阅读说明：本技术 一种利用金属插层大面积制备单层石墨烯的方法 (Method for preparing single-layer graphene in large area by utilizing metal intercalation ) 是由 惠欣 胡廷伟 杨东 马飞 马大衍 徐可为 于 2019-10-23 设计创作，主要内容包括：本发明公开一种大面积单层石墨烯的制备技术,利用插层技术对缓冲层进行In原子插层,原来只有缓冲层的表面,In原子插入到缓冲层与SiC基底之间并使缓冲层转变为石墨烯,一方面制备出单层大面积的石墨烯,另一方面降低了石墨烯的制备温度。原缓冲层与单层外延石墨烯共存的表面,In原子插入到缓冲层与SiC基底之间,缓冲层变为石墨烯并与原有的外延石墨烯完美相连,形成大面积的单层石墨烯。此外,插层形成的石墨烯与衬底的相互作用较弱,为分离态的石墨烯,达到了离化的效果。用这种技术不仅可以制备出大面积的石墨烯,还可以控制石墨烯的层厚,这对于相关微电子、超导以及应变工程等领域的应用提供重要的指导与借鉴价值。(The invention discloses a preparation technology of large-area single-layer graphene, which is characterized In that an In atom intercalation technology is utilized to carry out In intercalation on a buffer layer, only the surface of the buffer layer is originally arranged, In atoms are inserted between the buffer layer and a SiC substrate and the buffer layer is converted into graphene, so that single-layer large-area graphene is prepared on one hand, and the preparation temperature of the graphene is reduced on the other hand. In atoms are inserted between the buffer layer and the SiC substrate on the surface where the original buffer layer and the single-layer epitaxial graphene coexist, the buffer layer is changed into graphene and is perfectly connected with the original epitaxial graphene, and large-area single-layer graphene is formed. In addition, the interaction between the graphene formed by intercalation and the substrate is weaker, and the graphene is in a separated state, so that the ionization effect is achieved. The technology can be used for preparing large-area graphene and controlling the thickness of the graphene layer, thereby providing important guidance and reference values for the application in the fields of related microelectronics, superconduction, strain engineering and the like.)

1. A method for preparing single-layer graphene in a large area by utilizing metal intercalation is characterized by comprising the following steps:

1) a single crystal SiC substrate is used as a growth base material of epitaxial graphene;

2) placing the single crystal SiC substrate in a vacuum preparation chamber, heating to 800-850K, degassing, and removing water vapor and residues adsorbed on the surface of the single crystal SiC;

3) heating the single crystal SiC substrate obtained in the step 2) to 1470-1620K, and keeping for 5-15 min to form a buffer layer on the surface of the SiC or a coexistence surface of the buffer layer and the single-layer epitaxial graphene;

4) heating a source of metallic In a crucible;

5) maintaining the temperature of the single crystal SiC substrate at 80K, opening a baffle of a metal beam source, and depositing metal In atoms to obtain a single crystal SiC sample with the surface covered by a metal In island;

6) annealing the single crystal SiC substrate covered by the metal In islands on the surface obtained In the step 5) at 770-1020K, keeping for 15-30 min, inserting metal In atoms below the buffer layer, and changing the buffer layer into single-layer graphene or changing the buffer layer into graphene and then connecting the graphene with the original epitaxial graphene to form the single-layer graphene.

2. The method for preparing single-layer graphene in a large area by using metal intercalation according to claim 1, wherein the single crystal SiC substrate in the step 1) is a single-side polished long strip shape with the size of 15mm x 3mm and the thickness of 330 ± 25 μm.

3. The method for preparing the single-layer graphene in a large area by using the metal intercalation as claimed in claim 1, wherein the heating current in the step 2) is 0.48-0.52A, and the heating time is 8 h.

4. The method for preparing the single-layer graphene with the metal intercalation large area according to claim 1, wherein the pressure of the vacuum preparation chamber in the step 2) is 5 x 10^-10Torr。

5. The method for preparing single-layer graphene in a large area by using metal intercalation according to claim 1, wherein the step 3) is replaced by heating the single crystal SiC substrate obtained in the step 2) to 1470K and then keeping for 10-15 min, so that a buffer layer is formed on the surface of SiC.

6. The method for preparing the single-layer graphene in a large area by using the metal intercalation according to claim 1 or 5, wherein the buffer layer in the step 3) is a reconstructed surface of single crystal SiC 6 x 6, and the surface is enriched with amorphous C atoms.

