TWI768149B - Oxide sintered body, sputtering target and transparent conductive film - Google Patents

Abstract

An oxide sintered body according to one of the embodiments of the present invention is an oxide sintered body containing indium, niobium, tin and oxygen, which contains indium in an amount of 90.0 mass% or more in terms of In₂O₃, niobium in an amount of 3.5 to 6.5 mass% in terms of Nb₂O₅, and tin in an amount of 0.5 to 2 mass% in terms of SnO₂.

Description

Oxide sintered body, sputtering target and transparent conductive film

Embodiments disclosed in the present invention relate to an oxide sintered body, a sputtered film, and a transparent conductive film.

Conventionally, a sputtering target for a transparent conductive film has been known, which is a transparent target for improving the transmittance in the purple region (for example, wavelength 400 nm) by adding niobium or the like to ITO (Indium Tin Oxide). A conductive film former (for example, refer to Patent Document 1).

[Prior Art Literature] [Patent Literature]

Patent Document 1: International Publication No. 2011/052375

However, there is still room for improvement in the transmittance of transparent conductive films formed by conventional sputtering targets in short wavelength regions such as ultraviolet light region (eg, wavelength 300 nm) or violet region (eg, wavelength 400 nm). .

A state of the present embodiment is based on the above-mentioned circumstances The purpose of the inventors is to provide an oxide sintered body, which can improve the transmittance of short wavelength regions such as ultraviolet light region and violet region in a transparent conductive film formed by using a sputtering target.

The oxide sintered body in one form of the present embodiment contains indium, niobium, tin and oxygen, and contains 90.0 mass % or more of the aforementioned indium in terms of In ₂ O ₃ and 3.5 to 6.5 in Nb ₂ O ₅ conversion. The aforementioned niobium in mass % contains 0.5 to 2 mass % of the aforementioned tin in terms of SnO ₂ .

According to the state of the present embodiment, the transmittance of the formed transparent conductive film in the short wavelength region such as the ultraviolet light region and the purple region can be improved.

FIG. 1 is a graph showing the wavelength dependence of transmittance before heat treatment of the transparent conductive films of Example 2 and Comparative Examples 1 and 4. FIG.

FIG. 2 is a graph showing the wavelength dependence of the transmittance of the transparent conductive films of Example 2 and Comparative Examples 1 and 4 after heat treatment.

Hereinafter, embodiments of the oxide sintered body, the sputtering target, and the transparent conductive film disclosed in the present invention will be described with reference to the accompanying drawings. In addition, this invention is not limited to embodiment shown below.

The oxide sintering system of the embodiment contains indium (In), niobium (Nb), tin (Sn) and oxygen (O), and can be used as a sputtering target. On the other hand, the oxide sintered body of the embodiment contains 90.0 mass % or more of indium in terms of In ₂ O ₃ , 3.5 to 6.5 mass % of niobium in terms of Nb ₂ O ₅ , and 0.5 to 2 mass % in terms of SnO ₂ . % of tin. That is, the oxide sintering system of the embodiment contains indium as a main component, and niobium, tin, and oxygen as other components.

Thereby, the transmittance of the transparent conductive film formed by using the oxide sintered body as a sputtering target in a short wavelength region such as an ultraviolet region or a violet region can be improved.

In addition, the transparent conductive film of the embodiment contains indium, niobium, tin and oxygen, and contains 90.0 mass % or more of indium in terms of In ₂ O ₃ conversion, and 3.5 to 6.5 mass % of niobium in terms of Nb ₂ O ₅ conversion. It contains 0.5 to 2 mass % of tin in terms of SnO ₂ . That is, the transparent conductive film of the embodiment contains indium as a main component, and niobium, tin, and oxygen as other components.

Thereby, the transmittance of the transparent conductive film in a short wavelength region such as an ultraviolet region or a violet region can be improved. Therefore, according to the embodiment, for example, when the transparent conductive film is applied to the transparent electrode of the solar cell, the light (that is, the ultraviolet light) incident in the ultraviolet region of the solar cell can also be used for power generation, so that the solar energy can be improved. The luminous efficiency of the battery.

