A kind of ultra-large single crystal domain semiconductor graphene and preparation method thereof

Abstract

The invention belongs to the technical field of semiconductor devices, and discloses an ultra-large single-crystal domain semiconductor graphene and a preparation method thereof. The semiconductor graphene is a single layer and grows uniformly. The crystal domain width of the semiconductor graphene can reach 500 microns, the length is sub-centimeter level, and the room temperature mobility reaches at least 4500cm 2 / (V·s); it can use the carbon film-assisted method to greatly increase the platform area, and can realize the preparation of ultra-large single-crystal domain semiconductor graphene on two SiC substrates at the same time; it can also realize the preparation of ultra-large single-crystal domain semiconductor graphene by specifically arranging two SiC substrates without the assistance of carbon film; it can also use the modified crucible to prepare ultra-large single-crystal domain semiconductor graphene on a SiC substrate. It can be seen that the present invention can realize the direct growth of a single-layer single-crystal semiconductor graphene on an insulating substrate, which has ultra-large crystal domains and ultra-high room temperature high mobility, and can be used as a key material for electronic devices.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor devices, and in particular, relates to semiconductor graphene and a preparation method thereof. Background Art

[0002] Graphene is a two-dimensional material made of carbon atoms, while graphite consists of multiple layers of graphene. Single layers of graphene can be peeled off from graphite and have electronic properties similar to those of graphite. Graphene is a semimetal, neither a metal nor a semiconductor, and can be described as a semiconductor without a band gap (Wallace 1947). The electronic properties of graphene are now well understood, with high electron mobility and good electrical conductivity, making it a promising two-dimensional electronic material for a wide range of applications. However, due to the lack of a band gap, graphene cannot be used in conventional digital electronics, i.e. it cannot be switched on and off by applying an electric field, which is required for electronics in conventional semiconductors such as silicon. Although various schemes have been discovered to "modify" graphene so that it has a band gap, for example by creating narrow graphene ribbons (Han 2010) or by chemically modifying the properties of graphene (Elias 2009), these "modifications" severely degrade its electrical properties, so that so far, no effective method has been found to produce semiconducting graphene with semiconducting properties while taking into account high mobility (Schwierz 2015).

[0003] It has also been found that when silicon carbide is heated to above 1000°C in an inert atmosphere, graphene forms on its surface. This form of graphene is called epitaxial graphene (van Bommel, 1975). Van Bommel also found that when the silicon face of hexagonal polycrystalline silicon carbide is heated to above 1000°C in a vacuum, its surface becomes graphitized (van Bommel, 1975). Graphitization occurs because silicon sublimates from the surface at high temperatures and the surface is covered with carbon atoms. At high temperatures, the carbon atoms react chemically and cover the surface of the silicon carbide in the form of silicon-carbon bonds. This form of graphene is called a buffer layer. Subsequent studies have shown that due to the presence of silicon-carbon bonds, the buffer layer does not have the intrinsic electrical properties of graphene, but is an insulator (Emtsev, 2008). In subsequent studies, an optimized high-temperature annealing method, the so-called confinement-controlled sublimation method (de Heer in 2011), was used to control the sublimation of silicon from the SiC surface. The electronic structure measurements showed that the electronic structure of this buffer layer does have a semiconductor band gap (Nair in 2017), but the measurement of its electronic performance in electronic devices showed that the electron mobility was very low (Turmaud in 2018), which was due to the disorder of the binding between the buffer layer and the SiC surface. In addition, the measurements also showed that a considerable part of the buffer layer was "contaminated" by graphene, which was caused by the graphene strips "decorated" on the atomic steps of the SiC surface. Therefore, the buffer layer produced by the CCS method (Nevius in 2015) is not suitable for electronics. Due to the bunching effect on the silicon surface during the growth of the buffer layer, its morphology is stepped, that is, the alternating morphology of step-terrace-step, which will restrict the size of the crystal domain and affect its transport properties. Summary of the invention

[0004] The present invention aims to solve the related technical problems of semiconductor graphene preparation, and provides a super-large single crystal domain semiconductor graphene and a preparation method thereof, which can directly grow a single layer of single crystal semiconductor graphene on an insulating substrate. The super-large crystal domain and super-high room temperature high mobility can be used as a key material for electronic devices.

