Two-dimensional amorphous carbon nitride material, preparation method thereof, thin film and electronic device

Abstract

The application discloses a two-dimensional amorphous carbon nitride material and a preparation method, a thin film and an electronic device thereof, wherein the carbon nitride material has a two-dimensional morphology and an amorphous structure. The preparation method of the carbon nitride material comprises the following steps: etching the A component in a MAX phase material by using an etchant to obtain an MXene material; and mixing the MXene material with a metal bromide and / or bromine gas, and then sintering at a predetermined temperature to obtain the carbon nitride material. The application provides a novel carbon nitride material with a different structure, and the carbon nitride material exhibits an ultra-low dielectric constant, and has application values in electronic devices and electronic apparatuses, in particular, flexible electronic devices or communication apparatuses.

Description

Technical Field

[0001] This invention belongs to the field of new materials, and in particular relates to a two-dimensional amorphous carbon nitride material, its preparation method, thin film, and electronic device. Background Technology

[0002] With the rapid development of integrated circuits, the size of electronic devices is constantly shrinking to the nanometer scale. However, the parasitic capacitance induced by interconnects increases significantly, reducing the circuit's response speed and increasing power consumption. According to equation... Parasitic capacitance (C) is proportional to the dielectric constant (κ) of the dielectric material between the metal layers (A and d are the sample contact area and the distance between the two metal layers of the capacitor, respectively). The dielectric constant of silicon dioxide (SiO2), a common dielectric material, is approximately 4, twice that of the integrated circuit dielectric material recommended by the International Devices and Systems Roadmap (IRDS) (κ<2) (by 2028), hindering its application in next-generation integrated circuits.

[0003] To reduce the dielectric constant, several effective strategies have been employed in the development of dielectric materials, such as introducing heteroatoms to reduce polarization intensity, introducing porosity to reduce density, and increasing the amorphous phase to reduce crystallinity. In particular, introducing porosity and amorphous phases significantly alters the local environment, thereby providing low dielectric materials with κ values ​​of 2.2–3.5. With the introduction of porosity, the dielectric material can be considered as a two-component material, where the dielectric constant of the solid framework component is close to that of the compact prototype, while the dielectric constant of the second component (pores) is 1. With the introduction of the amorphous phase, the local coordination environment is enriched, which allows for a reduction in electronic polarization within the dielectric material, thus significantly lowering its dielectric constant. For example, materials with high... sp 3 Amorphous carbon materials at the C level (35%) have a low κ value (3) because sp 3 Localized electrons in atomic orbitals restrict electronic polarization. However, in sp 3 When the CC level is >50%, the density of amorphous carbon increases from 1.7 to 2.3 g / cm³. -3 Increase to 3.0~3.5 g cm -3 This leads to an increase in the κ value to ~6.5. Development of a product with <1.0g cm⁻¹ -3 Ideal low density and high sp 3 Low-carbon-based dielectric materials with amorphous structures and high C content are a key area of ​​research and development. Summary of the Invention

[0004] The object of the present invention is to provide a carbon nitride material with an ultra-low dielectric constant, wherein the carbon nitride material has a two-dimensional morphology and an amorphous structure.

[0005] In some embodiments, the thickness of the carbon nitride material is ≤5 nm.

[0006] In some embodiments, XPS testing of the carbon nitride material shows that it includes sp 3 Hybrid CN bonds and sp 2 Hybrid CN bonds.

[0007] In some embodiments, the spherical aberration electron microscopy diffraction image of the carbon nitride material shows no diffraction spots.

[0008] In some embodiments, aberration-corrected electron microscopy images of the carbon nitride material show no lattice fringes.

[0009] In some embodiments, the XRD pattern of the carbon nitride material has diffuse diffraction peaks between 20° and 30°.

[0010] In some embodiments, the dielectric constant of the carbon nitride material is ≤2, preferably ≤1.7.

[0011] In some embodiments, the density of the carbon nitride material is ≤1 g / cm³. 3 Preferably ≤0.6g / cm 3 .

[0012] A second aspect of the present invention provides a method for preparing the above-mentioned carbon nitride material, characterized in that the steps include: etching the A component in the MAX phase material with a first etchant to obtain an MXene material; mixing the MXene material with a second etchant, a metal bromide and / or bromine gas, and sintering at a predetermined temperature to obtain the carbon nitride material; wherein the MAX phase material is composed of M, A and X elements, wherein M is one or more transition metal elements, A is selected from metal elements of Group III or IV, and X is carbon and nitrogen elements.