The oxide sintered body of the embodiment contains 90.0 mass % or more of indium in terms of In ₂ O ₃ . Thereby, when the oxide sintered body is used as a transparent conductive film formed by a sputtering target, the conductivity and transmittance can be well maintained.

In addition, the oxide sintered body of the embodiment preferably contains 91.5 to 96.0 mass % of indium in terms of In ₂ O ₃ , more preferably 92.5 to 95.0 mass %, and still more preferably 93.6 to 94.4 mass % .

Further, the oxide sintered body of the embodiment preferably contains 4.0 to 6.0 mass % of niobium in terms of Nb ₂ O ₅ and 0.5 to 2 mass % of tin in terms of SnO ₂ . Thereby, when the oxide sintered body is used as a transparent conductive film formed as a sputtering target, the conductivity can be maintained favorably.

Further, the oxide sintered body of the embodiment preferably contains 4.5 to 5.5 mass % of niobium in terms of Nb ₂ O ₅ and 0.5 to 2 mass % of tin in terms of SnO ₂ , and more preferably contains Nb It contains 4.8 to 5.2 mass % of niobium in terms of ₂ O ₅ and 0.8 to 1.2 mass % of tin in terms of SnO ₂ .

The transparent conductive film of the embodiment contains 90.0 mass % or more of indium in terms of In ₂ O ₃ . Thereby, the conductivity and transmittance of the transparent conductive film can be maintained favorably.

In addition, the transparent conductive film of the embodiment preferably contains 91.5 to 96.0 mass % of indium in terms of In ₂ O ₃ , more preferably 92.5 to 95.0 mass %, and still more preferably 93.6 to 94.4 mass %.

Further, the transparent conductive film of the embodiment preferably contains 4.0 to 6.0 mass % of niobium in terms of Nb ₂ O ₅ and 0.5 to 2 mass % of tin in terms of SnO ₂ . Thereby, the conductivity of the transparent conductive film can be maintained favorably.

Furthermore, the transparent conductive film of the embodiment preferably contains 4.5 to 5.5 mass % of niobium in terms of Nb ₂ O ₅ , and 0.5 to 2 mass % of tin in terms of SnO ₂ , and more preferably contains Nb ₂ It contains 4.8 to 5.2 mass % of niobium in terms of O ₅ , and 0.8 to 1.2 mass % of tin in terms of SnO ₂ .

Furthermore, the oxide sintered body and the transparent conductive film of the embodiment are more preferably composed of indium as the main component, and niobium, tin, and oxygen as other components.

In addition, the oxide sintered body and the transparent conductive film of the embodiment may contain unavoidable impurities derived from raw materials and the like. The unavoidable impurities in the oxide sintered body of the embodiment include, for example, Fe, Cr, Ni, Si, W, Zr, and the like, and the content of these is usually 100 ppm or less.

Furthermore, the specific resistance of the oxide sintered body of the embodiment is preferably 7.0×10 ^-4 Ω. cm below. Thereby, when this oxide sintered body is used as a sputtering target, sputtering using an inexpensive DC power supply can be performed, and the film-forming speed can be improved.

In addition, the specific resistance of the oxide sintered body of the embodiment is more preferably 5.0×10 ^-4 Ω. cm or less, and more preferably 4.0×10 ^-4 Ω. cm or less, more preferably 3.0×10 ^-4 Ω. cm below.

In addition, the relative density of the oxide sintered body of the embodiment is 95% or more. Thereby, when this oxide sintered body is used as a sputtering target, the discharge state of DC sputtering can be stabilized. In addition, the oxide sintered body of the embodiment preferably has a relative density of 97% or more, and more preferably has a relative density of 99% or more.

When the relative density is 95% or more, when the oxide sintered body is used as a sputtering target, the voids in the sputtering target can be reduced, and it is easy to Prevent the intrusion of gaseous components in the atmosphere. In addition, during sputtering, abnormal discharge originating from the void and cracking of the sputtering target are less likely to occur.

