JP7480943B2 - Graphene nanoribbons and their manufacturing method, graphene nanoribbon precursor, and semiconductor device - Google Patents

Description

The present invention relates to graphene nanoribbons and their manufacturing method, graphene nanoribbon precursors, and semiconductor devices.

Graphene is a two-dimensional sheet-structure material in which carbon atoms are tightly covalently bonded to each other in a honeycomb lattice pattern. It is known that when graphene is processed into ribbon-shaped graphene with a width of about nanometers, so-called graphene nanoribbons (GNRs), it has a band gap that is roughly inversely proportional to the width.

Attempts are being made to take advantage of this to process graphene using top-down techniques such as electron beam lithography to create devices such as transistors. However, to achieve the required band gap, an extremely narrow width of around 1 nm is required, which is extremely difficult to achieve reproducibly using top-down techniques.

On the other hand, a method has been reported in which a width of less than 1 nm can be achieved by surface polymerization of precursor molecules (see, for example, Non-Patent Document 1). A brominated aromatic compound is used as the precursor molecule, which is polymerized by an Ullmann reaction on a heated gold substrate. The width of the GNR can be controlled by the design of the precursor molecule. GNRs fabricated by such bottom-up methods are expected to be used in high-frequency devices, etc.

In addition, simulation results have been obtained that suggest that by forming a PN junction and fabricating, for example, a tunnel field effect transistor (tunnel FET), it is possible to achieve characteristics that exceed those of silicon MOSFETs (for example, see Non-Patent Document 2).

Nature 466, 470 (2010) IEEE Electron Device Letters 29, 1344-1346 (2008).

To fabricate electronic devices such as tunnel FETs, a heterojunction (a GNR structure that creates a band gap) of GNRs is formed. One method for controlling the electronic state of GNRs to realize a heterojunction is to modify the edges of the GNRs.

However, the method of adding a modifying group to the edge of the synthesized GNR has a problem of low yield, and when, for example, fluorine is added to the edge of the precursor, there is a problem that the fluorine atom on the edge is released during the ribbon formation process.
In addition, compounds known as graphene nanoribbon precursors have a limited band gap width that can be realized, which makes it difficult to synthesize GNRs with different suitable band gap widths for each semiconductor device.

The present invention aims to provide graphene nanoribbons suitable for semiconductor devices, a method for producing the same, a graphene nanoribbon precursor, and a semiconductor device.

In one embodiment, the graphene nanoribbons disclosed herein are represented by structural formula (1) or structural formula (2).
In the structural formulas (1) and (2), n represents an integer.

In one embodiment, the graphene nanoribbon precursor disclosed herein is represented by structural formula (3) or structural formula (4).
In the structural formulas (3) and (4), X represents iodine or bromine, and Y represents hydrogen or a halogen atom.

In one embodiment, the method for producing graphene nanoribbons disclosed herein comprises polymerizing a graphene nanoribbon precursor represented by structural formula (3) or structural formula (4).
In the structural formulas (3) and (4), X represents iodine or bromine, and Y represents hydrogen or a halogen atom.

In one embodiment, the semiconductor device disclosed herein has a graphene nanoribbon represented by structural formula (1) or structural formula (2).
In the structural formulas (1) and (2), n represents an integer.

As one aspect, it is possible to provide graphene nanoribbons suitable for semiconductor devices, a manufacturing method thereof, a graphene nanoribbon precursor, and a semiconductor device.

