An alternating ultrathin doped diamond exciton insulator and its preparation method

Abstract

This invention discloses an alternating ultrathin doped diamond exciton insulator and its preparation method, involving a novel exciton insulator mechanism. This invention introduces additional bound electrons and holes by alternating doping of diamond with ultrathin boron and phosphorus / nitrogen atomic layers, forming an ultrathin bound exciton layer through bulk layered coupling. These excitons share relatively similar polarization orientations, creating conditions for the formation of Bose-Einstein condensates containing excitons. Furthermore, as the temperature decreases, strong interactions form between the excitons, inducing the formation of exciton insulators in diamond. Alternating ultrathin doping significantly enhances the exciton binding energy through quantum confinement effects, while the ultra-high surface area to volume ratio allows for more flexible control of exciton properties by external electric fields, temperature, and other factors, providing a solid foundation for applications such as light-emitting diodes and quantum computing.

Description

Technical Field

[0001] This invention relates to an exciton insulator using boron, phosphorus / nitrogen alternating ultrathin doped diamond and its preparation method, belonging to the field of semiconductor and condensed matter technology. Background Technology

[0002] Since the exciton was proposed in 1930, the exploration of exciton-Bose-Einstein condensates and exciton-insulating states has never ceased. Excitons have also influenced optoelectronic applications in various fields such as photovoltaics and light-emitting diodes. Diamond possesses excellent electrical and thermal conductivity and has been widely studied and applied in various electronic devices. However, the electrical properties of doped diamond typically exhibit conductor or semiconductor behavior, and exciton-insulator properties of diamond have not yet been reported. Currently, the most promising material systems are semiconductor quantum well structures and layered two-dimensional materials, but the former requires specific lattice-matched heterojunction materials, while the latter has lower interlayer coupling and exciton binding energies. These novel materials or topologies under the influence of excitons will provide new evidence for exciton insulation. Although theoretical articles are constantly emerging, there is still a lack of practical, direct, and effective experimental verification. Scientists are spending a significant amount of time searching for practical materials or structures to address these issues. However, diamond structures with alternating layers of ultrathin boron and phosphorus atoms deviate from the two aforementioned material systems. The exciton binding energy of boron and phosphorus atoms exceeds 2 eV, and the donor level of phosphorus atoms is 0.58 eV below the conduction band; the exciton binding energy of boron and nitrogen atoms exceeds 6 eV, and the donor level of nitrogen atoms is 1.7 eV below the conduction band, while the acceptor level of boron atoms is 0.37 eV above the valence band. Therefore, bound electrons are formed around phosphorus or nitrogen atoms, which then form strongly bound excitons with the acceptors of boron atoms, satisfying the strong exciton binding energy condition for exciton insulators. This drives electrons and holes to form bound excitons within the bulk, enabling the production of novel exciton insulators. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing diamond exciton insulators by effectively achieving alternating ultrathin doping technology of boron, phosphorus / nitrogen atoms in diamond.

[0004] The technical solution adopted in this invention is as follows:

[0005] An alternating ultrathin doped diamond exciton insulator is disclosed, prepared by microwave plasma chemical vapor deposition (MPCVD). During the preparation process, two doping gases are introduced alternately at different times: a boron-containing doping gas and a phosphorus / nitrogen-containing doping gas. This achieves layered doping of boron and phosphorus / nitrogen elements during diamond growth, forming alternating ultrathin heavily doped boron and phosphorus / nitrogen atom layers within the diamond. This allows the holes formed by boron doping to couple with the electrons formed by phosphorus / nitrogen doping, creating a bound exciton layer. Furthermore, lowering the system temperature induces strong interactions between excitons, thereby inducing the formation of an exciton insulator in the diamond. This method can increase the insulation transition temperature of diamond, allowing phase transition to be induced at temperatures below 100 K.

[0006] In the above technical solution, the boron-doped gas is one or more boron-containing gases such as borane and diborane.

[0007] The phosphorus / nitrogen doped gas is one or more of phosphine, phosphate ester, nitrogen, ammonia, etc.

