Structure and method for manufacturing structure

Abstract

To provide a new structural body in which a coating of titanium nitride is formed on a substrate and the real parts of optical constants take values close to zero at wavelengths longer than that of 460nm.SOLUTION: The structure 10 includes a substrate 12 and a coating portion 14 of titanium nitride formed in a film shape or a particle shape on the substrate 12. In the coating portion 14, the molar ratio MN / MTi of N to Ti is 1.05 or more and 1.45 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a structure and a method for manufacturing a structure. [Background technology]

[0002] Conventionally, structures in which a titanium nitride coating is formed on a substrate are known (for example, Non-Patent Document 1). It has also been proposed to use a mixture of titanium nitride and titanium oxide as the coating to control the electrical resistance (Patent Document 1) and the optical constants (Non-Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-29382 [Non-patent literature]

[0004] [Non-Patent Document 1] "Dielectric properties of TiCx, TiNx, VCx, and VNx from 1.5 to 40 eV determined by electron-energy-loss spectroscopy", Phys. Rev. B 30, 1155 [Non-patent document 2] "Titanium Oxynitride Thin Films with Tunable Double Epsilon-NearZero Behavior for Nanophotonic Applications", ACS Appl. Mater. Interfaces 2017, 9, 35, 29857-29862 Summary of the Invention [Problem to be solved by the invention]

[0005] Recently, attention has been drawn to structures in which the real part of the optical constant (dielectric constant) is close to 0. Such materials are also called epsilon-near-zero (ENZ) materials, and have unique properties such as enhancing the optical electric field at wavelengths where the real part of the dielectric constant is close to 0, and are expected to be used in a variety of applications. The structure in Non-Patent Document 1 uses TiN as a titanium nitride coating. x (x=1), and the real parts of the optical constants are close to 0 at wavelengths longer than 460 nm. For example, a titanium nitride and titanium oxide coating may be used, as in Patent Document 1 and Non-Patent Document 2, but the real parts of the optical constants may be close to 0 at wavelengths longer than 460 nm. However, this method can result in poor manufacturing efficiency due to factors such as the slow oxide film formation rate. Therefore, it has been desired to provide a novel structure in which a titanium nitride coating is formed on a substrate, and in which the real parts of the optical constants are close to 0 at wavelengths longer than 460 nm.

[0006] The present disclosure has been made to solve these problems, and its main objective is to provide a novel structure in which a titanium nitride coating is formed on a substrate, in which the real part of the optical constants has a value close to 0 at wavelengths longer than 460 nm. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the present inventors have prepared a substrate containing a N-Ti alloy having a molar ratio of M N / M Ti They found that in a structure coated with titanium nitride having a refractive index of 1.05 or more and 1.45 or less, the real part of the optical constant takes a value close to 0 at wavelengths longer than 460 nm, and have completed the present disclosure.

[0008] That is, the structure of the present disclosure is A substrate; a coating portion of titanium nitride formed in the form of a film or particles on the substrate; Equipped with In the coating portion, the molar ratio M of N to Ti is N / MTi is between 1.05 and 1.45.

[0009] The method for manufacturing a structure of the present disclosure includes: A manufacturing method for manufacturing the above-mentioned structure, The method includes a coating step of forming the coating portion on the substrate by a sputtering film formation method. [Effects of the Invention]

[0010] In the present disclosure, it is possible to provide a structure in which a titanium nitride coating is formed on a substrate, in which the real part of the optical constant is close to 0 at wavelengths longer than 460 nm. The reason for this effect is presumed to be as follows. For example, when the molar ratio M of N to Ti is N / M Ti In the titanium nitride coating where λ is between 1.05 and 1.45, the carrier concentration and the number of impurity levels are appropriate, so it is thought that the real part of the optical constant takes a value close to 0 at wavelengths longer than 460 nm. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a perspective view showing an outline of the configuration of a structure 10. [Figure 2] 1 is a graph showing the wavelength dependence of the refractive index n and extinction coefficient k of the samples of Experimental Examples 1 to 7. [Figure 3] 1 is a graph showing the wavelength dependence of the real and imaginary parts of the optical constants of the samples of Experimental Examples 1 to 7. [Figure 4] 1 is a graph showing the relationship between the wavelength at which the real part of the optical constant becomes 0 and the composition ratio of the TiNx film. [Figure 5] Raman scattering measurement results for Experimental Examples 1 to 7. DETAILED DESCRIPTION OF THE INVENTION