FIG. 1A is a diagram showing the CC dimer line in the ribbon width direction in the general formula of 7-AGNR. Figure 1B shows the results of first-principles simulations of the positions of the top of the valence band (VB top) and the bottom of the conductor band (CB bottom) for compounds with various modifying groups on the edges of 7-AGNR (both ends of the central anthracene moiety). FIG. 2 is a diagram showing a method for synthesizing a graphene nanoribbon precursor in which X=Br in structural formula (4). FIG. 3 illustrates an example of the polymerization of the disclosed graphene nanoribbon precursors. FIG. 4 is a diagram showing the ¹ H-NMR spectrum of the compound 8 obtained in Example 1. FIG. 5A is a scanning tunneling microscope (STM) image of the anthracene polymer obtained in Example 2. FIG. 5B is an enlarged view of the STM image, incorporating an STM simulation image by the Tersoff-Hamann method. FIG. 5C is a diagram showing the measurement positions of the cross-sectional profile of the STM image. FIG. 5D is a diagram showing the cross-sectional profile results at the measurement positions of the cross-sectional profiles in FIG. 5C. FIG. 6A shows an STM image of the graphene nanoribbons obtained in Example 2. FIG. 6B is a diagram showing measurement positions of the cross-sectional profile of the graphene nanoribbon in an STM image. FIG. 6C is a diagram showing the cross-sectional profile results at the measurement positions of the cross-sectional profiles in FIG. 6B. FIG. 7 is a diagram showing an example of the disclosed semiconductor device (a top-gate field effect transistor). FIG. 8 is a diagram showing an example (Schottky barrier diode) of the disclosed semiconductor device. FIG. 9 is a diagram showing an example (Schottky barrier diode) of the disclosed semiconductor device, in which a thiophene ring at the edge of the disclosed graphene nanoribbon is cleaved and bonded to a gold electrode.

There are two types of graphene nanoribbons: armchair-edged, which has an armchair-shaped edge structure at both ends along the length, and zigzag-edged, which has a zigzag-shaped edge structure at both ends along the length. Armchair-edged GNRs (AGNRs) with the armchair edges have a finite band gap due to the quantum confinement effect and edge effect, and AGNRs exhibit semiconducting properties. On the other hand, zigzag-edged GNRs (ZGNRs) with the zigzag edges exhibit magnetic and metallic properties.

An AGNR with "N" number of C-C dimer lines in the ribbon width direction is called "N-AGNR". For example, an AGNR in which an anthracene with three six-membered rings arranged in the ribbon width direction is used as a basic unit and the basic unit is condensed in the ribbon length direction is called 7-AGNR. Figure 1A shows the general formula of 7-AGNR. The bonds shown in bold in Figure 1A are the C-C dimer lines in the ribbon width direction. Of the C-C bonds that form anthracene, there are "four" C-C bonds that extend in the ribbon width direction, and there are "three" C-C bonds in the ribbon width direction that connect adjacent anthracenes, which add up to "7".

Figure 1B shows the results of first-principles simulations of the positions of the top of the valence band (VB top) and the bottom of the conductor band (CB bottom) for compounds with various modifying groups on the edges (both ends of the central anthracene portion) of the 7-AGNR shown in Figure 1A.

When combined with hydrogen termination, fluorine (F) terminated GNRs are N-type, while when a thiophene ring (thiophone) is added, for example, a P-type GNR can be obtained.

As a result of intensive research conducted by the inventors, it was found that when creating GNRs using conventional bottom-up methods, even if the edges of the precursor molecules are modified, the modification groups are removed during the ribbon formation process, and the designed GNR cannot be obtained.
In addition, the compounds known to date as precursors of graphene nanoribbons have the problem that, due to their structure, it is not possible to synthesize graphene nanoribbons with a band gap width suitable for semiconductor devices.
In contrast, the graphene nanoribbons represented by the structural formulas (1) and (2) have been found to be capable of controlling the electronic state of the GNRs by introducing thiophene rings into the edges of the 7-AGNRs, thereby enabling the production of GNRs suitable for semiconductor devices, leading to the completion of the disclosed technology.

(Graphene nanoribbons)
The disclosed graphene nanoribbons are represented by structural formula (1) or structural formula (2).
In the structural formulas (1) and (2), n represents an integer.

The graphene nanoribbon represented by the structural formula (1) or (2) has a structure in which the edges of the 7-AGNR (both ends of the central anthracene portion) are modified with thiophene rings. The structural formulas (1) and (2) are structural isomers. In the structural formula (1), the S of the thiophene rings are arranged asymmetrically with respect to the length direction of the ribbon. On the other hand, in the structural formula (2), the S of the thiophene rings are arranged symmetrically with respect to the length direction of the ribbon.