[0005] In order to solve the above technical problems, the present invention is implemented by the following technical solutions:

[0006] According to one aspect of the present invention, there is provided an ultra-large single-crystal domain semiconductor graphene, which is directly grown on the silicon surface of a silicon carbide substrate. The semiconductor graphene is a single layer and grows uniformly. The crystal domain width of the semiconductor graphene can reach 500 microns, the length is sub-centimeter level, and the room temperature mobility is at least 4500cm 2 / (V·s).

[0007] Furthermore, the semiconductor graphene has a graphene lattice structure, is partially bonded to the SiC substrate, and has a band gap.

[0008] Furthermore, the crystal domain width of the semiconductor graphene is greater than 200 microns.

[0009] Preferably, the silicon carbide substrate is 6H, 4H or 3C.

[0010] According to another aspect of the present invention, a method for preparing the above-mentioned ultra-large single-crystal domain semiconductor graphene is provided, comprising the following preparation process:

[0011] (1) taking two SiC substrates for pretreatment, and preparing a carbon film on the C surface of one of the SiC substrates after the pretreatment;

[0012] (2) stacking two SiC substrates and placing them in a crucible, with the Si surfaces of the two SiC substrates facing each other;

[0013] (3) annealing the crucible stacked with two SiC substrates under vacuum conditions to clean the SiC substrates;

[0014] (4) heating the crucible stacked with two SiC substrates in an argon atmosphere; heating the SiC substrates in an argon atmosphere to perform preliminary morphology focusing;

[0015] (5) The crucible stacked with two SiC substrates is further heated in an argon atmosphere to grow semiconductor graphene, and semiconductor graphene is obtained on both SiC substrates.

[0016] Preferably, in the pretreatment of step (1), the two SiC substrates are subjected to mechanical and chemical polishing, followed by ultrasonic cleaning and N 2 dry.

[0017] Furthermore, the carbon film in step (1) is one of photoresist, PMMA and amorphous carbon, and the carbon film is prepared by one of high temperature decomposition, physical evaporation, chemical plating and coating.

[0018] Preferably, the annealing temperature under vacuum conditions in step (3) is 900-950° C. and the time is 20-30 min;

[0019] Preferably, the temperature of heating the SiC substrate in step (4) is 1250-1300° C., and the heating time is 20-30 min.

[0020] Preferably, the further heating in step (5) is performed at a temperature of 1560°C-1700°C and for a time of 50-600 min.

[0021] According to another aspect of the present invention, a method for preparing the above-mentioned ultra-large single-crystal domain semiconductor graphene is provided, comprising the following preparation process:

[0022] (1) Take two SiC substrates for pretreatment;

[0023] (2) stacking two SiC substrates and placing them in a crucible, with the C surfaces of the two SiC substrates facing the Si surfaces;

[0024] (3) annealing the crucible stacked with two SiC substrates under vacuum conditions to clean the SiC substrates;

[0025] (4) heating the crucible stacked with two SiC substrates in an argon atmosphere; heating the SiC substrates in an argon atmosphere to perform preliminary morphology focusing;

[0026] (5) The crucible stacked with two SiC substrates is further heated in an argon atmosphere to grow semiconductor graphene, thereby obtaining semiconductor graphene on a SiC substrate.

[0027] Preferably, in the pretreatment of step (1), the two SiC substrates are subjected to mechanical and chemical polishing, followed by ultrasonic cleaning and N 2 dry.

[0028] Preferably, the annealing temperature under vacuum conditions in step (3) is 900-950° C. and the time is 20-30 min;

[0029] Preferably, the temperature of heating the SiC substrate in step (4) is 1250-1300° C., and the heating time is 20-30 min.

[0030] Preferably, the further heating in step (5) is performed at a temperature of 1560°C-1700°C and for a time of 50-600 min.