[0008] The specific steps of preparing diamond using the MPCVD method include: placing a clean single-crystal diamond substrate into an MPCVD reaction chamber, evacuating the chamber, and then introducing hydrogen gas to etch the non-diamond phases on the diamond surface; after etching the substrate, introducing carbon source gas and dopant gas into the reaction chamber to grow diamond. The evacuation process is carried out until the background vacuum level in the reaction chamber is not less than 1 × 10⁻⁶. -3 Torr.

[0009] The carbon source gas is methane or other commonly used carbon source gases. During the growth process, the input power of the microwave source is controlled within the range of 1–10 kW, and the cavity gas pressure ranges from 10 to 300 Torr. The doping gases are boron-containing gas and phosphorus / nitrogen-containing gas, respectively. The flow ratio of carbon source gas to boron-containing gas is typically 2:1, and the flow ratio of carbon source gas to phosphorus / nitrogen-containing gas is typically 2:1 to 6:1. Diamond is layered doped by alternating the introduction of the two doping gases at different time intervals. For example, boron-containing gas is introduced first for 0.5–10 seconds, followed by phosphorus / nitrogen-containing gas for 0.5–10 seconds, achieving layered co-doping of boron-doped and phosphorus / nitrogen-doped diamond. The acceptor and donor coupling brought by the two types of doped atoms forms a bound exciton layer. This bound exciton layer can significantly enhance the exciton binding energy through quantum confinement effects. Simultaneously, the ultra-high specific surface area / volume ratio makes the properties of the bound exciton layer more sensitive to external electric fields, temperature, and other factors. Furthermore, when the temperature decreases, the Coulomb binding energy of the excitons becomes greater than the energy required for electron excitation, causing the excitons in the diamond to become unstable and thus transition to an insulating state, promoting the research and practical application of exciton insulation theory.

[0010] According to a specific embodiment of the present invention, an exciton insulator with alternating ultrathin diamond doping and its preparation method includes the following steps:

[0011] 1) Use single-crystal diamond with (100) or (110) crystal orientation as a substrate;

[0012] 2) Before growth on the substrate surface, the substrate is ultrasonically cleaned using acetone, isopropanol, ethanol and deionized water.

[0013] 3) Use MPCVD equipment to create a vacuum; after vacuuming, introduce hydrogen gas to etch the non-diamond phase on the diamond surface;

[0014] 4) During the growth stage, maintain the microwave source input power at 1-10kW and the cavity gas pressure at 10-300Torr, using methane gas as the main carbon source;

[0015] 5) During the doping growth stage, boron-containing doping gas and phosphorus / nitrogen-containing doping gas are introduced alternately in a time-division manner as doping sources, each for 0.5 to 10 seconds. The flow rate ratio of carbon source gas to boron-containing doping gas is 2:1, and the flow rate ratio of carbon source gas to phosphorus / nitrogen-containing doping gas is 2:1 to 6:1; thus achieving alternating ultrathin heavy doping of boron atoms and phosphorus / nitrogen atoms during diamond growth.

[0016] 6) Lower the temperature to below 100K to induce a phase transition by forming Bose-Einstein condensates in the excitons within the system.

[0017] The beneficial effects of this invention compared to the prior art are:

[0018] Traditional diamonds are mostly conductors or semiconductors, lacking the ability to undergo phase transitions. This invention presents an exciton insulator using ultrathin diamond with alternating boron and phosphorus / nitrogen atom doping, along with its preparation method. Based on single-crystal diamond, it innovates the exciton material system by introducing boron acceptors and phosphorus / nitrogen donors during the growth of single-crystal diamond using MPCVD equipment. By controlling the flow rate ratio and the dopant gas introduction time, an ultrathin heavily doped layer is formed. Unlike simultaneous doping, alternating doping allows for better pairing of donors and acceptors, introducing a large number of bound excitons with the same orientation, making it easier for excitons to interact. When the temperature decreases, the excitons within the heavily doped diamond form a Bose-Einstein condensate, inducing a phase transition from semiconductor to exciton insulator, providing a solid material foundation for diamond materials in applications such as light-emitting diodes and quantum detectors. Attached Figure Description

[0019] Figure 1The graph shows the low-temperature resistance of the exciton insulator, which is simultaneously doped with boron and phosphorus atoms in diamond, obtained by the method in Example 1. The test range is from 2K to 300K. When the temperature gradually decreases to 6.68K, the resistance of the exciton insulator begins to increase exponentially. The maximum resistance of the exciton insulator is 4873 times that at room temperature (298.15K).