7. The method for preparing single-layer graphene In large area by using metal intercalation according to claim 1 or 5, wherein the purity of the In metal source In the step 4) is 99.999%.

8. The method for preparing single-layer graphene in a large area by using metal intercalation according to claim 1 or 5, wherein the heating current in the deposition process in the step 5) is 2.5-3.0A, the heating temperature is 950-1020K, and the heating time is 10-25 min.

[ technical field ] A method for producing a semiconductor device

The invention belongs to the field of preparation and modification of two-dimensional materials, and relates to a method for preparing single-layer graphene in a large area by utilizing metal intercalation.

[ background of the invention ]

The invention of silicon-based integrated circuit accelerates the informatization process of human society, however, with the technological progress, the characteristic dimension of the device tends to nanometer level, and for the silicon-based integrated circuit, the product with stable electrical performance and higher integration level is difficult to be effectively manufactured under the influence of photoetching precision and microcosmic physical effect when the online width is less than ten nanometers, so that the exploration of new technology or new material is in the spotlight. Graphene is a two-dimensional system material, and is a novel material capable of replacing traditional silicon due to the excellent characteristics of small volume, controllable shape, high electron movement speed (reaching 1/300) and the like. The graphene has a wide application prospect in the aspect of transistor manufacturing, electrons in the single-layer graphene cannot be scattered, and a transistor device with a very high conversion speed can be manufactured by utilizing the characteristic. Graphene discoverers Andre Geim and KostyaNovoselov have fabricated the smallest worldwide transistors that are only one atom thick and 10 atoms wide, which is an important step people have taken in the field of fabricating nanodevices. The graphene can be used for manufacturing nano-scale electronic devices such as transistors and the like, and has wide application prospects in the fields of solar energy, energy storage materials, composite multifunctional materials and aerospace. The research is not limited to the theoretical basis, but is promoted to the research of the preparation process and the application field. Among the existing methods for preparing graphene, the SiC epitaxy method is compatible with the current silicon planar process because substrate transfer is not needed, and can be directly used for preparing devices, so that the method has great competitive advantages in all methods for preparing graphene. Epitaxial graphene is prepared by high-temperature pyrolysis of a single crystal SiC matrix, the temperature is generally over 1620K and even up to 1870K, the high preparation temperature is unfavorable for industrial production, the graphene prepared by the method is difficult to transfer from a SiC substrate, and the epitaxial graphene is influenced by a SiC substrate to a certain extent, so that the excellent performance of the graphene is weakened. For example, the Chinese patent CN107316804A discloses a metal atom-doped large-area regular epitaxial grapheneThe preparation method of (1) synchronously realizes large-area preparation and metal atom doping of the regular epitaxial graphene by introducing pretreatment of metal atoms and Ar protective atmosphere. On one hand, the method can not eliminate the influence of the SiC substrate on the graphene layer because the integrity of the graphene layer is influenced by the doping of the metal atoms, so that the electron transmission efficiency of the epitaxial graphene is greatly reduced; on the other hand, the temperature for preparing the graphene by the method is high, and the application of the epitaxial graphene is not facilitated. Therefore, in order to maximize the excellent properties of graphene, the preparation of near-free graphene is very urgent. Nicolas Camara et al, by applying a standard secondary vacuum (SSV, l 0)^-8～10^-6Torr) condition, adding a graphite capping layer on a 6H-SiC (000-1) surface to reduce the sublimation rate of silicon atoms during high-temperature epitaxy so as to obtain wide-strip single-layer graphene with excellent consistency. For the Si surface, the Virojanadara et al and the Emtsev et al optimize the process in sequence, and the sublimation rate of Si is slowed down by using a high-pressure Ar atmosphere during high-temperature epitaxy, so that single-layer and multi-layer alternate stripe graphene with high surface consistency in a large area is obtained. IBM corporation has produced FETs with cut-off frequencies up to 100GHz in 2010 by epitaxial graphene on SiC substrates and produced the world's first graphene-based RF integrated circuit in 2011.