[0031] According to another aspect of the present invention, a method for preparing the above-mentioned ultra-large single-crystal domain semiconductor graphene is provided, comprising the following preparation process:

[0032] (1) Pre-treating a SiC substrate and placing it in a modified crucible, wherein the modified crucible has a structure in which the outer surface of the bottom is a plane;

[0033] (2) annealing the modified crucible stacked with two SiC substrates under vacuum conditions to clean the SiC substrates;

[0034] (3) heating the modified crucible stacked with two SiC substrates in an argon atmosphere; heating the SiC substrates in an argon atmosphere to perform preliminary morphology focusing;

[0035] (4) The modified crucible stacked with two SiC substrates is further heated in an argon atmosphere to grow semiconductor graphene, thereby obtaining semiconductor graphene on the SiC substrate.

[0036] Preferably, in the pretreatment of step (1), the two SiC substrates are subjected to mechanical and chemical polishing, followed by ultrasonic cleaning and N 2 dry.

[0037] Preferably, the annealing temperature under vacuum conditions in step (3) is 900-950° C. and the time is 20-30 min;

[0038] Preferably, the temperature of heating the SiC substrate in step (4) is 1250-1300° C., and the heating time is 20-30 min.

[0039] Preferably, the further heating in step (5) is performed at a temperature of 1560°C-1700°C and for a time of 50-600 min.

[0040] The beneficial effects of the present invention are:

[0041] The ultra-large single-crystal domain semiconductor graphene and its preparation method of the present invention are prepared directly on an insulating substrate without the need for additional means for transfer or "modification". The prepared semiconductor graphene is a single layer and grows uniformly, with an optimal crystal domain width of 500 microns and a length of sub-centimeter order, and a room temperature mobility of 4500 cm 2 / (V·s) and above, the ultra-large single-crystal domain semiconductor graphene prepared by the present invention can be used as a key material for electronic devices.

[0042] The present invention provides a new feasible path for the industrial preparation of semiconductors: first, the SiC wafer as a substrate is a variety of crystal types, including 6H, 4H and 3C, etc.; in particular, it can be based on two low-cost commercial 4H SiC substrates, which reduces the cost; second, it can realize the simultaneous preparation of semiconductor graphene on the Si surface of two SiC substrates, which increases the output; this greatly improves the utilization efficiency of SiC wafers, and further saves costs; third, the source of the required carbon film is wide, not limited to photoresist, PMMA (electron beam photoresist) and amorphous carbon, etc., including all carbon films prepared by all means such as high temperature decomposition, physical evaporation, chemical plating or coating, and the factory can flexibly formulate the required carbon film preparation plan according to its own instrument and equipment framework; fifth, after the crucible is modified, the preparation of semiconductor graphene can be carried out without the help of carbon film, which reduces one more link for industrial production and greatly saves costs. In summary, the preparation method of the present invention provides an important way for semiconductor graphene to truly embark on industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Schematic diagram of the growth of ultra-large single-crystal domain semiconductor graphene prepared by using two SiC substrates in Example 1 of the present invention;

[0044] Figure 2 is a SEM image of ultra-large single-crystal domain semiconductor graphene prepared by using a double SiC substrate in Example 1 of the present invention;

[0045] Figure 3 This is a Raman image of the ultra-large single-crystal domain semiconductor graphene prepared by using a double SiC substrate in Example 1 of the present invention;

[0046] Figure 4 This is an STS image of ultra-large single-crystal domain semiconductor graphene prepared by using two SiC substrates in Example 1 of the present invention;

[0047] Figure 5 is a mobility diagram of ultra-large single-crystal domain semiconductor graphene prepared using a double SiC substrate in Example 1 of the present invention;

[0048] Figure 6 Schematic diagram of the growth of ultra-large single-crystal domain semiconductor graphene prepared by using a single SiC substrate in Example 2 of the present invention;

[0049] Figure 7 is a SEM image of ultra-large single-crystal domain semiconductor graphene prepared using a single SiC substrate in Example 2 of the present invention;

[0050] Figure 8 This is a schematic diagram of the growth of ultra-large single-crystalline domain semiconductor graphene prepared by using a modified crucible in Example 3 of the present invention.