In the structural formulas (1) and (2), n represents an integer. There are no particular limitations on the size of n, so long as it is a size that allows a heterojunction to be formed when the graphene nanoribbons represented by the structural formulas (1) and (2) are made into a semiconductor device, and n can be appropriately selected depending on the purpose.

(Graphene nanoribbon precursor)
The disclosed graphene nanoribbon precursor is represented by structural formula (3) or structural formula (4).
In the structural formulas (3) and (4), X represents iodine or bromine, and Y represents hydrogen or a halogen atom.

The disclosed graphene nanoribbon precursor is preferably a graphene nanoribbon precursor represented by structural formula (5) or structural formula (6).
In the structural formulas (5) and (6), X represents iodine or bromine.

The graphene nanoribbon precursor represented by the structural formula (3) or (4) has a structure in which anthracene having thiophene rings at both ends is bonded to other anthracene at the 9th and 10th positions. The anthracenes on both sides have iodine or bromine bonded as X at the 9th or 10th position, and hydrogen or halogen atoms bonded as Y at the 1st to 8th positions. The structural formulas (3) and (4) are structural isomers. In the structural formula (3), the S of the thiophene ring is arranged asymmetrically with respect to the direction of the bond connecting the anthracenes. On the other hand, in the structural formula (4), the S of the thiophene ring is arranged symmetrically with respect to the direction of the bond connecting the anthracenes.

The graphene nanoribbon precursor represented by the structural formula (3) or (4) undergoes a polymerization reaction (polymerization) between the compounds represented by the structural formula (3) or (4) due to the elimination of X, and then aromatic ring formation occurs between the compounds represented by the structural formula (3) or (4), synthesizing GNRs.

In the structural formulas (3) and (4), X represents iodine or bromine, and Y represents hydrogen or a halogen atom. If a halogen other than iodine or bromine is used for X, the polymerization may not occur. For example, when chlorine is used, the iodine bond breaks and is eliminated at about 100°C, and the bromine bond breaks and is eliminated at just under 200°C, but chlorine requires even higher temperatures. At such temperatures, the molecules start to re-evaporate from the substrate in the bottom-up method, making it difficult to synthesize GNRs.

<Synthesis of graphene nanoribbon precursor>
A method for synthesizing a graphene nanoribbon precursor in which X=Br and Y=H in the structural formula (4) is shown in FIG.
The detailed procedure will be described in the Examples described later. First, compound 3 is obtained using 1,4-cyclohexanediol as a starting material, then compound 7 is obtained from compound 5 and compound 3, and compound 8 is obtained from compound 7 and anthracene obtained by lithiating 9,10-dibromoanthracene.

(Method for producing graphene nanoribbons)
The disclosed method for producing graphene nanoribbons involves polymerizing a graphene nanoribbon precursor represented by structural formula (3) or structural formula (4). The polymerization of the graphene nanoribbon precursor will be described with reference to FIG.
In the structural formulas (3) and (4), X represents iodine or bromine, and Y represents hydrogen or a halogen atom.

Polymerization means that GNRs are produced by a bottom-up method. Specifically, first, a catalytic metal substrate cleaned in an ultra-high vacuum is kept at about 200°C, and the GNR precursor (a) produced by the above synthesis method is vacuum-deposited. It is desirable to adjust the amount of deposition so that it is about one molecular layer. On the catalytic metal substrate, Br in the GNR precursor (a) is eliminated, and an Ullmann reaction occurs, and a polymerization reaction (polymerization) between molecules occurs, producing an anthracene polymer (b) (I in Figure 3). Furthermore, by heating the substrate at 350°C to 450°C in a vacuum, an aromatization reaction occurs, forming bonds that connect anthracenes together, and a GNR (c) with thiophene rings modified on the edges is synthesized (II in Figure 3).

