CN113683083B

CN113683083B - Method for high-cleanliness lossless transfer of graphene nanoribbons

Info

Publication number: CN113683083B
Application number: CN202111105455.6A
Authority: CN
Inventors: 蔡金明; 陈其赞; 林泽斯
Original assignee: Guangdong Morion Nanotech Co Ltd
Current assignee: Guangdong Morion Nanotech Co Ltd
Priority date: 2021-09-22
Filing date: 2021-09-22
Publication date: 2022-04-15
Anticipated expiration: 2041-09-22
Also published as: WO2023045453A1; CN113683083A

Abstract

The invention provides a high-cleanness lossless transfer method of graphene nanoribbons, which comprises the steps of growing an Au (111) layer with a certain thickness on a Mica substrate to obtain an Au (111)/Mica growth substrate; growing a full monolayer of N =7GNR on an Au (111) surface by using a CVD (chemical vapor deposition) growth process to obtain an N =7GNR/Au (111)/Mica sample, lightly scratching the periphery of the Au (111) plating surface of the N =7GNR/Au (111)/Mica sample on which the graphene nanoribbon is grown by using a thin blade to destroy the integrity of the amorphous carbon film layer on the surface layer, and then lightly brushing a potassium iodide iodine solution with a certain concentration and weak etching capacity by using a soft brush for several times to enable the amorphous carbon film layer on the surface to fall off, and simultaneously exposing the N =7GNR/Au (111) layer to facilitate the separation of a subsequent Mica substrate from the Au (111) plating layer. In the transfer process, no new impurity or new defect is introduced, and the rapid transfer of the graphene nanoribbon is realized by purposefully removing the amorphous carbon layer.

Description

Method for high-cleanliness lossless transfer of graphene nanoribbons

Technical Field

The invention relates to the field of graphene nanoribbon transfer, in particular to a high-cleanness lossless transfer method of graphene nanoribbons.

Background

Semiconductor devices are important basic electronic components for integrated circuit and chip manufacture, and with the rapid development of high integration and microscale of electronic components, the nanoscale of electronic components is bound to be more challenging. Currently, the most advanced semiconductor lithography process has reached 7nm, 5nm, and even 1nm in the laboratory. Although the length of the silicon material gate conventionally used for manufacturing semiconductor devices is more than or equal to 5nm, which is quite ideal, when the length of the silicon material gate is less than 5nm, a more obvious "tunnel effect" appears along with the shortening of the gate length, which hinders the source current from flowing to the drain, and causes the semiconductor devices to fail. This "Mole Effect" arising from the physical limitations of silicon materials will greatly restrict the development of highly integrated technologies. Research for finding an atomic-scale ultra-thin semiconductor material is receiving much attention and research from researchers.

Since the graphene is prepared by Novoselov and Geim through a mechanical stripping method in 2004, the excellent electrical, thermal and optical properties of the graphene are widely concerned by scientific research circles. Graphene is a novel two-dimensional material with a cellular crystal structure composed of carbon atoms, and the honeycomb thereof2S and 2P of carbon atoms in the plane of a very stable six-membered ring consisting of a crystal structure_xAnd 2P_yHybridization to form sp²Track, 2P in vertical direction_zThe tracks form pi-pi bonds vertical to the plane of the six-membered ring, namely, the graphene and the graphene layer are combined in the form of pi-pi bonds of van der waals interaction, and the single-layer and stable single-layer thickness graphene can be obtained by mechanical, chemical and other methods. At present, high-quality single-layer graphene can be obtained by a CVD (chemical vapor deposition) preparation method, and the ultra-thin two-dimensional nano material with the single atom thickness is a very ideal nanoscale electronic component material. However, graphene is a zero band gap two-dimensional nanomaterial, i.e., it is not a semiconductor material and cannot be directly used for preparing nano electronic devices. Fortunately, a method for opening the energy level band gap of the graphene is successfully found through the diligent efforts of researchers, the growth width of the graphene is controlled to obtain the graphene nanoribbon, the method is a mature method for opening the energy level band gap of the graphene at present, and the graphene nanoribbon with the opened energy level band gap is an ultrathin nanoscale semiconductor material with the thickness of a single atom and is expected to become a pioneer in the era of carbon-based semiconductor electronic components.

The graphene nanoribbons are classified into armchair type graphene nanoribbons (AGNR) with relatively flat edges and zigzag type graphene nanoribbons (ZGNR) with relatively rough edges according to the difference of long-edge structures. The energy level band gap width delta of the armchair-type graphene nanoribbon and the width (atomic number) of the graphene nanoribbon follow the 3P relationship: Δ 3P +1 >. DELTA.3P +2 > 0, where P is a positive integer. And the energy level band gap width of the zigzag graphene nanoribbon is reduced as the width of the graphene nanoribbon is increased. At present, the preparation process of the graphene nanoribbon is relatively mature, and the graphene nanoribbon with atomic-scale width can grow on the Au (111) surface by a CVD method. According to a specific growth mechanism, the growth direction of graphene is controlled by utilizing a highly-crystallized Au (111) surface, and the transverse growth of a graphene nanoribbon is inhibited, so that the graphene nanoribbon with the controllable width at the atomic level is grown. The preparation of the adjustable band gap practice nanoribbon with the atomic-scale width accurate control can enable the graphene nanoribbon to be expected to be applied to the field of nano-electronics and photoelectricity, and breaks the physical limit of silicon materials.

However, the graphene nanoribbon is different from the traditional graphene preparation method. In the traditional graphene growth, a copper foil and a nickel layer are usually used for growing large-area single-layer graphene by an auxiliary CVD method, a high molecular polymer is usually used as a support film for transfer, and the transfer of the graphene is realized through steps of etching, photoresist removal and the like. The width of the graphene nanoribbon is atomic, which is different from that of the graphene thin film, and the width (number of atoms) of the graphene nanoribbon directly affects the energy level band gap of the graphene nanoribbon. Therefore, impurities and defects cannot be introduced into the graphene nanoribbons in the transfer process, and the transferred graphene nanoribbons are arranged neatly and are not agglomerated or peeled off. This makes the transfer work of the graphene nanoribbon more complicated, and it is more difficult to obtain an ultra-clean high-quality graphene nanoribbon. The transfer process of ultra-clean lossless transfer of graphene nano cannot overcome the defect that a graphene nano belt is difficult to apply to a nano electronic component, and the dream of ultra-integration of a process less than 5nm by breaking the Moore's law of the physical limit of a silicon material cannot be realized. The process technology for transferring the graphene nanoribbon in a high-cleanness and lossless manner is particularly important, and is a key bridge for realizing production and application of the graphene nanoribbon.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention firstly aims to provide a high-cleanness lossless transfer method of graphene nanoribbons.

The invention further aims to provide application of the high-cleanness lossless transfer graphene nanoribbon.

The purpose of the invention is realized by the following technical scheme:

the invention provides a high-cleanness lossless transfer graphene nanoribbon processing technology which mainly comprises the following steps: preparing GNR/Au (111)/Mica, removing the surface amorphous carbon layer by-product, removing the Mica base, transferring to the supporting substrate, removing the Au (111) layer, and the like, and a multi-step washing process is also included in the steps. The process for preparing the high-cleanness lossless transfer graphene nanoribbon is simple and general as follows: firstly, growing an Au (111) layer with a certain thickness on a Mica substrate to obtain an Au (111)/Mica growth substrate; using a CVD growth process to grow a full monolayer of N =7GNR on the Au (111) plane, where N =7 means that the graphene nanoribbon width is 7 atoms wide, a N =7GNR/Au (111)/Mica sample is obtained. Due to the fact that a by-product of an amorphous carbon layer usually exists on the surface of a sample in the growing process, the amorphous carbon layer exists in a five-membered ring or six-membered ring graphene-like form, and exists in a van der Waals interaction form with a lower graphene nanoribbon layer, the coverage area of the amorphous carbon layer is usually larger than that of an Au (111) surface, and the difficulty is brought to the subsequent work of obtaining ultra-clean high-quality graphene nanoribbon transfer. The integrity of the surface amorphous carbon film layer was destroyed using a thin blade to scratch around the Au (111) coated face of the N =7GNR/Au (111)/Mica sample grown with graphene nanoribbons. And then, slightly brushing a potassium iodide iodine solution with a certain concentration and weak etching capacity by using a soft brush for several times to enable the surface amorphous carbon film layer to fall off, and simultaneously exposing the N =7GNR/Au (111) layer to facilitate the separation of the subsequent Mica substrate and the Au (111) plating layer. After being gently washed with deionized water and dried, the sample was placed in concentrated hydrochloric acid solution and the Au (111) plating was separated from the Mica substrate by molecular intercalation to obtain a N =7GNR/Au (111) sample. After replacing the concentrated hydrochloric acid solution with deionized water, a clean silicon wafer (supporting substrate) was used for fishing out, and a N =7GNR/Au (111)/Si substrate sample was obtained. After the solution is fished out, a deionized N =7GNR/Au (111) film layer is soaked in a dropwise manner, then a small amount of absolute ethyl alcohol is added by using a syringe, and the N =7GNR/Au (111) film layer is flatly spread on a Si substrate by the characteristic that ethanol molecules are rapidly dispersed in water and is dried by using a heating platform. An iodine solution of potassium iodide with a certain concentration is prepared to be dripped on the sample, and the Au (111) layer is slowly etched and removed. And finally, repeatedly washing the sample by using deionized water and absolute ethyl alcohol and then drying the washed sample to obtain the high-cleanness lossless transferred graphene nanoribbon sample.

Compared with the prior art, the invention has the following beneficial effects:

1. the invention provides a method for transferring a graphene nanoribbon in an ultra-high clean and lossless manner.

2. According to the method for high-cleanliness lossless transfer of the graphene nanoribbon, provided by the invention, a high polymer material is not used as a support film for assisting transfer, and the graphene nanoribbon is free of impurities and defects in the transfer process.

3. The invention provides a high-cleanness lossless transfer method of graphene nanoribbons, which realizes the rapid separation of N =7GNR/Au (111) and a Mica substrate by using concentrated hydrochloric acid intercalation.

4. According to the method for highly-clean lossless transfer of the graphene nanoribbon, provided by the invention, the N =7GNR/Au (111) film layer is tiled on the load substrate by utilizing the characteristics of deionized infiltration and rapid diffusion of ethanol molecules in water, so that the graphene nanoribbon is prevented from being stacked due to wrinkles.

5. According to the method for high-cleanliness lossless transfer of the graphene nanoribbon, provided by the invention, the Au (111) coating is etched by using the potassium iodide solution with relatively weak etching performance, so that the graphene nanoribbon on the Au (111) surface is prevented from being stripped from the load substrate by virtue of gentle etching, and meanwhile, the graphene nanoribbon is prevented from being agglomerated in the etching process.

6. The high-cleanness lossless transfer method of the graphene nanoribbon can be carried out at room temperature, the process is simple, and special environment protection is not needed.

7. The method for transferring the graphene nanoribbons with high cleanliness and no damage can obtain the graphene nanoribbons with high cleanliness, no damage, high quality, no stacking and smooth sequencing, and has a vital effect on the subsequent preparation of electronic devices.

8. The method for high-cleanness lossless transfer of the graphene nanoribbon provided by the invention provides an important reference for high-cleanness lossless transfer research of other two-dimensional nanomaterials.

Drawings

Fig. 1 is a process flow diagram of a high-cleanliness lossless transfer method of graphene nanoribbons according to the present invention.

Fig. 2 is a Raman characterization map of a graphene nanoribbon sample obtained after transfer in example 1 of the present invention.

Detailed Description

The following examples are presented to further illustrate the present invention and should not be construed as limiting the invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art. Reagents, methods and apparatus used in the present invention are conventional in the art unless otherwise indicated.

The following are specific examples:

example 1

The invention provides a high-cleanness lossless transfer method of graphene nanoribbons, which comprises the following specific steps:

(1) ultrasonically cleaning a Mica substrate for 20min by using acetone, absolute ethyl alcohol and deionized water in sequence, wherein the aim is to remove organic impurities and dust on the surface of Mica;

(2) and transferring the cleaned Mica substrate to a plasma-assisted magnetron sputtering instrument, replacing a pure gold target, and growing an Au (111) layer with the thickness of 30nm on the Mica substrate to obtain an Au (111)/Mica growth substrate.

(3) The Au (111)/Mica sample obtained in step (2) was cleaned with absolute ethanol to remove surface impurities, transferred to a plasma-assisted CVD furnace, and a full monolayer of N =7GNR was grown on the Au (111) plane using ethylene as the growth source gas, where N =7 indicates that the graphene nanoribbon width was 7 atomic wide, yielding an N =7GNR/Au (111)/Mica sample.

(4) A layer of graphene-like amorphous carbon film with a five-membered ring structure and a six-membered ring structure is arranged on the surface of a sample in the growth process. In order to remove the amorphous carbon film layer on the outermost surface to obtain a clean graphene nanoribbon sample, the Au (111) plating layer is exposed, and the Au (111) plating layer and the Mica substrate are conveniently separated subsequently. Here, a thin blade was used to scratch around the Au (111) coated face of the N =7GNR/Au (111)/Mica sample grown with graphene nanoribbons, destroying the integrity of the surface amorphous carbon film layer. Then, a potassium iodide iodine solution with the concentration of 0.01-0.5M and weak etching capacity is taken by a soft brush for light brushing for several times, and the solution is washed twice by deionized water and then placed on a heating platform to complete drying at the temperature of 60 ℃. The purpose is to remove the amorphous carbon film layer on the outermost surface of the sample.

(5) The sample obtained in step (4) was gently placed in a concentrated hydrochloric acid solution using ceramic tweezers, when N =7GNR/Au (111)/Mica floated on the surface of the solution. A small drop of concentrated hydrochloric acid solution was dropped using a dropper on the Au (111) plating and the edge of the Mica substrate, and then covered with a glass petri dish. Since concentrated hydrochloric acid has strong volatility, hydrochloric acid vapor inside the glass culture dish quickly reaches saturation, slowly permeates and is intercalated between the Au (111) plating layer and the Mica substrate from the edge of the Au (111) plating layer and the Mica substrate slowly, and the Au (111) plating layer is completely separated from the Mica substrate after 1h, so that a sample of N =7GNR/Au (111) is obtained.

(6) And ultrasonically cleaning the cut Si sheet for 10min by using acetone, ethylene glycol and deionized water in sequence, wherein the aim is to remove organic impurities and dust on the surface of the Si sheet, and then placing the cleaned Si sheet on a heating platform (60 ℃) for drying to obtain a clean substrate for loading.

(7) The concentrated hydrochloric acid was displaced with deionized water until the solution PH = 7. And (4) fishing the N =7GNR/Au (111) film layer by using the clean silicon wafer (load substrate) prepared in the step (6) to obtain an N =7GNR/Au (111)/Si substrate sample.

(8) And (3) dripping two drops of deionized water on the N =7GNR/Au (111)/Si substrate sample obtained in the step (7) to soak the N =7GNR/Au (111) film layer, and then dripping a trace amount (-5 mu l) of absolute ethyl alcohol at the edge of the deionized water by using a liquid-transferring gun. An N =7GNR/Au (111) film layer is evenly spread on a Si substrate by utilizing the characteristic of ethanol molecules which are rapidly dispersed in water, and is dried under the condition of 100 ℃ by using a heating platform. The purpose of this step is to avoid the N =7GNR/Au (111) film layer from wrinkling, which leads to the phenomenon that the transferred graphene nanoribbons are stacked, and to obtain a N =7GNR/Au (111)/Si substrate sample which is flatly attached to the Si load substrate.

(9) A1M iodine solution of potassium iodide is dripped on the surface of a sample, and the Au (111) layer is slowly etched and separated by the iodine solution of potassium iodide. And after about 20min, completely etching the Au (111) plating layer, sucking the etching solution by using the corners of the dust-free paper, repeatedly washing the Au (111) plating layer by using deionized water and absolute ethyl alcohol, and drying the Au (111) plating layer at the temperature of 60 ℃ of a heating platform to obtain the high-cleanness lossless transferred graphene nanoribbon sample.

(10) And (3) performing characterization test on the sample obtained in the step (9) by using characterization means such as SEM and Raman, wherein SEM results show that the surface of the transferred graphene nanoribbon is very clean and has no impurity, and multipoint Raman results show that the transferred thickness graphene nanoribbon is introduced without defect, which shows that the transfer technology provided by the invention realizes high-cleanness lossless transfer of the graphene nanoribbon.

Example 2

A method for high-cleanness lossless transfer of graphene nanoribbons comprises the following specific steps:

(8) And (3) dripping two drops of deionized water on the N =7GNR/Au (111)/Si substrate sample obtained in the step (7) to soak the N =7GNR/Au (111) film layer, and then dripping a trace amount (-5 mu l) of absolute ethyl alcohol at the edge of the deionized water by using a liquid-transferring gun. An N =7GNR/Au (111) film layer is evenly spread on a Si substrate by utilizing the characteristic of ethanol molecules which are rapidly dispersed in water, and is dried at 50 ℃ by using a heating platform. The purpose of this step is to avoid the N =7GNR/Au (111) film layer from wrinkling, which leads to the phenomenon that the transferred graphene nanoribbons are stacked, and to obtain a N =7GNR/Au (111)/Si substrate sample which is flatly attached to the Si load substrate.

This example differs from example 1 in that a baking temperature of 50 ℃ was used for N =7 in step (8)

The GNR/Au (111)/Si substrate sample was dried, and the other operations were the same as in example 1. The method aims to investigate whether the drying temperature influences the bonding strength of the graphene nanoribbon and the Si loading substrate. The multi-point test result of Raman shows that no characteristic peak of graphene is detected at each position. The phenomenon that the transferred graphene nanoribbon and the Si substrate have glass is illustrated under the condition, and the lower drying temperature is not beneficial to enhancing the bonding strength of the graphene nanoribbon and the load substrate.

Example 3

This example is different from example 1 in that a nitrohydrochloric acid prepared by a concentrated hydrochloric acid and a concentrated nitric acid at a volume ratio of 1:3 is used instead of the iodine solution of potassium iodide of step (9) in example 1, the solution is dropped on the surface of the sample, and the iodine solution of potassium iodide slowly etches the Au (111) layer. And completely etching the Au (111) plating layer, absorbing the etching solution by using the corners of the dust-free paper, repeatedly washing the etching solution by using deionized water and absolute ethyl alcohol, and drying the etching solution at the temperature of 60 ℃ on a heating platform to obtain the graphene nanoribbon sample. Purpose of this exampleThe method is used for verifying the influence of the etching speed of the Au (111) plating layer on the transfer quality of the graphene nanoribbon. Raman multi-point test results show that I of the transferred graphene nanoribbon_2d/I_GThe value of (a) is reduced and a blank phenomenon occurs at individual positions. This shows that the strong oxidizing nitrohydrochloric acid introduces defects to the graphene nanoribbon, and the nitrohydrochloric acid etches the Au (111) plating layer too fast, resulting in that part of the graphene nanoribbon shifts the growth position in the etching process.

Comparative group 1

This example differs from example 1 in that a support film assisted transfer step of spin-coating a PMMA solution with a mass fraction of 6% was inserted between steps (4) and (5) of example 1, and then the PMMA support film was removed using acetone after the transfer was completed. The method aims to explore the influence of auxiliary transfer of the PMMA high-molecular support film on the transfer quality of the graphene nanoribbon. The result shows that residual glue which is difficult to remove partially exists on the surface of the transferred graphene nanoribbon sample. This shows that the polymer film support assisted transfer introduces impurities, and the effect of high-cleanness transfer cannot be achieved.

Comparative group 2

This example is different from example 1 in that it does not have step (4) of example 1, and the other steps are the same as example 1. The purpose of this example is to investigate the difficulty of peeling the Au (111) plating layer from the Mica substrate during the transfer process of the sample surface amorphous carbon film. The results show that without step (4), the N =7GNR/Au (111)/Mica sample did not achieve Mica substrate separation after soaking in concentrated hydrochloric acid for 4 h. This is attributed to the fact that the surface carbon film layer formed in the growth process of the graphene nanoribbon has a larger area than the Au (111) plating layer, and the Au (111) plating layer is covered by the surface amorphous carbon layer, which prevents subsequent hydrochloric acid molecules from being immersed between the Au (111) plating layer and the Mica substrate, resulting in difficulty in separation of the Mica substrate.

Blank control group

The comparative group differs from example 1 in that the Au (111)/Mica sample without the graphene nanoribbons grown was used instead of the N =7GNR/Au (111)/Mica sample in example 1, and the other operation steps were not changed. The purpose of this comparative group was to verify the effect of the presence or absence of an amorphous carbon film on the sample surface on the speed of Mica substrate separation. The result shows that the Mica substrate separation can be realized by the Au (111)/Mica sample in concentrated hydrochloric acid solution for 15 min. This indicates that the amorphous carbon film layer on the surface of the sample is one of the major factors affecting the separation of the Mica substrate.

Claims

1. A high-cleanness lossless transfer method of graphene nanoribbons is characterized by comprising the following steps:

1) growing an Au (111) layer on the Mica substrate to obtain an Au (111)/Mica growth substrate;

2) self-assembling and growing a single-layer graphene nanoribbon on the surface of the Au (111) layer to obtain a GNR/Au (111)/Mica sample with an amorphous carbon layer growing on the surface; breaking the amorphous carbon layer to separate it from the GNR/Au (111)/Mica sample;

3) placing the GNR/Au (111)/Mica sample obtained in the step 2) in concentrated hydrochloric acid solution to obtain a GNR/Au (111) sample;

4) after the concentrated hydrochloric acid solution is replaced by deionized water, the GNR/Au (111) sample is fished by using a load substrate, and a GNR/Au (111)/load substrate sample is obtained;

5) and dropping an iodine solution of potassium iodide or nitrohydrochloric acid on the GNR/Au (111)/load substrate sample, etching and removing the Au (111) layer after soaking, and washing and drying to obtain the GNR/load substrate sample.

2. The method for highly-clean lossless transfer of graphene nanoribbons according to claim 1, wherein before the step 3, a process for removing the amorphous carbon layer is further performed, and the specific steps include: and (3) breaking the amorphous carbon layer at the periphery of the Au (111) layer of the GNR/Au (111)/Mica sample by using a sharp object, and lightly brushing the path track of the sharp object by using a potassium iodide iodine solution with the concentration of less than or equal to 0.5M to strip the amorphous carbon layer.

3. The method for high-cleanness lossless transfer of the graphene nanoribbon as claimed in claim 2, wherein: in the process step of destroying the amorphous carbon layer, a concentration of the potassium iodide-iodine solution is 0.01-0.5M.

4. The method for high-cleanness lossless transfer of the graphene nanoribbon as claimed in claim 1, wherein the method comprises the following steps: in step 3, during the intercalation treatment of concentrated hydrochloric acid, the container is kept sealed after concentrated hydrochloric acid is dripped at the position where the edge of the Au (111) is contacted with the Mica substrate.

5. The method for high-cleanness lossless transfer of the graphene nanoribbon as claimed in claim 1, wherein the method comprises the following steps: before the step 1, removing organic impurities and dust on the surface of the Mica substrate, wherein the specific steps comprise ultrasonic cleaning for 20min by using acetone, absolute ethyl alcohol and deionized water in sequence.

6. The method for high-cleanness lossless transfer of the graphene nanoribbon as claimed in claim 5, wherein: in step 1, the specific step of growing the Au (111) layer on the Mica substrate includes: and transferring the cleaned Mica substrate to a plasma-assisted magnetron sputtering instrument, replacing a pure gold target, and growing an Au (111) layer with the thickness of 30nm on the Mica substrate to obtain an Au (111)/Mica growth substrate.

7. The method for high-cleanness lossless transfer of the graphene nanoribbon as claimed in claim 1, wherein the method comprises the following steps: in step 2, the specific step of growing the graphene nanoribbon on the Au (111) layer includes: transferring the Au (111)/Mica sample obtained in the step 1 into a plasma-assisted CVD furnace, and growing graphene nanoribbons on the surface of the Au (111)/Mica sample by using ethylene as a growth source gas.

8. The method for high-cleanness lossless transfer of the graphene nanoribbon as claimed in claim 1, wherein the method comprises the following steps: and step 5, before processing, further performing tiling processing on GNR/Au (111) on the load substrate.

9. The method for high-cleanliness lossless transfer of graphene nanoribbons according to any one of claims 1 to 8, wherein: the load substrate is a silicon wafer; the graphene nanoribbons are 7 atoms wide.