[0051] Fig. 9 is a SEM image of ultra-large single-crystal domain semiconductor graphene prepared by using a modified crucible in Example 3 of the present invention;

[0052] Fig.10 is a SEM image of ultra-large single-crystal domain semiconductor graphene prepared by using a double SiC substrate in Example 4 of the present invention;

[0053] Fig.11 is a mobility diagram of ultra-large single-crystal domain semiconductor graphene prepared using a double SiC substrate in Example 4 of the present invention;

[0054] Fig.12 is a SEM image of ultra-large single-crystal domain semiconductor graphene prepared by using a double SiC substrate in Example 5 of the present invention;

[0055] Fig.13 is a mobility diagram of ultra-large single-crystal domain semiconductor graphene prepared using a double SiC substrate in Example 5 of the present invention;

[0056] Fig.14 is a SEM image of ultra-large single-crystal domain semiconductor graphene prepared by using a double SiC substrate in Example 6 of the present invention;

[0057] Fig.15 is a mobility diagram of ultra-large single-crystal domain semiconductor graphene prepared using a double SiC substrate in Example 6 of the present invention;

[0058] Fig.16 is a SEM image of ultra-large single-crystal domain semiconductor graphene prepared by using a double SiC substrate in Example 7 of the present invention;

[0059] Fig.17 is a SEM image of ultra-large single-crystal domain semiconductor graphene prepared by using a double SiC substrate in Example 8 of the present invention;

[0060] Fig.18 is a SEM image of ultra-large single-crystal domain semiconductor graphene prepared by using a double SiC substrate in Example 9 of the present invention;

[0061] Fig.19 This is a SEM image of semiconductor graphene prepared using a conventional crucible in Example 10 of the present invention.

[0062] In the above figure:

[0063] 100-conventional graphite crucible, 300-modified graphite crucible, 101 / 201-SiC substrate upper sheet, 102 / 202-SiC substrate lower sheet, 301-SiC substrate, 103-carbon film, 104 / 204 / 304-gas atmosphere, 105 / 205-gas exchange hole. DETAILED DESCRIPTION

[0064] The present invention is further described in detail below through specific examples. The following examples can enable those skilled in the art to more fully understand the present invention, but do not limit the present invention in any way.

[0065] Example 1

[0066] Semiconductor graphene grows directly on the Si surface of the SiC substrate. The specific steps are as follows:

[0067] (1) Selecting two silicon carbide wafers, referred to as silicon carbide substrate A and silicon carbide substrate B, respectively; performing chemical mechanical polishing (CMP) on the silicon carbide substrate A and the silicon carbide substrate B, removing paraffin wax and thoroughly cleaning;

[0068] (2) Silicon carbide substrate A and silicon carbide substrate B were ultrasonicated in acetone, anhydrous ethanol, and deionized water for 15-30 min, and then N 2 dry;

[0069] (3) The C surface of the silicon carbide wafer A is covered with a carbon film, and the silicon carbide wafer B is not coated with a carbon film; wherein the carbon film can be prepared by high temperature decomposition, spin coating, physical evaporation and chemical plating;

[0070] (4) placing a silicon carbide wafer A coated with a carbon film and a silicon carbide wafer B not coated with a carbon film into a conventional graphite crucible; specifically, the silicon carbide wafer A at the bottom is stacked with the silicon carbide wafer B at the top, and the Si surface of the silicon carbide wafer A is opposite to the Si surface of the silicon carbide wafer B;

[0071] (5) Place the graphite crucible containing silicon carbide sheet A and silicon carbide sheet B into an induction heating furnace:

[0072] The first stage is to maintain the temperature in a vacuum environment at 900-950°C for 20-30 minutes;

[0073] The second stage is 400 sccm flowing argon, constant temperature 1250-1300°C for 20-30 min;

[0074] The third stage was 400 sccm flowing argon at 1605°C for 95 min;

[0075] (6) After furnace cooling, a sample is obtained.

