A WTe2 electrode single molecule test chip and its preparation method

Abstract

The present invention relates to a WTe2 electrode single-molecule test chip and a preparation method thereof, comprising the following steps: performing magnetron sputtering to plate metal tungsten on the electrode pattern so that the metal tungsten covers the electrode pattern to form a metal tungsten film, washing away the photoresist, and obtaining a metal tungsten electrode corresponding to the electrode pattern; performing high-temperature thermal oxidation on the metal tungsten electrode to generate electrode-patterned tungsten oxide, adding tellurium powder, and performing high-temperature tellurization on the electrode-patterned tungsten oxide under the action of a carrier gas and a reducing gas to generate electrode-patterned 1T'-WTe2; performing cutting on the middle position to form a pointed structure to obtain a 1T'-WTe2 electrode; and suspending the pointed structure to obtain an electrode-patterned 1T'-WTe2 electrode single-molecule chip.

Description

Technical Field

[0001] The present invention relates to the field of electrode single molecule test chips, and in particular to a WTe2 electrode single molecule test chip and a preparation method thereof. Background Art

[0002] The fundamental idea of ​​molecular electronics is to connect molecules to circuits via electrodes, forming molecular junctions and characterizing their electrical properties. A molecular junction consists of three parts: electrode / molecule / electrode. Its structure shows that during charge transport in the molecular junction, charge is first injected into the molecule from one electrode and then collected by the other electrode. Both charge injection and collection occur at the molecule-electrode interface, so the interaction between the molecule and the electrode significantly affects the electrical properties of the molecular junction.

[0003] The coupling effect between the electrode and the molecule affects the relative position of the molecular frontier orbital and the electrode Fermi level, and determines the mechanism of charge transport in the molecular junction. Current research reports usually use metal materials as electrodes, such as Au, Ag, Pt, Cu and other metals. The metal electrode forms a covalent bond with the anchoring group of the molecule to achieve the construction of the molecular junction, which will lead to a strong coupling effect between the electrode and the molecule. However, the quenching effect caused by strong coupling will inhibit the expression of the intrinsic properties of the molecule, such as fluorescence, optical switching, thermoelectricity, etc. Therefore, reducing the coupling effect between the molecular electrodes will make it more likely to obtain the intrinsic properties of the molecule and realize the preparation of high-performance molecular devices.

[0004] Meanwhile, if the electrode and molecule are connected via van der Waals interactions, the coupling between them is typically weak. For example, using non-metallic electrodes such as single-walled carbon nanotubes and graphene to construct molecular junctions via van der Waals interactions can effectively reduce the coupling between molecules and electrodes. However, these molecular junctions exhibit significant contact resistance, hindering charge transport and resulting in low junction conductance.

[0005] In summary, how to balance coupling and contact resistance is a difficulty in existing technologies, and no method has yet been found in this field to make motor materials compatible with cracking technology.

[0006] The purpose of this invention is to design a WTe2 electrode single molecule test chip and its preparation method to address the above-mentioned problems in the prior art. Summary of the Invention

[0007] In response to the problems existing in the above-mentioned prior art, the present invention provides a WTe2 electrode single molecule test chip and a preparation method thereof, which can effectively solve at least one problem existing in the above-mentioned prior art.

[0008] The technical solution of the present invention is:

[0009] A method for preparing a WTe2 electrode single molecule test chip comprises the following steps:

[0010] Double-sided polished molybdenum sheet was used as the substrate, ultrasonically cleaned and then dried;

[0011] growing a silicon oxide layer on the upper surface of the molybdenum sheet by plasma enhanced chemical vapor deposition;

[0012] Spin-coating photoresist on the upper surface of the silicon oxide layer and drying the photoresist;

[0013] Performing mask photolithography and development on the photoresist, thereby developing an electrode pattern corresponding to a mask template on the photoresist, wherein the mask template includes a conductive external circuit area template arranged bilaterally symmetrically and a wire template connected between the conductive external circuit areas;

[0014] performing magnetron sputtering to plate metal tungsten on the electrode pattern so that the metal tungsten covers the electrode pattern to form a metal tungsten film, and then washing away the photoresist to obtain a metal tungsten electrode corresponding to the electrode pattern;

[0015] The metal tungsten electrode is subjected to high-temperature thermal oxidation to generate electrode-patterned tungsten oxide, tellurium powder is added, and the electrode-patterned tungsten oxide is subjected to high-temperature tellurization under the action of a carrier gas and a reducing gas to generate electrode-patterned 1T'-WTe2;

[0016] Using FIB to cut the electrode-patterned 1T'-WTe2 at the middle position corresponding to the wire template to form a pointed structure, thereby obtaining a 1T'-WTe2 electrode;

[0017] The silicon oxide layer near the tip structure is wet-etched to make the tip structure suspended in the air, thereby obtaining a 1T'-WTe2 electrode single-molecule chip with electrode patterning.

[0018] Furthermore, SiH 4 and O 2 are used as reaction gases to perform plasma enhanced chemical vapor deposition to grow a silicon oxide layer, and / or the thickness of the silicon oxide layer is 1-3 μm.

[0019] Furthermore, the photoresist is a positive photoresist;

[0020] The masking and developing of the photoresist comprises:

[0021] performing a first ultraviolet exposure on the positive photoresist according to the mask template to generate carboxylic acid by photolysis reaction;

[0022] Under high temperature, the carboxylic acid promotes a cross-linking reaction of the resin in the first UV-exposed region of the positive photoresist, so that the UV-exposed region of the positive photoresist becomes insoluble in an alkaline developer;

[0023] The mask template is removed and subjected to a second UV exposure. The area not exposed to the first UV exposure generates carboxylic acid, which is then dissolved in an alkaline developer after development to obtain a pattern identical to that of the mask template.

[0024] Furthermore, the metal tungsten electrode is subjected to high-temperature thermal oxidation to generate electrode-patterned tungsten oxide, comprising:

[0025] The metal tungsten electrode is placed in a tube furnace and subjected to high temperature thermal oxidation at 600-660 degrees Celsius.

[0026] Further, tellurium powder is added, and the electrode-patterned tungsten oxide is subjected to high-temperature tellurization under the action of a carrier gas and a reducing gas to generate electrode-patterned 1T'-WTe2, which includes:

[0027] Placing the tellurium powder and the molybdenum sheet with the electrode-patterned tungsten oxide in sequence in the tube furnace along a gas flow path;

[0028] The tellurium powder is sublimated by heating to 600-660 degrees Celsius in a tube furnace, and the tellurium is brought into contact with the electrode-patterned tungsten oxide by the carrier gas, and the reducing gas participates in the reduction reaction to generate the electrode-patterned 1T'-WTe2.

[0029] Furthermore, the carrier gas is Ar, the reducing gas is H2, and the volume ratio of Ar to H2 is 95:5.

[0030] Furthermore, the tellurium powder is tellurium powder containing molecular sieve.

[0031] Furthermore, after generating the electrode-patterned 1T'-WTe2, the following steps are performed:

[0032] Obtain a Raman spectrum of the electrode-patterned 1T'-WTe2 and / or an electron diffraction pattern of the electrode-patterned 1T'-WTe2 to determine that the product is 1T'-WTe2.

[0033] A WTe2 electrode single molecule test chip, comprising:

[0034] A substrate, wherein a silicon oxide layer is grown on the upper surface of the substrate, and a groove is formed in the middle region of the silicon oxide layer by wet etching;

[0035] The 1T'-WTe2 electrode includes a conductive external circuit area, a wire, and a pointed structure. There are two conductive external circuit areas, one on the left and one on the right, respectively, on the silicon oxide layer. The two ends of the wire respectively start from the conductive external circuit area and extend to the middle area of ​​the silicon oxide layer. The pointed structure is arranged in the middle position of the wire and is suspended in the middle area of ​​the silicon oxide layer.

[0036] Furthermore, the method for using the WTe2 electrode single molecule test chip includes:

[0037] Fixing the left and right ends of the WTe2 electrode single molecule test chip;

[0038] The WTe2 electrode single molecule test chip is bent by pushing up from just below the middle area of ​​the WTe2 electrode single molecule test chip by a stepping motor, so that the pointed structure is subjected to tension on both sides, thereby breaking and forming a nanogap;

[0039] The stepping motor is controlled to move back and forth, and the tip-to-tip structure is controlled to achieve precise changes in the size of the nano-gap and the cracking process.

[0040] Therefore, the present invention provides the following effects and / or advantages:

[0041] This application uses WTe2 as the electrode material. The advantage is that WTe2 is a typical layered TMDs material with many properties, such as unsaturated magnetoresistance, ferroelectricity, topological state, superconductivity, Weyl semimetal, etc. The natural state of WTe2 is 1T' phase, which is a semimetal with high conductivity and is suitable as an electrode material for molecular junctions. In addition, materials such as 1T'-WTe2 have dangling bonds on the surface, so no interfacial chemical bonds are introduced, thereby reducing contact resistance; on the other hand, 1T'-WTe2 can be connected to molecules through weak van der Waals interactions, so that the electrode-molecule interface is moderately coupled. Therefore, this application uses 1T'-WTe2, which is very suitable as an electrode material to construct a molecular junction.

[0042] Existing CVD methods produce tungsten telluride by reacting a precursor with vaporized tellurium at high temperature to generate gaseous tungsten telluride, which is then deposited onto a substrate surface. This method cannot produce tungsten telluride films with specific shapes. The preparation method provided in this application effectively addresses this difficulty in patterning. A patterned tungsten film is first obtained through photolithography and magnetron sputtering coating processes. Oxidation and in-situ tellurization are then performed to obtain a tungsten telluride film with the desired electrode pair shape.

[0043] This application realizes the preparation of 1T'-WTe2 electrode single-molecule test chip for the first time. 1T'-WTe2 can be prepared conveniently and quickly through a self-designed two-step reaction, and this method can be combined with micro-nano processing technology to realize chip preparation. The 1T'-WTe2 electrode single-molecule chip is connected to the molecule through van der Waals interaction, so that the molecule and the electrode form a weak coupling so as not to cause quenching effect to inhibit the expression of the intrinsic properties of the molecule. In addition, compared with other metal electrode materials, 1T'-WTe2 has a smaller work function, which is expected to reduce contact resistance and thus improve charge transport in the molecular junction.

[0044] The molecules studied in molecular electronics are typically below 5nm, and the nanogap at the center of the chip can be precisely controlled to match the length of a single organic molecule to be tested.

[0045] It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 FIG. 1 is a flow chart of one embodiment of the present invention.

[0047] Figure 2 FIG. 1 is a schematic diagram of the result obtained in step S2 of one embodiment of the present invention.

[0048] Figure 3 FIG. 1 is a schematic diagram of the result obtained in step S3 of one embodiment of the present invention.

[0049] Figure 4 FIG. 1 is a schematic diagram of the result obtained in step S4 of one embodiment of the present invention.

[0050] Figure 5 FIG. 1 is a schematic diagram of the result obtained in step S5 of one embodiment of the present invention.

[0051] Figure 6 FIG. 1 is a schematic diagram of a reaction apparatus for the tellurization process of tungsten oxide in step S6 according to one embodiment of the present invention.

[0052] Figure 7 FIG. 1 is a schematic diagram of the result obtained in step S6 of one embodiment of the present invention.

[0053] Figure 8 The actual photos obtained in step S6 include: (a) a photo of the chip after thermal oxidation; (b) a photo of the chip after tellurization reaction.

[0054] Figure 9 Schematic diagram of the 1T′-WTe2 electrode generated in step S7.

[0055] Figure 10 These are photos of the objects obtained in steps S9-S10, where (a) SEM characterization shows a schematic diagram of the tip structure after FIB processing; (b) SEM characterization shows a schematic diagram of the suspended 1T'-WTe2 electrode pair after wet etching.

[0056] Figure 11 This is a schematic diagram of a 1T'-WTe2 electrode single-molecule chip with electrode patterning obtained in step S8 of one embodiment of the present invention.

[0057] Figure 12This is an experimental data diagram of one embodiment of the present invention, wherein (a) is a Raman spectrum of the sample, and (b) is an electron diffraction pattern.

[0058] Figure 13 This is a schematic structural diagram of the WTe2 electrode single molecule test chip provided by the present invention.

[0059] Figure 14 Schematic diagram of the usage status of the WTe2 electrode single molecule test chip provided by the present invention. DETAILED DESCRIPTION

[0060] In order to facilitate understanding by those skilled in the art, the structure of the present invention is further described in detail with reference to the embodiments and the accompanying drawings:

[0061] refer to Figure 1 A method for preparing a WTe2 electrode single molecule test chip comprises the following steps:

[0062] S1, double-sided polished molybdenum sheet as substrate, ultrasonically cleaned and then dried;

[0063] In this step, a 4-inch diameter double-sided polished molybdenum sheet is used as the substrate, and after ultrasonic cleaning with acetone and ethanol, it is dried in an oven for 2 hours. Among them, the 4-inch double-sided polished molybdenum sheet has a large area, so multiple WTe2 electrodes can be prepared on the 4-inch double-sided polished molybdenum sheet at one time through subsequent steps, and then multiple WTe2 electrode single-molecule test chips can be obtained at the same time by cutting. In addition, each WTe2 electrode single-molecule test chip can contain one or more WTe2 electrodes. This is not limited here.

[0064] This embodiment is the first in the art to use a molybdenum sheet as a substrate. Molybdenum has relatively stable chemical properties. At room temperature or a not too high temperature, molybdenum is chemically stable in air or water.

[0065] S2, growing a silicon oxide layer on the upper surface of the molybdenum sheet by plasma enhanced chemical vapor deposition;

[0066] In this step, the plasma enhanced chemical vapor deposition (PECVD) method is directly adopted from the prior art. Furthermore, SiH4 and O2 are used as reaction gases to perform plasma enhanced chemical vapor deposition to grow a silicon oxide layer, and / or, the thickness of the silicon oxide layer is 1-3um. The thickness of the silicon oxide layer is selected to be 1-3um, which can provide sufficient thickness space when wet etching is performed in subsequent steps, and at the same time provide a corresponding structural basis in the subsequent use method, so as to facilitate the reciprocating motion of the motor to regulate the precise change of the gap size. In addition, the silicon oxide layer also acts as an insulating layer to play an insulating role. Because the molybdenum substrate is a metal that can conduct electricity, if there is no silicon oxide insulation, the substrate and the WTe2 electrode will be short-circuited. As shown in the following example, Figure 2The substrate on which the silicon oxide layer is grown is shown.

[0067] S3, spin coating photoresist on the upper surface of the silicon oxide layer and drying;

[0068] In this step, the steps of spin coating the photoresist and drying are conventional techniques. The drying process allows the organic solvent in the photoresist film to volatilize. Figure 3 A substrate is shown coated with a photoresist film layer.

[0069] S4, performing mask photolithography and development on the photoresist, thereby developing an electrode pattern corresponding to a mask template on the photoresist, wherein the mask template includes a conductive external circuit area template arranged bilaterally symmetrically and a wire template connected between the conductive external circuit areas;

[0070] Prior to this step, a mask template can be prepared in advance. The mask template includes a template for conductive external circuit areas arranged symmetrically on both sides, and a template for conductive lines connecting the conductive external circuit areas. The mask template can be used to generate an electrode pattern corresponding to the mask template in the subsequent preparation process.

[0071] The photoresist is subjected to mask photolithography and development, which is also directly adopted in the prior art. Figure 4 The photoresist film layer with the electrode pattern is shown.

[0072] S5, performing magnetron sputtering to coat the electrode pattern with metal tungsten to cover the electrode pattern with metal tungsten to form a metal tungsten film, and then washing away the photoresist to obtain a metal tungsten electrode corresponding to the electrode pattern;

[0073] This step is the core improvement step of this application. By magnetron sputtering tungsten, the patterning technology effect of the metal dock is achieved. Then the substrate is placed in an acetone solution for swelling and peeling (Lift-off) to obtain the same Figure 5 The electrode pattern shown corresponds to the metal tungsten electrode. If a large-sized substrate is used in step S1, a laser scribing machine can be used to scribble the molybdenum sheet according to the cutting marks to obtain multiple 10mm*30mm small unit chips.

[0074] S6, performing high-temperature thermal oxidation on the metal tungsten electrode to generate electrode-patterned tungsten oxide, adding tellurium powder, and performing high-temperature tellurization on the electrode-patterned tungsten oxide under the action of a carrier gas and a reducing gas to generate electrode-patterned 1T'-WTe2;

[0075] This step is the core improvement step of this application. This step uses a two-step method to generate 1T'-WTe2, using metallic tungsten and tellurium powder as raw materials, and adopts a two-step method to realize the preparation of 1T'-WTe2. Compared with the traditional method, the method designed in this embodiment can easily and quickly realize the specific pattern of 1T'-WTe2, which is convenient for combining with micro-nano processing technology to realize the preparation of WTe2 electrode single molecule chip.

[0076] The two-step process is as follows:

[0077] The first step is the thermal oxidation process of tungsten, which involves placing the tungsten film obtained by magnetron sputtering in a high-temperature atmosphere of a tube furnace to cause an oxidation reaction to occur to generate tungsten oxide.

[0078] The second step is the tellurization process of tungsten oxide, the device is as follows Figure 6 As shown, tellurium powder and tungsten oxide obtained in the first step are placed at the left and right ends of a porcelain boat, respectively. The porcelain boat is placed in a quartz tube and aligned with the central heat source area of ​​a tube furnace. Then, a tellurization reaction is carried out in a high-temperature atmosphere of carrier gas and reducing gas to generate 1T'-WTe2. Tellurium powder will sublime at high temperatures. The gas in this atmosphere acts as a carrier gas, carrying the vaporized tellurium to the chip surface at a certain flow rate. The reducing gas participates in the reduction reaction to generate tungsten telluride and 1T'-WTe2, as shown in FIG. Figure 7 The physical photos generated by the two-step method are shown in Figure 8 shown.

[0079] Through this two-step method, electrode patterned 1T'-WTe2 is generated in this step, realizing the preparation of 1T'-WTe2 electrodes. The independently designed two-step reaction can conveniently and quickly prepare 1T'-WTe2, and this method can be combined with micro-nano processing technology to realize chip preparation. This method can directly oxidize tungsten to tungsten oxide, and then in situ tellurization to generate tungsten telluride, and single crystal 1T'-WTe2 can also be obtained. Because tungsten telluride can be generated in situ, the tungsten film can be patterned in advance, ultimately obtaining tungsten telluride of a specific shape.

[0080] S7, using FIB to cut the electrode-patterned 1T'-WTe2 corresponding to the middle position of the wire template to form a pointed structure, thereby obtaining a 1T'-WTe2 electrode;

[0081] In this step, the small unit chip of 1T'-WTe2 is cut by FIB to obtain a bowtie structure, which is also a pointed structure. The pointed tips of the pointed structure are connected, and the following is obtained: Figure 9 The 1T'-WTe2 electrode shown. Figure 10 (a) is a photo of the object obtained in this step.

[0082] S8, wet-etching the silicon oxide layer near the pointed structure to suspend the pointed structure, thereby obtaining a 1T'-WTe2 electrode single-molecule chip with electrode patterning.

[0083] Finally, hydrofluoric acid was used for wet etching to obtain a 1T'-WTe2 electrode single molecule chip with a suspended center area, as shown in Figure 11 shown. Figure 10 (b) is a photo of the object obtained in this step.

[0084] Furthermore, the photoresist is a positive photoresist;

[0085] In this embodiment, AZ5214E ​​positive photoresist is selected, and post-bake reversal can be performed according to the characteristics of AZ5214E ​​photoresist, which is a positive photoresist.

[0086] Specifically, performing mask photolithography and development on the photoresist includes:

[0087] performing a first ultraviolet exposure on the positive photoresist according to the mask template to generate carboxylic acid by photolysis reaction;

[0088] Under high temperature, the carboxylic acid promotes a cross-linking reaction of the resin in the first UV-exposed region of the positive photoresist, so that the UV-exposed region of the positive photoresist becomes insoluble in an alkaline developer;

[0089] The mask template is removed and subjected to a second UV exposure. The area not exposed to the first UV exposure generates carboxylic acid, which is then dissolved in an alkaline developer after development to obtain a pattern identical to that of the mask template.

[0090] AZ5214 photoresist mainly consists of three parts: photosensitive component, resin and solvent.

[0091] When the mask is exposed, the photosensitive components in the exposed area are converted into carboxylic acid. After baking again, the carboxylic acid will promote the cross-linking reaction of the resin in the exposed area, making the exposed area insoluble in the alkaline developer. This step is also called gel reversal baking. After that, a flood exposure step is performed, that is, maskless exposure. The first unexposed area produces carboxylic acid, which is dissolved in the alkaline developer after development to obtain the same pattern as the mask.

[0092] Two UV exposures are required for photolithography to obtain an inverted trapezoidal morphology, which facilitates the subsequent stripping of the magnetron sputtered tungsten film. The atoms sputtered by magnetron sputtering have high kinetic energy, resulting in good adhesion between the coating and the substrate. This inverted trapezoidal morphology allows for better stripping of the desired electrode pattern.

[0093] Furthermore, the metal tungsten electrode is subjected to high-temperature thermal oxidation to generate electrode-patterned tungsten oxide, comprising:

[0094] The metal tungsten electrode is placed in a tube furnace and subjected to high temperature thermal oxidation at 600-660 degrees Celsius.

[0095] Further, tellurium powder is added, and the electrode-patterned tungsten oxide is subjected to high-temperature tellurization under the action of a carrier gas and a reducing gas to generate electrode-patterned 1T'-WTe2, which includes:

[0096] Placing the tellurium powder and the molybdenum sheet with the electrode-patterned tungsten oxide in sequence in the tube furnace along a gas flow path;

[0097] The tellurium powder is sublimated by heating to 600-660 degrees Celsius in a tube furnace, and the tellurium is brought into contact with the electrode-patterned tungsten oxide by the carrier gas, and the reducing gas participates in the reduction reaction to generate the electrode-patterned 1T'-WTe2.

[0098] Furthermore, the carrier gas is Ar, the reducing gas is H2, and the volume ratio of Ar to H2 is 95:5.

[0099] Furthermore, the tellurium powder is tellurium powder containing molecular sieve.

[0100] Tellurium powder containing molecular sieves is selected in this step because the molecular sieves can slow down the release of tellurium after sublimation, thereby controlling the desired reaction rate.

[0101] Furthermore, after generating the electrode-patterned 1T'-WTe2, the following steps are performed:

[0102] Obtain a Raman spectrum of the electrode-patterned 1T'-WTe2 and / or an electron diffraction pattern of the electrode-patterned 1T'-WTe2 to determine that the product is 1T'-WTe2.

[0103] like Figure 12 As shown in the Raman spectrum of the sample, its characteristic peaks are located at 87 cm -1 、117cm -1 , 130cm -1 、160cm -1 、208cm -1 , which completely corresponds to the Raman spectrum of 1T'-WTe2 in existing literature. The verification method of the electron diffraction pattern of the electrode pattern is similar. Through this step, it can be determined that the product of the above reaction is 1T'-WTe2.

[0104] A WTe2 electrode single molecule test chip can be obtained by the above-mentioned WTe2 electrode single molecule test chip preparation method, referring to Figure 13 ,include:

[0105] A substrate 1, wherein a silicon oxide layer 2 is grown on the upper surface of the substrate 1, and a groove 4 is formed in the middle region of the silicon oxide layer 2 by wet etching;

[0106] The 1T'-WTe2 electrode 3 includes a conductive external circuit area, a wire, and a pointed structure 301. There are two conductive external circuit areas, one on the left and one on the right, respectively, on the silicon oxide layer 2. The two ends of the wire start from the conductive external circuit area and extend to the middle area of ​​the silicon oxide layer 2. The pointed structure 301 is arranged in the middle position of the wire and is suspended in the middle area of ​​the silicon oxide layer 2.