The catalytic metal substrate may be, for example, a (111) surface of gold, silver, copper, etc. In addition, high index surfaces such as a (110) surface or a (788) surface may also be used. Among these, the (111) surface of gold is preferred.

(Semiconductor device)
The disclosed semiconductor device has a graphene nanoribbon represented by structural formula (1) or structural formula (2).
In the structural formulas (1) and (2), n represents an integer.
The graphene nanoribbon represented by the structural formula (1) or (2) may be the same as the graphene nanoribbon described above.

Examples of semiconductor devices having graphene nanoribbons represented by structural formula (1) or structural formula (2) include top-gate field-effect transistors (FETs) using the graphene nanoribbons as a channel, and Schottky barrier diodes having the graphene nanoribbons and electrodes on a supporting substrate.

Below, examples of the disclosed technology are described, but the disclosed technology is in no way limited to these examples.

Example 1
<Synthesis of graphene nanoribbon precursor>
A suspension of calcium hypochlorite (9.3 g, 65 mmol) in water (200 ml) was added dropwise to a solution of 1,4-cyclohexanediol (15 g, 129.0 mmol) in acetic acid (150 ml, containing a few potassium bromide crystals) at 0° C. The reaction mixture was then stirred at 0° C. for 3 hours. The reaction solution was then neutralized with an aqueous potassium carbonate solution and extracted with ethyl acetate (500 ml×6). After further drying over sodium sulfate, the organic solvent was concentrated under vacuum. The residue was purified by column chromatography (ethyl acetate/hexane=7/3), and the solution was concentrated under vacuum to obtain compound 1 (8.9 g, 60%) as a pale yellow oil.
The ¹ H-NMR data of the obtained compound 1 is shown below.
¹ H-NMR (400 MHz, CDCl ₃ ): 4.23-4.18 (m, 1H), 2.73-2.58 (m, 2H), 2.35-2.28 (m, 2H), 2.11-1.80 (m, 5H).

Concentrated sulfuric acid (6.0 ml) was added dropwise to a solution of compound 1 (5.0 g, 43.8 mmol) in methanol (100 ml) at 0° C. Molecular sieves 3A (powder, 30 g) was added to the solution at 0° C., and the reaction mixture was then stirred at room temperature for 2 days. It was then cooled to −78° C., triethylamine (120 ml) was added dropwise, and the mixture was then warmed to room temperature. The molecular sieves were removed by filtration, and the reaction mixture was concentrated in vacuum to remove the solvent. The residue was purified by column chromatography (ethyl acetate/hexane=7/3), and the solvent was concentrated in vacuum to give compound 2 (5.2 g, 75%) as a pale yellow oil.
The ¹ H-NMR data of the obtained compound 2 is shown below.
¹ H-NMR (400 MHz, DMSO-d ₆ ): 4.46 (d, J=4.0 Hz, 1H), 3.55-3.50 (m, 1H), 3.05 (s, 6H), 1.80-1.29 (m, 8H).

Pyridinium dichromate (3.5 g, 9.36 mmol) and molecular sieves 3A (powder, 5 g) were added to a solution of compound 2 (500 mg, 3.12 mmol) in dichloromethane. The reaction mixture was then stirred at room temperature overnight. After filtration through Celite, the filtrate was concentrated under vacuum. The residue was purified by column chromatography (ethyl acetate/hexane=1/1), and the solvent was concentrated under vacuum to give compound 3 (353 mg, 72%) as a colorless oil.
The ¹ H-NMR data of the obtained compound 3 is shown below.
¹ H-NMR (400 MHz, CDCl ₃ ): 3.27 (s, 6H), 2.40 (t, J=8.0 Hz, 4H), 2.04 (t, J=8.0 Hz, 4H).

