Method for in-situ synthesis of graphene nanobelt on semiconductor surface

Abstract

The invention discloses a method for in-situ synthesis of graphene nanoribbons on the surface of a semiconductor. The method realizes direct surface synthesis of a monatomic layer nanostructure on semiconductor titanium dioxide. The method comprises the following steps: further annealing by adopting ion sputtering and circulating the operation to modify the surface of a semiconductor substrate, and carrying out two-step synthesis reaction of the graphene nanobelt on the modified semiconductor surface. According to the method, n-type self-doping occurs on the originally inert titanium dioxide surface through repeated argon ion sputtering and high-temperature annealing steps, then specific precursor molecule brominated dianthracene is heated and evaporated to the heated surface for reaction, and the form of the generated graphene nanobelt can be represented through a scanning tunneling microscope. According to the method, the catalytic inertia of the semiconductor surface on the nanobelt synthesis reaction can be overcome, so that the relatively long graphene nanobelt with controllable width can be directly generated on the semiconductor.

Description

Technical Field

[0001] This invention relates to the field of nanomaterials, and more specifically to a method for in-situ synthesis of graphene nanoribbons on a semiconductor surface. Background Technology

[0002] Graphene nanoribbons have broad application prospects in electronic devices, sensors, and energy storage due to their excellent electrical, mechanical, and thermal properties. However, applications of nanodevices involving graphene nanoribbons require them to be mounted on the surface of semiconductor or insulator electrodes (such as graphene nanotube field-effect transistors). In existing technologies, graphene nanodevices are typically prepared by chemical vapor deposition (CVD) on the surface of rare metals (such as gold, silver, and copper) followed by liquid-phase transfer methods. However, these methods suffer from high cost, complex processes, and low yields.

[0003] The synthesis of graphene nanoribbons on metal surfaces involves two steps. The first step is the deposition of the brominated bianthracene precursor DBBA onto the metal surface, where a debromination coupling reaction occurs to form long polyanthracene chains. The second step is further heating of the substrate, causing the generated bianthracene to undergo intramolecular cyclization and dehydrogenation to form the final product, the nanoribbons. However, the second cyclization and dehydrogenation reaction cannot occur smoothly on semiconductor surfaces using the same method. In 2013, Kolmer et al. demonstrated that due to the low catalytic activity of the semiconductor titanium oxide surface, the brominated bianthracene precursor molecules can only undergo the first step of debromination coupling and cannot undergo the second step of cyclization and dehydrogenation (Angew Chem, Int Ed52, 1030010303 (2013)), thus failing to synthesize graphene nanoribbons.

[0004] Therefore, a new method is urgently needed to improve the synthesis process of graphene nanoribbons so that they can be synthesized directly on semiconductor surfaces in situ. Summary of the Invention

[0005] To address the aforementioned problems in existing technologies, the present invention aims to provide a simple method for directly synthesizing graphene nanoribbons on the surface of a semiconductor substrate in situ through surface modification. This method involves subjecting the semiconductor substrate surface to multiple rounds of sputtering and annealing treatments to increase its electron doping level and impart catalytic activity. Then, using readily available biamethylene bromide precursors, a two-step thermal reaction is performed, successfully synthesizing graphene nanoribbons directly on the surface of titanium dioxide.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for in-situ synthesis of graphene nanoribbons on a semiconductor surface includes the following steps:

[0008] (1) The semiconductor substrate surface is modified by further annealing and recycling by ion sputtering to form a surface with specific reduced state and chemical properties;

[0009] (2) The brominated anthracene precursor DBBA is deposited on the semiconductor surface modified in step (1), and a debromination coupling reaction of graphene nanoribbons is carried out to form a polyanthracene long chain.

[0010] (3) Further heating treatment causes the generated polyanthracene long chains to undergo intramolecular cyclization and dehydrogenation reaction to complete the synthesis of graphene nanoribbons.

[0011] The semiconductor substrate is a titanium dioxide, zinc oxide, aluminum oxide, tungsten oxide, or other oxide that can be reduced self-doped oxide semiconductors through sputtering annealing.

[0012] In step (1), ion sputtering is performed using an argon ion gun with an emission current of 3.0–5.0 mA, an ionization voltage of 1.0–1.2 kV, and a sputtering time of 15–30 min.

[0013] The annealing temperature is 570–630℃, the annealing time is 25–30 min, and the number of cycles is 15–25.