In recent years, various researches show that the intercalation of metal atoms is expected to regulate and control the electronic structure of graphene, so that the graphene is represented as a free monolayer characteristic while self integrity is maintained. Sandin et al found that the adjustment effects of Na atom intercalation performed between graphene layers and between the SiC buffer layer and graphene on the electronic structure of graphene are completely different. Emtsev et al insert a Ge atomic layer into graphene, forming two phase structures at different annealing temperatures, and having electron and hole injection effects on graphene, respectively. Chuang et al found that the insertion of Au atoms into graphene layers generates stress, which affects the electronic structure of graphene. Virojanadara et al found that Li atom intercalation had an electron injection effect on graphene, but annealing at 770K resulted in volatilization of Li atoms and subsequent recovery of graphene to the eigenstate.

Therefore, it is not difficult to imagine that when metal atoms enter between the buffer layer and the SiC substrate, the effect of the buffer layer and the substrate can be weakened, and the buffer layer is changed into single-layer graphene, so that the preparation of the graphene is realized. As a widely used excellent electrode material, In atoms have been put into practical use In solar cells and other devices. With the recent continuous emergence of graphene electronic devices, the contact of In and graphene has attracted attention. The In atom intercalation technology is simple and easy to operate, has strong repeatability, can realize the complete ionization of single-layer graphene, has low temperature requirement, provides important guidance and reference for the performance optimization of the graphene and the preparation of electronic devices, and has wide application prospect In the fields of microelectronics, superconduction, strain engineering and the like.

[ summary of the invention ]

The invention aims to solve the problems that the method for preparing graphene by metal intercalation in the prior art has more defects and the layer thickness of the graphene is difficult to control, and provides a method for preparing single-layer graphene in a large area by using the metal intercalation.

In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:

a method for preparing single-layer graphene in a large area by utilizing metal intercalation comprises the following steps:

1) a single crystal SiC substrate is used as a growth base material of epitaxial graphene;

2) placing the single crystal SiC substrate in a vacuum preparation chamber, heating to 800-850K, degassing, and removing water vapor and residues adsorbed on the surface of the single crystal SiC;

3) heating the single crystal SiC substrate obtained in the step 2) to 1470-1620K, and keeping for 5-15 min to form a buffer layer on the surface of the SiC or a coexistence surface of the buffer layer and the single-layer epitaxial graphene;

4) heating a source of metallic In a crucible;

5) maintaining the temperature of the single crystal SiC substrate at 80K, opening a baffle of a metal beam source, and depositing metal In atoms to obtain a single crystal SiC sample with the surface covered by a metal In island;

6) annealing the single crystal SiC substrate covered by the metal In islands on the surface obtained In the step 5) at 770-1020K, keeping for 15-30 min, inserting metal In atoms below the buffer layer, and changing the buffer layer into single-layer graphene or changing the buffer layer into graphene and then connecting the graphene with the original epitaxial graphene to form the single-layer graphene.

The invention is further improved in that:

the single crystal SiC substrate in the step 1) is a single-side polished long strip, the size is 15mm multiplied by 3mm, and the thickness is 330 +/-25 mu m.

In the step 2), the heating current is 0.48-0.52A, and the heating time is 8 h.

The pressure of the vacuum preparation chamber in the step 2) is 5 multiplied by 10^-10Torr。

And 3) replacing the single crystal SiC substrate obtained in the step 2) with a buffer layer formed on the surface of the SiC substrate by heating the single crystal SiC substrate to 1470K and then keeping the temperature for 10-15 min.

The buffer layer in the step 3) is a reconstructed surface of single crystal SiC 6 multiplied by 6, and amorphous C atoms are enriched on the surface.

The purity of the metal In source In the step 4) is 99.999%.

In the step 5), the heating current in the deposition process is 2.5-3.0A, the heating temperature is 950-1020K, and the heating time is 10-25 min.