Furthermore, the transparent conductive film of the embodiment preferably has a transmittance at a wavelength of 300 nm of 52% or more, more preferably 55% or more, still more preferably 58% or more, and still more preferably 60% or more.

<Each production step of oxide sputtering target>

The oxide sputtering target of the embodiment can be produced, for example, by the method shown below. First, the raw material powders are mixed. The raw material powders are usually In ₂ O ₃ powder, Nb ₂ O ₅ powder and SnO ₂ powder. The average particle diameter of each raw material powder is preferably 5 μm or less, and the difference between the average particle diameters of the raw material powders is preferably 2 μm or less. In addition, the average particle diameter of the raw material powder is the volume cumulative diameter D ₅₀ at 50 volume % of the cumulative volume measured by a laser diffraction scattering particle size distribution measurement method.

The mixing ratio of each raw material powder can be appropriately determined so that the oxide sintered body has a desired constituent element ratio.

Each of the raw material powders is preferably pulverized in advance and then mixed, or pulverized while being mixed, since generally particles are aggregated.

The pulverization method or mixing method of the raw materials is not particularly limited. For example, the raw material powder can be put into a bottle and pulverized or mixed with a ball mill.

The obtained mixed powder can be directly formed as a formed body and then sintered, but it can also be formed as a formed body by adding a binder to the mixed powder as required. The binder can be a well-known binder used in powder metallurgy to prepare a shaped body, such as polyvinyl alcohol, acrylic latex binder, and the like. In addition, it can also be prepared by adding a dispersion medium to the mixed powder. slurry, and spray-drying the slurry to prepare pellets, and then shaping the pellets.

As the molding method, a conventional powder metallurgy method, such as cold pressing or CIP (Cold Isostatic Pressing: Cold Isostatic Pressing), can be used.

Alternatively, the mixed powder may be temporarily pressurized to prepare a temporary compact, and then the pulverized powder obtained by pulverizing it may be subjected to full pressure to prepare a compact.

In addition, a formed body can also be produced by a wet molding method such as slip casting. The relative density of the shaped body is usually 50 to 75%.

Next, the obtained molded body is fired to produce a sintered body. The sintering furnace for producing the sintered body is not particularly limited, and a sintering furnace that can be used for producing a ceramic sintered body can be used.

The firing temperature is preferably 1300°C to 1600°C, more preferably 1400°C to 1600°C. The higher the sintering temperature, the more dense a sintered body can be obtained. On the other hand, it is preferable to control the temperature below the above-mentioned temperature from the viewpoint of suppressing the enlargement of the structure of the sintered body and preventing cracking.

The holding time at the firing temperature is preferably 3 to 30 hours, more preferably 5 to 20 hours. When the holding time is within the above range, a high-density sintered body can be obtained. From the viewpoints of densification and crack prevention, the temperature increase rate is preferably 100 to 500°C/h. The firing environment is preferably an oxygen environment.

Next, the obtained sintered body is subjected to cutting processing. This cutting process is performed using a surface grinder or the like. Also, the table after cutting The surface roughness Ra can be appropriately controlled by selecting the size of the abrasive grains of the grindstone used for cutting.

A sputtering target is produced by joining the sintered body after cutting and the base material. The material of the substrate can be appropriately selected from stainless steel, copper, or titanium. As the bonding material, low melting point solder such as indium can be used.

(Example)

[Example 1]

The In ₂ O ₃ powder with an average particle size of 0.7 μm, the Nb ₂ O ₅ powder with an average particle size of 1.2 μm, and the SnO ₂ powder with an average particle size of 0.9 μm were placed in a bottle by zirconia balls. Mix to make a mixed powder.

In addition, the average particle diameter of a raw material powder was measured using the particle size distribution measuring apparatus HRA by Nikkiso Co., Ltd. product. In this measurement, water was used as the solvent, and the measurement was performed at a refractive index of 2.20 of the measurement substance.