[0076] Figure 1 The growth diagram of Example 1 of the present invention is shown, which includes a graphite crucible 100, which can be heated by resistance heating by passing an electric current through the crucible wall or by induction heating using radio frequency heating. The graphite crucible 100 has a gas exchange hole 105, so it can be evacuated to a high vacuum (pressure p = 10 -5 Torr) and filled with inert gas, such as Ar gas atmosphere 104, with a pressure of up to 1 bar. Two silicon carbide substrates are placed in a graphite crucible 100, the lower SiC substrate 102 is used as a source, the upper SiC substrate 101 is used as a seed, and the carbon film 103 is located at the lower part of the lower SiC substrate 102. The system is designed so that the temperature of the lower SiC substrate 102 is slightly higher than that of the upper SiC substrate 101. The graphite crucible 100 is heated in several stages from room temperature to about 1605°C.

[0077] Among them, a preferred heating mode is as follows: in the first stage, the temperature is increased from room temperature to 900-950°C in vacuum, the heating rate is 2°C per second, and the temperature is kept at 900-950°C for 20-30 minutes. The purpose of the first stage is to clean the source and seed surface. In the second stage, the pressure in the graphite crucible 100 chamber is increased to 1 Bar of argon, and the temperature is increased to 1250-1300°C at a rate of about 1°C per second, and the residence time at 1250-1300°C is 20-30 minutes. In the second stage, well-developed, atomically flat, and regularly spaced micrometer-level steps are formed on the seed layer. In the third stage, the temperature is increased to about 1605°C at a rate of 1°C per second, and the residence time at 1605°C is 95 minutes, after which the temperature is reduced to room temperature at a rate of about 1°C per second.

[0078] Figure 2 is a SEM image of the sample prepared by using a double SiC substrate in Example 1; Figure 2 It can be seen that the crystal domain width of semiconductor graphene reaches 500μm and the length reaches sub-centimeter level. Figure 3 is the Raman graph of the sample obtained in Example 1, Figure 4 is the STS diagram of the sample obtained in Example 1. Figure 3 and Figure 4 It can be seen that the sample is a single-layer semiconductor graphene in a single crystal domain, which has a graphene lattice structure, is partially bonded to the SiC substrate, and has a band gap. Figure 5 is the mobility diagram of the sample obtained in Example 1 of the present invention; Figure 5 It can be seen that the room temperature mobility of the sample obtained in Example 1 can reach 4500 cm 2 / (V·s) or above.

[0079] Example 2

[0080] Semiconductor graphene grows directly on the Si surface of the SiC substrate.

[0081] (1) Selecting two silicon carbide wafers, referred to as silicon carbide substrate A and silicon carbide substrate B, respectively; performing chemical mechanical polishing (CMP) on the silicon carbide substrate A and the silicon carbide substrate B, removing paraffin wax and thoroughly cleaning;

[0082] (2) Silicon carbide substrate A and silicon carbide substrate B were ultrasonicated in acetone, anhydrous ethanol, and deionized water for 15-30 min, and then N 2 dry;

[0083] (3) placing silicon carbide wafer A and silicon carbide wafer B into a conventional graphite crucible, specifically, the C surface of silicon carbide wafer A is opposite to the Si surface of silicon carbide wafer B;

[0084] (4) Placing the crucible stacked with the silicon carbide substrate into an induction heating furnace:

[0085] The first stage is to maintain the temperature in a vacuum environment at 900-950°C for 20-30 minutes;

[0086] The second stage is 400 sccm flowing argon, constant temperature 1250-1300°C for 20-30 min;

[0087] The third stage was 400 sccm flowing argon at 1610 °C for 105 min;

[0088] (5) After furnace cooling, a sample is obtained.

[0089] Figure 6 The growth schematic diagram of Example 2 of the present invention is shown. Example 2 is to prepare semiconductor graphene without the aid of a carbon film, and requires two silicon carbide substrates in a specific arrangement, i.e., Si faces C faces. A graphite crucible 200 is included, which can be heated by resistance heating by passing an electric current through the crucible wall or by induction heating using a radio frequency heating method. The graphite crucible 200 has a gas exchange hole 205, so it can be evacuated to a high vacuum (pressure p = 10-5Torr) and filled with an inert gas, such as an Ar gas atmosphere 204, with a pressure of up to 1 bar. Two silicon carbide wafers are placed in the graphite crucible 200, the lower SiC substrate 202 is used as a source, and the upper SiC substrate 201 is used as a seed. The graphite crucible 200 is heated in several stages during the process of heating from room temperature to about 1610°C.