[0013] In some embodiments, the etchant is one or more of HF, HCl, HBr, HI, I2, fluoride salt + hydrochloric acid, and metal halide salt; preferably, the first etchant is HF or HCl.

[0014] In some embodiments, the etching temperature of the second etchant is between 280°C and 1000°C, and / or the etching time is ≥60 min.

[0015] A third aspect of the present invention provides a thin film comprising the carbon nitride material described above; or, a carbon nitride material obtained by the preparation method described above; or, composed of the carbon nitride material described above, or, a carbon nitride material obtained by the preparation method described above.

[0016] In some embodiments, the dielectric constant of the above-mentioned thin film is ≤2; preferably ≤1.7.

[0017] In some embodiments, the breakdown strength of the above-described film is ≥5 MV cm⁻¹ -1 .

[0018] In some embodiments, the aforementioned film is an insulating material.

[0019] In some embodiments, the thickness of the above-mentioned film is ≥3nm; preferably, the thickness is between 3nm and 100μm; more preferably, it is between 3nm and 25μm.

[0020] A fourth aspect of the present invention provides an electronic device comprising the carbon nitride material described above; or, the carbon nitride material obtained by the preparation method described above; or, the thin film described above.

[0021] In some embodiments, the electronic device is flexible.

[0022] The fifth aspect of the present invention provides an integrated circuit comprising the carbon nitride material described above, or the thin film described above, or the electronic device described above.

[0023] A sixth aspect of the present invention provides a communication device comprising the aforementioned carbon nitride material, or the aforementioned thin film, or the aforementioned electronic device. This communication device can be a wireless communication device such as a mobile phone, computer, or base station.

[0024] This invention obtains a two-dimensional amorphous carbon nitride material (a-CN) by etching carbon-nitrogen-containing MXene materials with metal bromides and / or bromine gas. This material has a low density (0.55 g / cm³). -3 Its density is much lower than that of other amorphous materials (1.0~2.3 g / cm³). -3 ), higher sp The 3C content (~35.7%) leads to a significant reduction in electronic polarization. This unique structure results in α-CN exhibiting an ultra-low dielectric constant of 1.69 at 100 kHz, lower than previously reported dielectric materials (~4). In other words, this invention provides a novel carbon nitride material with a different structure, exhibiting an ultra-low dielectric constant, which has application value in electronic devices, integrated circuits, and especially flexible electronic devices or apparatuses. Attached Figure Description

[0025] Figure 1In embodiment (a) of the present invention, the process involves the conversion from Ti3AlCN to MXene-Ti3CNT. x (a) Schematic diagram of the topological transformation to amorphous a-CN; (b) Ti3AlCN, MXene-Ti3CNT x (c) XRD patterns of α-CN powder; (d) MXene-Ti3CNT etched by bromine vapor. x Raman spectra at different times.

[0026] Figure 2 The (a) MXene-Ti3CNT obtained in the embodiments of the present invention x The photo of (b)a-CN.

[0027] Figure 3 In this embodiment of the invention, MXene-Ti3CNT is used. x XRD patterns of products obtained at different etching times during the topological transformation process to a-CN.

[0028] Figure 4 The following is a characterization of a-CN in the embodiments of the present invention, wherein (a) is a TEM image of a-CN nanosheet; (b) is a selected region electron diffraction (SAED) image of a region with a diameter of 200 nm, showing a diffuse pattern without diffraction points and polycrystalline rings; (c) is a high-resolution bright-field TEM image with spherical aberration correction; (d) is a magnified image of the region marked in red in (c), showing a disordered atomic arrangement; and (e) is a fast Fourier transform of the selected region in (c), showing a typical diffusion diffraction pattern of an amorphous layer.

[0029] Figure 5 MXene-Ti3CNT in the embodiment of the present invention x (a) TEM image and (b) SAED image.

[0030] Figure 6 The images shown are (a) STEM images of the a-CN layer and (b) EDS images of carbon and (c) nitrogen elements in the red area of ​​(a) in this embodiment of the invention, showing a uniform distribution of carbon and nitrogen elements.

[0031] Figure 7 For characterization of the coordination structure in the embodiments of the present invention, (a) carbon and (b) nitrogen K-edge XANES spectra of a-CN and g-C3N4; (c) C 1s high-resolution XPS spectrum, (d) Raman spectrum and (e) FTIR spectrum of a-CN and g-C3N4; (f) film resistance curves of a-CN and g-C3N4, showing high resistance.

[0032] Figure 8The N1s high-resolution spectrum of a-CN in this embodiment of the invention shows the presence of pyridine N (398.6 eV), pyrrole N (400.0 eV) and graphite N (401.6 eV).