To a solution of thiophene-3-carboxaldehyde (10 ml, 110 mmol) in toluene (300 mL) were added ethylene glycol (50 ml) and p-toluenesulfonic acid monohydrate (1.4 g, 8.0 mmol). The solution was stirred and refluxed for 5 hours while trapping the water generated with a Dean-Stark trap. The reaction mixture was cooled to room temperature and poured into 10% aqueous sodium bicarbonate solution (300 mL). The solution was extracted with ethyl acetate, dried over sodium sulfate, and concentrated in vacuum. The residue was purified by column chromatography (ethyl acetate/hexane=1/4), and the solution was concentrated in vacuum to give compound 4 (16.6 g, containing 5% starting material) as a yellow oil.
The ¹ H-NMR data of the obtained compound 4 is shown below.
^1H -NMR (400MHz, _CDCl3 ): 7.42 (d, J = 4.0Hz, 1H), 7.32 (t, J = 4.0Hz, 1H), 7.16 (d, J = 8.0Hz, 1H), 5.91 (s, 1H), 4.15-3.98 (m, 4H).

Under an argon atmosphere, n-butyllithium hexane solution (2.6M, 25ml, 65mmol) was added dropwise to a solution of compound 4 (9.2g, 50mmol) in tetrahydrofuran (100ml) at -78°C, and the reaction mixture was stirred at -78°C for 30 minutes. Dimethylformamide (4.9ml, 63mmol) was added dropwise to the reaction mixture at -78°C. The reaction mixture was then warmed to room temperature and stirred at room temperature overnight. Next, the mixture was quenched with water, filtered through Celite, and the residue was washed with ethyl acetate. Next, the residue was extracted with ethyl acetate, dried over sodium sulfate, and concentrated under vacuum. The residue was purified by column chromatography (ethyl acetate/hexane=1/4), and the solution was concentrated to obtain compound 5 (8.2g, 89%) as an orange oil.
The ¹ H-NMR data of the obtained compound 5 is shown below.
¹ H-NMR (400 MHz, CDCl ₃ ): 10.24 (s, 1H), 7.65 (d, J=4.0 Hz, 1H), 7.26 (d, J=4.0 Hz, 1H), 6.24 (s, 1H), 4.17-4.05 (m, 4H).

To a mixed solution of compound 5 (807 mg, 4.38 mmol) and compound 3 (346 mg, 2.19 mmol) in tetrahydrofuran (5 ml) and ethanol (15 ml), 10% aqueous potassium hydroxide solution (0.2 ml) was added. The reaction mixture was then stirred overnight at room temperature. After concentrating the organic solvent under vacuum, the crude solid was reprecipitated with dichloromethane/methanol to give compound 6 (870 mg, 81%) as yellow crystals.
The ¹ H-NMR data of the obtained compound 6 is shown below.
^1H -NMR (400MHz, _CDCl3 ): 8.27 (s, 2H), 7.48 (d, J = 8.0Hz, 2H), 7.29 (d, J = 8.0Hz, 2H), 6.12 (s, 2H), 4.20-4.04 (m, 8H), 3.23 (s, 6H), 3.18 (s, 4H).

In an argon atmosphere, indium trifluoromethanesulfonate (III) salt (143 mg, 0.25 mmol) was added to compound 6 (500 mg, 1.02 mmol) suspended in dehydrated acetone (15 ml). The reaction mixture was then refluxed overnight. After the reaction solution was cooled to room temperature, the mixture was filtered, and the obtained solid was washed with acetone and dichloromethane in that order to obtain compound 7 (193 mg, 59%) as a reddish brown solid.
The ¹ H-NMR data of the obtained compound 7 is shown below.
^1H -NMR (400MHz, _CDCl3 ): 8.92 (s, 2H), 8.84 (s, 2H), 7.79 (d, J = 5.6Hz, 2H), 7.61 (d, J = 5.6Hz, 2H).

