in the process, the Au nano-pillar is locally melted, the melted Au nano-pillar is divided into 2 parts, one part is transferred to the tip of the tungsten probe under the action of the electric field force of the tungsten probe and is welded with the tip of the tungsten probe to form the tungsten probe (figure 3) with the tip of the Au nano-pillar as the Au nano-ball, and the rest of the tips of the Au nano-pillar also form the nano-ball correspondingly.

Example 2

1) Fixing a Pt substrate with a Pt nano column array on the surface, which is prepared by superplastic nano die casting, on a sample stage of a scanning electron microscope, and enabling the Pt substrate to be in short circuit connection with a tungsten needle point arranged on a nano manipulator through a wire;

2) Under the condition that a scanning electron microscope electron beam is started, a nano manipulator is driven to move in situ, so that a tungsten needle point is close to and contacts with a Pt nano column, then the tungsten probe is retracted to be separated from the Pt nano column by a certain distance (usually less than 1 micron), meanwhile, a wire between the tungsten needle point and an Au substrate is disconnected, and the tungsten needle point and the Pt substrate are respectively connected to a positive electrode and a negative electrode of a voltage source, wherein the power supply of the voltage source is in a closed state;

3) Driving the tungsten probe to approach the Pt nanopillar, during which the Pt nanopillar is locally melted and partially transfer welded to the tungsten probe tip to form a tungsten probe tip of Pt nanosphere (fig. 4 (a) - (b));

4) Moving the sample stage, repeating the steps (1) - (3) above for other Pt nanopillars, and making the following changes for the tungsten tip and the input end of the Pt substrate: changing the polarity of the tungsten tip or turning on the voltage source, we found that tungsten tips with Pt nanostructures welded at the tip could be made.

It is noted that the phenomenon of melting of the middle part of the Pt nano-pillar sometimes occurs, so that the tungsten tip-Pt nano-pillar-Pt nano-sphere structure (fig. 5 (a)); more and more Pt nanostructures can be soldered at the tip of the tungsten tip (fig. 5 (b), fig. 7 (a)) using the same probe repeatedly approaching different Pt nanopillars, while leaving an array of Pt nanopillars with Pt nanospheres at the tip on the surface of the Pt substrate (fig. 7 (b)).

Example 3

The specific process steps for preparing the typical Pt-Ag nano heterojunction device are as follows:

1) Adopting the method steps of the embodiment, firstly preparing a tungsten needle tip with a Pt nano column welded at the tip;

2) Changing a Pt sample on a scanning electron microscope sample table into an Ag substrate, and connecting a tungsten needle point with a Pt nano column welded at the tip with the Ag substrate in a short circuit manner;

3) Under the condition that the scanning electron beam of the scanning electron microscope is started, the nanometer manipulator is driven to move in situ, so that the tungsten needle point is close to and contacts with one Ag nanometer column on the Ag substrate;

4) Disconnecting the short circuit connection between the tungsten needle point and the Ag substrate, applying small voltage between the tungsten needle point and the Ag substrate, and continuously increasing the input voltage value until welding between the Pt nano-pillar and the Ag nano-pillar;

5) The tungsten tip was driven to reciprocate and move laterally so that the Ag nanorods were broken from its connection at the root of the Ag substrate to produce a tungsten tip-Pt nanorod-Ag nanorod heterojunction device (fig. 6).

Example 4

1) Fixing an Ag substrate with an Ag nano column array on the surface, which is prepared by superplastic nano die casting, on a sample stage of a scanning electron microscope, and enabling the Ag substrate to be in short-circuit connection with a tungsten needle point arranged on a nano manipulator through a wire;

2) Under the condition that the scanning electron beam of the scanning electron microscope is started, the nanometer manipulator is driven to move in situ, so that the tungsten needle point is close to and contacts with an Ag nanometer column;

3) Disconnecting the short circuit connection between the tungsten needle point and the Ag substrate, applying small voltage between the tungsten needle point and the Ag substrate, and continuously increasing the input voltage value until welding occurs between the tungsten needle point and the Ag nano-pillar;

4) Reducing the input voltage to weaken the Joule heating effect, so that the welding area is solid, driving the tungsten needle tip to move reversely, and enabling the welding area to generate necking deformation (fig. 9 (a));

5) The tungsten tip was driven to continue to move in reverse until the weld zone was necked off to produce a tungsten tip with a sharp tip and an Ag nanopillar tip (fig. 9 (b)).

Example 5

1) Driving the prepared tungsten probe with the Pt nanospheres soldered at the tip to contact the Pt nanostructure and form a liquid bridge (fig. 10 (a) and (c));

2) The fixed Pt nano structure is fixed, and the tungsten probe is driven to retract;

3) The tungsten probe was withdrawn and the tungsten probe tip and Pt nanostructure tip were changed in shape (fig. 10 (b) and (d)).