[0012] [Structure] The structure of the present disclosure includes a substrate and a titanium nitride coating formed on the substrate. The coating may be formed on only one surface of the substrate, or may be formed on two opposing surfaces, for example. This structure may be used by irradiating it with light having a wavelength of 532 nm or 775 nm. Light of these wavelengths is used, for example, to generate quantum light (e.g., quantum entangled light) at a wavelength of 1550 nm, which is in the communication wavelength band. By using the structure of the present disclosure to enhance the optical electric field, highly efficient quantum light generation is expected.

[0013] The substrate is, for example, a flat substrate, preferably a plane-parallel substrate. The substrate may be, for example, a glass substrate such as fused silica glass or synthetic quartz glass, a ceramic substrate, or a resin substrate. The substrate is preferably light-transmitting, and is preferably transparent. The thickness T of the substrate may be, for example, 0.1 mm or more and 20 mm or less.

[0014] The titanium nitride of the coating portion may be formed in the form of a film or particles. When titanium nitride is formed in the form of particles, it is preferable that the particles form an aggregate, and it is more preferable that the particles are arranged without any gaps. When titanium nitride is formed in the form of particles, it is preferable that the titanium nitride particles are nanoparticles having a particle size of nano-size (1 nm or more but less than 1000 nm). The titanium nitride of the coating portion has a molar ratio M of N to Ti. N / M Ti The value is 1.05 or more and 1.45 or less. x Expressed as x=M N / M Ti Therefore, in the following, the molar ratio M N / M Tiis sometimes substituted with x. The value of x is preferably 1.1 or more and 1.4 or less. From the viewpoint of making the real part of the optical constant close to 0 at a wavelength of 775 nm, the value of x is more preferably 1.1 or more and 1.15 or less. From the viewpoint of making the real part of the optical constant close to 0 at a wavelength of 532 nm, the value of x is more preferably 1.15 or more and 1.25 or less, or 1.35 or more and 1.4 or less. The thickness t of the coating portion is preferably 10 nm or more and 200 nm or less, more preferably 20 nm or more and 150 nm or less, and even more preferably 40 nm or more and 70 nm or less. When the thickness t of the coating portion is 10 nm or more, the electric field can be enhanced due to the boundary conditions of the ENZ material. Furthermore, when the thickness t of the coating portion is 200 nm or less, the film formation time can be shortened, and manufacturing costs can be reduced. The titanium nitride coating is preferably not a mixture with titanium oxide. For example, in Raman scattering measurement, the Raman peaks characteristic of TiO2 (anatase type: 394, 514, 634 cm) are not present. -1 , Rutile type: 443,610 cm -1 In the structure of the present disclosure, titanium nitride in the coating portion is not mixed with oxide, but is TiN. x The desired optical properties can be obtained simply by changing the value of x in

[0015] In the structure of the present disclosure, the real part of the optical constant takes a value close to 0 (for example, within ±1) at wavelengths longer than 460 nm. The real part of the optical constant is calculated as follows. First, a spectroscopic ellipsometer is used to measure the refractive index n and extinction coefficient k at each wavelength. Then, from the measured refractive index n and extinction coefficient k, n 2 -k 2 The value of is calculated and used as the real part of the optical constant.

[0016] The structure of the present disclosure preferably has a real part of its optical constants that is 0 when irradiated with light having a wavelength of 475 nm or more and 800 nm or less. In such a structure, the real part of the optical constants is close to 0 at wavelengths such as 532 nm and 775 nm used in quantum light generation, and more efficient quantum light generation is expected. From the viewpoint of having the real part of the optical constants close to 0 at a wavelength of 775 nm, the structure preferably has a real part of its optical constants that is 0 when irradiated with light having a wavelength of 750 nm or more and 800 nm or less. Furthermore, from the viewpoint of having the real part of the optical constants close to 0 at a wavelength of 532 nm, the structure preferably has a real part of its optical constants that is 0 when irradiated with light having a wavelength of 490 nm or more and 570 nm or less. Furthermore, the structure of the present disclosure preferably has a real part of its optical constants that is within ±1 when irradiated with light having a wavelength of 532 nm or 775 nm, more preferably within ±0.5, and even more preferably within ±0.1. In such materials, the real part of the dielectric constant approaches 0 at the wavelengths used for quantum light generation, and highly efficient quantum light generation is expected.

[0017] The structure of the present disclosure may be used by irradiating it with light having a wavelength exceeding 460 nm. The wavelength of the irradiated light may be 475 nm or more and 800 nm or less, or 750 nm or more and 800 nm or less, or 490 nm or more and 570 nm or less. The structure of the present disclosure may be used by irradiating it with light having a wavelength at which the real part of the optical constant is close to 0, or by irradiating it with light having a wavelength other than that. The structure of the present disclosure may be used as an optical material. The structure of the present disclosure may be used by irradiating it with TiN x Since optical properties such as refractive index n and extinction coefficient k and their wavelength dependence vary depending on the value of x in the structure, the value of x and wavelength that provide the desired optical properties may be appropriately selected. The optical properties may be transmitted light properties or reflected light properties. The light irradiated onto the structure may be laser light. The light irradiation direction may be perpendicular to the substrate, along the substrate, or any other direction.

[0018] The structure of the present disclosure may be used, for example, for generating quantum light. x It is possible to form a film (ENZ material) and efficiently extract quantum light generated from a nonlinear optical crystal.

[0019] An example of a structure according to the present disclosure is shown in Fig. 1. Fig. 1 is a perspective view showing the outline of the configuration of a structure 10. As shown in Fig. 1, the structure 10 includes a substrate 12 and a titanium nitride coating 14 formed on the substrate 12. In the coating 14, the molar ratio M of N to Ti is 1 / 2. N / M Ti is greater than or equal to 1.05 and less than or equal to 1.45.

[0020] [Method of manufacturing the structure] The method for manufacturing a structure according to the present disclosure is a method for manufacturing the structure described above. This method for manufacturing a structure includes a coating step of forming a coating portion on a substrate by a sputtering film formation method. The substrate and the coating portion are as described in the structure described above.

[0021] As a sputtering film formation method, for example, magnetron sputtering film formation is preferable, and radio frequency (RF) magnetron sputtering film formation is more preferable. Sputtering film formation is preferably carried out using metallic titanium as a target under nitrogen flow rate control. In this way, the molar ratio M N / M Ti The base vacuum during sputtering is 1×10 -4 The sputtering deposition is preferably carried out under a mixed gas flow of N2 gas and an inert gas such as Ar. The N2 gas flow rate F A The inert gas flow rate F during sputtering deposition may be, for example, 0.1 sccm to 20 sccm, or 0.5 sccm to 10 sccm, depending on the size of the device. BThe flow rate [sccm] may vary depending on the size of the device, but may be, for example, 1 sccm to 100 sccm, or 10 sccm to 50 sccm. The volumetric ratio of nitrogen gas in the mixed gas may be, for example, 1% to 50%, or 1.5% to 35%. The volumetric ratio of nitrogen gas in the mixed gas is, for example, F A / (F A +F B The gas pressure during film formation P depo The pressure may be, for example, 0.1 Pa or more and 1 Pa or less, or 0.2 Pa or more and 0.6 Pa or less. The film formation may be performed at room temperature (for example, 0°C or more and 30°C or less) without heating the substrate. The film formation time may be, for example, 1 minute or more and 120 minutes or less.

[0022] In the embodiment described above, it is possible to provide a structure in which a titanium nitride coating is formed on a substrate, in which the real part of the optical constant is close to 0 at wavelengths longer than 460 nm. The reason for this effect is presumed to be as follows. For example, when the molar ratio M of N to Ti is N / M Ti In the titanium nitride coating where λ is between 1.05 and 1.45, the carrier concentration and the number of impurity levels are appropriate, so it is thought that the real part of the optical constant takes a value close to 0 at wavelengths longer than 460 nm.