A n-butyllithium hexane solution (1.6 M, 1.92 ml, 3 mmol) was slowly dropped at −15° C. into a dehydrated ether solution (24 ml) of 9,10-dibromoanthracene (1.0 g, 3 mmol) under an argon atmosphere. The reaction solution was then slowly heated to 0° C. and stirred for 30 minutes to obtain lithiated anthracene. Compound 7 (50 mg, 0.16 mmol) and dehydrated ether (6 ml) were added to another reaction vessel under an argon atmosphere. Next, the resulting suspension of compound 7 was slowly added to the lithiated anthracene ether solution prepared above at 0° C. After stirring at 0° C. for 2 hours, the temperature was raised to room temperature and further stirred for 12 hours. After adding methanol to quench the reaction, the residue was purified by column chromatography (ethyl acetate/hexane=1/4), and the solution was concentrated to obtain a diol form of compound 8. Then, the diol form of compound 8, sodium iodide (0.99 g, 6.6 mmol), and sodium phosphinate monohydrate (0.85 g, 8.0 mmol) were suspended in acetic acid (50 ml) and refluxed for 2 hours. After cooling to room temperature, water was added, and the resulting precipitate was filtered and washed with methanol and hexane. Finally, the target compound 8 (10 mg, 8%) was obtained as an orange solid by reprecipitation with chloroform and methanol.
The ¹ H-NMR data of the obtained compound 8 is shown below, and ^{the 1} H-NMR spectrum is shown in FIG.
^1H -NMR (600MHz, _CDCl3 ): 8.83 (d, J = 8.4Hz, 2H), 7.71 (s, 2H), 7.69-7.66 (m, 6H), 7.31-7.30 (m, 8H), 7.21 (d, J = 5.4Hz, 2H), 6.92 (d, J = 5.4Hz, 2H).

Example 2
<Production of graphene nanoribbons>
Graphene nanoribbons were synthesized by a bottom-up approach using the graphene nanoribbon precursor obtained in Example 1. In the bottom-up approach, the graphene nanoribbon precursor is vacuum-deposited onto a catalytic metal substrate in a vacuum.

First, a 5 mm x 10 mm substrate with a Au (111) evaporated film (PHASIS) on a mica substrate was prepared as a catalytic metal substrate. The substrate was introduced into a four-terminal scanning tunneling microscope (UNISOKU Co., Ltd.) and cleaned by Ar sputtering and annealing at 450°C in the attached substrate preparation chamber. The acceleration voltage of the Ar ions was 0.7 kV, and the ion current was 0.4 to 0.6 μA.

The Au(111) surface of the cleaned substrate was kept at 200°C, and the graphene nanoribbon precursor synthesized in Example 1 was vacuum-deposited. An organic deposition source (KOD-CELL, Kitano Seiki Co., Ltd.) was used for deposition, and the deposition rate was determined with a film thickness rate monitor (Inficon Co., Ltd.). It is desirable to adjust the deposition amount at this time so that it is about one molecular layer. In this Example 2, when an amount of about 3 nm was deposited as measured by the film thickness meter, it was found that it re-evaporated from the substrate, leaving about one layer.

On the Au(111) surface, Br in the graphene nanoribbon precursor is removed, causing an Ullmann reaction, which causes a molecular polymerization reaction (polymerization) to occur, producing an anthracene polymer. Furthermore, by heating the substrate at 350°C to 450°C in a vacuum, an aromatization reaction occurs, forming bonds that connect the anthracenes together, resulting in graphene nanoribbons with thiophene rings modified on the edges.

Fig. 5A shows a scanning tunneling microscope (STM) image of the anthracene polymer formed on a Au(111) surface held at 200° C. Fig. 5B shows an enlarged view of the STM image incorporating a Tersoff-Hamann simulated STM image.
It is seen from Fig. 5A that the obtained anthracene polymer has a length of more than 100 nm, and it is seen from Fig. 5B that the STM image and the simulation image are in good agreement with each other.

Next, the cross-sectional profile of the STM image was measured. The measurement was performed between A-A' shown in Figure 5C. From the cross-sectional profile results shown in Figure 5D, it was found that the obtained anthracene polymer had a height of approximately 0.4 nm.