In addition, when preparing the mixed powder, it was prepared so that indium would be 94.5 mass % in terms of In ₂ O ₃ , niobium would be 5.0 mass % in terms of Nb ₂ O ₅ , and tin would be 0.5 mass % in terms of SnO ₂ . each raw material powder.

Next, 6 mass % of polyvinyl alcohol diluted to 4 mass % was added to the mixed powder, and polyvinyl alcohol was sufficiently applied to the powder using a mortar and passed through a 5-mesh sieve. Next, the obtained powder was temporarily pressurized under the condition of 200 kg/cm ² , and the obtained temporary compact was pulverized with a mortar. Next, the obtained pulverized powder was filled in a press mold, and molded at a press pressure of 1 t/cm ² for 60 seconds to obtain a molded body.

Next, the formed body is fired to obtain a sintered body. The firing was carried out in a furnace in an oxygen flow environment with oxygen flowing at 10 L/min at a firing temperature of 1550°C, a firing time of 9 hours, a temperature increase rate of 350°C/h, and a temperature drop rate of 100°C/h.

Next, the obtained sintered body was machined to obtain an oxide sintered body having a surface roughness Ra of 1.0 μm and a width of 210 mm×length 710 mm×thickness 6 mm. In addition, the grinding stone of #170 was used for this cutting process.

[Examples 2 to 7]

In the same manner as in Example 1, an oxide sintered body was obtained. In addition, in Examples 2 to 7, when the mixed powder was prepared, the contents of indium, niobium and tin were converted into the contents described in Table 1 in terms of In ₂ O ₃ , Nb ₂ O ₅ and SnO ₂ . way to prepare each raw material powder.

[Comparative Examples 1 to 6]

In the same manner as in Example 1, an oxide sintered body was obtained. In addition, in Comparative Examples 1 to 6, when the mixed powder was prepared, the contents of indium, niobium and tin were converted into the contents described in Table 1 in terms of In ₂ O ₃ , Nb ₂ O ₅ and SnO ₂ . way to prepare each raw material powder.

In addition, in Examples 1 to 7 and Comparative Examples 1 to 6, the content ratio of each element measured when preparing each raw material powder was measured by ICP-AES (Inductively Coupled Plasma Atomic Emission Spectroscopy: Inductively Coupled Plasma Atomic Emission Spectrometry) was confirmed to be equal to the content of each element in the obtained oxide sintered body.

Next, the above-obtained Examples 1 to 7 and their comparison The relative density of the oxide sintered bodies of Examples 1 to 6 was measured. The relative density was measured according to the Archimedes method.

Specifically, the air mass of the oxide sintered body is divided by the volume (the water mass of the sintered body/the water specific gravity at the measurement temperature), and the value of the percentage relative to the theoretical density ρ (g/cm ³ ) is used as the relative Density (unit: %).

In addition, the theoretical density ρ (g/cm ³ ) is calculated from the mass % and the density of the raw material powder used for producing the oxide sintered body. Specifically, it is calculated according to the following formula.

ρ={(C ₁ /100)/ρ ₁ +(C ₂ /100)/ρ ₂ +(C ₃ /100)/ρ ₃ } ^-1

In addition, C ₁ to C ₃ and ρ ₁ to ρ ₃ in the above formula represent the following values, respectively.

. C ₁ : Mass % of the In ₂ O ₃ powder used in the production of the oxide sintered body

． ρ ₁ : Density of In ₂ O ₃ (7.18 g/cm ³ )

. C ₂ : Mass % of Nb ₂ O ₅ powder used in the production of oxide sintered body

． ρ ₂ : Density of Nb ₂ O ₅ (4.47g/cm ³ )

. C ₃ : Mass % of SnO ₂ powder used in the production of oxide sintered body

. ρ ₃ : Density of SnO ₂ (6.95g/cm ³ )

Next, the specific resistance (bulk resistance) was measured for the oxide sintered bodies for sputtering targets of Examples 1 to 7 and Comparative Examples 1 to 6 obtained above, respectively.

