CN115568261B - Method for opening band gap of double-layer graphene and prepared double-layer graphene device - Google Patents
Method for opening band gap of double-layer graphene and prepared double-layer graphene device Download PDFInfo
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Abstract
The invention discloses a method for opening a band gap of double-layer graphene and a prepared double-layer graphene device. The method has the advantages of convenient operation, simple device structure and wide application, avoids the micro-nano processing process of the traditional electric grid voltage regulation and control method, and has important significance for applying the double-layer graphene to the field of semiconductor electronic devices.
Description
Technical Field
The invention relates to the technical field of semiconductor electronics, in particular to a method for opening a band gap of double-layer graphene and a prepared double-layer graphene device.
Background
Graphene, an important two-dimensional material, has attracted much attention because of its excellent properties and novel physical phenomena. Two single-layer graphenes AB (or BA) are stacked, and double-layer graphenes are formed. The intrinsic double-layer graphene which is in inversion symmetry is a semiconductor with zero band gap, but the spatial inversion symmetry of the intrinsic double-layer graphene can be broken through applying a vertical electric field to the double-layer graphene, so that the band gap of the double-layer graphene is opened and adjustable within a certain range, and the property gives the double-layer graphene application prospect in the aspects of semiconductor devices and nanoelectronics.
The method for opening the band gap is mainly an electric grid voltage method [ aperture 459,820 (2009) ], namely an electric displacement field is formed on an intermediate dielectric layer by applying voltage to the top electrode and the bottom electrode of a material, and an electric field in the vertical direction is regulated to open the band gap. However, the method needs to manufacture electrodes at the top and the bottom of the material, and the material and the electrodes are separated by adopting insulating materials such as silicon dioxide, aluminum oxide, boron nitride and the like, so that micro-nano processing technology such as photoetching, etching, evaporation coating and the like is required to be introduced in the preparation process, the operation is complex, and organic residual glue is very easy to be introduced in the process, so that pollution is caused, the properties of the material are influenced, and besides, the properties of the surface of the material cannot be directly detected due to the fact that the surface of the material is covered by the electrodes, and the research of the optical properties such as absorption spectrum and the like and the characterization of scanning probe microscopy are greatly limited. Therefore, how to provide a simple, effective and widely applied method for opening the band gap of double-layer graphene has great significance for the development of graphene in the field of semiconductors.
Disclosure of Invention
Based on the technical problems, the invention provides a method for opening a double-layer graphene band gap and a prepared double-layer graphene device, so as to solve the problems of complex operation and limited applicability in the method for opening the double-layer graphene band gap in the prior art.
The invention firstly provides a method for opening a band gap of double-layer graphene, which is to arrange the double-layer graphene between a first molecular layer and a second molecular layer, wherein the first molecular layer is used for carrying out electron (N type) doping on the double-layer graphene, and the second molecular layer is used for carrying out hole (P type) doping on the double-layer graphene, so that the band gap of the double-layer graphene is opened.
In some embodiments of the invention, the molecules of the first molecular layer are aminopropyl triethoxysilane (APTES) molecules, the APTES molecules having exposed-NH 2 And (3) carrying out electron (N type) doping on the graphene by the group.
In some embodiments of the invention, the molecules of the second molecular layer are nitric acid (HNO 3 ) A molecule.
Further, the invention provides a specific method for opening the band gap of double-layer graphene, which comprises the following steps:
step A: preparing a functional substrate, wherein the substrate sequentially comprises the following steps of: a silicon substrate, a silicon dioxide layer and a first molecular layer;
and (B) step (B): forming a double-layer graphene layer on the functional substrate obtained in the step A;
step C: b, forming a second molecular layer on the double-layer graphene layer obtained in the step B;
step D: and C, preparing an electrode on the second molecular layer obtained in the step C.
In some embodiments of the present invention, the specific method of step a is: the silicon substrate with the silicon dioxide layer is irradiated by ultraviolet light to enable the silicon dioxide layer to generate activity, then the substrate is soaked into a solution of first molecules, and the first molecules perform monolayer self-assembly on the silicon dioxide with activity to form a first molecule layer.
In some embodiments of the invention, in step B, the bilayer graphene layer is formed directly on the target substrate by a mechanical lift-off process.
In some embodiments of the present invention, the specific method of step C is: placing the substrate with the double-layer graphene layer on the opening of a beaker containing a second molecular solution with one side of the double-layer graphene facing downwards, volatilizing the second molecules and forming a second molecular layer on the surface of the double-layer graphene layer.