Figure 6A shows an STM image of a graphene nanoribbon obtained by further heating the anthracene polymer to a substrate at 350°C to 450°C in a vacuum. Unlike the STM image of the anthracene polymer shown in Figure 5A, a flat ribbon shape was observed for the obtained graphene nanoribbon. For example, in the graphene nanoribbon at the center of Figure 6A, the number n in the structural formula (1) or (2) is 10.

Next, the cross-sectional profile of the STM image of the obtained graphene nanoribbon was measured. The measurement was performed between B-B' shown in Figure 6B. From the cross-sectional profile results shown in Figure 6C, it was found that the obtained graphene nanoribbon had a height of approximately 0.2 nm.

The cross-sectional profile results shown in Figures 5D and 6C show that the graphene nanoribbons are shorter in height than the anthracene polymer, which is one piece of evidence that the anthracene polymer has been transformed into graphene nanoribbons.

The obtained graphene nanoribbons were measured by X-ray photoelectron spectroscopy (XPS).
It is known that in the XPS spectrum, a characteristic peak of 2p _3/2 of S in the thiophene ring appears around 163.6 eV (Chem. Sci., 2019, 10, 5167-5175). The XPS spectrum measured in this example also had a peak at 163.6 eV, confirming that the obtained graphene nanoribbon contains a thiophene ring.

Example 3
<Top-gate field-effect transistor (FET)>
As an example, FIG. 7 shows the use of the disclosed graphene nanoribbons in a transistor channel.
7 is an example of a top-gate FET. The semiconductor device 600 includes a support substrate 610, a graphene nanoribbon 620, an electrode 630a, an electrode 630b, a gate insulating film 640, and a gate electrode 650.

Various substrates can be used as the support substrate 610, and various substrates having an inorganic or organic insulating material, for example, silicon oxide (SiO ₂ ), provided at least on the surface layer are used. Graphene nanoribbons 620 are provided on such a support substrate 610.

The graphene nanoribbon 620 is the graphene nanoribbon obtained in Examples 1 and 2. The graphene nanoribbon 620 can be provided, for example, by transferring the graphene nanoribbon obtained by the bottom-up method onto the support substrate 610.

An electrode 630a and an electrode 630b are provided on both ends of a graphene nanoribbon 620 provided on a support substrate 610. Metals such as Au, Ti, Cr, Co, Ni, Pd, Pt, Al, Cu, and Ag are used for the electrodes 630a and 630b.

A gate electrode 650 is provided on the graphene nanoribbon 620 between the electrodes 630a and 630b via a gate insulating film 640. The gate insulating film 640 is made of various insulating materials such as SiO. The gate electrode 650 is made of various conductive materials such as polysilicon and metal.

In the semiconductor device 600 used as a top-gate FET, the graphene nanoribbon 620 is used as a channel. By controlling the potential of the gate electrode 650, the on/off state of the graphene nanoribbon 620 connecting the electrodes 630a and 630b, i.e., the channel, is controlled. A high-speed FET is realized by taking advantage of the high carrier mobility of the graphene nanoribbon 620.

Example 4
<Schottky barrier diode>
As an example, the use of the disclosed graphene nanoribbons in a Schottky barrier diode is shown in FIG.
8 is an example of a Schottky barrier diode. The semiconductor device 700 includes a support substrate 710, a graphene nanoribbon 720, an electrode 730, and an electrode 740.

Various substrates can be used as the support substrate 710, and various substrates having at least a surface layer of an inorganic or organic insulating material, such as silicon oxide (SiO ₂ ) or hexagonal boron nitride (h-BN), are used. Graphene nanoribbons 720 are provided on such a support substrate 710.

An electrode 730 is provided on one end of a graphene nanoribbon 720 provided on a support substrate 710, and an electrode 740 is provided on the other end of the graphene nanoribbon 720. One electrode 730 is a gold electrode that makes an ohmic connection with the graphene nanoribbon 720. As shown in FIG. 9, the thiophene rings at the edge of the graphene nanoribbon are cleaved directly under the gold electrode and bonded to the gold electrode. Therefore, the gold electrode side can be in an ohmic connection. The other electrode 740 is a metal such as Al that makes a Schottky connection with the graphene nanoribbon 720.