[0033] Figure 9 The XPS spectra of (a) a-CN and g-C3N4 in the embodiments of the present invention show that C, N and O elements are retained in the atomic layer of a-CN; (b) MXene-Ti3CNT x The XPS spectrum indicates the presence of Ti, C, N, O, F and Cl elements.

[0034] Figure 10 The (a) a-CN and (b) aC-Ti3C2T obtained by vacuum filtration in this embodiment of the invention are examples of materials. x A cross-sectional SEM image of the membrane, showing the horizontal orientation of the prepared membrane.

[0035] Figure 11 Characterization of the a-CN atomic layer as a low-κ dielectric material in this embodiment of the invention; (a) Typical current-voltage curve of the a-CN atomic layer (4.2 nm), AFM set to peak force tunneling mode (PF-TUNA), inset as a schematic diagram of the test setup; (b) Statistical distribution of breakdown intensity based on breakdown voltage data (inset), showing regions with 75% and 100% distribution relative to the average value, with the top and bottom lines representing the maximum and minimum values; (c) Tauc plot of the UV-Vis-NIR diffuse reflectance spectrum of a-CN (inset); (d) Capacitance-voltage curves of the metal-insulator (310 nm thick a-CN film)-metal structure at different frequencies; (e) Dielectric constant of the ~310 nm thick a-CN film as a function of frequency; (f) Comparison of the dielectric constant of a-CN in this work (red histogram) with that of previously reported low-κ materials.

[0036] Figure 12 The following are examples of the embodiments of the present invention: (a) AFM image of a-CN and (b) corresponding peak current plot; (c) height distribution of a-CN (#1 and #2); (d) I-V curve collected on AFM image (a) #2.

[0037] Figure 13 The following are (a) current-voltage curves and (b) corresponding current-field intensity curves of an a-CN film with a thickness of approximately 310 nm in an embodiment of the present invention. Detailed Implementation

[0038] The technical solution of the present invention is illustrated below through specific embodiments. It should be understood that the one or more steps mentioned in the present invention do not preclude the existence of other methods and steps before or after the combined steps, or that other methods and steps may be inserted between these explicitly mentioned steps. It should also be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Unless otherwise stated, the numbering of each method step is only for the purpose of identifying each method step, and not for limiting the order of each method or limiting the scope of the present invention. Changes or adjustments to their relative relationships, without substantial changes to the technical content, can also be considered as within the scope of the present invention.

[0039] The raw materials and instruments used in the examples are not subject to any specific restrictions on their source; they can be purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0040] Raw materials: Mo (99.5%, 10μm, Aladdin reagent), Ti (99.99%, 300 mesh, Aladdin reagent), Al (99.95%, 25μm, Aladdin reagent), graphite (99.9%, 10 mesh, Alfa Aesar), HCl (35%-37%, Beijing reagent), H2SO4 (98%, Beijing reagent), HF (48%-51%, Innochem reagent), NaF (99.9%, Aladdin reagent), ZnCl2 (anhydrous, 98%, Innochem reagent), isopropanol (99.5%, Innochim reagent), nylon membrane filter (φ50 mm, 0.22μm, Shanghai Xinya Purification Equipment Co., Ltd.), anodized aluminum oxide (AAO) template (200 nm pore size, Whatman), silicon wafer (boron doped, <0.005Ωcm, 500±25μm thickness, cis-generated). MAX phases Ti3AlC2, Ti3AlCN, and Mo2Ga2C were purchased from Beijing Sanchuan Energ Technology Co., Ltd.

[0041] Synthesis of MAX phase Mo2Ti2AlC3: Following the reported method, Mo, Ti, Al, and graphite powders were mixed in a ratio of 2:2:1.3:2.7 and sealed in an agate container in a glove box, and ground at 600 rpm for 20 h. The mixed powder was heated to 1600 °C at a rate of 5 °C / min and held under an Ar gas flow for 4 h. After cooling, the sintered body was ground and sieved through a 200-mesh sieve.

[0042] Synthesis of control sample carbon nitride (g-C3N4): Bulk g-C3N4 was synthesized by pyrolysis of urea at 500°C for 2 hours. Yellow g-C3N4 was obtained by ultrasonic treatment in isopropanol.