In some embodiments of the invention, in step D, the electrode is at least one of titanium, chromium, and gold, and the thickness of the electrode is not less than 30nm.
In some embodiments of the present invention, the specific method of step D is: and placing a hard mask plate with an electrode pattern above the second molecular layer, observing and operating by an optical microscope, aligning the electrode pattern on the double-layer graphene, fixing, and then obtaining the electrode pattern by electron beam evaporation coating.
Furthermore, the invention also provides a double-layer graphene device prepared by the method, which sequentially comprises the following steps: a silicon substrate; a silicon dioxide layer; a first molecular layer formed over the silicon dioxide layer; the double-layer graphene layer is formed above the first molecular layer; the second sub-layer is formed above the double-layer graphene layer; and an electrode formed over the second molecular layer and in contact with the bilayer graphene (the second molecular layer does not affect contact of the electrode with the graphene).
From the above technical scheme, the method for opening the band gap of the double-layer graphene and the prepared double-layer graphene device have the following beneficial effects:
(1) The method for opening the double-layer graphene band gap is simple and convenient to operate, does not need complicated micro-nano processing steps, and avoids the condition that the material property is influenced due to pollution of organic residual glue.
(2) The double-layer graphene device provided by the invention has a simple structure, and no insulating layer and top gate electrode cover are arranged above the double-layer graphene, so that compared with the device obtained by the traditional electric gate voltage method, the double-layer graphene device provided by the invention has wide application, and can be applied to transport tests, optical property research and characterization research in the aspect of scanning probe microscopy.
Drawings
Fig. 1 to fig. 4 are schematic step diagrams of a method for opening a band gap of a bilayer graphene according to the present invention, where fig. 4 is a schematic structural diagram of a finally obtained bilayer graphene device.
Fig. 5 is a raman spectrum characterization of bilayer graphene obtained by mechanical exfoliation method according to example 1 of the present invention.
Fig. 6 is an optical microscope image of a bilayer graphene device prepared in example 1 of the present invention.
Fig. 7 is a graph showing the result of the resistance regulation with the gate voltage, which is tested in the room temperature environment, of the double-layer graphene device prepared in the embodiment 1 of the present invention.
Reference numerals in the drawings: 10-a functional substrate; 11-a silicon substrate; 12-a silicon dioxide layer; 13-a first molecular layer; 20-bilayer graphene layers; 30-a second sub-layer; 40-electrode.
Detailed Description
The method for opening the band gap of the double-layer graphene and the double-layer graphene device prepared by the method are simple in device structure, convenient to operate and wide in application, and have great significance for the development of graphene in the field of semiconductors.
The present disclosure will be further described in detail below with reference to specific embodiments and with reference to the accompanying drawings, in order to make the objects, technical solutions and advantages of the present disclosure more apparent.
As shown in fig. 1-4, the method for opening the band gap of the double-layer graphene provided by the invention comprises the following steps:
step A: a functional substrate 10 is prepared, which comprises, in order from bottom to top: a silicon substrate 11, a silicon dioxide layer 12, a first molecular layer 13;
and (B) step (B): forming a bilayer graphene layer 20 on the functional substrate 10 obtained in step a;
step C: forming a second molecular layer 30 on the bilayer graphene layer 20 obtained in the step B;
step D: an electrode 40 is prepared on the second molecular layer 30 obtained in step C.
The method for opening the band gap of the double-layer graphene is simple and convenient to operate, wide in application and strong in adjustability.
Specifically, the molecules in the first molecular layer 13 in the functional substrate 10 are aminopropyl triethoxysilane (APTES) molecules. APTES molecule has exposed-NH 2 And (3) carrying out electron (N type) doping on the graphene by the group.
Specifically, the method of forming the bilayer graphene layer 20 on the functional substrate 10 includes: formed directly on the functional substrate 10 using a mechanical lift-off process.
Specifically, the second molecular layer 30 is nitric acid (HNO 3 ) Molecules, hole (P-type) doping is performed on the bilayer graphene layer 20.
Specifically, the material of the electrode 40 is at least one of titanium, chromium and gold, and the thickness of the electrode 40 is not less than 30nm.
Specifically, the electrode 40 is prepared by combining a hard mask with an electron beam evaporation coating to obtain an electrode pattern. The electrode prepared by adopting the hard mask method can avoid pollution of organic residual glue to the double-layer graphene layer in the micro-nano processing process.
As shown in fig. 4, the present invention further provides a double-layer graphene device prepared by the above method, which sequentially includes, from bottom to top: a silicon substrate 11; a silicon dioxide layer 12; a first molecular layer 13 (i.e., APTES molecular layer) formed over the silicon dioxide layer; a bilayer graphene layer 20 formed over the first molecular layer 13; a second molecular layer 30 (i.e., nitric acid molecules) formed over the bilayer graphene layer 20; and an electrode 40 formed over the second molecular layer 30 and in contact with the bilayer graphene 20. Wherein the silicon substrate 11, the silicon dioxide layer 12 and the first molecular layer 13 constitute a functional substrate 10.
From the above description, those skilled in the art should clearly recognize the method for opening the bandgap of bilayer graphene and the prepared bilayer graphene device provided by the present invention.
The method for opening the band gap of the double-layer graphene and the prepared double-layer graphene device provided by the invention are verified in a specific embodiment.
Example 1
The method for opening the band gap of the double-layer graphene and the prepared double-layer graphene device provided by the embodiment specifically comprise the following steps:
step a: the silicon knife is used for growing SiO 2 The Si substrate of the layer (hereinafter referred to as SiO 2 Si substrate) into square with side length of about 1cm, siO is used 2 SiO in Si substrate 2 The thickness is 285-300nm, and SiO is irradiated by 365nm ultraviolet light 2 /Si substrate for 15 minutes. Ozone is generated in the air after ultraviolet light irradiation, and the ozone can enable the silicon dioxide layer to generate activity. Placing the substrate irradiated by ultraviolet light into a prepared aminopropyl triethoxysilane solution, wherein the concentration of aminopropyl triethoxysilane in the solution is one percent, the solvent is toluene, and the aminopropyl triethoxysilane (APTES) molecules will be on active SiO 2 Monolayer self-assembly was performed thereon. And (3) soaking the substrate for 3 hours, taking out, putting into toluene solution, and performing ultrasonic treatment for 15 minutes, so that the superfluous aminopropyl triethoxysilane molecules on the surface of the substrate are cleaned, and only one layer of molecules after self-assembly is left on the substrate. And then placing the substrate cleaned by toluene in an acetone solution for ultrasonic treatment for 5 minutes to remove residual toluene solution, then carrying out ultrasonic treatment for 5 minutes by ethanol, taking out the substrate, and drying by a nitrogen gun to obtain the functional substrate, as shown in figure 1.
Step b: and (3) placing graphene on the functional substrate by adopting a mechanical stripping method, observing and finding double-layer graphene under an optical microscope, and determining that the obtained graphene is double-layer graphene by auxiliary judgment of Raman spectrum test, wherein the double-layer graphene is shown in fig. 2 and 5.
Step c: and c, sticking the functional substrate with the double-layer graphene layer obtained in the step b on a glass sheet by using solid Polydimethylsiloxane (PDMS), pouring the glass sheet on a bottle mouth of a 100mL beaker, pouring about 20mL of concentrated nitric acid (with the content of 65.0% -68.0%) into the beaker, placing the concentrated nitric acid liquid 4-6cm away from the double-layer graphene in a sealed box or a fume hood for a period of time, wherein the time is generally not longer than 12 hours, and the doping degree of nitric acid molecules to double-layer graphene holes (P type) is larger as shown in fig. 3.
Step d: and placing a hard mask on the double-layer graphene, observing and operating by an optical microscope, aligning and fixing the electrode pattern on the double-layer graphene, and sequentially and physically depositing titanium 5nm and gold 30nm by an electron beam evaporation coating technology to obtain the electrode pattern, wherein the electrode pattern is shown in figures 4 and 6.
Through the above preparation steps, the dual-layer graphene device shown in fig. 4 is obtained in this embodiment, which sequentially includes, from bottom to top: a silicon substrate 11; a silicon dioxide layer 12; a first molecular layer 13 (i.e., APTES molecular layer) formed over the silicon dioxide layer 12; a bilayer graphene layer 20 formed over the first molecular layer 13; a second molecular layer 30 (i.e., nitric acid molecules) formed over the bilayer graphene layer 20; and an electrode 40 formed over the second molecular layer 30 and in contact with the bilayer graphene 20. Wherein the silicon substrate 11, the silicon dioxide layer 12 and the first molecular layer 13 constitute a functional substrate 10.
The device obtained in this example was subjected to a gate voltage change test in a room temperature environment, and compared with a bilayer graphene device without the first molecular layer and the second molecular layer, and the result is shown in fig. 7. It can be seen that the resistance of the electric neutral point (CNP) in the variation curve of the resistance along with the gate voltage obtained in the embodiment is increased by about 9 times compared with the comparison sample, so that the band gap of the double-layer graphene is effectively opened, and the fermi energy and the band gap can be changed by adjusting the size of the gate voltage or changing the doping time of nitric acid molecules to the double-layer graphene.
In summary, the method for opening the band gap of the double-layer graphene and the prepared double-layer graphene device provided by the invention can realize the opening of the band gap of the double-layer graphene and the continuous regulation and control of the Fermi surface, and the device has the advantages of simple structure, convenience in operation, strong regulation and control and wide application. Compared with the traditional method for regulating and controlling the electric grid voltage, the method avoids pollution of organic residual glue in the micro-nano processing process, and meanwhile, the obtained double-layer graphene device with the open band gap is free of an insulating layer and is covered by a top grid electrode, so that the method can be applied to transport tests, optical property research and characterization research in the aspect of scanning probe microscopy, and has important significance for applying the double-layer graphene to the field of semiconductor electronic devices.
It should be further noted that, the directional terms mentioned in the embodiments, such as "upper", "lower", "front", "rear", "left", "right", etc., are only referring to the directions of the drawings, and are not intended to limit the scope of the present disclosure. Like elements are denoted by like or similar reference numerals throughout the drawings. Conventional structures or constructions will be omitted when they may cause confusion in understanding the present disclosure. And the shapes and dimensions of the various elements in the drawings do not reflect actual sizes and proportions, but merely illustrate the contents of embodiments of the present invention.
While the foregoing is directed to embodiments of the present invention, other and further details of the invention may be had by the present invention, it should be understood that the foregoing description is merely illustrative of the present invention and that no limitations are intended to the scope of the invention, except insofar as modifications, equivalents, improvements or modifications are within the spirit and principles of this invention.
Claims (8)
1. The method for opening the band gap of the double-layer graphene is characterized by comprising the following steps of: arranging the double-layer graphene between a first molecular layer and a second molecular layer, wherein the first molecular layer carries out electron doping on the double-layer graphene, and the second molecular layer carries out hole doping on the double-layer graphene, so that the band gap of the double-layer graphene is opened; the molecules of the first molecular layer are aminopropyl triethoxysilane molecules, and the molecules of the second molecular layer are nitric acid molecules.
2. The method of opening a bilayer graphene bandgap according to claim 1, comprising the steps of:
step A: preparing a functional substrate, wherein the substrate sequentially comprises the following steps of: a silicon substrate, a silicon dioxide layer and a first molecular layer;
and (B) step (B): forming a double-layer graphene layer on the functional substrate obtained in the step A;
step C: b, forming a second molecular layer on the double-layer graphene layer obtained in the step B;
step D: and C, preparing an electrode on the second molecular layer obtained in the step C.
3. The method for opening a double-layer graphene bandgap according to claim 2, wherein the specific method of step a is: the silicon substrate with the silicon dioxide layer is irradiated by ultraviolet light to enable the silicon dioxide layer to generate activity, then the substrate is soaked into a solution of first molecules, and the first molecules perform monolayer self-assembly on the silicon dioxide with activity to form a first molecule layer.
4. The method of opening a bilayer graphene bandgap of claim 2, wherein: in the step B, the double-layer graphene layer is directly formed on the target substrate through a mechanical stripping method.
5. The method of opening a bilayer graphene bandgap of claim 2, wherein: the specific method of the step C is as follows: placing the substrate with the double-layer graphene layer on the opening of a beaker containing a second molecular solution with one side of the double-layer graphene facing downwards, volatilizing the second molecules and forming a second molecular layer on the surface of the double-layer graphene layer.
6. The method of opening a bilayer graphene bandgap of claim 2, wherein: in the step D, the electrode is at least one of titanium, chromium and gold, and the thickness of the electrode is not less than 30nm.
7. The method of opening a bilayer graphene bandgap of claim 2, wherein: the specific method of the step D is as follows: and placing a hard mask plate with an electrode pattern above the second molecular layer, observing and operating by an optical microscope, aligning the electrode pattern on the double-layer graphene, fixing, and then obtaining the electrode pattern by electron beam evaporation coating.
8. A bilayer graphene device prepared according to the method of any one of claims 1 to 7, characterized in that: the double-layer graphene device sequentially comprises the following components from bottom to top: a silicon substrate; a silicon dioxide layer; a first molecular layer formed over the silicon dioxide layer; the double-layer graphene layer is formed above the first molecular layer; the second sub-layer is formed above the double-layer graphene layer; and an electrode formed over the second molecular layer and in contact with the bilayer graphene.
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