[0090] Among them, a preferred heating mode is as follows: in the first stage, the temperature is increased from room temperature to 900-950°C in vacuum, the heating rate is 2°C per second, and the temperature is kept at 900-950°C for 20-30 minutes. The purpose of the first stage is to clean the source and seed surface. In the second stage, the pressure in the graphite crucible 200 chamber is increased to 1 Bar of argon, and the temperature is increased to 1250-1300°C at a rate of about 1°C per second, and the residence time at 1250-1300°C is 20-30 minutes. In the second stage, well-developed, atomically flat, and regularly spaced micrometer-level steps are formed on the seed layer. In the third stage, the temperature is increased to about 1610°C at a rate of 2°C per second, and the residence time at 1610°C is 105 minutes, after which the temperature is reduced to room temperature at a rate of about 2°C per second.

[0091] Figure 7 is a SEM image of a sample prepared using a single SiC substrate in Example 2; Figure 7 It can be seen that a large single-crystal domain monolayer semiconductor graphene with a width of over 200 μm is obtained.

[0092] Example 3

[0093] Semiconductor graphene grows directly on the Si surface of the SiC substrate. The specific steps are as follows:

[0094] (1) Select a silicon carbide wafer as a silicon carbide substrate for chemical mechanical polishing (CMP), remove the paraffin wax and clean it thoroughly;

[0095] (2) The silicon carbide substrate was ultrasonicated in acetone, anhydrous ethanol, and deionized water for 15-30 minutes, and then N 2 dry;

[0096] (3) placing the silicon carbide sheet into a modified graphite crucible, wherein the modified graphite crucible is to change the outer surface of the bottom of the crucible from a curved surface to a flat surface;

[0097] (4) Place the modified graphite crucible containing the silicon carbide substrate into an induction heating furnace:

[0098] The first stage is to maintain the temperature in a vacuum environment at 900-950°C for 20-30 minutes;

[0099] The second stage is 400 sccm flowing argon, constant temperature 1250-1300°C for 20-30 min;

[0100] The third stage was 400 sccm flowing argon at 1700 °C for 80 min;

[0101] (5) After furnace cooling, a sample is obtained.

[0102] Figure 8 The growth schematic diagram of Example 3 of the present invention is shown. The process is carried out in a modified graphite crucible 300, 304 is an Ar gas atmosphere, and the modified graphite crucible 300 is to change the outer surface of its bottom from a curved surface to a flat surface. This will cause the induced eddy current to be distributed differently in the plane than in other parts, thereby generating different temperatures. In the embodiment of the present invention, the edge of the source wafer SiC substrate 301 directly contacts the crucible wall of the graphite crucible 300, which will cause the edge temperature of the substrate to be inconsistent with the middle temperature.

[0103] Fig. 9 is a SEM image of a sample prepared using a single SiC substrate in Example 2; Fig. 9 It can be seen that a large single-crystal domain monolayer semiconductor graphene with a width of over 200 μm is obtained.

[0104] Example 4

[0105] Semiconductor graphene is directly grown on the Si surface of the SiC substrate using the preparation method of Example 1, the only difference being that the heating time of the third stage in step (5) is 50 minutes.

[0106] Fig.10is a SEM image of a sample prepared using a double SiC substrate in Example 4; Fig.10 It can be seen that the crystal domain width of semiconductor graphene exceeds 200 μm. Fig.11 is the mobility diagram of the sample prepared by using two SiC substrates in Example 4; Fig.11 It can be seen that the mobility exceeds 4500 cm 2 / (V·s).

[0107] Example 5

[0108] Semiconductor graphene is directly grown on the Si surface of the SiC substrate using the preparation method of Example 1, the only difference being that the heating temperature in the third stage in step (5) is 1580°C.

[0109] Fig.12 is a SEM image of a sample prepared using a double SiC substrate in Example 5; Fig.12 It can be seen that the crystal domain width of semiconductor graphene exceeds 200 μm. Fig.13 is the mobility diagram of the sample prepared by using two SiC substrates in Example 3; Fig.13 It can be seen that the mobility exceeds 4500 cm 2 / (V·s).