[0043] XRD patterns were obtained on a Rigaku D / MAX-2500 diffractometer (Cu Kα radiation). SEM images were acquired using a Zeiss Gemini SEM500 field emission scanning electron microscope. TEM and STEM-EDS elemental maps were collected in a FEI-Tecnai F30 microscope operating at 300 kV at 200 × 200 nm. 2 Selected-region electron diffraction images were obtained over the selected area. Aberration-corrected high-resolution bright-field TEM images were collected in a monochromatic NionHERMES-100 microscope equipped with an α-type monochromator and a fifth-order aberration corrector. Raman spectra were measured on a LabRAM HR Evolution Raman spectrometer using a 633 nm excitation laser. Elemental analysis measurements were performed on a Vario EL cube. C and NK edge XANES spectra were obtained at the MCD end station of the BL12B-a beamline at the National Synchrotron Radiation Laboratory (NSRL) in Hefei, China. EPR spectra were measured using a Bruker A300−10 / 12 instrument. XPS spectra were obtained on a Thermo Scientific Escalab 250Xi spectrometer. FTIR spectra were collected on a Thermo Fisher Scientific Nicolet 6700 spectrometer. Absorption spectra were collected in diffuse reflectance mode using a Shimadzu UV-3600 analyzer. True density measurements were performed on an AccuPyc II 1340 gas hydrometer. Thin-film resistance measurements were performed using a CHI760E electrochemical workstation. Capacitance-voltage (CV) characteristics were measured at different frequencies under ambient conditions using a K4200A-SCS parameter analyzer system and probe station equipment. Capacitance was tested at room temperature using an Agilent 4294A impedance analyzer to measure frequency and dielectric loss tangent curves, with the surface of the filtered a-CN film directly connected to the Ag electrode. Nanoindentation was performed using a G200XP nanoindenter with a surface approach speed of 10 nm / s.

[0044] Atomic Force Microscopy (AFM): Surface morphology and peak force TUNA (PF-TUNA) measurements were performed using a Bruker Dimension Icon AFM. The AFM was equipped with ScanAsyst® imaging and NanoScope® software 1.8. For PF-TUNA measurements, selected a-CN nanosheets were centrifuged at 2000 rpm and dispersed in ethanol at 7000 rpm to form a colorless dispersion. This dispersion, along with 5 µL, was further dropped onto the center of a Pt-deposited Si / SiO2 wafer using electron beam deposition as a back grid. The Pt substrate was electrically connected to a stainless steel disk (e.g., using silver paint) Figure 11(as shown in a). Prior to measurement, the apparatus was heated at 120°C for 2 hours in an Ar atmosphere to remove solvent. During measurement, the disk was placed on an AFM platform (metal) and grounded. An external bias voltage was applied using a 25 nm radius Bruker SCM-PIT-V2 platinum / iridium coated AFM tip as the source gate. Topographic images of the sheet were measured using a standard imaging tip (ScanAsyst air). During current imaging, a 1 V bias voltage was applied to obtain a conductivity map. For IV characterization of points on the sample, a 5 V bias voltage was applied to the sample, and the current was measured. The current was limited by the selected sensitivity range (2 nA / V). Therefore, all current measurements were limited to 2 nA. All PF-TUNA measurements were performed in PF-TUNA mode.

[0045] This embodiment provides an amorphous two-dimensional carbon nitride material (labeled a-CN) and its preparation method. In this embodiment, MAX phase Ti3AlCN is used as the raw material, and the specific preparation steps include:

[0046] MXene-Ti3CNT x Synthesis: 2 g of Ti3AlCN powder was immersed in a mixture of 60 ml 9 M hydrochloric acid (HCl) and 4.8 g lithium fluoride (LiF) and stirred at 35 °C for 24 hours using a magnetic rod. The resulting mixture was filtered and washed with distilled water to bring the pH close to 6. The obtained powder was then redispersed in 100 ml glass vials and sonicated in an ice bath for 1 hour. The sonicated suspension was centrifuged at 3500 rpm for 15 min to collect samples containing at least one layer of MXene-Ti3CNT monolayer. x The supernatant was then freeze-dried under vacuum to obtain Ti3CNTs. x powder;

[0047] Synthesis of α-CN: 50 mg Ti3CNT x The powder was placed in an alumina crucible with a diameter of 10 mm. The filled alumina crucible and 1 g of CuBr2 powder were sealed in a quartz tube (20 mm in diameter and 100 mm in length). The vacuum-sealed tube was heated at 280°C for 1 hour and then cooled to room temperature. The obtained α-CN was then treated with 5% HF for 24 hours to remove the tiny TiO2 particles formed during heating. The product was then transferred to a 50 mL polypropylene centrifuge tube and washed three times with distilled water. The precipitate was dispersed in 20 mL of isopropanol (IPA) and sonicated for 1 hour. The α-CN was then collected by centrifuging the sonicated dispersion at 2000 rpm for 5 minutes. Finally, the powder was freeze-dried under vacuum.

[0048] This embodiment also provides an a-CN thin film prepared by vacuum filtration. More specifically, the steps include: vacuum filtration of the a-CN / IPA dispersion (centrifugation at 2000 rpm / min) on a nylon membrane filter. Before complete drying, the membrane filter is removed from the vacuum filter apparatus and allowed to air dry. The a-CN membrane is obtained by peeling it off from the membrane filter. The a-CN / IPA dispersion is then vacuum filtration (centrifugation at 2000 rpm / min) on an AAO template with a pore size of ~200 nm. The filtered a-CN membrane is then transferred to a Si substrate (approximately 500 nm thick, <0.005 Ωcm), and the membrane attached to the Si substrate is heated at 150°C under an Ar gas flow to remove the solvent effect.

[0049] Using a similar method, MXene-Ti3C2T was obtained by etching A atoms (Al / Ga) from MAX phase Ti3AlC2, Mo2Ga2C, and Mo2Ti2AlC3. x MXene-Mo2CT x MXene-Ti3C2Cl2 and MXene-Mo2Ti2C3T x ;

[0050] Synthesis of MXene-Ti3C2Cl2: 1 g of Ti3AlC2MAX powder and 1 g of ZnCl2 powder were weighed and mixed uniformly in an agate mortar in an argon-filled glove box. The mixture was then transferred to an alumina crucible and heated in a quartz tube at 550 °C under an Ar flow for 5 h. After cooling, the reactants were washed with 1 M HCl and deionized water to remove impurities.

[0051] aC-Ti3C2T x Synthesis of aC-Ti3C2Cl2: Except for the reaction temperature, all conditions were the same as those for Ti3CNT. x The conditions for synthesizing α-CN are the same; in this case, the reaction temperature is increased to 350℃ because the Ti-C bond is stronger than the Ti-N bond; α-C-Mo2CT x and aC-Mo2Ti2C3T x The synthesis of Ti3CNT is the same as that of α-CN, except that the reaction temperature is increased to 400°C. It is worth noting that Ti3CNT... x and Ti3C2T x The reaction with Br2 can also be carried out in a quartz tube under vacuum at the same temperature with an Ar flow, using 100 mg MXene powder and 10 g CuBr2 powder as reactants.

[0052] aC-Ti3C2T was obtained using a similar film formation method. xMembrane, aC-Ti3C2Cl2 membrane, aC-Mo2CT x and aC-Mo2Ti2C3T x membrane.

[0053] Figure 1 a illustrates the process from Ti3AlCN to MXene-Ti3CNT x Schematic diagram of the topological transformation to amorphous α-CN, MXene-Ti3CNT x MXene-Ti3CNT was obtained by etching Al atoms in Ti3AlCN with HF. x The topological transformation to α-CN occurs under the influence of bromine vapor generated by the thermal decomposition of copper bromide in a sealed tube (Equation 1) at a temperature of 280 °C. During the transformation, MXene-Ti3CNT... x According to equation (2), the Ti atoms in the MXene-Ti3CNT are gradually etched by bromine to generate the gaseous product TiBr4. After etching the Ti atoms, MXene-Ti3CNT... x The unsaturated carbon and nitrogen atoms in the carbon will combine to form an amorphous carbon nitride layer (a-CN), the color of which changes from dark purple to dark brown. Figure 2 It is worth noting that the topological reaction can also occur in an Ar flow at atmospheric pressure. The true density of α-CN (the actual mass of a solid substance per unit volume at absolute density) measured by a true density analyzer is 0.55 g / cm³. -3 The levels were significantly lower than those of the parent MXene (0.9 g cm⁻¹). -3 ) and amorphous materials (1.0~2.3 gcm) -3 ).

[0054] 2CuBr2 = 2CuBr + Br2 (G) (Equation 1);

[0055] Ti3CNT x +Br2→TiBr4(G)+CN(Amorphous) (Equation 2)

[0056] To gain a deeper understanding of MXene-Ti3CNT x The topological transformation process to a-CN was investigated using X-ray diffraction (XRD) and Raman spectroscopy, with results as follows: Figure 1 As shown in b and c. Figure 3 XRD patterns of the products at different etching times are presented. It can be seen that as the conversion reaction time increases from 0 min to 30 min, the MXene-Ti3CNT... x The (002) peak value shifts to a lower angle (from 7.5° to 6.9°) in MXene-Ti3CNT. xThe other non-baseline peaks of (004), (008), and (0012) disappeared after 1 hour of reaction, and the (002) peak also disappeared, with a new broad peak of 20°~30° appearing, indicating the formation of an amorphous structure. Figure 1 b). Furthermore, Raman spectroscopy reveals a ~1340 cm⁻¹ in the product obtained after 1 hour of bromine etching. -1 Broadband D-band and ~1571 cm -1 G-band, MXene-Ti3CNT x The EG band completely disappeared ( Figure 1 c).

[0057] TEM images show that a-CN has a two-dimensional morphology and is ultrathin and transparent. Figure 4 a) Selected area electron diffraction (SAED) patterns showed characteristic diffusion halos, confirming the amorphous structure of the product's atomic layers. Figure 4 b), which contrasts sharply with crystalline MXene exhibiting a hexagonal diffraction pattern. Figure 5 The amorphous structure can be further verified by distortion-corrected HRTEM (spherical aberration electron microscopy), which shows a random region (). Figure 4 (c and d) show no obvious lattice fringes, similar to reported amorphous materials. STEM images and energy-dispersive X-ray spectroscopy (EDS) elemental analysis results are as follows: Figure 6 As shown, C and N elements are evenly distributed.

[0058] To further investigate the local coordination environment of a-CN, near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR) were performed. In the C K-edge spectrum of a-CN (… Figure 7 a) The broad characteristic resonance of σ*CC / CN appears at ~293 eV, which was not observed in g-C3N4, indicating that the prepared a-CN contains a large number of CC / CN bonds. In the nitrogen-K edge region ( Figure 7 (b) The distinct resonance of pyrrole N composed of a single CN bond at 400.1 eV, absent in g-C3N4, indicates a high level of CN in α-CN. Similarly, the generalized characteristic resonance of σ*NC at ~407 eV confirms the presence of numerous CN bonds in α-CN. The presence of CC and CN bonds can be further confirmed by C1s and N1s in high-resolution XPS spectra. sp 3 The C content is estimated to be 35.7%, from sp 3 CN (13.0%) and sp 3CC (22.7%) composition, which is not present in g-C3N4 ( Figure 7 c); Figure 8 Notably, the three peaks of Ti 2p, F1s, and Cl ls disappeared in the XPS measurement spectrum, indicating that MXene-Ti3CNT x Ti atoms and surface functional groups on the surface are completely removed during the topological transformation process. Figure 9 Raman spectroscopy further proved... sp 3 The existence of CC / CN ( Figure 7 d). In particular, the I of a-CN D / I G A value of 1.36 indicates that the average defect distance in a-CN is <2 nm, lacking any long-range order, further confirming its amorphous structure. FTIR spectrum ( Figure 7 e) indicates that a-CN is at ~1330 cm -1 and ~1608 cm -1 It exhibits characteristic vibrational peaks of CN and C=N, but does not show Ti3CNT. x The Ti-O peak in the middle layer is different from the characteristic peak of g-C3N4, which includes s-triazine, indicating that α-CN has a large number of CN bonds, consistent with the NK edge and XPS analysis results of C1s.

[0059] Furthermore, amorphous atomic layers can be easily assembled into large-area thin films. Figure 10 The thin-film resistance of a-CN is 1.08 × 10⁻⁶. 10 Ω / □, compared to Ti3CNT x The film has an 8-order-of-magnitude improvement (40.7 Ω / □), which is close to the reported nitrogen-introduced amorphous carbon (~2.5 × 10⁻⁶). 10 Ωcm -1 This reveals the topological transformation reaction from conductive Ti3CNTs. x The complete transformation to insulating a-CN; in contrast, aC-Ti3C2T x The thin-film resistance is 343 MΩ / □, which can be attributed to the large I. D / I G Value (2.4).