[0014] In step (2), the precursor DBBA molecules are deposited onto the modified semiconductor surface by heating and evaporation. The heating and evaporation temperature is 120-130℃ and the deposition time is 2 min. The debromination coupling reaction temperature is 220-250℃ and the reaction time is 3-5 min.

[0015] Step (3) involves heating at a temperature of 350–400°C for a reaction time of 10–15 min.

[0016] All operations in this method are performed in an ultra-high vacuum environment. The vacuum degree of ion sputtering in step (1) is better than 10E-6 mbar (i.e., the vacuum pressure is less than 10E-6 mbar), and the background vacuum degree of annealing in step (1), and operations in steps (2) and (3) is better than 1.0E-9 mbar (i.e., the vacuum pressure is less than 1.0E-9 mbar).

[0017] Through the above steps, this invention enables the efficient and controllable synthesis of high-quality graphene nanoribbons. This invention offers the following beneficial effects:

[0018] This invention enables the direct synthesis of graphene nanoribbons on the surface of semiconductor oxides. Furthermore, this method can be extended to nanostructures with similar reaction processes, broadening the types and methods of in-situ synthesis on the surface of semiconductor oxides. It also provides a convenient method for constructing graphene-like nanoelectronic devices without the need for transfer. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the process for synthesizing nanoribbons on the surface of titanium oxide in Example 1 of the present invention.

[0020] Figure 2 The image shows a scanning tunneling microscope image of polyanthracene long chains and graphene nanoribbons formed on a titanium dioxide single crystal substrate in Example 1. Detailed Implementation

[0021] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. All operations in the following embodiments are performed within an ultra-high vacuum chamber. An ultra-high vacuum chamber is defined as one that can achieve a vacuum level of 1×10⁻⁸ mbar or better by using a molecular pump. "Better" means an even lower vacuum level. The vacuum chamber can be connected to various vacuum devices, including vacuum gauges, vacuum heating devices, vacuum evaporation sources, and other commercially available ultra-high vacuum equipment.

[0022] Example 1

[0023] Evaporation source degassing: 5 mg of 10,10'-dibromo-9,9'-bidianthracene (DBBA CAS: 121848-75-7) molecules were loaded into an evaporation source (thermal evaporation source ICF70, Dalian Qiwei Technology Development Co., Ltd.) installed in an ultra-high vacuum chamber. A molecular pump was used to evacuate the main vacuum chamber to a vacuum level of 1×10⁻⁸ mbar. The molecular pump remained on throughout all subsequent steps to maintain the vacuum level in the chamber. The evaporation source was switched on, and the cooling water was turned on (cooling water must be continuously supplied to the evaporation source shell during heating). The molecules inside the evaporation source were slowly heated, starting from room temperature and gradually increasing the temperature by 20 degrees Celsius at a time. After each temperature increase, it was maintained for approximately 30 minutes. The vacuum level in the chamber was observed using a vacuum gauge. Once the vacuum level returned to 1.0E-8 mbar, the next temperature increase was initiated. This process was repeated until the temperature reached 100°C and was maintained for 12 hours. Degassing was then complete, and the evaporation source and cooling water were turned off.

[0024] like Figure 1 As shown, a brand-new, clean, pale yellow titanium dioxide single crystal sample (5.0 × 10.0 × 1.0 mm) was first placed... 3The sample is placed in the transfer chamber of an ultra-high vacuum chamber. A molecular pump is used to evacuate the transfer chamber for 2 hours to achieve a vacuum level of 1×10⁻⁸ mbar. Then, the gate valve between the transfer chamber and the main chamber is opened, and a robotic arm transfers the sample from the transfer chamber to the sample slot on the displacement stage inside the main chamber. The displacement stage can be moved in three dimensions and rotated 360° within the chamber via a handwheel control outside the chamber, allowing the sample surface to be aligned with different devices (such as an argon lance or molecular evaporation source) installed in various positions within the chamber, thus enabling various sample processing operations. A heating filament is installed on the back of the sample slot to heat the single-crystal sample inside, and a K-type thermocouple is connected to the slot to read the temperature in real time. The molecular pump is used to evacuate the main vacuum chamber to achieve a vacuum level of 1×10⁻⁸ mbar, and the molecular pump remains on throughout all subsequent steps to maintain this vacuum.