[0020] Figure 2 The graph shows the low-temperature resistance of the exciton insulator, which is simultaneously doped with boron and phosphorus atoms in diamond, obtained by the method in Example 2. The test range is from 10K to 300K. When the temperature gradually decreases to 17.21K, the resistance of the exciton insulator begins to increase exponentially. The maximum resistance of the exciton insulator is 2785 times that at room temperature (298.15K).

[0021] Figure 3 This is a schematic diagram of the exciton insulator structure of alternating ultrathin diamond prepared by the method in Example 3;

[0022] Figure 4 The graph shows the low-temperature resistance of the exciton insulator using boron and phosphorus atoms alternately doped with ultrathin diamond, obtained by the method in Example 3. The test range is from 50K to 300K. When the temperature gradually decreases to 51.3K, the resistance of the exciton insulator begins to increase exponentially. The maximum resistance of the device is 4615 times that at room temperature (298.15K). Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0024] Reference Figure 3 This invention discloses an exciton insulator using boron and phosphorus / nitrogen-doped diamond in an alternating ultrathin doping process. During the MPCVD growth of diamond, borane gas and phosphorus- and / or nitrogen-containing gases are used for separate doping to obtain a single-crystal diamond material grown with alternating boron and phosphorus / nitrogen ultrathin doping. By layering boron and phosphorus / nitrogen elements in the diamond, holes and electrons are introduced as charge carriers, forming exciton layers with roughly consistent orientations within the bulk, resulting in strong interactions between excitons. Compared to the exciton insulator in Example 1, which uses boron and phosphorus atoms to simultaneously dope diamond, the excitons in the exciton insulator of Example 3, with alternating ultrathin doping, can form a Bose-Einstein condensate at a relatively higher temperature, inducing a semiconductor phase transition in diamond to an exciton insulator. This alternating ultrathin doped diamond exciton insulator can effectively provide an experimental basis for the theory of exciton insulation, promoting the development of condensed matter theory and its application in diamond quantum detection.

[0025] Example 1:

[0026] 1) Take a single crystal diamond with a (100) crystal orientation and a size of 9mm×9mm as a substrate, and polish the growth surface to ensure that the growth surface is smooth and flat;

[0027] 2) The substrate was sequentially immersed in acetone, isopropanol, ethanol and deionized water for ultrasonic cleaning. Each solvent was used for 10 minutes to remove organic impurities attached to the surface and then dried with N2.

[0028] 3) Use MPCVD equipment to evacuate to 10 -3 After Torr, hydrogen gas is introduced to etch the substrate surface. During the etching process, the chamber pressure is maintained at 100 Torr, the temperature at 820℃, and the etching time at 30 min, in order to remove the non-diamond phase on the substrate surface.

[0029] 4) During the growth stage, maintain the microwave source input power at 5kW, the cavity gas pressure at 140Torr, the growth temperature at 920℃, and use methane gas as the main carbon source with a gas flow rate of 30sccm.

[0030] 5) During the growth stage, a mixture of borane and phosphine gas is introduced as a direct doping source, with the gas flow rates of borane and phosphine being 15 sccm and 5 sccm, respectively, to achieve co-doping of diamond with boron and phosphorus atoms.

[0031] The resistance of the boron-phosphorus co-doped diamond prepared in this example varies with temperature as follows: Figure 1 As shown, the resistance increases exponentially when the ambient temperature drops to 6.68K. The graph showing the relationship between diamond resistance and temperature reveals that this invention uses boron-phosphorus co-doped diamond as an exciton insulator. The boron and phosphorus elements in the diamond interact and couple to form excitons. As the temperature decreases, strong interactions form between the excitons, resulting in a Bose-Einstein condensate, leading to an exponential increase in resistance and thus achieving an exciton insulator.

[0032] Example 2:

[0033] 1) Take a single crystal diamond with (111) crystal orientation and a size of 9mm×9mm as a substrate, and polish the growth surface to ensure that the growth surface is smooth and flat;

[0034] 2) The substrate was sequentially immersed in acetone, isopropanol, ethanol and deionized water for ultrasonic cleaning. Each solvent was used for 10 minutes to remove organic impurities attached to the surface and then dried with N2.

[0035] 3) Use MPCVD equipment to evacuate to 10-4 After Torr, hydrogen gas is introduced to etch the substrate surface. During the etching process, the chamber pressure is maintained at 100 Torr, the temperature at 820℃, and the etching time at 30 min, in order to remove the non-diamond phase on the substrate surface.

[0036] 4) During the growth stage, maintain the microwave source input power at 5kW, the cavity gas pressure at 140Torr, the growth temperature at 920℃, and use methane gas as the main carbon source with a gas flow rate of 30sccm.

[0037] 5) During the growth stage, a mixture of borane and phosphine gas is introduced as a direct doping source, with the gas flow rates of borane and phosphine being 15 sccm and 15 sccm, respectively, to achieve co-doping of diamond with boron and phosphorus atoms.

[0038] The boron and phosphorus co-doped diamond obtained in step 5) exhibits the following relationship between its resistance and temperature: Figure 2 As shown, the resistance increases exponentially when the ambient temperature drops to 17.21K. (This is in contrast to...) Figure 1 In comparison, after treatment in step 5), i.e., increasing the phosphine gas flow rate by 5 sccm during the growth stage, the exciton insulation transition temperature of diamond increased to 17.21 K. Therefore, increasing the phosphine gas doping flow rate is beneficial for electron-hole coupling to form excitons, which helps to increase the exciton insulation transition temperature of diamond and achieve exciton insulation.

[0039] Example 3:

[0040] 1) Take a single crystal diamond with a (110) crystal orientation and a size of 12mm×12mm as a substrate, and polish the growth surface to ensure that the growth surface is smooth and flat;

[0041] 2) The substrate was sequentially immersed in acetone, isopropanol, ethanol and deionized water for ultrasonic cleaning. Each solvent was used for 10 minutes to remove organic impurities attached to the surface and then dried with N2.

[0042] 3) Use MPCVD equipment to evacuate to 10 -3 After Torr, hydrogen gas is introduced to etch the substrate surface. During the etching process, the chamber pressure is maintained at 100 Torr, the temperature at 820℃, and the etching time at 30 min, in order to remove the non-diamond phase on the substrate surface.

[0043] 4) During the growth stage, maintain the microwave source input power at 5kW, the cavity gas pressure at 150Torr, the growth temperature at 920℃, and use methane gas as the main carbon source with a gas flow rate of 30sccm.

[0044] 5) During the growth stage, borane gas and phosphine gas are alternately introduced as direct doping sources, with borane and phosphine gas flow rates of 15 sccm and 15 sccm, respectively, to achieve alternating ultrathin doping of diamond with boron and phosphorus atoms.

[0045] The resistance of the boron and phosphorus-doped diamond obtained in step 5) varies with temperature as follows: Figure 4 As shown, the resistance increases exponentially when the ambient temperature drops to 51.3K. (This is in contrast to...) Figure 2 In comparison, after step 5), alternating doping is used during the growth stage (its structural schematic is shown in Figure 1). Figure 3 After substitution with simultaneous doping, the exciton-insulator transition temperature of boron / phosphorus co-doped diamond increases significantly. Therefore, compared with diamond exciton insulators co-doped with boron / phosphorus, alternating ultrathin boron / phosphorus doping is beneficial for interlayer exciton coupling of boron and phosphorus atoms, significantly increasing the exciton binding energy through quantum confinement effect, and facilitating the high-temperature exciton-insulator transition of diamond.