[0060] To evaluate the dielectric properties of the prepared material, a-CN nanosheets were coated onto a SiO2 wafer with Pt deposited for conductivity AFM measurements, such as... Figure 11 a to 11b Figure 12 and 13As shown, the obtained current-voltage (I−V) curves reveal that for a-CN nanosheets (3.8 nm and 4.2 nm) and a-CN films (~310 nm), the current increases sharply in the voltage ranges of approximately 2–3 V and 165–180 V, respectively (Poole-Frenkel tunneling). The corresponding critical field strengths calculated from the ratio of critical voltage to thickness are approximately 6.6 ± 0.8 MV cm⁻¹. -1 and 5.6±0.2MV cm -1 It is close to the reported amorphous boron carbide film (7.3 MV cm⁻¹). -1 This is the highest value reported for materials with a dielectric constant less than 2. This slow decrease in breakdown strength as the thickness of a-CN increases from 4.2 nm to 310 nm should be attributed to the formation and dynamics of space charge, similar to those reported for SrTiO3 and polyethylene films. The current is significantly enhanced compared to the region without the sample, saturating at minimum bias voltage. The direct optical bandgap of 1.45 eV calculated from the absorption spectrum also confirms the insulating properties. Figure 11 c). The capacitance of the ~310 nm thick a-CN film at 100 kHz exhibits a small value of ~0.24 pF, greater than the capacitance of air (~0.05 pF), and decreases slightly to ~0.2 pF as the frequency increases from 100 kHz to 1 MHz, similar to the reported capacitance of a-BN. Impedance analyzer was further used to calculate the dielectric constant of a-CN films with thicknesses of ~310 nm and 25 μm ( Figure 11 d), at a frequency of 100 kHz, the dielectric constants are approximately 1.69 ± 0.01 (~310 nm) and 1.62 ± 0.01 (25 μm), respectively, which are much lower than the reported g-C3N4 (~62) and still lower than other reported amorphous films and other low-dielectric materials. Dielectric loss represents the energy consumed by converting electrical energy into heat. For a 25 μm thick a-CN film without a substrate, the dielectric loss is less than 0.03 in the frequency range of 100 kHz to 100 MHz, which is much lower than the dielectric loss of SiO2 (~0.07), indicating that if a-CN film is used in integrated circuits, the energy loss is low. Such low dielectric constant and dielectric loss can be attributed to the favorable structure and characteristics of a-CN: 1) with sp 3 C-analysis correlation, in amorphous phases with localized electrons sp 3 A high level of C reduces electronic polarization, effectively lowering the dielectric constant; 2) 0.55g cm -3 The very low density introduces a large number of voids and vacancies with a dielectric constant of 1, which significantly reduces the dielectric constant of a-CN.

[0061] To further evaluate the hardness and Young's modulus of the a-CN film, nano-identification measurements were performed at a surface approach velocity of 10 nm / s. The hardness of the a-CN film was approximately 0.12 GPa, close to that of porous SiCOH (0.28 GPa), but lower than that of commercial SiO2 (10–12 GPa). The Young's modulus of the a-CN film was approximately 2 GPa, which does not meet the chemical mechanical polishing requirements of current dielectric materials with Young's moduli as high as 8 GPa, but is advantageous for flexible electronic devices. With further densification processing, the a-CN film can be used in current integrated circuits.

[0062] In summary, this invention prepares amorphous two-dimensional amorphous carbon nitride materials via topological transformation of MXene containing carbon and nitrogen at the X-site under bromine vapor. The resulting α-CN has a density of 0.55 g / cm³. -3 Its very low density and 35.7% high sp 3 The C level was thus achieved. Therefore, an ultra-low dielectric constant of 1.69 was obtained at 100 kHz on our assembled a-CN film, lower than reported amorphous films and other low-dielectric materials (1.8–4). Furthermore, the breakdown strength of the assembled a-CN film reached 5.6 MV cm⁻¹. -1 This meets the application requirements. Our results demonstrate that amorphous two-dimensional carbon nitride atomic layers with excellent low-κ dielectric properties have the potential for application in future nanoelectronics.

[0063] It should be noted that MXene is the precursor for synthesizing the two-dimensional amorphous carbon nitride material in this invention. MXene itself is a class of two-dimensional materials with similar structures. In other embodiments, the MXene used as the precursor can also be MXene with different elemental compositions, represented by the chemical formula M. n+1 X n T x M is selected from one or more transition metal elements; X is selected from carbon and nitrogen elements; T represents a functional group, including one or more of -F, -Cl, Br, I, -O, -S, -OH, and -NH4; 1≤ n ≤4. Similarly, MAX phase materials, which are precursors to MXene, are also a type of ceramic material, represented by the chemical formula M. n+1 AX n In other embodiments, M is selected from one or more transition metals; A is selected from metals of Group III and / or Group IV; X is selected from carbon and nitrogen; 1 ≤ n ≤4. In another specific embodiment, the MAX phase is selected from Ti2AlC. 0.5 N 0.5 , Nb3AlCN, Mo3GaCN, Ti3SnCN, V3AlC 0.8 N0.2 By adjusting the etching conditions, the amorphous two-dimensional carbon nitride material of this invention can also be obtained.

[0064] In other embodiments, CuBr2 can be replaced with other metal bromides that can decompose into Br2 upon heating, such as FeBr3.

[0065] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for preparing a carbon nitride material, characterized in that, The carbon nitride material has a two-dimensional morphology and an amorphous structure; the preparation method includes the following steps: The A component in the MAX phase material was etched using the first etchant to obtain the MXene material; The MXene material is mixed with a second etching agent, metal bromide, and / or bromine gas, and then sintered at a predetermined temperature to obtain carbon nitride material. The MAX phase material is composed of elements M, A and X, where M is one or more transition metal elements, A is selected from metal elements of Group III or IV, and X is carbon and nitrogen.

2. The preparation method according to claim 1, characterized in that, The first etching agent is one or more of HF, HCl, HBr, HI, I2, fluoride salt + hydrochloric acid, and metal halide salt; And / or, the etching temperature of the second etchant is between 280°C and 1000°C; And / or, the etching time of the second etchant is ≥60 min.

3. The preparation method according to claim 2, characterized in that, The first etching agent is HF, fluoride salt + hydrochloric acid, or HCl.

4. The preparation method according to claim 1, characterized in that, The thickness of the carbon nitride material is ≤5nm.

5. The preparation method according to claim 1, characterized in that, XPS tests on the carbon nitride material showed that it included sp 3 Hybrid CN bonds and sp 2 Hybrid CN bonds; And / or, the spherical aberration electron microscopy diffraction image of the carbon nitride material has no diffraction spots; And / or, the aberration-corrected electron microscopy image of the carbon nitride material shows no lattice fringes; And / or, the XRD pattern of the carbon nitride material has diffuse diffraction peaks between 20° and 30°.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The dielectric constant of the carbon nitride material is ≤2; And / or, the density of the carbon nitride material is ≤1 g / cm³. 3 .

7. The preparation method according to claim 6, characterized in that, The dielectric constant of the carbon nitride material is ≤1.7; And / or, the density of the carbon nitride material is ≤0.6 g / cm³. 3 .

8. A carbon nitride material, characterized in that, The carbon nitride material has a two-dimensional morphology and an amorphous structure. XPS tests of the carbon nitride material show that it includes... sp 3 Hybrid CN bonds, sp 3 Hybrid C-C bonds and sp 2 Hybridized CN bonds; the carbon nitride material is obtained by any one of the preparation methods described in 1 to 7.

9. A carbon nitride material, characterized in that, The carbon nitride material has a two-dimensional morphology and an amorphous structure, and the dielectric constant of the carbon nitride material is ≤2; the carbon nitride material is obtained by any one of the preparation methods described in 1 to 7.

10. The carbon nitride material as described in claim 9, characterized in that, The dielectric constant of the carbon nitride material is ≤1.

7.

11. The carbon nitride material according to any one of claims 8 to 10, characterized in that, The density of the carbon nitride material is ≤1 g / cm³ 3 ; And / or, the thickness of the carbon nitride material is ≤5nm.

12. The carbon nitride material as described in claim 11, characterized in that, The density of the carbon nitride material is ≤0.6 g / cm³. 3 .

13. A thin film, characterized in that, Includes carbon nitride materials obtained by the preparation method according to any one of claims 1 to 7, or carbon nitride materials according to any one of claims 8 to 12; Alternatively, it may be composed of a carbon nitride material obtained by any one of the preparation methods described in claims 1 to 7, or a carbon nitride material as described in any one of claims 8 to 12.

14. The thin film as claimed in claim 13, characterized in that, The dielectric constant of the thin film is ≤2; And / or, the breakdown strength of the film is ≥5MV cm⁻¹ -1 ; And / or, the film is an insulating material; And / or, the thickness of the film is ≥3nm.

15. The thin film as claimed in claim 14, characterized in that, The thickness of the film is between 3 nm and 100 μm.

16. The thin film as claimed in claim 14, characterized in that, The thickness of the film is between 3 nm and 25 μm.

17. An electronic device, characterized in that, Includes carbon nitride materials obtained by the preparation method as described in any one of claims 1 to 7; Or, the carbon nitride material as described in any one of claims 8 to 12; Or, the film as described in any one of claims 13 to 16.

18. The electronic device as claimed in claim 17, characterized in that, The electronic device is flexible.

19. An integrated circuit, characterized in that, The invention includes carbon nitride materials prepared by any one of claims 1 to 7; or carbon nitride materials prepared by any one of claims 8 to 12; or thin films prepared by any one of claims 13 to 16; or electronic devices prepared by any one of claims 17 or 18.

20. A communication device, characterized in that, The invention includes carbon nitride materials prepared by any one of claims 1 to 7; or carbon nitride materials prepared by any one of claims 8 to 12; or thin films prepared by any one of claims 13 to 16; or electronic devices prepared by any one of claims 17 or 18.

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