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

the existing method for preparing graphene by metal intercalation has more defects and is difficult to control the layer thickness. The invention utilizes In atoms to carry out intercalation on the buffer layer, and successfully realizes the aim of controllable preparation of high-quality large-area single-layer graphene. Heating a clean single crystal SiC sample at a certain temperature to enable the surface of the single crystal SiC sample to be covered by a large-area uniform buffer layer or the coexisting surface of the buffer layer and the single-layer epitaxial graphene, and then depositing In atoms on the surface of the single crystal SiC sample to obtain the single crystal SiC sample completely covered by the In atoms. During annealing at a certain temperature, In atoms are inserted under the buffer layer and are converted into single-layer graphene with an ordered structure. Originally, only the surface of the buffer layer is provided, In atoms are inserted between the buffer layer and the SiC substrate and the buffer layer is converted into graphene, so that on one hand, single-layer large-area graphene is prepared, and on the other hand, the preparation temperature of the graphene is reduced. In atoms are inserted between the buffer layer and the SiC substrate on the surface where the original buffer layer and the single-layer epitaxial graphene coexist, the buffer layer is changed into graphene and is perfectly connected with the original epitaxial graphene, and large-area single-layer graphene is formed. In addition, the interaction between the graphene formed by intercalation and the substrate is weaker, and the graphene is in a separated state, so that the ionization effect is achieved. The method is simple in preparation conditions, good in repeatability and low in temperature dependence, facilitates rapid and low-cost preparation of large-area graphene, and is expected to be applied to the fields of microelectronics, superconductivity, strain engineering and the like.

[ description of the drawings ]

FIG. 1 is a topographical view of a surface of single crystal SiC according to example 1 of the present invention; wherein, (a) is a topography of a single crystal SiC surface covered by a buffer layer; (b) is a topography of In islands after In atom deposition; (c) is a topography map of the single crystal SiC surface after In atom intercalation.

FIG. 2 is a graph showing a comparison of Raman spectra before and after intercalation with In atoms In example 1 of the present invention.

Fig. 3 is a schematic diagram of the mechanism of the In atom intercalation process of example 1 of the present invention.

FIG. 4 is a topography of a single crystal SiC surface of example 2 of the present invention; wherein, (a) is a topography of a single crystal SiC surface covered by a buffer layer and epitaxial graphene; (b) is a topography of In islands after In atom deposition; (c) is a macroscopic topography map of the single crystal SiC surface after In atom intercalation; (d) is a microscopic topography picture of the single crystal SiC surface after In atom intercalation.

Fig. 5 is a schematic diagram of the mechanism of the In atom intercalation process of example 2 of the present invention.

Fig. 6(a) is a morphology diagram of a surface of single crystal SiC after In atom intercalation In example 3 of the present invention.

Fig. 6(b) is an atomic structural image of the surface of single crystal SiC after In atom intercalation In example 3 of the present invention.

Fig. 7(a) is a morphology diagram of a surface of single crystal SiC after In atom intercalation In example 4 of the present invention.

Fig. 7(b) is a macroscopic atomic structural image of the surface of single crystal SiC after In atom intercalation In example 4 of the present invention.

Fig. 7(c) is a microscopic atomic structural image of the surface of single crystal SiC after In atom intercalation In example 4 of the present invention.

[ detailed description ] embodiments

The invention is described in further detail below with reference to the accompanying drawings:

the invention discloses a method for preparing single-layer graphene in a large area by utilizing metal intercalation, which comprises the following steps:

1) selecting an A-grade single crystal 6H-SiC (0001) substrate with the specification of 15mm multiplied by 3mm multiplied by 330 mu m as a growth base material of epitaxial graphene;

2) placing the single crystal SiC substrate in a vacuum preparation chamber, heating to 800-850K for degassing, and maintaining the pressure of the vacuum preparation chamber at 5 x 10^-10Torr, the size of a used direct current power supply is 0.48-0.52A, and water vapor and residues adsorbed on the surface of the single crystal SiC are removed after 8 hours of degassing;

3) heating the single crystal SiC substrate obtained in the step 2) to 1470-1620K, and keeping for 5-15 min to form a large-area buffer layer on the SiC surface or a coexistence surface of the buffer layer and the single-layer epitaxial graphene;

4) heating a metal source in the crucible K-Cell device;

5) maintaining the temperature of the single crystal SiC substrate at 80K, opening a baffle of a metal beam source, and depositing metal In atoms, wherein the heating current of the metal In source is 2.5-3.0A In the deposition process, the heating temperature is 950-1020K, and the heating time is 10-25 min, so that a single crystal SiC sample with the surface covered by the metal In island is obtained;

6) annealing the single crystal SiC substrate covered by the metal In island on the surface, which is obtained In the step 5), at 770-1020K, keeping for 15-30 min, and In the process, inserting an In atom layer between the single crystal SiC sample and the buffer layer, so that covalent connection between the single crystal SiC sample and the buffer layer is broken, the effect between the buffer layer and the single crystal SiC sample is weakened, the buffer layer is changed into single-layer graphene, and the preparation of the graphene is realized.

Several specific embodiments of the invention are listed below: