Bolometer and manufacturing method

Abstract

To provide a bolometer and a manufacturing method that makes it easy to achieve low resistance.SOLUTION: A bolometer includes a substrate having a stacking surface, two electrodes respectively having a main surface and a side extending from the main surface to the stacking surface, and a film including carbon nanotubes, the film includes a first portion stacked on the main surface, a second portion stacked on the stacking surface between the two electrodes, and a connecting portion connecting the first portion and the second portion at the side, the second portion has an average film thickness of less than 10 nm.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present disclosure relates to bolometers and methods of manufacture. [Background technology]

[0002] It is known to use a bolometer as an infrared sensor.

[0003] For example, Patent Document 1 discloses a bolometer equipped with a film made of carbon nanotubes. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2022-25051 Summary of the Invention [Problem to be solved by the invention]

[0005] The bolometer disclosed in Patent Document 1 uses a printing technique to form a film made of carbon nanotubes, and in this case, it may be difficult to reduce the resistance of the bolometer.

[0006] An object of the present disclosure is to provide a bolometer and a manufacturing method thereof that solves the above-mentioned problems. [Means for solving the problem]

[0007] The bolometer of the present disclosure comprises a substrate having a stacking surface, two electrodes each having a main surface and a side extending from the main surface to the stacking surface, and a film including carbon nanotubes, the film having a first portion stacked on the main surface, a second portion stacked on the stacking surface between the two electrodes, and a connecting portion at the side connecting the first portion and the second portion, and the average film thickness of the second portion is less than 10 nm.

[0008] The manufacturing method of the present disclosure includes the steps of preparing a substrate having a laminated surface and two electrodes, each having a main surface and a side surface extending from the main surface to the laminated surface of the substrate; immersing the substrate in a dispersion liquid containing carbon nanotubes; and lifting the immersed substrate at a moving speed of 0.3 μm / s or less so that the laminated surface passes through the liquid surface of the dispersion liquid, wherein the dispersion liquid contains carbon nanotubes at a concentration of 0.0001 to 0.005% and a surfactant at a concentration of 0.05 to 0.08%. Effect of the Invention

[0009] According to the bolometer and manufacturing method according to the present disclosure, the resistance can be easily reduced. [Brief description of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view I showing an example of the configuration of a bolometer according to the present disclosure. [Diagram 2] 1 is a flowchart I showing an example of a process of a manufacturing method according to the present disclosure. [Diagram 3] FIG. 1 is an explanatory diagram I of dip coating in one step of the manufacturing method according to the present disclosure. [Figure 4] FIG. 2 is an explanatory diagram II of dip coating in one step of the manufacturing method according to the present disclosure. [Diagram 5] 1 is a cross-sectional view of an element in which an electrode is formed on a CNT film in Comparative Example 1. FIG. [Figure 6] FIG. 11 is a cross-sectional view of an element in Comparative Example 2 in which a CNT film is formed by a casting method after forming an electrode. [Figure 7] This is an SEM image taken along the line indicated by the arrow B in FIG. [Figure 8] 2 is a cross-sectional view II showing an example of the configuration of a bolometer according to the present disclosure. [Figure 9] 11 is a flowchart II showing an example of a process of a manufacturing method according to the present disclosure. [Figure 10] 1 is a cross-sectional view showing an example of the configuration of a bolometer according to the present disclosure. [Figure 11]1 is a flowchart illustrating an example of a process of a manufacturing method according to the present disclosure. [Figure 12] 1 is an SEM image of a bolometer film in an embodiment. [Figure 13] ii is an SEM image of a bolometer film in the embodiment; [Figure 14] FIG. 14 is an enlarged view of part C in FIG. [Figure 15] 1 is a cross-sectional TEM image of a bolometer film in an embodiment. [Figure 16] 1 is a comparison table of the average film thickness of each film in the examples, and the resistance value and TCR value at 3 V. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, each embodiment of the present disclosure will be described with reference to the drawings. Note that the drawings and specific configurations used in each embodiment should not be used to interpret the disclosure. The same or corresponding configurations in all drawings are given the same reference numerals, and common descriptions are omitted. It should be noted that in this disclosure, the drawings may relate to one or more embodiments.

[0012] An example of the configuration of a bolometer according to the present disclosure will now be described with reference to FIGS.

[0013] (Bolometer configuration) For example, a cross-sectional view of a bolometer in this disclosure is taken as a cross-sectional view taken along line XX' in FIG. The bolometer 1 is used as a sensor for detecting infrared rays. As shown in FIG. 1, the bolometer 1 includes a substrate 11 , an electrode 12 , and a film 13 . The substrate 11 has a lamination surface P. For example, the base material 11 is a Si substrate processed using a silicon wafer. For example, the substrate 11 may be a monomer such as Parylene (registered trademark), a resin such as polyimide, or an organic material such as plastic. For example, the base material 11 may have a readout circuit formed thereon. For example, the base material 11 may have an electrically insulating base insulating layer. Methods for forming the base insulating layer include a method of subjecting the base material 11 to heat treatment and a method of directly forming the base insulating layer by a CVD (Chemical Vapor Deposition) method. The base insulating layer is, for example, silicon oxide, silicon nitride, or the like.

[0014] (electrode 12) The electrode 12 includes two electrodes (a first electrode 12a and a second electrode 12b) each having a main surface M and a side surface S extending from the main surface M to the stacking surface P. For example, the electrode 12 is an electrode using Au, Al, Ti, or an alloy mainly made of these materials. As an example, the first electrode 12a includes an electrode underlayer (12ax). Similarly, the second electrode 12b includes an electrode underlayer (12bx). The underlayers (12ax, 12bx) may be layers containing Ti. The thickness of the electrode 12 can be adjusted appropriately. For example, the thickness of the electrode 12 is 10 nm to 1.0 mm. For example, the thickness of the electrode 12 is 50 nm to 1.0 μm. The distance between the two electrodes (first electrode 12a, second electrode 12b) can be adjusted as appropriate. For example, the distance between the two electrodes (first electrode 12a, second electrode 12b) is 1.0 μm to 500 μm. For example, the distance between the two electrodes (first electrode 12a, second electrode 12b) is 5.0 μm to 200 μm.

[0015] (film) The film 13 includes carbon nano tubes (CNTs) 51. For example, the film 13 including the CNTs 51 may act as an infrared light receiving portion. The film 13 has a first portion 13c laminated on the main surface M of the electrode 12, a second portion 13e laminated on a laminate surface P between two electrodes (first electrode 12a, second electrode 12b), and a connection portion 13d connecting the first portion 13c and the second portion 13e on a side surface S. As a result, the CNTs laminated on the main surface M of the electrode 12 and the CNTs laminated on the laminate surface P between the two electrodes are electrically connected by the CNTs formed in the connection portion 13d. For example, the second portion 13e of the film 13 may include a first orientation layer 131 in which the CNTs 51 are aligned. This allows a plurality of aligned CNTs to connect two electrodes (the first electrode 12a and the second electrode 12b), and thus the CNTs 51 in the film 13 are electrically connected with an increased number of conductive paths. This reduces the resistance of the entire film 13, making it easier to reduce the resistance of the bolometer 1. For example, the first alignment layer 131 may be an alignment layer in which the wall surfaces of CNTs are bonded to each other and aligned in the same direction. For example, the first alignment layer 131 may be an alignment layer in which several to several tens of CNTs are bundled in the same direction with parts of the wall surfaces of the CNTs bonded together, and these CNT bundles are aligned in the same direction. For example, first alignment layer 131 may be an alignment layer in which bundles of CNTs are aligned in the same direction at intervals of at least the diameter of one CNT. For example, the first alignment layer 131 may be an alignment film containing CNTs or CNT bundles that have a different orientation direction and angle from the CNTs, connecting the CNTs or CNT bundles aligned in the same direction as described above. For example, the second portion 13 e of the film 13 may include an underlayer 132 between the stacking plane P and the first alignment layer 131 . For example, the underlayer 132 may be a second alignment layer in which the CNTs 51 are aligned. In this case, the second alignment layer may be an alignment layer having the characteristics of the first alignment layer described above. For example, the density of CNTs in the underlayer 132 (second alignment layer) may be higher than the density of CNTs in the first alignment layer 131 . For example, the underlayer 132 may be a non-oriented layer in which the CNTs are randomly oriented to form a network. For example, the underlayer 132 may be a non-oriented layer in which CNTs form locally oriented domains, and these locally oriented domains are oriented in random directions to form a network. For example, the average thickness of the second portion 13e is 1.0 nm or more and less than 10 nm. For example, the average total thickness of the first alignment layer 131 and the underlayer 132 of the second portion 13e is 1.0 nm or more and less than 10 nm. For example, the average thickness of the first alignment layer 131 in the second portion 13e is 9.0 nm or less For example, the average thickness of the first alignment layer 131 in the second portion 13e is 0.5 nm or more and 5.0 nm or less. The thickness of the second portion 13e of the film 13 can be set to 60% of the center of the second portion 13e. For example, in FIG. 1, when the distance between the electrodes is w, the thickness is set to a range of 0.6w centered on the center line of the distance w, specifically, when the left end of the region between the electrodes is 0w and the right end is 1w, the thickness is set to a range of 0.2w to 0.8w. The thickness of the second portion 13e can be measured directly using a microscope or obtained from an image obtained by capturing an observation image through the microscope, as described later.

[0016] (CNT) CNT51 is a fibrous material with a diameter of 0.6 to 1.5 nm and a length of 100 nm to 5.0 um. The properties of CNT51 change depending on the arrangement of the six-membered rings in the circumferential direction. In CNT51, a cylindrical CNT made of a single graphene sheet is called a single-walled CNT, a CNT in which multiple CNTs of different diameters are stacked coaxially to form multiple layers is called a multi-walled CNT, and a CNT with two layers is called a double-walled CNT. For example, the CNT 51 may be any of a single-walled CNT, a double-walled CNT, and a multi-walled CNT. As an example, the CNTs 51 of the present disclosure are single-walled CNTs. CNT51 exists in two types: semiconducting type, which exhibits semiconducting properties, and metallic type, which exhibits metallic properties. Single-walled CNTs usually contain semiconducting CNTs and metallic CNTs in a ratio of 2:1. Therefore, when using a large amount of CNTs that exhibit one type of properties, a separation process is necessary. The CNT51 of the present disclosure contains a mixture of semiconducting CNTs and metallic CNTs. For example, the CNT51 may be obtained by performing a step of separating semiconducting CNTs from single-walled CNTs, and may contain 90% or more semiconducting CNTs. For example, the CNT51 may contain 92% or more semiconducting CNTs. For example, the CNT51 may contain 94% or more semiconducting CNTs. For example, the CNT51 may contain 96% or more semiconducting CNTs. For example, the CNT51 may contain 98% or more semiconducting CNTs.

[0017] (Manufacturing method) The manufacturing method according to the present disclosure will be described. The manufacturing method according to the present disclosure is carried out according to the flow chart shown in FIG.

[0018] First, an operator prepares a substrate 11 and two electrodes (a first electrode 12a and a second electrode 12b) (ST1). Specifically, the electrode 12 is formed on the lamination surface P of the base material 11 by vapor deposition, sputtering, or the like. In the present disclosure, the electrode 12 is formed by vapor deposition.

[0019] For example, in order to remove unnecessary portions of the film 13 by lift-off in ST5 described later, an operator may form a resist film on the stacking surface P in advance in ST1.

[0020] Next, the operator prepares dispersion liquid 5 (ST2). Specifically, an operator prepares dispersion liquid 5 by mixing CNTs 51, a surfactant 52, and a dispersion medium 53. For example, ultrasonic treatment is used to mix dispersion liquid 5. The operator can disperse the CNTs 51 sufficiently by using a surfactant 52 in the dispersion liquid 5. The surfactant 52 may be non-ionic. A non-ionic surfactant is more easily removed by washing, heat treatment, or the like than an ionic surfactant. For example, the non-ionic surfactant may be a solution of polyoxyethylene alkyl ether such as polyoxyethylene (100) stearyl ether or polyoxyethylene (23) lauryl ether. The dispersion medium 53 is not particularly limited as long as it is a solvent that can disperse and suspend the CNTs 51 in the dispersion liquid 5, and for example, water, heavy water, an organic solvent, an ionic liquid, or a mixture thereof can be used. The operator can sufficiently disperse the aggregated metallic CNTs and semiconducting CNTs by subjecting the mixture of the dispersion liquid 5 to ultrasonic treatment. In addition, the operator can appropriately control the length of the CNTs 51 by controlling the ultrasonic output and treatment time in the ultrasonic treatment. For example, a dispersion liquid in which a surfactant 52, metallic CNTs, and semiconducting CNTs are uniformly dispersed in a dispersion medium 53 may be used as the dispersion liquid 5. For example, in order to obtain a high TCR in a bolometer, semiconducting CNTs may be separated or concentrated and used. Carbon nanotubes can be separated, for example, by an electric field induced layer formation method (ELF method: see, for example, K. Ihara et al. J. Phys. Chem. C. 2011, 115, 22827-22832, and Japanese Patent No. 5717233, which are incorporated herein by reference). An example of a separation method using the ELF method is explained below. CNT dispersion A, in which metallic CNTs and semiconducting CNTs are dispersed with a nonionic surfactant, is introduced into a vertical separation device with a double-tube structure, and separation is performed by carrier-free electrophoresis by applying a voltage to the electrodes placed above and below. In this method, semiconducting CNTs move to the anode side, and metallic CNTs move to the cathode side. The dispersion of semiconducting CNT obtained by the separation step generally contains semiconducting CNT in an amount of 67% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, particularly preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more (the upper limit may be 100% by mass) out of the total amount of CNT contained in the dispersion. The separation ratio of metallic and semiconducting CNTs can be analyzed by microscopic Raman spectroscopy and ultraviolet-visible-near-infrared absorptiometry. A part of the surfactant 52 was removed from the dispersion liquid 5 containing the semiconducting CNTs (showing the dispersion liquid of the semiconducting CNTs that had migrated to the anode side) to prepare a dispersion liquid 5 in which the concentration of the surfactant 52 and the concentration of the CNTs 51 were adjusted. The concentration of the CNTs 51 and the concentration of the surfactant 52 contained in the dispersion liquid 5 can be estimated from measurements by ultraviolet-visible-near infrared absorptiometry. In ST2, the prepared dispersion liquid 5 contains CNTs 51 in a concentration range of 0.0001 to 0.005% and surfactant 52 in a concentration range of 0.05 to 0.08%. For example, the prepared dispersion liquid 5 contains CNTs 51 in a concentration range of 0.0002 to 0.0005% and surfactant 52 in a concentration range of 0.05 to 0.08%.

[0021] Next, as shown in FIG. 3, the operator immerses the substrate 11 in the dispersion liquid 5 containing the CNTs 51 (ST3).

[0022] Next, the worker lifts up the immersed substrate 11 so that the lamination surface P passes over the liquid surface of the dispersion liquid 5 (ST4). For example, a dip coater may be used to pull up the substrate 11 at a constant speed. When the worker pulls up the substrate 11, the angle θ (-90°≦θ≦90°) between the interface L and the substrate 11 is not particularly limited. For example, the angle θ between the interface L and the substrate 11 is -30°≦θ≦30°. For example, the angle θ between the interface L and the substrate 11 is -20°≦θ≦20°. For example, the angle θ between the interface L and the substrate 11 is -10°≦θ≦10°. For example, the moving speed when the immersed substrate 11 is pulled up is 0.3 μm / s or less.For example, the moving speed when the immersed substrate 11 is pulled up is 0.1 μm / s or less. The operator can control the orientation of the first alignment layer 131 by appropriately changing the moving speed when lifting it up. For example, the worker sets the lifting speed at 0.3 μm / s or less, so that the CNTs 51 move onto the layering surface P of the substrate 11 in a state where they are oriented parallel to the interface of the dispersion liquid 5. For example, by setting the moving speed during pulling to 0.1 μm / s or less, the operator can more easily align the CNTs 51 in the first alignment layer 131 included in the film 13 of the manufactured bolometer 1. In the manufactured bolometer 1, a plurality of more aligned CNTs connect two electrodes (first electrode 12a, second electrode 12b), and thus the film 13 is electrically connected with an increased number of conductive paths. This reduces the overall resistance value of the film 13, making it easier to reduce the resistance of the bolometer 1. For example, as shown in Figures 1 and 4, the worker pulls up the substrate 11 along the stacking surface P of the substrate 11 in a direction O that intersects with the opposing direction F of the side surfaces S of the two electrodes (first electrode 12a, second electrode 12b). The first orientation layer 131 in which the CNTs 51 are aligned is formed by gradually lifting the immersed substrate 11 from the interface L of the dispersion liquid 5 (ST41), and then gradually drying the dispersion liquid 5 adhering to the layering surface P (ST42). Immediately after the lamination surface P passes through the interface L of the dispersion liquid 5, a second alignment layer in which the CNTs 51 are aligned is formed on the underlayer 132. In this case, a film 13 including a first alignment layer 131 and an underlayer 132 (second alignment layer) present between the lamination surface P and the first alignment layer 131 is formed on the lamination surface P. For example, the underlayer 132 (second alignment layer) formed in ST4 may be an alignment layer having the following characteristics. For example, the density of CNTs in the underlayer 132 (second alignment layer) may be higher than the density of CNTs in the first alignment layer 131 . For example, the underlayer 132 (second alignment layer) may be an alignment layer in which the wall surfaces of CNTs are bonded to each other and aligned in the same direction. For example, the underlayer 132 (second alignment layer) may be an alignment layer in which several to several tens of CNTs are bundled in the same direction with parts of the wall surfaces of the CNTs bonded together, and the CNT bundles are aligned in the same direction. For example, the underlayer 132 (second alignment layer) may be an alignment layer in which bundles of CNTs are aligned in the same direction at intervals of at least the diameter of one CNT. For example, the underlayer 132 (second alignment layer) may be an alignment layer that includes CNTs or CNT bundles that have a different angle from the alignment direction of the CNTs, connecting the CNTs or CNT bundles aligned in the same direction as described above. As a result of the above, the film 13 including the first alignment layer 131 is formed in the second portion 13e. The film 13 formed on the stacking surface P has a first portion 13c, a second portion 13e, and a connection portion 13d that connects the first portion 13c and the second portion 13e. As a result, the CNTs stacked on the main surface M of the electrode 12 and the CNTs stacked on the stacking surface P between the two electrodes (the first electrode 12a and the second electrode 12b) are electrically connected by the CNTs formed in the connection portion 13d. That is, it is possible to easily form a conductive path of the CNTs 51 and to reduce the resistance of the bolometer 1. For example, the first alignment layer 131 may be formed over the first portion 13c, the second portion 13e, and the connection portion 13d connecting the first portion 13c and the second portion 13e. As a result, the CNTs stacked on the main surface M of the electrode 12 and the CNTs stacked on the stacking surface P between the two electrodes (the first electrode 12a and the second electrode 12b) are electrically connected by the CNTs formed in the connection portion 13d. That is, the manufacturing method in the present disclosure makes it easy to form a conductive path of the CNTs, and can reduce the resistance of the bolometer 1. In this case, the base layer 132 (second alignment layer) may be formed mainly in the second portion 13e. For example, the base layer 132 (second alignment layer) formed in 13e does not need to be connected to 13c. For example, the base layer 132 (second alignment layer) does not need to be formed in the first portion 13c or the connection portion 13d connected to 13c.

[0023] Next, the worker processes unnecessary carbon nanotubes from the film 13 formed on the substrate 11 when it is pulled up, as necessary (ST5). For example, in ST1, it is considered that the worker has previously formed a resist film on the lamination surface P. In that case, the worker uses the protective film to remove unnecessary portions included in the film 13 by lift-off.

[0024] For example, in order to remove unnecessary portions of film 13 by etching, an operator may form a protective film or an infrared absorbing structure directly on film 13. In this case, the operator uses the protective film to remove unnecessary portions of film 13 by etching, oxygen plasma treatment, or the like. Examples of the protective film include a resist film and an acrylic resin such as polymethyl methacrylate resin (PMMA).

[0025] Here, the film 13 electrically connecting the electrodes 12 is formed on the lamination surface P of the substrate 11. (Complete)

[0026] (film thickness measurement) Moreover, the film thickness in the second portion 13e of the manufactured bolometer is measured as an average film thickness. The thickness of the second portion 13e of the film 13 may be 60% of the center of the second portion 13e. For example, in FIG. 1, when the distance between the electrodes is w, the thickness is within a range of 0.6w centered on the center line of the distance w, specifically, within a range of 0.2w to 0.8w when the left end of the region between the electrodes is 0w and the right end is 1w. In this case, the worker may directly measure using an atomic force microscope (AFM), a scanning electron microscope (SEM), a transmission electron microscope (TEM), or the like, or may obtain the value from images captured from observations made using these microscopes.

[0027] (Action and Effects) According to the bolometer of the present disclosure, the CNTs stacked on the main surface M of the electrode 12 and the CNTs stacked on the stacking surface P between the two electrodes (first electrode 12a, second electrode 12b) are electrically connected by the CNTs formed in the connection portion 13d. This makes it easier to form a conductive path for the CNTs 51, thereby lowering the resistance of the bolometer 1. In addition, as shown by the first orientation layer 131, the electrically connected CNTs 51 are aligned, thereby further lowering the resistance. Therefore, the resistance of the bolometer of the present disclosure can be easily reduced.

[0028] 5 to 7 show the bolometers of Comparative Example 1 and Comparative Example 2. FIG. As shown in FIG. 5, in the "bolometer in which an electrode is formed on a CNT film containing CNTs 51" of Comparative Example 1, the lower side of the electrode and the CNT film are electrically connected. However, as shown in FIG. 6, in the case of Comparative Example 2, "a bolometer in which electrodes are formed first and then films containing CNTs (CNT film on electrodes, CNT film between electrodes) are formed by a casting method," the CNT film on electrodes and the CNT film between electrodes are sometimes difficult to electrically connect. In Figure 7, which is an arrow view of region A in Figure 6 viewed from direction B, it is clear that CNTs are difficult to adhere to the electrode wall surfaces, and that the CNT film on the electrode and the CNT film between the electrodes are not electrically connected. The light receiving part of the bolometer of the CNT uncooled infrared sensor has a structure in which the CNT film formed between the electrodes is electrically connected to the electrodes. Therefore, how the CNT is bonded to the electrodes affects the resistance value. However, if the CNT film between the electrodes is thickened to make it easier to form conductive paths for the CNTs 51 and reduce the resistance, the content of metallic CNTs in the CNT film between the electrodes increases, which causes a problem of a decrease in the absolute value of the temperature coefficient of resistance (TCR). Therefore, in order to lower the resistance value of the bolometer without decreasing the absolute value of the TCR, it is necessary to be able to electrically connect the CNT film between the electrodes and the CNT film on the electrodes.

[0029] In contrast to the comparative example, in the bolometer 1 of the present disclosure, the film 13 is electrically connected to the CNTs stacked on the main surface M of the electrode 12 and the CNTs stacked on the stacking surface P between the two electrodes (first electrode 12a, second electrode 12b) by the CNTs formed in the connection portion 13d. This makes it easier to form a conductive path for the CNTs 51, thereby making it possible to reduce the resistance of the bolometer 1. Furthermore, since the CNTs 51 in the first alignment layer 131 are aligned, the resistance of the film 13 including the CNTs 51 can be further reduced. Therefore, the bolometer 1 of the present disclosure is easily able to reduce its resistance. In addition, the bolometer 1 of the present disclosure does not need to be thickened to reduce the resistance, so the content of metallic CNTs in the film 13 does not increase, and the resistance can be reduced without decreasing the absolute value of the TCR.

[0030] Furthermore, the bolometer of the present disclosure "includes a substrate having a stacking surface, two electrodes each having a main surface and a side surface extending from the main surface to the stacking surface, and a film including carbon nanotubes, the film having a first portion stacked on the main surface, a second portion stacked on the stacking surface between the two electrodes, and a connecting portion at the side surface connecting the first portion and the second portion," thereby achieving the following effects. In the bolometer of the present disclosure, the CNTs stacked on the main surface M of the electrode 12 and the CNTs stacked on the stacking surface P between the two electrodes (first electrode 12a, second electrode 12b) are electrically connected by the CNTs formed in the connection portion 13d. This provides the effect that "the bolometer 1 of the present disclosure can easily form a conductive path of the CNTs 51, thereby enabling low resistance." Therefore, the bolometer of the present disclosure is easy to achieve low resistance.

[0031] In addition, the bolometer of the present disclosure has an average film thickness of less than 10 nm, and therefore has the following effect: "When CNT51 in which semiconducting and metallic CNTs are mixed is used, metallic CNTs can only exist within a range in which the average film thickness of second portion 13e is less than 10 nm, and therefore a decrease in the absolute value of TCR can be suppressed."

[0032] Additionally, in the bolometer of the present disclosure, "the second portion includes a first orientation layer in which the carbon nanotubes are oriented," which provides the following effect: "By connecting the two electrodes (first electrode 12a, second electrode 12b) with a plurality of aligned CNTs, film 13 is electrically connected with an increased number of conductive paths. This reduces the overall resistance of film 13, making it easier to reduce the resistance of bolometer 1."

[0033] Although the CNTs 51 disclosed above are a mixture of semiconducting and metallic CNTs, separated semiconducting CNTs may be used instead, which can improve the absolute value of the TCR of the bolometer 1.

[0034] The first alignment layer 131 disclosed above may be included across the first portion 13c, the connection portion 13d, and the second portion 13e. This allows the CNTs stacked on the main surface M of the electrode 12 and the CNTs stacked on the stacking surface P between the two electrodes (the first electrode 12a and the second electrode 12b) to be electrically connected by the CNTs formed in the connection portion 13d. In this case, the conductive path of the CNTs 51 is increased, so that the resistance of the bolometer 1 can be reduced.

[0035] The second portion 13e disclosed above may include a plurality of first alignment layers 131. By arranging a number of first alignment layers in which a plurality of CNTs are aligned in the stacking direction of the stacking surface P, it is expected that a conductive path to the electrode 12 will be easily formed, and the resistance of the bolometer 1 will be reduced.

[0036] In the above disclosure, the second portion 13e of the bolometer 1 includes a first orientation layer in which CNTs 51 are oriented, and thus the two electrodes (first electrode 12a, second electrode 12b) are electrically connected by a plurality of oriented CNTs connecting them, thereby electrically connecting the film 13. This reduces the overall resistance value of the film 13, making it easier to reduce the resistance of the bolometer 1. In contrast, the bolometer disclosed below focuses on the fact that the first alignment layer 131 is easily formed as a well-defined alignment layer by uniformly forming the underlayer 1320 in the second portion 13e. An example of the configuration of a bolometer according to the present disclosure will be described below with reference to FIGS. In addition, components common to those disclosed above are given the same reference numerals and detailed explanations are omitted.

[0037] (composition) As shown in FIG. 8, the bolometer 1000 includes a substrate 11, an electrode 12, and a film 13. For example, the film 1300 includes a first alignment layer 131 in which the CNTs 51 are aligned, and an underlayer 1320 in which the CNTs 51 are randomly oriented compared to the first alignment layer 131 . For example, the underlayer 1320 may be a non-oriented layer in which the CNTs are randomly oriented to form a network. For example, the underlayer 1320 may be a non-oriented layer in which CNTs form locally oriented domains, and these locally oriented domains are oriented in random directions to form a network. For example, the second portion 1300 e of the film 1300 includes the first alignment layer 131 . For example, the second portion 1300 e of the film 1300 includes an underlayer 1320 between the stacking plane P and the first alignment layer 131 . For example, the membrane 1300 may include an attachment layer 1340 . For example, the average film thickness of the second portion 1300e is not less than 1.0 nm and less than 10 nm. For example, the total average thickness of the first alignment layer 131 and the underlayer 1320 included in the second portion 1300e of the film 1300 is 1.0 nm or more and less than 10 nm. For example, the average thickness of the first alignment layer 131 in the second portion 1300e is 9.0 nm or less For example, the average thickness of the first alignment layer 131 in the second portion 1300e is 0.5 nm or more and 5.0 nm or less. The thickness of the second portion 1300e of the film 13 is measured in the same manner as the thickness of the second portion 1300e of the film 13 in the first embodiment. For example, the second portion 1300e of the film 1300 may include an adhesion layer 1340. The adhesion layer 1340 is a thin film for improving the adhesion performance of the CNTs 51 to the insulating layer of the base material 11. The adhesion layer 1340 includes a silane coupling agent 6 for forming the underlayer 1320 on the base material 11. Examples of the silane coupling agent 6 include 3-aminopropyltriethoxysilane (APTES), 3-aminopropyltrimethoxysilane, 3-aminopropylmethyltriethoxysilane, 3-aminopropylmethyltrimethoxysilane, and the like. For example, the worker may use a silane coupling agent 6 having an amino group to improve the adhesion of the CNTs 51 . For example, when the adhesion layer 1340 is formed on the lamination surface P of the substrate 11, the CNTs 51 adhere to the substrate 11 when the substrate 11 is immersed in the dispersion liquid 5 in the immersion process of ST3 due to the effect of the silane coupling agent 6, and a uniform underlayer 1320 with little unevenness is laminated. The second portion 1300e has the following advantages by including the underlayer 1320 between the lamination surface P and the first alignment layer 131. The first alignment layer 131 is likely to form a clean alignment layer due to the presence of the uniform underlayer 1320. That is, a space SP (void) in which the CNTs 51 are sparsely formed by the CNTs 51 adhering in a scattered manner is unlikely to be formed in the first alignment layer 131. This makes it easier for the CNTs 51 in the film 1300 to be electrically connected to each other, and makes it easier to reduce the resistance of the bolometer 1000.

[0038] (method) The manufacturing method according to the present disclosure will be described. The manufacturing method according to the present disclosure is carried out according to the flow shown in FIG. The same components as those in the bolometer 1 are denoted by the same reference numerals and detailed description thereof will be omitted.

[0039] First, an operator prepares a substrate 11 and two electrodes (a first electrode 12a and a second electrode 12b) (ST1). When performing ST1, the worker may apply a silane coupling agent 6 to the lamination surface P of the base material 11 (ST1a). The worker applies the silane coupling agent 6 to the lamination surface P to form an adhesion layer 1340. As a result, in ST3 described later, the CNTs 51 are adhered by the effect of the silane coupling agent 6 contained in the adhesion layer 1340, and the base layer 1320 is further formed. Examples of the silane coupling agent 6 include 3-aminopropyltriethoxysilane (APTES), 3-aminopropyltrimethoxysilane, 3-aminopropylmethyltriethoxysilane, 3-aminopropylmethyltrimethoxysilane, and the like. For example, the operator may use a silane coupling agent 6 having an amino group to improve the adhesion of the CNTs 51 .

[0040] In the subsequent steps ST2 to ST5, the same processes as those in FIG. 2 are performed. However, when the worker performs ST1a, the following changes are observed in ST3 and ST4 compared to the case of FIG. In ST3, when an operator performs the process of ST1a, when the substrate 11 is immersed in the dispersion liquid 5, an underlayer 1320 is formed on the lamination surface P of the substrate 11. In the underlayer 1320, the CNTs are oriented in random directions compared to the first alignment layer 131.

[0041] In ST4, when the worker performs the process of ST1a, in the second portion 1300e, the first alignment layer 131 is formed on the underlayer 1320 already formed in ST3 while the CNTs 51 are gradually deposited during drying. In this case, a film 1300 including the first alignment layer 131 and the underlayer 1320 present between the stacking surface P and the first alignment layer 131 is formed on the stacking surface P. In the bolometer 1000 according to the present disclosure, which is formed by performing ST1, the second portion 1300e includes the first alignment layer 131 and the underlayer 1320.

[0042] (Action and Effects) According to the bolometer 1000 of the present disclosure, the second portion 1300e includes an underlayer 1320 between the stacking surface P and the first alignment layer 131. Since the underlayer is a uniform layer with little unevenness, the first alignment layer 131 is likely to form a clean alignment layer. In other words, spaces (voids) where the CNTs 51 are sparse are unlikely to be formed in the first alignment layer 131. This can make it easier for the CNTs 51 in the film 1300 to be electrically connected to each other. Therefore, the resistance of the bolometer of the present disclosure can be easily reduced.

[0043] In the bolometer 1000 of the present disclosure, in addition to the effects of the bolometer 1, "the second portion 1300e includes, between the stacking surface P and the first alignment layer 131, a uniform base layer 1320 in which the carbon nanotubes are oriented in a random direction compared to the first alignment layer 131", thereby making it easier for the first alignment layer 131 to form a clean alignment layer. In other words, spaces SP (described later) in the first alignment layer 131 in which the CNTs 51 are sparsely arranged due to the CNTs 51 being attached in a scattered manner are less likely to be formed. This makes it easier for the CNTs 51 in the film 1300 to be electrically connected to each other, making it easier to reduce resistance."

[0044] An example of the configuration of a bolometer according to the present disclosure will be described below with reference to FIG.

[0045] (composition) The bolometer 1z comprises a substrate 11z having a stacking surface P, two electrodes 12z (first electrode 12za, second electrode 12zb), each having a main surface M and a side surface S extending from the main surface M to the stacking surface P, and a film 13z containing carbon nanotubes, the film 13z having a first portion 13cz stacked on the main surface M, a second portion 13ez stacked on the stacking surface P between the two electrodes, and a connection portion 13dz connecting the first portion 13cz and the second portion 13ez at the side surface S, and the average film thickness of the second portion 13ez is less than 10 nm.

[0046] (Action and Effects) According to the bolometer of the present disclosure, the CNTs stacked on the main surface M of the electrode 12z and the CNTs stacked on the stacking surface P between the two electrodes (the first electrode 12za and the second electrode 12zb) are electrically connected by the CNTs formed in the connection portion 13dz. This makes it easier to form a conductive path of the CNTs 51, thereby making it possible to reduce the resistance of the bolometer 1z. Therefore, the resistance of the bolometer of the present disclosure can be easily reduced.

[0047] An example of the manufacturing method according to the present disclosure will now be described with reference to FIG. The manufacturing method according to the present disclosure is carried out according to the flow shown in FIG.

[0048] The manufacturing method includes the steps of (ST10) preparing a substrate having a laminated surface and two electrodes, each having a main surface and a side surface extending from the main surface to the laminated surface of the substrate, (ST20) immersing the substrate in a dispersion liquid containing carbon nanotubes, and (ST30) lifting the immersed substrate at a moving speed of 0.3 μm / s or less so that the laminated surface passes over the liquid surface of the dispersion liquid, the dispersion liquid containing carbon nanotubes at a concentration of 0.0001 to 0.005% and a surfactant at a concentration of 0.05 to 0.08%.

[0049] (Action and Effects) According to the manufacturing method of the present disclosure, the CNTs stacked on the main surface of the electrode and the CNTs stacked on the stacking surface between the two electrodes are electrically connected by the CNTs formed in the connection portion. This makes it easier to form a conductive path of the CNTs 51, thereby reducing the resistance of the bolometer. Therefore, the manufacturing method according to the present disclosure makes it easy to achieve low resistance. EXAMPLES

[0050] The effects of the present disclosure will be described in more detail below with reference to examples. The conditions in the examples are examples of conditions adopted to confirm the feasibility and effects of the present disclosure, and the present disclosure is not limited to these examples. Various conditions may be adopted in the present disclosure as long as they do not deviate from the gist of the present disclosure and the purpose of the present disclosure is achieved.

[0051] In this embodiment, two types of bolometers were produced. On the other hand, in the bolometer (A), ST1 to ST5 were performed in the flow chart of Fig. 2. In the bolometer (A), for example, Example 1 was performed. In Example 1, the CNT concentration in the dispersion liquid 5 was 0.0005%, and the surfactant concentration was 0.05%. On the other hand, in the bolometer (B), the process of ST1a was performed during ST1. That is, in the flow chart of FIG. 9, ST1 (ST1a) to ST5 were performed. In the bolometer (B), for example, Examples 2 to 6 were performed. In Example 2, the CNT concentration of the dispersion was 0.0001%, and the surfactant concentration was 0.05%. Next, in Example 3, the CNT concentration of the dispersion was 0.0002%, and the surfactant concentration was 0.05%. Next, in Example 4, the CNT concentration of the dispersion was 0.0005%, and the surfactant concentration was 0.05%. Next, in Example 5, the CNT concentration of the dispersion was 0.005%, and the surfactant concentration was 0.05%. Next, in Example 6, the CNT concentration of the dispersion was 0.0005%, and the surfactant concentration was 0.08%. The bolometer was fabricated in the following manner.

[0052] (ST2) Preparation of carbon nanotube dispersion In ST2, Dispersion 5 was prepared in the following manner. 100 mg of single-walled CNTs (Meijo Nanocarbon Co., Ltd., EC1.0 (diameter: approximately 1.1 to 1.5 nm, average diameter 1.2 nm) were placed in a quartz boat and heat-treated in an electric furnace under a vacuum atmosphere. The heat treatment was performed at 900°C for 2 hours. The weight after heat treatment was reduced to 80 mg, indicating that the surface functional groups and impurities had been removed. The resulting single-walled CNTs were crushed with tweezers, and 12 mg of the crushed CNTs were immersed in 40 ml of a 1 wt % aqueous solution of surfactant 52 (polyoxyethylene (100) stearyl ether) and thoroughly submerged, after which they were subjected to ultrasonic dispersion treatment (BRANSON ADVANCED-DIGITAL The dispersion was run for 30 minutes each time in a SONIFIER device (50W output). This resulted in no CNT aggregates remaining in the solution. The CNT dispersion was then transferred to two ultracentrifuge tubes and ultracentrifuged. This operation removed bundles and residual catalyst, yielding CNT dispersion A. To observe the length and diameter of the CNTs, the dispersion was applied to a SiO2 substrate, dried at 100°C, and observed with an atomic force microscope (AFM). As a result, it was found that 70% of the single-walled CNTs were in the range of 500nm to 3μm in length, with the average length being approximately 800nm. The CNT dispersion A obtained above was introduced into a separation device with a double-tube structure. About 15 ml of water, about 70 ml of CNT dispersion A, and about 10 ml of 2 wt% surfactant 52 aqueous solution were placed in the outer tube of the double tube, and about 20 ml of 2 wt% surfactant 52 aqueous solution was placed in the inner tube. After that, the lower lid of the inner tube was opened to form a three-layer structure with different concentrations of surfactant 52. The lower side of the inner tube was set as the anode and the upper side of the outer tube was set as the cathode, and a voltage of 200 V was applied, causing the semiconducting CNT to move to the anode side. Meanwhile, the metallic CNT moved to the cathode side. The semiconducting and metallic CNTs were neatly separated about 80 hours after the start of separation. The separation process was carried out at room temperature (about 25°C). The semiconducting CNT dispersion that had moved to the anode side was collected and analyzed by optical absorption spectroscopy, and it was found that the metallic CNT components had been removed. In addition, Raman spectroscopy showed that 98 wt% of the dispersion of semiconducting CNTs that had migrated to the anode side was semiconducting carbon nanotubes. The diameter of single-walled carbon nanotubes was approximately 1.2 nm, the majority (70% or more), and the average diameter was 1.2 nm. A portion of the surfactant 52 was removed from the dispersion 5 containing 98 wt % of the semiconducting CNTs (showing a dispersion of the semiconducting CNTs that had migrated to the anode side), and a dispersion 5 in which the concentration of the surfactant 52 and the concentration of the CNTs 51 were adjusted was prepared. In ST2, the prepared dispersion liquid 5 contained the CNTs 51 in a concentration range of 0.0001 to 0.005% and the surfactant 52 in a concentration range of 0.05 to 0.08%, as described above. In ST4, the moving speed when the immersed substrate 11 was pulled up was 0.1 μm / s or less. In ST4, the worker lifted up the substrate 11 along the lamination surface P of the substrate 11 in a direction intersecting the opposing direction of the side surfaces of the two electrodes (first electrode 12a, second electrode 12b). In ST4, the dispersion 5 was moved onto the lamination surface P of the substrate 11 in a state of being oriented parallel to the interface, and then dried.

[0053] The worker also measured the average thickness of the second portion 13e of the manufactured bolometer (A) and the second portion 1300e of the manufactured bolometer (B). At that time, the worker measured directly using a SEM or a TEM, or obtained the average thickness from images captured by observing the film with these microscopes.

[0054] FIG. 12 is an SEM image of the film 13 in the second portion 13e of the bolometer (A). 12, it was confirmed that the film 13 included an underlayer 132 (second alignment layer) and a first alignment layer 131. In addition, the first alignment layer was formed with a larger gap between them than the second alignment layer. In Figure 12, it was confirmed that in the second portion 13e, the base layer 132 (second orientation layer) and the first orientation layer 131 have spaces SP (porosity) where the CNTs 51 are sparsely formed by the CNTs 51 adhering in a scattered manner.

[0055] FIG. 13 is an SEM image of the film 1300 in the second portion 1300e of the bolometer (B). FIG. 14 is an enlarged view of region C of the SEM image of FIG. From FIG. 14, it can be seen that the second portion 1300e includes an underlayer 1320 between the stacking surface P and the first alignment layer 131, in which the CNTs 51 are oriented in random directions compared to the first alignment layer 131. It was confirmed from FIG. 13 that the film 1300 of the bolometer (B) contains the underlayer 1320, and thus the space SP (void) where the CNTs 51 are sparse, which was seen in the bolometer (A), is less likely to be formed. FIG. 15 is a cross-sectional TEM image taken along the cutting line YY′ of the SEM image of FIG. From FIG. 15, it was confirmed that the film 1300 of the bolometer (B) has an underlayer 1320 laminated on the substrate 11, and further has a first alignment layer 131 laminated thereon. It was confirmed from FIG. 15 that, in the underlayer 1320, the CNTs 51 were oriented in random directions compared to the first alignment layer 131. 15, the underlayer 1320 was composed of approximately one layer of CNTs 51 and had a film thickness of 2 nm or less. The first alignment layer 131 was composed of 1 to 3 layers of CNTs 51. The total thickness of the underlayer 1320 and the first alignment layer 131 was often 6.0 to 9.0 nm, and was no greater than 10 nm. The maximum average thickness was 3.4 nm to 9.0 nm, and was confirmed to be less than 10 nm.

[0056] Figure 16 shows a comparison of the average film thickness of each film in the bolometer, and the resistance and TCR values ​​at 3 V. The concentration of the dispersion liquid 5 used in forming each film is also shown. In this embodiment, TCR (% / °C) is the rate of change in resistance due to temperature when the reference temperature is 25°C. In FIG. 16, Comparative Example X is a film made by the casting method, and Comparative Example Y is a thick film made by the casting method. It was confirmed that the film 13 of the bolometer (A) in Example 1 and the film 1300 of the bolometer (B) in Examples 2 to 6 had a lower resistance value than the films (Comparative Examples 1 and 2) produced by the casting method. It was confirmed that the film 13 of the bolometer (A) and the film 1300 of the bolometer (B) have the same absolute value of TCR as that of Comparative Example X. In the film manufactured by the casting method (Comparative Example X) and the thick film manufactured by the casting method (Comparative Example Y), the resistance of the film 13 and the film 1300 could be reduced by making the conductive path easier to form as the film becomes thicker. However, it was confirmed that the absolute value of TCR, which is the temperature coefficient of resistance, decreases as the film becomes thicker when manufactured by the casting method. This is because when CNT51, which contains a mixture of semiconducting CNT and metallic CNT, is used, the content of metallic CNT51 increases as the film becomes thicker. Although the amount of metallic CNT contained in CNT51 is small compared to semiconducting CNT (98 wt%), an increase in the content (number) of metallic CNT increases the conductive path of metallic CNT, which has the effect of reducing the absolute value of TCR.

[0057] Although the present disclosure has been described above with reference to the embodiments, the present disclosure is not limited to the above-described embodiments. The present disclosure is not intended to be limiting. Various modifications that can be understood by a person skilled in the art may be made to the configuration and details of the present disclosure within the scope of the present disclosure. Furthermore, each embodiment may be appropriately combined with other embodiments.

[0058] A part or all of the above-described embodiments can be described as, but is not limited to, the following supplementary notes.

[0059] (Appendix 1) A substrate having a lamination surface; Two electrodes each having a main surface and a side surface extending from the main surface to the stacking surface; A film including carbon nanotubes; Equipped with The membrane comprises: A first portion laminated on the main surface; a second portion laminated on the lamination surface between the two electrodes; a connection portion that connects the first portion and the second portion in the side surface; having The second portion has an average thickness of less than 10 nm. Bolometer.

[0060] (Appendix 2) The second portion includes a first alignment layer in which the carbon nanotubes are aligned. 2. A bolometer as described in appended claim 1.

[0061] (Appendix 3) The second portion includes an underlayer between the lamination surface and the first alignment layer, in which the carbon nanotubes are oriented in a random direction compared to the first alignment layer. A bolometer as described in appended note 2.

[0062] (Appendix 4) the second portion includes a second alignment layer between the lamination surface and the first alignment layer, in which the carbon nanotubes are aligned; The density of the carbon nanotubes in the second alignment layer is greater than the density of the carbon nanotubes in the first alignment layer. A bolometer as described in appended note 2.

[0063] (Appendix 5) A substrate having a lamination surface; providing two electrodes, each having a main surface and a side surface extending from the main surface to a lamination surface of the substrate; Immersing the substrate in a dispersion liquid containing carbon nanotubes; a step of lifting the immersed substrate at a moving speed of 0.3 μm / s or less so that the lamination surface passes through the liquid surface of the dispersion; Including, The dispersion liquid is Carbon nanotubes with a concentration of 0.0001 to 0.005%; A surfactant with a concentration of 0.05 to 0.08% Includes Manufacturing method.

[0064] (Appendix 6) In the passing step, The immersed substrate is lifted up at a moving speed of 0.1 μm / s or less. The manufacturing method described in Appendix 5.

[0065] (Appendix 7) In the step of preparing, A silane coupling agent is applied to the laminated surface. The method of production according to claim 5 or 6.

[0066] (Appendix 8) In the step of lifting, The substrate is lifted up along the lamination surface in a direction intersecting the opposing direction of the side surfaces of the two electrodes. The manufacturing method described in Appendix 7.

[0067] (Appendix 9) In the step of immersing in the dispersion, The dispersion liquid is Contains carbon nanotubes at a concentration of 0.0002-0.0005% The manufacturing method described in Appendix 5.

[0068] (Appendix 10) In the step of preparing, The silane coupling agent has an amino group. The manufacturing method described in Appendix 7. [Explanation of symbols]

[0069] 1 Bolometer 11 Base material 12 electrodes 12a First electrode 12b Second electrode 1z Bolometer 11z base material 12z electrode 12za first electrode 12zb second electrode 13 membrane 13c first part 13d Connection part 13e Second part 5 Dispersion 51 Carbon nanotube (CNT) 52 Surfactants 53 Dispersion medium 6. Silane coupling agents 13z membrane 13cz first part 13dz Connection part 13ez second part 131 First orientation layer 132 Base layer (second orientation layer) 1000 bolometers 1300 membrane 1300e second part 1320 Base layer 1340 Adhesion layer

Claims

1. A substrate having a lamination surface; two electrodes each having a main surface and a side surface extending from the main surface to the stacking surface; A film including carbon nanotubes; Equipped with The membrane comprises: A first portion laminated on the main surface; a second portion laminated on the lamination surface between the two electrodes; a connection portion that connects the first portion and the second portion in the side surface; having The second portion has an average thickness of less than 10 nm. Bolometer.

2. The second portion includes a first alignment layer in which the carbon nanotubes are aligned.

2. The bolometer of claim 1.

3. The second portion includes an underlayer between the lamination surface and the first alignment layer, in which the carbon nanotubes are oriented in a random direction compared to the first alignment layer.

3. The bolometer of claim 2.

4. the second portion includes a second alignment layer between the lamination surface and the first alignment layer, in which the carbon nanotubes are aligned; The density of the carbon nanotubes in the second alignment layer is greater than the density of the carbon nanotubes in the first alignment layer.

3. The bolometer of claim 2.

5. A substrate having a lamination surface; providing two electrodes, each having a main surface and a side surface extending from the main surface to a lamination surface of the substrate; Immersing the substrate in a dispersion liquid containing carbon nanotubes; a step of lifting the immersed substrate at a moving speed of 0.3 μm / s or less so that the lamination surface passes through the liquid surface of the dispersion; Including, The dispersion liquid is Carbon nanotubes having a concentration of 0.0001 to 0.005%; A surfactant having a concentration of 0.05 to 0.08%; Includes Manufacturing method.

6. In the passing step, The immersed substrate is lifted up at a moving speed of 0.1 μm / s or less. The method according to claim 5 .

7. In the preparing step, A silane coupling agent is applied to the laminated surface. The method according to claim 5 or 6.

8. In the step of lifting, The substrate is lifted up along the lamination surface in a direction intersecting the opposing direction of the side surfaces of the two electrodes. The method of claim 7.

9. In the step of immersing in the dispersion, The dispersion liquid is Contains carbon nanotubes at a concentration of 0.0002 to 0.0005% The method according to claim 5 .

10. In the preparing step, The silane coupling agent has an amino group. The method of claim 7.

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