[0110] Example 6

[0111] Semiconductor graphene is directly grown on the Si surface of the SiC substrate using the preparation method of Example 1, the only difference being that the heating temperature in the third stage in step (5) is 1560°C.

[0112] Fig.14 is a SEM image of a sample prepared using a double SiC substrate in Example 6; Fig.14 It can be seen that the crystal domain width of semiconductor graphene exceeds 200 μm. Fig.15 is the mobility diagram of the sample prepared by using two SiC substrates in Example 6; Fig.15 It can be seen that the mobility exceeds 4500 cm 2 / (V·s).

[0113] Example 7

[0114] Semiconductor graphene is grown directly on the Si surface of the SiC substrate using the preparation method of Example 1, the only difference being that amorphous carbon is sputtered in step (3).

[0115] Fig.16 is a SEM image of a sample prepared using a double SiC substrate in Example 7; Fig.16 It can be seen that the crystal domain width of semiconductor graphene exceeds 200 μm.

[0116] Example 8

[0117] Semiconductor graphene is directly grown on the Si surface of the SiC substrate using the preparation method of Example 1, the only difference being that the argon gas flow rate in the second and third stages of step (5) is 50 sccm.

[0118] Fig.17 is a SEM image of a sample prepared using a double SiC substrate in Example 8; Fig.17 It can be seen that the crystal domain width of semiconductor graphene exceeds 200 μm.

[0119] Example 9

[0120] Semiconductor graphene is directly grown on the Si surface of the SiC substrate using the preparation method of Example 1, the only difference being that the argon gas flow rate in the second and third stages of step (5) is 800 sccm.

[0121] Fig.18 is a SEM image of a sample prepared using a double SiC substrate in Example 9; Fig.18 It can be seen that the crystal domain width of semiconductor graphene exceeds 200 μm.

[0122] Example 10

[0123] Semiconductor graphene is grown directly on the Si surface of the SiC substrate using the preparation method of Example 3, the only difference being that a conventional graphite crucible that has not been modified is used.

[0124] Fig.19 is a SEM image of a sample prepared using a double SiC substrate in Example 10; Fig.19 It can be seen that the crystal domain width of semiconductor graphene is only about 30 μm.

[0125] The present invention discusses in detail how to increase the crystal domain size of semiconductor graphene and apply semiconductor graphene with large crystal domain size to logic devices. Considering that the Si surface of ordinary SiC is alternately distributed between platforms and steps due to the bunching effect, the size of the single crystal is limited. The above embodiments provide three methods for preparing semiconductor graphene, which greatly expand its crystal domain area: one is to use a carbon film-assisted method to greatly increase the platform area. The carbon-containing polymer (polymer with carbon)-carbon film plays a key role in this process, and the crystal domain size of the prepared semiconductor graphene reaches 500μm and the mobility is 4500cm 2 / (V·s) or more; secondly, this method is used to realize the preparation of large single-domain semiconductor graphene on two SiC substrates at the same time, which improves the utilization rate of SiC, thereby increasing the output and becoming a key factor in improving production capacity in actual industrial production. Second, in the method without the assistance of carbon film, only two SiC substrates are required to be arranged specifically to realize the preparation of large single-domain semiconductor graphene. This method can avoid the technical difficulties in the preparation of carbon film, and the crystal domain size prepared by this method exceeds 200μm, which provides more convenient conditions for industrial application. Third, semiconductor graphene with a crystal domain size exceeding 200μm is successfully prepared on a SiC substrate using a modified crucible. Therefore, the three methods of preparing semiconductor graphene in the present invention provide different options for industrial production, and the preparation method can be flexibly selected according to the industrial situation, which provides an important technical route for the practical application of semiconductor graphene in terms of quality and technology, thereby having great potential value in breaking through technical barriers, increasing production capacity and utilization, etc.

[0126] In addition, the above embodiments do not limit the crystal type of the silicon carbide substrate, and 6H, 4H and 3C, etc. can be used. An n-type doped substrate or a semi-insulating substrate can also be used, which shows that the preparation method of the present invention has the characteristics of universality, simplicity and flexibility.

[0127] Although the preferred embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the above-mentioned specific embodiments, which are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms of specific changes without departing from the scope of protection of the present invention and the claims, all of which fall within the scope of protection of the present invention.

Claims

1. An ultra-large single-crystal domain semiconductor graphene is directly grown on the silicon surface of a silicon carbide substrate, characterized in that: The semiconductor graphene has a graphene lattice structure, is partially bonded to a SiC substrate, and has a band gap; the semiconductor graphene is a single layer and grows uniformly, the crystal domain width of the semiconductor graphene is greater than 200 microns and less than or equal to 500 microns, the length is sub-centimeter level, and the room temperature mobility is at least 4500cm 2 / (V·s).

2. The ultra-large single-crystal domain semiconductor graphene according to claim 1, characterized in that: The silicon carbide substrate is 6H, 4H or 3C.

3. A method for preparing ultra-large single-crystal domain semiconductor graphene as claimed in any one of claims 1 to 2, characterized in that: The preparation process includes the following: (1) taking two SiC substrates for pretreatment, and preparing a carbon film on the C surface of one of the SiC substrates after the pretreatment; (2) stacking two SiC substrates and placing them in a crucible, with the Si surfaces of the two SiC substrates facing each other; (3) annealing the crucible stacked with two SiC substrates at 900-950° C. for 20-30 min under vacuum conditions to clean the SiC substrates; (4) heating the crucible with two stacked SiC substrates at 1250-1300° C. for 20-30 min in an argon atmosphere; heating the SiC substrates in an argon atmosphere to perform preliminary morphology focusing; (5) The crucible stacked with two SiC substrates is further heated at 1560° C.-1700° C. in an argon atmosphere to grow semiconductor graphene for 50-600 min, thereby obtaining semiconductor graphene on both SiC substrates.

4. The ultra-large single-crystal domain semiconductor graphene according to claim 3, characterized in that: The carbon film is one of photoresist, PMMA and amorphous carbon, and the carbon film is prepared by one of high temperature decomposition, physical evaporation, chemical plating and coating.

5. A method for preparing ultra-large single-crystal domain semiconductor graphene as claimed in any one of claims 1 to 2, characterized in that: The preparation process includes the following: (1) taking two SiC substrates for pretreatment, wherein neither of the two SiC substrates is provided with a carbon film; (2) stacking two SiC substrates and placing them in a crucible, with the C surfaces of the two SiC substrates facing the Si surfaces; (3) annealing the crucible stacked with two SiC substrates at 900-950° C. for 20-30 min under vacuum conditions to clean the SiC substrates; (4) heating the crucible stacked with two SiC substrates in an argon atmosphere; heating the SiC substrates at 1250-1300° C. for 20-30 min in an argon atmosphere to perform preliminary morphology focusing; (5) The crucible stacked with two SiC substrates is further heated at 1560° C.-1700° C. in an argon atmosphere to grow semiconductor graphene for 50-600 min, thereby obtaining semiconductor graphene on a SiC substrate.

6. A method for preparing ultra-large single-crystal domain semiconductor graphene as claimed in any one of claims 1 to 2, characterized in that: The preparation process includes the following: (1) a SiC substrate is pre-treated and then placed in a modified crucible, wherein the structure of the modified crucible is that the outer surface of the bottom is changed from a curved surface to a flat surface, causing the induced eddy current to be distributed differently in the flat surface than in other parts, and the edge of the SiC substrate directly contacts the crucible wall of the modified crucible, resulting in the inconsistency between the edge temperature of the substrate and the middle temperature; (2) annealing a modified graphite crucible containing a SiC substrate at 900-950° C. for 20-30 min under vacuum conditions to clean the SiC substrate; (3) heating a modified graphite crucible containing a SiC substrate under an argon atmosphere; heating the SiC substrate at 1250-1300° C. for 20-30 min under the argon atmosphere to perform preliminary morphology focusing; (4) The modified crucible with a SiC substrate placed thereon is further heated at 1560° C.-1700° C. in an argon atmosphere to grow semiconductor graphene for 50-600 min, thereby obtaining semiconductor graphene on the SiC substrate.

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