It was found experimentally that the greater the tungsten probe withdrawal speed, the sharper the shape of the nanodevices obtained at the tungsten probe tip and Pt nanostructure tip (fig. 10 (b) and 10 (d)). FIG. 10 (b) shows the case of FIG. 10 (a) at the retracting speed V ₁ Is produced under the condition of (d) in FIG. 10 (c) at the withdrawal speed V ₂ Is prepared under the condition of (1) and has V ₂ >V ₁ (the same retraction time, FIG. 10 (c) shows the probe leaving the field of view of FIG. 10 (d)).

Example 6

1) The tungsten needle tip with the Pt nanospheres welded on the needle tip is prepared (upper graph of FIG. 11);

2) Driving the prepared tungsten needle tip to approach and contact the Pt substrate, and adjusting the potential difference between the tungsten needle tip and the Pt substrate to enable a Pt liquid bridge to be formed between the tungsten needle tip and the Pt substrate (lower diagram of FIG. 11);

3) Maintaining a constant input voltage, driving the tungsten probe to move in a telescopic manner to change the size of the Pt liquid bridge, and once the size of the Pt liquid bridge is changed, correspondingly mutating the monitored current (FIG. 12 (a));

4) Loop resistance and corresponding Pt liquid bridge size were measured (experimental data points in fig. 12 (b));

5) Based on formulas (5) and (6), experimental data were fitted to obtain the resistivity of the Pt liquid bridge.

For this example, the resistivity of the Pt liquid was measured to be 1.3 times its solid resistivity at room temperature.

The above examples schematically illustrate that the methods and principles of the present invention can be used generally to tailor various metal nanostructures and assemble into various nano-devices, as well as to electrically characterize the nano-devices produced in situ. These nano-devices include, but are not limited to, nanotip probes, nanosphere probes, nanopillar probes, and nano-heterojunctions.

The present invention is not limited to the above-mentioned embodiments, but any modifications, equivalents, improvements and modifications within the scope of the invention will be apparent to those skilled in the art.

Claims

1. A method for cutting and assembling a metal nano structure into a nano device is characterized in that,

the method is completed in situ under a scanning electron microscope, and the cutting of the shape of the metal nano structure is realized under the irradiation of incident electrons, and comprises the following steps:

(1) The conductive probe is connected with the metal nanostructure through a wire in a short circuit manner, and the conductive probe is controlled to be close to and contact with the metal nanostructure; the accelerating voltage of the scanning electron microscope is more than or equal to 1 kiloelectron volt;

(3) Moving the conductive probe to be close to the metal nanostructure, so that the metal nanostructure is locally melted and partially transferred and attached to the tip of the conductive probe, forming a nano device with the tip attached with the metal nanostructure, and forming a metal nanostructure of a nanosphere at the tip of the metal nanostructure; the conductive probe is moved to be in the range of 0.1nm to 1000nm adjacent to the metal nanostructure.

2. The method of tailoring and assembling metallic nanostructures into a nanodevice of claim 1, wherein: the conductive probe comprises W, ag and Au.

3. The method of tailoring and assembling metallic nanostructures into a nanodevice of claim 1, wherein: the shape of the metal nanostructure in step (1) comprises a rod-like, columnar, cone-like or wire-like configuration, and the material comprises a metal of Au, cu, pt, ag, in, sn, bi, pb, zn, al, pd, ti, ni, co, fe or an alloy thereof.

4. The method of tailoring and assembling metallic nanostructures into a nanodevice of claim 1, wherein: the nanodevices include nanotip probes, nanosphere probes, nanopillar probes, heterojunctions, and combinations thereof.

5. The method of tailoring and assembling metallic nanostructures into a nanodevice of claim 1, wherein: the conductive probe is moved by a driving device, and the shape of the nano device is modulated by controlling the moving speed of the driving device in the step (2).

6. The method of tailoring and assembling metallic nanostructures into a nanodevice of claim 1, wherein: the method for cutting and assembling the metal nano structure into the nano device can be repeatedly implemented, namely, the prepared nano device is used as a new conductive probe, and the steps of the method for cutting and assembling the metal nano structure into the nano device are repeated to form the nano device with the metal nano structure attached to the tip of the nano device again.

7. The method of tailoring and assembling metallic nanostructures into nanodevices of claim 1, wherein: the potential difference U applied between the conductive probe and the metal nano structure after the conductive probe is contacted with or in the approaching process is in the range of 0-100 volts.

8. A method of in situ characterization of a nanodevice prepared by the method of tailoring and assembling metallic nanostructures into a nanodevice of claim 1, comprising the steps of: