CN112240942B - Method for regulating and controlling charge density and defect number of defect sites on surface of high-orientation pyrolytic graphite - Google Patents
Method for regulating and controlling charge density and defect number of defect sites on surface of high-orientation pyrolytic graphite Download PDFInfo
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- 230000007547 defect Effects 0.000 title claims abstract description 89
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 58
- 229910002804 graphite Inorganic materials 0.000 title claims abstract description 57
- 239000010439 graphite Substances 0.000 title claims abstract description 57
- 238000000034 method Methods 0.000 title claims abstract description 28
- 230000001276 controlling effect Effects 0.000 title claims abstract description 12
- 230000001105 regulatory effect Effects 0.000 title claims abstract description 9
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Substances N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 64
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 32
- 238000012360 testing method Methods 0.000 claims abstract description 24
- 238000010884 ion-beam technique Methods 0.000 claims abstract description 17
- 230000005641 tunneling Effects 0.000 claims description 38
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 21
- 239000000523 sample Substances 0.000 claims description 19
- 238000000137 annealing Methods 0.000 claims description 9
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 9
- 239000012670 alkaline solution Substances 0.000 claims description 8
- 239000000243 solution Substances 0.000 claims description 8
- 238000007872 degassing Methods 0.000 claims description 7
- 238000006056 electrooxidation reaction Methods 0.000 claims description 7
- 229910052721 tungsten Inorganic materials 0.000 claims description 6
- 239000010937 tungsten Substances 0.000 claims description 6
- 238000005530 etching Methods 0.000 claims description 3
- 230000004907 flux Effects 0.000 claims 1
- 230000002950 deficient Effects 0.000 abstract description 6
- 125000004432 carbon atom Chemical group C* 0.000 abstract description 3
- 238000005259 measurement Methods 0.000 description 36
- 238000004574 scanning tunneling microscopy Methods 0.000 description 23
- 229910001873 dinitrogen Inorganic materials 0.000 description 5
- 238000010849 ion bombardment Methods 0.000 description 5
- 108010083687 Ion Pumps Proteins 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- 150000002500 ions Chemical class 0.000 description 4
- CKUAXEQHGKSLHN-UHFFFAOYSA-N [C].[N] Chemical compound [C].[N] CKUAXEQHGKSLHN-UHFFFAOYSA-N 0.000 description 3
- 125000004429 atom Chemical group 0.000 description 3
- -1 nitrogen ions Chemical class 0.000 description 3
- 238000003775 Density Functional Theory Methods 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 230000005684 electric field Effects 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical group [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 1
- 238000005411 Van der Waals force Methods 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 150000001721 carbon Chemical group 0.000 description 1
- 238000003776 cleavage reaction Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000011010 flushing procedure Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000000004 low energy electron diffraction Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910021382 natural graphite Inorganic materials 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000007017 scission Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000004627 transmission electron microscopy Methods 0.000 description 1
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- G01Q—SCANNING-PROBE TECHNIQUES OR APPARATUS; APPLICATIONS OF SCANNING-PROBE TECHNIQUES, e.g. SCANNING PROBE MICROSCOPY [SPM]
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- C01B32/21—After-treatment
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01Q—SCANNING-PROBE TECHNIQUES OR APPARATUS; APPLICATIONS OF SCANNING-PROBE TECHNIQUES, e.g. SCANNING PROBE MICROSCOPY [SPM]
- G01Q60/00—Particular types of SPM [Scanning Probe Microscopy] or microscopes; Essential components thereof
- G01Q60/10—STM [Scanning Tunnelling Microscopy] or apparatus therefor, e.g. STM probes
- G01Q60/16—Probes, their manufacture, or their related instrumentation, e.g. holders
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Abstract
The invention provides a method for regulating and controlling the charge density and the number of defective sites on the surface of highly oriented pyrolytic graphite, and belongs to the technical field of graphite regulation and control. According to the method, the energy of the ion beam is limited, so that the HOPG surface can be bombarded to form an atomic level point defect structure, and the graphite surface is prevented from being damaged due to overlarge energy; by controlling the bias voltage of the scanning tunnel test, the charge density of defect sites and the number of defect sites are changed, nitrogen ions form C-N bonds with carbon atoms on the surface of the high-orientation pyrolytic graphite after being bombarded by low energy, N-type doping states locally occur, extra electrons carried by nitrogen elements can increase the electron state density near point defects, after the bias voltage is changed, part of point defects can show high electron state density under positive bias voltage, part of point defects show high electron state density under low bias voltage, and the electron state density of part of point defects is unchanged along with the change of bias voltage values, so that the number regulation of the point defects is realized.
Description
Technical Field
The invention relates to the technical field of graphite regulation and control, in particular to a method for regulating and controlling the charge density and the number of defective sites on the surface of highly oriented pyrolytic graphite.
Background
In graphite, each carbon atom has four valence electrons, three of which participate in forming covalent bonds and the fourth electron forms pi bond. Adjacent layers interact by weak van der waals forces. Graphite is the simplest two-dimensional crystal and has been widely studied both theoretically and experimentally. Natural graphite contains many defective structures, which affect its electrical properties. Annealing the pyrolytic graphite under compressive stress at about 3300K produces Highly Oriented Pyrolytic Graphite (HOPG) having the highest degree of three-dimensional order, with impurity levels controlled to 10ppm or less. HOPG is a highly stable material that remains stable in air at 500 ℃ and in vacuum at 20-30 ten thousand ℃, and that exhibits high chemical inertness.
The process of bombarding HOPG with nitrogen and argon atoms has attracted considerable attention from scientists, and abundant electronic structures and transmission characteristics are obtained through the process. The process of forming such a specific structure has been studied extensively in recent years by various means including Scanning Tunneling Microscopy (STM), transmission Electron Microscopy (TEM), low Energy Electron Diffraction (LEED), X-ray diffraction, density functional theory RY (DFT), and the like. The study of the microstructure and electron state density processes of HOPG after bombardment is important because bombardment can change the mechano-thermo-electromagnetic properties of HOPG, but there is no way in the prior art of how to regulate the electron state density of point defects on the surface of HOPG.
Disclosure of Invention
In view of the above, the present invention aims to provide a method for controlling the charge density and the number of defective sites on the surface of highly oriented pyrolytic graphite. The invention achieves changing the charge density of defect bits and the number of defect bits on the surface of the HOPG.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a method for regulating and controlling the charge density and the number of defective sites on the surface of highly oriented pyrolytic graphite, which comprises the following steps of;
carrying out electrochemical corrosion on tungsten wires in an inorganic alkaline solution, and then annealing and degassing to obtain a scanning tunnel microscope probe;
bombarding the surface of the high-orientation pyrolytic graphite by using a nitrogen ion beam with low energy to obtain bombarded high-orientation pyrolytic graphite, wherein the energy of the nitrogen ion beam is 230-250 eV;
and carrying out a scanning tunnel test on the bombarded high-orientation pyrolytic graphite by using the scanning tunnel microscope probe to realize the regulation and control of the charge density of defect sites and the number of defect sites on the surface of the high-orientation pyrolytic graphite, wherein the bias voltage of the scanning tunnel test is 0.03-1V.
Preferably, the flow rate of the nitrogen ion beam is 0.1-0.3 nA/cm 2.
Preferably, the tunneling current of the scanning tunnel test is 0.2-2 nA.
Preferably, the electrochemical corrosion voltage is 8-10V and the time is 15-20 min.
Preferably, the annealing and degassing temperature is 450-500K, the time is 30-35 min, and the vacuum degree is 1X 10 - 9mbar～9×10-9 mbar.
Preferably, the inorganic alkaline solution is sodium hydroxide solution, and the concentration of the sodium hydroxide solution is 1.8-2.2 mol/L.
Preferably, the time of the low energy bombardment is 3-6 s.
Preferably, the pressure at the time of the low energy bombardment is 4X 10 -5～6×10-5 mbar.
Preferably, the bias voltage is 0.1, 0.146, 0.2, 0.4, 0.5 or 0.8V.
Preferably, the highly oriented pyrolytic graphite has a size of 5mm by 3mm.
The invention provides a method for regulating and controlling the charge density of defect sites and the number of defect sites on the surface of high-orientation pyrolytic graphite, which comprises the following steps of; carrying out electrochemical corrosion on tungsten wires in an inorganic alkaline solution, and then annealing and degassing to obtain a scanning tunnel microscope probe; bombarding the surface of the high-orientation pyrolytic graphite by using a nitrogen ion beam with low energy to obtain bombarded high-orientation pyrolytic graphite, wherein the energy of the nitrogen ion beam is 230-250 eV; and carrying out a scanning tunnel test on the bombarded high-orientation pyrolytic graphite by using the scanning tunnel microscope probe to realize the regulation and control of the charge density of defect sites and the number of defect sites on the surface of the high-orientation pyrolytic graphite, wherein the bias voltage of the scanning tunnel test is 0.03-1V. According to the invention, the scanning tunnel microscope probe is prepared by using the tungsten wire, the tungsten has high conductivity and mechanical strength and is easy to etch, and the prepared scanning tunnel microscope probe only has one or more atoms at the tail end of the tip, so that the regulation and control of the charge density of defect sites (point defects) and the number of the defect sites can be realized; the invention realizes low-energy bombardment by limiting the energy of the nitrogen ion beam, can form an atomic level point defect structure on the surface of the HOPG, and avoids the damage of graphite surface caused by excessive energy; by controlling the bias voltage of the scan tunnel test, the charge density and the defect number of the point defect positions are changed, nitrogen ions form C-N bonds with carbon atoms on the surface of the high-orientation pyrolytic graphite after being bombarded by low energy (the energy of an ion beam is 230-250 eV), N-type doping states can be locally generated, extra electrons carried by nitrogen elements can increase the electron state density near the point defect, in the process of increasing the scan tunnel test bias voltage, the electron orbit provided by the extra electrons can enable more electrons to occupy, so that the electron state density around the point defect can be gradually increased to a full state and then is changed, the electron state density influence range is also increased along with the increase of the bias voltage, after the bias voltage is changed, part of the point defects can show high electron state density under the positive bias voltage, part of the point defects show high electron state density under the low bias voltage, and the electron state density of part of the point defects is not changed along with the change of the bias voltage value, namely the quantity regulation and control of the point defects are realized. And the invention performs scanning tunnel test, and the STM image obtained by the scanning tunnel test has high precision.
Drawings
FIG. 1 is an STM image of the different stages of oriented pyrolytic graphite of example 1, wherein (a) is an atomic resolution STM image of HOPG after nitrogen ion bombardment, scanning dimensions are 5.04nm by 6.77nm; (b) a bias voltage of 0.5V and a tunneling current of 0.6nA; (c) bias voltage 0.146V, tunneling current 0.6nA;
FIG. 2 is an STM image after different modulation processes in example 1, wherein the scan area of (a) is 150nm by 150nm, the bias voltage is +0.4V, and the tunneling current is 0.6nA; (b) The scan area of (a) is 150nm×150nm, the bias voltage is-0.4V, the tunneling current is 0.6nA, the bright spots in (b) are point defects on the surface of HOPG (0111), wherein 1 and 2 represent type one and type two defects (nitrogen doped defects), and 3 represents type three defects (carbon-nitrogen gap defects);
FIG. 3 is a voltage test STM image of a type one defect of FIG. 2, wherein (a) has a bias of +0.5V, a tunneling current of 0.5nA, and a scan area of 100×100nm; (b) The bias voltage of (c) to (l) are high resolution STM images of square defects in (a) and (b), the bias voltage of (c) is +0.03eV, the tunnel current is 0.2nA, the measurement range is 15nm×15nm, (d) the bias voltage of-0.03 eV, the tunnel current is 0.2nA, the measurement range is 15nm×15nm, (e) the bias voltage of-0.1 eV, the tunnel current is 0.2nA, the measurement range is 15nm×15nm, (f) the bias voltage of +0.1eV, the tunnel current is 0.2nA, the measurement range is 15nm×15nm, (g) the bias voltage of-0.2 eV, the tunnel current is 0.2nA, the measurement range is 15nm×15nm, (h) the bias voltage of +0.2eV, the tunnel current is 0.2nA, the measurement range is 15nm×15nm, (i) the bias voltage of-0.2 nm×15nm, the bias voltage of +0.8 nm×15nm, (f) the bias voltage of +0.1eV, the tunnel current is 0.2nA, the measurement range is 15nm×15nm, the bias voltage of 0.8 nm×15nm;
FIG. 4 is a voltage test STM image of the type II defect of FIG. 2, wherein (a) has a bias of +0.5V, a tunneling current of 0.5nA, and a measurement range of 100nm by 100nm; (b) The bias voltage of (c) to (l) are high resolution STM images of square defects in (a) and (b), (c) is +0.03eV, the tunnel current is 0.6nA, the measurement range is 20nm×20nm, (d) is-0.03 eV, the tunnel current is 0.6nA, the measurement range is 20nm×20nm, (e) is 0.15eV, the tunnel current is 0.6nA, the measurement range is 15nm×15nm, (f) is-0.15 eV, the tunnel current is 0.6nA, the measurement range is 20nm×20nm, (g) is 0.4eV, the tunnel current is 0.6nA, the measurement range is 20nm×20nm, (h) is-0.4 eV, the tunnel current is 0.6 eV, the measurement range is 20nm×20nm, (i) is 0.6nA, the measurement range is 15nm×15nm, (f) is-0.15 eV, the tunnel current is 0.6nA, the measurement range is 20nm×20nm, and (g) is 0.4 eV.
Detailed Description
The invention provides a method for regulating and controlling the charge density of defect sites and the number of defect sites on the surface of high-orientation pyrolytic graphite, which comprises the following steps of;
carrying out electrochemical corrosion on tungsten wires in an inorganic alkaline solution, and then annealing and degassing to obtain a scanning tunnel microscope probe;
bombarding the surface of the high-orientation pyrolytic graphite by using a nitrogen ion beam with low energy to obtain bombarded high-orientation pyrolytic graphite, wherein the energy of the nitrogen ion beam is 230-250 eV;
and carrying out a scanning tunnel test on the bombarded high-orientation pyrolytic graphite by using the scanning tunnel microscope probe to realize the regulation and control of the charge density of defect sites and the number of defect sites on the surface of the high-orientation pyrolytic graphite, wherein the bias voltage of the scanning tunnel test is 0.03-1V.
In the present invention, unless otherwise specified, all raw materials used are commercially available.
The invention carries out annealing and degassing after carrying out electrochemical corrosion on tungsten wires in inorganic alkaline solution to obtain the scanning tunnel microscope probe.
In the present invention, the voltage of the electrochemical corrosion is preferably 8 to 10V, and the time is preferably 15 to 20 minutes. In the present invention, the electrochemical etching preferably uses a platinum coil as an electrode and a tungsten wire as an etching target.
In the present invention, the inorganic alkaline solution is preferably a sodium hydroxide solution, and the concentration of the sodium hydroxide solution is preferably 1.8 to 2.2mol/L, more preferably 1.9 to 2mol/L.
In the present invention, the temperature of the annealing deaeration is preferably 450 to 500K, the time is preferably 30 to 35min, and the vacuum degree is preferably 1X 10 -9mbar～9×10-9 mbar. The tip end of the scanning tunneling microscope probe obtained by the present invention has one or more atoms, more preferably only one atom.
The invention utilizes nitrogen ion beam low energy to bombard highly oriented pyrolytic graphite to obtain highly oriented pyrolytic graphite after bombardment, and the energy of the nitrogen ion beam is 230-250 eV. In the invention, the energy of the low-energy bombardment can not only avoid excessively damaging the graphite surface, but also form atomic scale point defects.
In the present invention, the preparation method of the highly oriented pyrolytic graphite preferably comprises the steps of: cleaving the surface of the graphite (0001) in air, and then performing heat treatment under vacuum conditions to obtain the highly oriented pyrolytic graphite, wherein the temperature of the heat treatment is preferably 800-1000K; the time is 30-60 min, preferably 40-50 min; the vacuum conditions have a pressure of 1X 10 -10～5×10-8 mbar, preferably 1X 10 -10～5×10-9 mbar.
In the present invention, the size of the highly oriented pyrolytic graphite is preferably 5mm×3mm.
In the present invention, the flow rate of the nitrogen ion beam is preferably 0.1 to 0.3nA/cm 2.
In the present invention, the pressure at which the bombardment is carried out at low energy is preferably 4X 10 -5～6×10-5 mbar.
In the present invention, the time of the low energy bombardment is preferably 3 to 6s, more preferably 4 to 5s.
In the present invention, the low energy bombardment is preferably performed in an ultra-high vacuum chamber, and the ion pump is preferably turned off before introducing nitrogen gas into the ultra-high vacuum chamber, so that the ion pump can be prevented from being contaminated by the nitrogen gas, and the purity of the nitrogen gas is preferably 99.999%. After the ion pump is turned off, the ultra-high vacuum chamber is maintained at vacuum only by the molecular pump.
In the present invention, the high purity nitrogen gas is preferably used to flush the gas line before the low energy bombardment, the number of flushing is preferably three or more, and the purity of the high purity nitrogen gas is preferably 99.999%.
The present invention preferably ionizes nitrogen with an ISE 5 ion gun and imparts initial kinetic energy to the ionized gas molecules by applying a localized electric field, thereby bombarding the (0001) surface of highly oriented pyrolytic graphite with nitrogen ions. ISE 5 ion gun is a cold anode ion gun, and the energy of generated nitrogen ions can be as high as 5keV, and the maximum beam current reaches 45A.
After the scanning tunnel microscope probe and the bombarded high-orientation pyrolytic graphite are obtained, the scanning tunnel microscope probe is utilized to carry out scanning tunnel test on the bombarded high-orientation pyrolytic graphite, so that the regulation and control on the charge density of defect sites and the number of defect sites on the surface of the high-orientation pyrolytic graphite are realized, and the bias voltage of the scanning tunnel test is 0.03-1V. In the present invention, the bias voltage is preferably 0.1, 0.146, 0.2, 0.4, 0.5 or 0.8V. In the present invention, the bias voltage includes a positive bias voltage, preferably 0.03 to 1V, or a negative bias voltage, preferably-1 to-0.03V.
In the present invention, the tunneling current of the scan tunnel test is preferably 0.2 to 2nA, more preferably 0.5 to 0.6nA.
In the present invention, the scanning area of the scanning tunnel test is preferably 15nm×15nm, 20nm×20nm, 100nm×100nm, 150nm×150nm or 5.04nm×6.77nm, and the data acquisition point is preferably 512 points/line pattern.
In the invention, the device for scanning tunnel test is preferably OmicronVT-STM instrument.
The present invention preferably quantifies the defect site charge density and the number of defect sites based on the resulting scanning tunneling microscope spectrogram.
In order to further illustrate the present invention, the following examples are provided to control the charge density of defect sites and the number of defect sites on the surface of highly oriented pyrolytic graphite, but they should not be construed as limiting the scope of the present invention.
Example 1
Step 1: preparing the surface of the atomically flat highly oriented pyrolytic graphite (HOPG (0001)).
After cleavage of the surface of the graphite (0001) under air, the graphite was heated at 1000K for 30min in an ultra-high vacuum chamber (vacuum degree of 1X 10 -10 mbar), and the size of HOPG was 5mm X3 mm.
Step 2: STM tips were prepared.
The tungsten wire was electrochemically etched in 1.8mol/L sodium hydroxide solution at 8V, and then annealed and degassed in an ultra-high vacuum chamber (1X 10 -10 mbar vacuum) at 500K for 30 minutes.
Step 3: nitrogen ions bombard the surface of the HOPG formed in the step1 with low energy to form atomic scale point defects: before introducing nitrogen (purity 99.999%) into the ultra-high vacuum chamber, the ion pump was turned off, the gas line was flushed three times with high purity nitrogen, the nitrogen was ionized with an ISE 5 ion gun and the ionized gas molecules were given initial energy by applying a local electric field, the ion beam energy was 250eV, the flow rate was 0.3nA/cm 2, and the pressure in the vacuum chamber was 4 x 10 -5 mbar. The ion bombardment process was continued for 3s.
Step 4: and (3) regulating and controlling the atomic scale point defect structure formed in the step (3) by adopting the STM needle point formed in the step (2). The scanning area was set to 1 μm×1 μm, and the data acquisition point was set to a 512 point/line pattern. Sample scanning is carried out by using an Omicon VT-STM, the bias voltage range is 0.03V to 1V, the tunneling current range is 0.5 nA-2 nA, and the STM scanning bias voltage is changed, so that the electron state density and the number of point defects are changed.
Fig. 1 is an STM image of the different stages of the oriented pyrolytic graphite of example 1, wherein (a) is an STM image of HOPG after nitrogen ion bombardment, white lines represent graphite of grain boundaries, and bright spots represent point defects generated by the ion bombardment process. (b) And (c) an STM image of atomic resolution of point defect features, (b) obtained at a bias voltage of 0.5V and a tunneling current of 0.6nA, and (c) obtained at a bias voltage of 0.146V and a tunneling current of 0.6 nA. As can be seen from fig. 1, a significant change occurs by adjusting the scanning conditions. When the distance of the needle tip sample becomes short (i.e., the bias voltage becomes small and the tunneling current becomes large), (b) the defect at the upper part in (c) disappears, and on the other hand, (b) the bright defect position at the lower part also changes in (c). This suggests that the tip effect of STM becomes stronger at small sample bias, it can be stated that the nature of point defects may be created by isolated carbon/nitrogen atoms, and that the structure of some defect features is not very stable after ion bombardment.
Fig. 2 is an STM image after different modulation processes. Wherein the scan area in (a) is 150nm by 150nm, the bias voltage is +0.4V, and the tunneling current is 0.6nA; (b) The bright spots in (b) are point defects on the surface of HOPG (0111) which can be summarized as three main types distinguished in fig. 2, namely 1,2 and 3 in fig. 2, wherein 1 and 2 represent type one and type two defects (nitrogen doping defects) and 3 represents type three defects (carbon-nitrogen gap defects), and as can be seen from fig. 2, the nitrogen doping defects show inversion, the carbon-nitrogen gap defects remain stable, i.e. the adjustment of the bias voltage from positive to negative, when the bias voltage changes from positive to negative, the number of nitrogen doping defects can be changed.
In the process of increasing the bias voltage of the sample, the contrast of the type one defect is increased firstly and then is reduced, and finally the change is finished under a certain bias voltage; the effective area of defect change also increases with increasing bias voltage. FIG. 3 is a voltage test STM image of a type one defect of FIG. 2. Wherein the bias voltage of (a) is +0.5V, the tunneling current is 0.5nA, and the scanning area is 100×100nm; (b) is-0.5V, tunneling current is 0.5nA, scan area is 100 x 100nm, and (c) through (l) are high resolution STM images of square defects in (a) and (b). (c) The bias voltage of (2) was +0.03eV, the tunneling current was 0.2nA, and the measurement range was 15nm. Times.15 nm. (d) Is-0.03 eV, tunneling current is 0.2nA, and measurement range is 15nm×15nm. (e) Is-0.1 eV, tunneling current is 0.2nA, and measurement range is 15nm×15nm. (f) The bias voltage of (2) was +0.1eV, the tunneling current was 0.2nA, and the measurement range was 15nm. Times.15 nm. (g) Is-0.2 eV, tunneling current is 0.2nA, and measurement range is 15nm×15nm. (h) The bias voltage of (2) was +0.2eV, the tunneling current was 0.2nA, and the measurement range was 15nm. Times.15 nm. (i) Is-0.4 eV, tunneling current is 0.2nA, and measurement range is 15nm×15nm. (j) The bias voltage of (2) was +0.4eV, the tunneling current was 0.2nA, and the measurement range was 15nm. Times.15 nm. (k) Is-0.8 eV, tunneling current is 0.2nA, and measurement range is 15nm×15nm. (l) The bias voltage of (2) was +0.8eV, the tunneling current was 0.2nA, and the measurement range was 15nm. Times.15 nm. It can be seen that when the bias voltage is adjusted from 0eV to ±0.8eV, one type of defect shows the graphite surface structure when the bias voltage approaches 0eV (fig. 3 (c) and (d)); increasing the bias to + -0.1eV, a type one defect starts to appear different, with no change in contrast (FIGS. 3 (e) and (f)); when the bias voltage is increased to ±0.2eV, the contrast starts to change (fig. 3 (g) and (h)), and the effective area of defect change becomes large; increasing the bias to + -0.4eV, the contrast becomes apparent (FIGS. 3 (i) and (j)); the next decrease in contrast change, which eventually ends when the bias voltage is + -0.8eV (FIGS. 3 (k) and (l)), illustrates that adjusting the bias voltage can change the number of type one defects and their surrounding electron density.
FIG. 4 is a voltage test STM image of the type two defect of FIG. 2. Wherein the bias voltage of (a) is +0.5V, the tunneling current is 0.5nA, and the measurement range is 100nm×100nm; (b) The bias voltage of (2) was-0.5V, the tunneling current was 0.5nA, and the measurement range was 100nm. Times.100 nm. (c) To (l) are high resolution STM images of square defects in (a) and (b). (c) The bias voltage of (2) was +0.03eV, the tunneling current was 0.6nA, and the measurement range was 20nm. Times.20 nm. (d) Is-0.03 eV, tunneling current is 0.6nA, and measurement range is 20nm×20nm. (e) Is 0.15eV, tunneling current is 0.6nA, and measurement range is 15nm×15nm. (f) Is-0.15 eV, tunneling current is 0.6nA, and measurement range is 20nm×20nm. (g) Is 0.4eV, the tunneling current is 0.6nA, and the measurement range is 20nm x 20nm. (h) Is-0.4 eV, the tunneling current is 0.6nA, and the measurement range is 20nm by 20nm. (i) The bias voltage of (2) was +0.8eV, the tunneling current was 0.6nA, and the measurement range was 20nm. Times.20 nm. (j) Is-0.8 eV, tunneling current is 0.6nA, and measurement range is 20nm×20nm. It can be seen that when the bias voltage is at a level close to 0eV, the type two defects exhibit normal graphite surface structure (fig. 4 (c) and (d)); as the bias voltage increases ±0.15eV, type two defects start to appear, and the contrast starts to change (fig. 4 (c) and (d)). In contrast, high contrast occurs under positive bias, and when the sample polarity bias becomes negative, the defective area darkens. As the bias voltage increases, the effective area of the defect becomes larger, which becomes apparent at a voltage of ±0.4eV (fig. 4 (g) and (h)). These changes stopped when the bias voltage was increased to + -0.8eV (FIGS. 4 (i) and (j)). Some bright spots appear in the middle defect area under the negative bias voltage, and the rest defect areas keep dark, which means that the quantity of type two defects and the surrounding electron density can be changed by adjusting the bias voltage.
The foregoing is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that modifications and adaptations to the present invention may occur to one skilled in the art without departing from the principles of the present invention and are intended to be comprehended within the scope of the present invention.
Claims (9)
1. The method for regulating and controlling the charge density and the number of defect sites on the surface of the highly oriented pyrolytic graphite is characterized by comprising the following steps:
carrying out electrochemical corrosion on tungsten wires in an inorganic alkaline solution, and then annealing and degassing to obtain a scanning tunnel microscope probe;
bombarding the surface of the high-orientation pyrolytic graphite by using a nitrogen ion beam with low energy to obtain bombarded high-orientation pyrolytic graphite, wherein the energy of the nitrogen ion beam is 230-250 eV;
And carrying out a scanning tunnel test on the bombarded high-orientation pyrolytic graphite by using the scanning tunnel microscope probe to realize the regulation and control of the charge density of defect sites and the number of defect sites on the surface of the high-orientation pyrolytic graphite, wherein the bias voltage of the scanning tunnel test is 0.4V.
2. The method of claim 1, wherein the nitrogen ion beam has a flux of 0.1 to 0.3nA/cm 2.
3. The method of claim 1, wherein the tunneling current of the scan tunnel test is 0.2-2 nA.
4. The method of claim 1, wherein the electrochemical etching is performed at a voltage of 8 to 10V for a time of 15 to 20min.
5. The method according to claim 1, wherein the annealing and degassing temperature is 450-500K, the time is 30-35 min, and the vacuum degree is 1X 10 -9mbar～9×10-9 mbar.
6. The method according to claim 1, wherein the inorganic alkaline solution is a sodium hydroxide solution, and the concentration of the sodium hydroxide solution is 1.8-2.2 mol/L.
7. The method of claim 1, wherein the time of the low energy bombardment is 3-6 s.
8. The method according to claim 1 or 7, wherein the pressure at low energy bombardment is 4 x 10 -5～6×10-5 mbar.
9. The method of claim 1, wherein the highly oriented pyrolytic graphite has a size of 5mm x 3mm.
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| JP2000174255A (en) * | 1998-12-08 | 2000-06-23 | Nec Corp | Microstructured element and manufacture thereof |
| CN103996616A (en) * | 2014-05-04 | 2014-08-20 | 江苏大学 | Method for graphene doping modification through Ga ion bombardment |
| DE102015001713A1 (en) * | 2015-02-13 | 2016-08-18 | Forschungszentrum Jülich GmbH | Scanning probe microscope and method for measuring local electric potential fields |
| CN108862388A (en) * | 2018-06-26 | 2018-11-23 | 北京理工大学 | A method of molybdenum disulfide is adulterated based on dynamic control enhancing heterogeneous molecular |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2000174255A (en) * | 1998-12-08 | 2000-06-23 | Nec Corp | Microstructured element and manufacture thereof |
| CN103996616A (en) * | 2014-05-04 | 2014-08-20 | 江苏大学 | Method for graphene doping modification through Ga ion bombardment |
| DE102015001713A1 (en) * | 2015-02-13 | 2016-08-18 | Forschungszentrum Jülich GmbH | Scanning probe microscope and method for measuring local electric potential fields |
| CN108862388A (en) * | 2018-06-26 | 2018-11-23 | 北京理工大学 | A method of molybdenum disulfide is adulterated based on dynamic control enhancing heterogeneous molecular |
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