[0023] Furthermore, in the above-described embodiment, for example, at wavelengths used for quantum light generation (e.g., 532 nm, 775 nm), when the real parts of the optical constants are close to zero, the optical electric field in and around titanium nitride is enhanced, and highly efficient quantum light generation is expected. Specifically, when the relative dielectric constant ε of the titanium nitride film approaches 0, the optical electric field is enhanced due to boundary conditions. For example, consider the interface where medium 1 (coating) and medium 2 (substrate) meet. If the relative dielectric constants of each medium and the optical electric field perpendicular to the interface are ε1, ε2, E1, and E2, respectively, then ε1E1 = ε2E2 holds based on the boundary conditions. If ε1 approaches 0, E1 becomes infinitely large, which is thought to enhance the optical electric field.

[0024] Furthermore, in the above-described embodiment, the coating is made of titanium nitride, which has high heat resistance, and therefore the structure is stable and is unlikely to undergo compositional changes even when exposed to strong light. Therefore, it is expected to be a highly durable structure that can withstand repeated use even when exposed to strong incident light, such as light with a wavelength of 775 nm.

[0025] It goes without saying that the present invention is not limited to the above-described embodiment, and can be embodied in various forms as long as they fall within the technical scope of the present invention.

[0026] The present disclosure may be any of the following [1] to [6]. [1] A method for manufacturing a titanium nitride substrate, comprising: a substrate; and a titanium nitride coating formed on the substrate in the form of a film or particles, wherein the molar ratio M of N to Ti in the coating is N / M Ti is greater than or equal to 1.05 and less than or equal to 1.45. [2] The molar ratio M N / M Ti is any one of 1.1 or more and 1.15 or less, 1.15 or more and 1.25 or less, and 1.35 or more and 1.4 or less. [3] The structure according to [1] or [2], wherein the thickness of the covering portion is 10 nm or more and 200 nm or less. [4] The structure according to any one of [1] to [3], wherein the real part of the optical constant of the structure is 0 when irradiated with light having a wavelength of 475 nm or more and 800 nm or less. [5] The structure according to any one of [1] to [4], wherein the real part of the optical constant has a value within ±1 when irradiated with light having a wavelength of 532 nm or 775 nm. [6] A method for producing the structure according to any one of [1] to [5], comprising a coating step of forming the coating portion on the substrate by a sputtering film formation method. [Example]

[0027] Specific examples of fabricating the structure of the present disclosure will be described as Examples, with Experimental Examples 1 to 3 and 5 to 7 corresponding to Examples of the present disclosure, and Experimental Example 4 corresponding to a Comparative Example.

[0028] Titanium nitride thin films (TiN) with different nitrogen contents were formed on a fused quartz substrate (0.5 mm thick) using a RF magnetron sputtering system with a target of metallic Ti (99.99% purity, 4 inches in size) under nitrogen flow control. x ) were fabricated and designated as Experimental Examples 1 to 7. The power input to the Ti target was 200 W, and the base vacuum before film formation was 1×10 -4 A mixed gas of Ar and N was used as the sputtering gas, with a flow rate of Ar and N during film formation at a pressure of 0.1 Pa or less. The substrate was not heated during film formation. depo are shown in Table 1. Table 1 also shows the film thickness after deposition in Experimental Examples 1 to 7. The film thickness was evaluated using a step gauge.

[0029] The Ti and N compositions (atomic ratio at%) of the samples of Experimental Examples 1 to 7 were determined using an electron probe micro analyzer (EPMA). The EPMA equipment used was a JXA-iHP200F (JEOL), and the measurement conditions were an acceleration voltage of 2 kV, a probe current of 20 nA, and an electron beam diameter of 50 μmφ. The Ti and N compositions were determined from the intensity ratio of the obtained characteristic X-rays (N Kα rays and Ti Lα rays). For correction of the composition analysis, a cross section of titanium nitride powder manufactured by Kojundo Chemical Laboratory, which had been ion-milled, was used. Table 1 shows the Ti and N compositions (atomic ratio at%) of the samples of Experimental Examples 1 to 7, which were analyzed for composition at five different points. The Ti and N composition ratio (TiN x The value of x in this case was calculated and shown in Table 1. As shown in Table 1, it was found that samples with different values ​​of x could be realized.