In the semiconductor device 700, a graphene nanoribbon 720 is used to realize an ohmic connection with an electrode 730 at one end and a Schottky connection with an electrode 740 at the other end. This realizes a Schottky barrier diode with excellent diode characteristics.

The following notes are further disclosed:
(Appendix 1)
A graphene nanoribbon represented by structural formula (1) or structural formula (2).
In the structural formulas (1) and (2), n represents an integer.
(Appendix 2)
a first anthracene having a first thiophene ring bonded to the 2- and 3-positions and a second thiophene ring bonded to the 7- and 8-positions;
a second anthracene having a 10-position bonded to the 9-position of the first anthracene;
and a third anthracene having a 9-position bonded to the 10-position of the first anthracene.
(Appendix 3)
A graphene nanoribbon precursor according to claim 2, characterized in that it is represented by structural formula (3) or structural formula (4).
In the structural formulas (3) and (4), X represents iodine or bromine, and Y represents hydrogen or a halogen atom.
(Appendix 4)
A method for producing graphene nanoribbons, comprising polymerizing a graphene nanoribbon precursor having a first anthracene having a first thiophene ring bonded to the 2- and 3-positions and a second thiophene ring bonded to the 7- and 8-positions, a second anthracene having a 10-position bonded to the 9-position of the first anthracene, and a third anthracene having a 9-position bonded to the 10-position of the first anthracene.
(Appendix 5)
The method for producing graphene nanoribbons described in Appendix 4, wherein the graphene nanoribbon precursor is represented by structural formula (3) or structural formula (4).
In the structural formulas (3) and (4), X represents iodine or bromine, and Y represents hydrogen or a halogen atom.
(Appendix 6)
A semiconductor device comprising: a graphene nanoribbon represented by structural formula (1) or structural formula (2); and two electrodes connected to the graphene nanoribbon.
In the structural formulas (1) and (2), n represents an integer.
(Appendix 7)
The semiconductor device described in Appendix 4, wherein one of the two electrodes is in ohmic contact with the graphene nanoribbon.
(Appendix 8)
a first anthracene having a first thiophene ring bonded to the 2- and 3-positions and a second thiophene ring bonded to the 7- and 8-positions;
a second anthracene having a 10-position bonded to the 9-position of the first anthracene;
and a third anthracene having a 9-position bonded to the 10-position of the first anthracene.
(Appendix 9)
The compound according to claim 8, which is represented by structural formula (3) or structural formula (4).
In the structural formulas (3) and (4), X represents iodine or bromine, and Y represents hydrogen or a halogen atom.
(Appendix 10)
A method for manufacturing a semiconductor device, comprising the step of contacting a pair of electrodes with a graphene nanoribbon represented by structural formula (1) or structural formula (2).
In the structural formulas (1) and (2), n represents an integer.

The disclosed technology is suitable for industries related to semiconductor devices including graphene nanoribbons and manufacturing methods thereof.

600 Semiconductor device 610 Support substrate 620 Graphene nanoribbon 630a Electrode 630b Electrode 640 Gate insulating film 650 Gate electrode 700 Semiconductor device 710 Support substrate 720 Graphene nanoribbon 730 Electrode 740 Electrode

Claims (4)

A graphene nanoribbon represented by structural formula (1) or structural formula (2).
In the structural formulas (1) and (2), n represents an integer. A graphene nanoribbon precursor represented by structural formula (3) or structural formula (4).
In the structural formulas (3) and (4), X represents iodine or bromine, and Y represents hydrogen or a halogen atom. A method for producing graphene nanoribbons, comprising polymerizing a graphene nanoribbon precursor represented by structural formula (3) or structural formula (4).
In the structural formulas (3) and (4), X represents iodine or bromine, and Y represents hydrogen or a halogen atom. A semiconductor device comprising a graphene nanoribbon represented by structural formula (1) or structural formula (2).
In the structural formulas (1) and (2), n represents an integer.