[0025] Sample degassing: Turn on the heating filament to slowly heat the sample from room temperature, increasing the temperature by 50°C each time. During the heating process, a large amount of gas and water adsorbed on the sample will be released, and the vacuum level will deteriorate. Use a vacuum gauge to observe the change in the vacuum level of the vacuum chamber. After each heating, wait until the vacuum level of the vacuum chamber returns to 1×10-8 mbar before proceeding with the next heating. Repeat this operation to heat the sample to 500°C.

[0026] The sample was degassed and heated to 500℃ and maintained at this temperature for 30 minutes. Argon gas was then introduced to achieve a vacuum level of 5.0E-6 mbar in the chamber. The displacement stage was moved using a handwheel to position the titanium dioxide single crystal surface directly opposite the argon ion gun, with the gun nozzle approximately 200 mm from the crystal. The argon ion gun focus was adjusted to the crystal surface. The argon filament emission current was set to 5.0 mA and the ionization voltage to 1.0 kV. Sputtering was then initiated for 20 minutes. After sputtering, the argon gas was turned off, allowing the vacuum level to return to 1×10⁻⁸ mbar. The heating filament was then turned on, slowly heating the sample to 600℃ for annealing for 30 minutes. After annealing, the heating filament was immediately turned off, and the sample was rapidly cooled to 200℃, completing one modification treatment. This process of ion sputtering and annealing was repeated 20 times until the titanium dioxide single crystal turned blue, completing the modification treatment.

[0027] The heating filament was then turned on again to raise and maintain the modified titanium dioxide single crystal at 250°C. Simultaneously, the precursor molecules DBBA in the evaporation source were heated to 120°C to initiate evaporation. The displacement stage was moved to position the titanium dioxide single crystal surface directly opposite the evaporation source, and the front baffle of the evaporation source was opened to allow DBBA molecules to begin depositing onto the surface of the modified titanium dioxide single crystal. After evaporation for 2 minutes, the evaporation source baffle was closed, and the molecules were cooled to stop evaporation. The modified titanium dioxide single crystal substrate was then maintained at 250°C for 5 minutes to complete the first step of the DBBA molecule debromination coupling reaction, forming polyanthracene long chains, such as... Figure 2 As shown.

[0028] The titanium dioxide single-crystal substrate, after the DBBA molecule debromination coupling reaction, was heated to 370℃ and maintained for 10 min to complete the second step of the polyanthracene molecule dehydrogenation cyclization reaction, forming the final product, graphene nanoribbons. The structure of each product was confirmed using scanning tunneling microscopy, such as... Figure 2 As shown.

Claims

1. A method for in-situ synthesis of graphene nanoribbons on a semiconductor surface, characterized in that, Includes the following steps: (1) The semiconductor substrate surface is modified by further annealing and cycling by ion sputtering to form a surface with specific reduced state and chemical properties; (2) The bromo-anthracene precursor 10,10'-dibromo-9,9'-bianethracene (DBBA) was deposited on the surface of the semiconductor substrate modified in step (1), and a debromination coupling reaction of graphene nanoribbons was carried out to form a polyanthracene long chain. (3) Further heating treatment causes the generated polyanthracene long chains to undergo intramolecular cyclization and dehydrogenation reaction, thus completing the in-situ synthesis of graphene nanoribbons on the semiconductor surface.

2. The method according to claim 1, characterized in that, The semiconductor substrate is an oxide semiconductor that can be reduced and self-doped by sputtering annealing, and is selected from one or more of titanium dioxide, zinc oxide, aluminum oxide, tungsten oxide, etc.

3. The method according to claim 1, characterized in that, In step (1), ion sputtering is performed using an argon ion gun with an emission current of 3.0–5.0 mA, an ionization voltage of 1.0–1.2 kV, and a sputtering time of 15–30 min. The annealing temperature is 570–630℃, the annealing time is 25–30 min, and the number of cycles is 15–25.

4. The method according to claim 1, characterized in that, In step (2), the precursor DBBA molecules are deposited onto the modified semiconductor surface by heating and evaporation, wherein the heating and evaporation temperature is 120-130℃ and the deposition time is 2-4 min; The debromination coupling reaction is carried out at a temperature of 220–250 °C for 3–5 min.

5. The method according to claim 1, characterized in that, Step (3) involves heating at a temperature of 350–400°C for a reaction time of 10–15 min.

6. The method according to claim 1, characterized in that, The vacuum level of ion sputtering in step (1) is better than 10E-6 mbar. The annealing in step (1), steps (2) and (3) are all carried out in an ultra-high vacuum environment with a background vacuum level better than 1.0E-8 mbar.

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