[0107] Furthermore, the method for using the WTe2 electrode single molecule test chip includes:

[0108] refer to Figure 14 , fixing the left and right ends of the WTe2 electrode single molecule test chip;

[0109] The stepping motor 5 is used to push up the WTe2 electrode single molecule test chip from just below the middle area to bend the WTe2 electrode single molecule test chip, so that the pointed structure is subjected to tension on both sides to break and form a nanogap;

[0110] The stepping motor 5 is controlled to move back and forth, and the tip-to-tip structure is controlled to achieve precise changes in the size of the nano-gap and the cracking process.

[0111] This embodiment uses WTe2 single-molecule material. Its advantage is that WTe2 is a typical layered TMDs material with many properties, such as unsaturated magnetoresistance, ferroelectricity, topological state, superconductivity, Weyl semimetal, etc. The natural state of WTe2 is 1T' phase, which is a semimetal with high conductivity and is suitable for use as an electrode material for molecular junctions. In addition, materials such as 1T'-WTe2 have dangling bonds on their surfaces, so no interfacial chemical bonds are introduced, thereby reducing contact resistance; on the other hand, 1T'-WTe2 can be connected to molecules through weak van der Waals interactions, so that the electrode-molecule interface is moderately coupled. Therefore, the 1T'-WTe2 selected in this application can be used as an electrode material to construct a molecular junction.

[0112] Existing CVD methods produce tungsten telluride by reacting a precursor with vaporized tellurium at high temperature to generate gaseous tungsten telluride, which is then deposited onto a substrate surface. This method cannot produce tungsten telluride films with specific shapes. The preparation method provided in this application effectively addresses this difficulty in patterning. A patterned tungsten film is first obtained through photolithography and magnetron sputtering coating processes. Oxidation and in-situ tellurization are then performed to obtain a tungsten telluride film with the desired electrode pair shape.

[0113] It should be noted that in the claims, any reference signs placed between parentheses shall not be construed as limiting the claims. The word "comprising" does not exclude the presence of components or steps not listed in the claim. The word "a" or "an" preceding a component does not exclude the presence of a plurality of such components. The invention can be implemented by means of hardware comprising several different components and by means of a suitably programmed computer. In a unit claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The use of the words first, second, third etc. does not indicate any order. These words may be interpreted as names.

[0114] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0115] In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they may refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0116] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms should not be understood as necessarily referring to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

Claims

1. A method for preparing a WTe2 electrode single molecule test chip, characterized by: The following steps are involved: Double-sided polished molybdenum sheet was used as substrate, ultrasonically cleaned and then dried; growing a silicon oxide layer on the upper surface of the molybdenum sheet by plasma enhanced chemical vapor deposition; Spin-coating photoresist on the upper surface of the silicon oxide layer and drying the photoresist; Performing mask photolithography and development on the photoresist, thereby developing an electrode pattern corresponding to a mask template on the photoresist, wherein the mask template includes a conductive external circuit area template arranged bilaterally symmetrically and a wire template connected between the conductive external circuit areas; performing magnetron sputtering to plate metal tungsten on the electrode pattern so that the metal tungsten covers the electrode pattern to form a metal tungsten film, and then washing away the photoresist to obtain a metal tungsten electrode corresponding to the electrode pattern; The metal tungsten electrode is subjected to high-temperature thermal oxidation to generate electrode-patterned tungsten oxide, tellurium powder is added, and the electrode-patterned tungsten oxide is subjected to high-temperature tellurization under the action of carrier gas and reducing gas to generate electrode-patterned 1T'-WTe2; Using FIB to cut the electrode-patterned 1T'-WTe2 at the middle position corresponding to the wire template to form a pointed structure, thereby obtaining a 1T'-WTe2 electrode; The silicon oxide layer near the tip structure is wet-etched to leave the tip structure suspended, thereby obtaining a 1T'-WTe2 electrode single-molecule chip with electrode patterning; SiH4 and O2 are used as reaction gases to perform plasma enhanced chemical vapor deposition to grow a silicon oxide layer, and / or the thickness of the silicon oxide layer is 1-3 μm; The photoresist is a positive photoresist; The masking and developing of the photoresist comprises: Performing a first ultraviolet exposure on the positive photoresist according to the mask template to generate carboxylic acid through a photolysis reaction; Under high temperature, the carboxylic acid promotes a cross-linking reaction of the resin in the first UV-exposed region of the positive photoresist, so that the UV-exposed region of the positive photoresist becomes insoluble in an alkaline developer; The mask template is removed and subjected to a second UV exposure. The area not exposed to the first UV exposure produces carboxylic acid, which is dissolved in an alkaline developer after development to obtain a pattern identical to the mask template. The inverted trapezoidal morphology obtained by the two UV exposures is then subjected to photolithography.

2. The method for preparing a WTe2 electrode single molecule test chip according to claim 1, characterized in that: The metal tungsten electrode is subjected to high-temperature thermal oxidation to generate electrode-patterned tungsten oxide, which includes: The metal tungsten electrode is placed in a tube furnace and subjected to high temperature thermal oxidation at 600-660 degrees Celsius.

3. The method for preparing a WTe2 electrode single molecule test chip according to claim 2, characterized in that: Adding tellurium powder and performing high-temperature tellurization on the electrode-patterned tungsten oxide under the action of a carrier gas and a reducing gas to generate electrode-patterned 1T'-WTe2 comprises: Placing the tellurium powder and the molybdenum sheet with the electrode-patterned tungsten oxide in sequence in the tube furnace along a gas flow path; The tellurium powder is sublimated by heating to 600-660 degrees Celsius in a tube furnace, and the tellurium is brought into contact with the electrode-patterned tungsten oxide by the carrier gas, and the reducing gas participates in the reduction reaction to generate the electrode-patterned 1T'-WTe2.

4. The method for preparing a WTe2 electrode single molecule test chip according to claim 1 or 3, characterized in that: The carrier gas is Ar, the reducing gas is H2, and the volume ratio of Ar to H2 is 95:

5.

5. The method for preparing a WTe2 electrode single molecule test chip according to claim 1 or 3, characterized in that: The tellurium powder is tellurium powder containing molecular sieve.

6. The method for preparing a WTe2 electrode single molecule test chip according to claim 1, characterized in that: After generating the electrode-patterned 1T'-WTe2, perform: Obtain a Raman spectrum of the electrode-patterned 1T'-WTe2 and / or an electron diffraction pattern of the electrode-patterned 1T'-WTe2 to determine that the product is 1T'-WTe2.

7. A WTe2 electrode single molecule test chip, characterized by: include: A substrate, wherein a silicon oxide layer is grown on the upper surface of the substrate, and a groove is formed in the middle region of the silicon oxide layer by wet etching; A 1T'-WTe2 electrode, comprising a conductive external circuit region, a wire, and a pointed structure, wherein the number of the conductive external circuit regions is two, one on the left and one on the right, respectively, of the silicon oxide layer; the ends of the wire respectively start from the conductive external circuit region and extend to the middle region of the silicon oxide layer; the pointed structure is disposed in the middle of the wire and is suspended in the middle region of the silicon oxide layer; The 1T'-WTe2 electrode is obtained by the preparation method according to any one of claims 1-6.

8. A WTe2 electrode single molecule test chip according to claim 7, characterized in that: The method for using the WTe2 electrode single molecule test chip includes: Fixing the left and right ends of the WTe2 electrode single molecule test chip; The WTe2 electrode single molecule test chip is bent by pushing up from just below the middle area of ​​the WTe2 electrode single molecule test chip by a stepping motor, so that the pointed structure is subjected to tension on both sides, thereby breaking and forming a nanogap; The stepping motor is controlled to move back and forth, and the tip-to-tip structure is controlled to achieve precise changes in the size of the nano-gap and the cracking process.

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