[0030] For the samples of Experimental Examples 1 to 7, the TiN xThe film thickness was determined. Then, the refractive index n and extinction coefficient k were measured using a spectroscopic ellipsometer. Figure 2 shows the wavelength dependence of the refractive index n and extinction coefficient k for the samples of Experimental Examples 1 to 7. It was found that the values ​​of n and k differed greatly depending on the sample.

[0031] From the measured refractive index n and extinction coefficient k, the real part of the optical constant (relative dielectric constant) of each sample (n 2 -k 2 ) and the imaginary part (2nk) were calculated. Figure 3 shows the wavelength dependence of the real and imaginary parts of the optical constants of the samples of Experimental Examples 1 to 7. Currently, laser light with wavelengths of 532 nm and 775 nm is used as a quantum light generation source. In order to generate quantum light with high efficiency, it is desirable that the real parts of the optical constants be close to 0 (zero) at the wavelength of the quantum light generation source. For the samples of Experimental Examples 1 to 7, the real parts of the optical constants at these wavelengths were calculated and are summarized in Table 1. Furthermore, for the samples of Experimental Examples 1 to 7, the wavelengths at which the real parts of the optical constants become 0 were calculated and are summarized in Table 1.

[0032] Figure 4 shows the real part of the optical constants (n 2 -k 2 ) becomes 0 and TiN x Film composition ratio (TiN x The relationship between the real part and the value of x in the above graph is shown in Figure 4. Figure 4 also shows an example from a previous report (Non-Patent Document 1 mentioned above). Comparing the previous report with the current experimental example, it was found that in samples with a low nitrogen content where x≦1.00, the wavelength at which the real part was 0 was limited to short wavelengths less than 500 nm, but in samples with a nitrogen content exceeding 1.00 (here, samples where 1.14≦x≦1.39), the real part was 0 at any wavelength between 500 nm and 800 nm. Of these, it was found that from the perspective of using a laser beam with a wavelength of 532 nm, 1.36≦x≦1.39 is more preferable, and from the perspective of using a laser beam with a wavelength of 775 nm, x=1.14 is preferable.

[0033] The samples of Experimental Examples 1 to 7 were subjected to Raman scattering measurements (NRS-3300 instrument, excitation wavelength 532 nm). In all samples, Raman peaks characteristic of TiO2 (anatase type: 394, 514, 634 cm) were observed. -1 , Rutile type: 443,610 cm -1 ), it was confirmed that the sample (coated portion) in this experimental example was not a mixture of TiN and TiO2 like the samples in Patent Document 1 and Non-Patent Document 2. The positions of the Raman peaks characteristic of anatase and rutile TiO2 were determined based on Reference 1 ("Raman Spectroscopy of Titania (TiO2) Nanotubular Water-Splitting Catalysts", Journal of the Arkansas Academy of Science, Vol. 65

[2011] , Art. 9).

[0034] [Table 1] [Explanation of symbols]

[0035] 10 structure, 12 substrate, 14 coating, T thickness, t thickness.

Claims

1. A substrate; a coating portion of titanium nitride formed in the form of a film or particles on the substrate; Equipped with In the coating portion, the molar ratio M of N to Ti is N / M Ti is greater than or equal to 1.05 and less than or equal to 1.

45.

2. The molar ratio M N / M Ti The structure according to claim 1 , wherein is any one of 1.1 or more and 1.15 or less, 1.15 or more and 1.25 or less, and 1.35 or more and 1.4 or less.

3. The structure according to claim 1 or 2, wherein the thickness of the covering portion is 10 nm or more and 200 nm or less.

4. 3. The structure according to claim 1, wherein the real part of the optical constant of the structure becomes 0 when the structure is irradiated with light having a wavelength of 475 nm or more and 800 nm or less.

5. 3. The structure according to claim 1, wherein the real part of the optical constant has a value within ±1 when irradiated with light having a wavelength of 532 nm or 775 nm.

6. A manufacturing method for manufacturing the structure according to claim 1 or 2, comprising: a coating step of forming the coating portion on the substrate by a sputtering film formation method, Method for manufacturing the structure.

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