[0046] It is obvious that this invention is not limited to the specific embodiments described above. Those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of this invention. The exemplary embodiments were chosen and described to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various exemplary embodiments of the invention, as well as various choices and modifications. The scope of this invention is intended to be defined by the claims and their equivalents.

Claims

1. An alternating ultrathin doped diamond exciton insulator, characterized in that, Diamond is prepared using microwave plasma chemical vapor deposition (MPCVD). During the preparation process, two doping gases are introduced alternately in a time-sequential manner: a boron-containing doping gas and a phosphorus / nitrogen-containing doping gas. This allows for layered doping of boron and phosphorus / nitrogen elements during diamond growth, forming alternating ultrathin, heavily doped boron atom layers and ultrathin, heavily doped phosphorus / nitrogen atom layers in the diamond. These layers couple to form bound excitons, thereby achieving an insulating transition in the diamond. The phase transition can be induced by lowering the temperature to below 100K. The phosphorus / nitrogen-containing doping gas contains one or more of phosphorus and nitrogen elements.

2. The alternating ultrathin doped diamond exciton insulator according to claim 1, characterized in that, The specific steps of preparing diamond using the MPCVD method include: using a clean single-crystal diamond as a substrate, placing it in an MPCVD reaction chamber, evacuating it, and then introducing hydrogen gas to etch the non-diamond phase on the diamond surface; after etching the substrate, introducing carbon source gas into the reaction chamber to grow diamond, and alternately introducing boron-doped gas and phosphorus / nitrogen-doped gas at different times.

3. The alternating ultrathin doped diamond exciton insulator according to claim 2, characterized in that, The vacuuming process is to ensure that the background vacuum level in the reaction chamber is not less than 1×10⁻⁶. -3 During the growth process, the input power of the microwave source is controlled within the range of 1 to 10 kW, and the cavity gas pressure ranges from 10 to 300 Torr.

4. The alternating ultrathin doped diamond exciton insulator according to claim 2, characterized in that, The carbon source gas is methane, wherein the flow ratio of the carbon source gas to the boron-doped gas is 2:1, and the flow ratio of the carbon source gas to the phosphorus / nitrogen-doped gas is 2:1 to 6:

1.

5. The alternating ultrathin doped diamond exciton insulator according to claim 2, characterized in that, Diamond was layered by alternating the introduction of two doping gases at different time intervals, with each doping gas introduced for 0.5-10 seconds, to form an ultrathin doped layer.

6. The alternating ultrathin doped diamond exciton insulator according to claim 1, characterized in that, The boron-doped gas is one or more of borane and diborane.

7. The alternating ultrathin doped diamond exciton insulator according to claim 1, characterized in that, The phosphorus / nitrogen doped gas is one or more of phosphine, phosphate ester, ammonia, and nitrogen.

8. A method for preparing an alternating ultrathin doped diamond exciton insulator, characterized in that, Includes the following steps: 1) Using single-crystal diamond as a substrate; 2) Before growth on the substrate surface, the substrate is ultrasonically cleaned using acetone, isopropanol, ethanol and deionized water. 3) Use MPCVD equipment to create a vacuum; after vacuuming, introduce hydrogen gas to etch the non-diamond phase on the diamond surface; 4) During the growth stage, maintain the microwave source input power at 1-10kW and the cavity gas pressure at 10-300Torr, and use methane gas as the carbon source. 5) During the doping growth stage, boron-containing doping gas and phosphorus / nitrogen-containing doping gas are introduced alternately in a time-division manner as doping sources, each for 0.5 to 10 seconds. The flow rate ratio of carbon source gas to boron-containing doping gas is 2:1, and the flow rate ratio of carbon source gas to phosphorus / nitrogen-containing doping gas is 2:1 to 6:1; thus achieving alternating ultrathin heavy doping of boron atoms and phosphorus / nitrogen atoms during diamond growth. 6) Lower the temperature to below 100K to induce the formation of Bose-Einstein condensates in the excitons within the system, thereby inducing a phase transition to an insulator.

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