Specifically, Loresta (registered trademark) HP MCP-T410 (tandem four-probe TYPE ESP) manufactured by Mitsubishi Chemical Co., Ltd. was used, the probe was brought into contact with the surface of the processed oxide sintered body, and the AUTO RANGE mode was used to measure. The measurement locations were five locations in total near the center and the four corners of the oxide sintered body, and the average value of each measured value was taken as the volume resistance value of the sintered body.

Here, about Examples 1 to 7 and Comparative Examples 1 to 6, Table 1 shows the content ratio of each element contained in the powder mixture, and the measurement results of relative density and specific resistance (volume resistance).

It can be seen that the specific resistances of the oxide sintered bodies of Examples 1 to 7 are all 7.0×10 ^-4 Ω. cm below. Therefore, according to the embodiment, when the oxide sintered body is used as the sputtering target, sputtering using an inexpensive DC power supply can be performed, and the film formation speed can be improved.

Next, from the above-mentioned Examples 1 to 7 and Comparative Examples 1 to 6 The oxide sintered bodies were produced as sputtering targets of Examples 1 to 7 and Comparative Examples 1 to 6. This sputtering target is produced by using indium, which is a low melting point solder, as a bonding material, and bonding the oxide sintered body obtained above to a copper base material.

Next, using the sputtering targets of Examples 1 to 7 and Comparative Examples 1 to 6 produced, sputtering was performed under the following conditions to form a thin film having a thickness of 100 nm.

． Film-forming device: EX-3013M (DC sputtering device) manufactured by Vacuum Machinery Industry Co., Ltd.

． Arrived vacuum degree: less than 1×10 ^-4 Pa

. Sputtering gas: Ar/O ₂ mixed gas

． Sputtering pressure: 0.4Pa

． O gas flow: ₀ to 2.0sccm

． Substrate: Glass substrate (EAGLE XG (registered trademark) manufactured by Corning Corporation)

． Substrate temperature: room temperature

. Sputtering power: 3W/cm ²

In addition, in Examples 1 to 7 and Comparative Examples 1 to 6, it was confirmed by ICP-AES that the content of each element in the oxide sintered body used for the sputtering target was the same as that in the formed transparent conductive film. The content of each element is equal.

Next, each glass substrate was cut out to a predetermined size, and the cut-out glass substrate was measured for the transmittance of the transparent conductive films of Examples 1 to 7 and Comparative Examples 1 to 6 formed by sputtering. wavelength dependence.

Furthermore, the cut glass substrate was heat-treated at 200°C for 1 hour in the atmosphere, and the penetration in the transparent conductive film after heat-treatment was also measured. The wavelength dependence of the rate. The measurement conditions of the wavelength dependence of the transmittance before and after the above-mentioned heat treatment are as follows.

． Measuring device: UV-Vis-NIR spectrophotometer UH4150 manufactured by Hitachi Advanced Technology Co., Ltd.

． Scanning speed: 600nm/min

． Wavelength range: 200 to 2600nm

In addition, in the transmittance measurement of the transparent conductive film, a plain glass substrate without film formation was first installed in the apparatus to measure the baseline, and then the transmittance of each film-forming sample was measured.

Figure 1 is a graph showing the wavelength dependence of transmittance before heat treatment of the transparent conductive films of Example 2 and Comparative Examples 1 and 4, and Figure 2 is a graph showing the wavelength dependence of transmittance after heat treatment of the same transparent conductive films Dependency chart. As shown in FIG. 1 and FIG. 2 , by applying a predetermined heat treatment to the transparent conductive film formed by sputtering, the transmittance of the transparent conductive film can be improved as a whole.

Next, the specific resistance of each heat-treated transparent conductive film after film formation was measured. The specific resistance of the transparent conductive film was measured using a four-point probe K-705RS manufactured by Kyowa Riken Co., Ltd.

Here, for the transparent conductive films of Examples 1 to 7 and Comparative Examples 1 to 6, the measurement results of transmittance at wavelengths of 300 nm, 400 nm, and 550 nm before and after heat treatment, and the results of specific resistance measurement after heat treatment are shown. in Table 2. In addition, the evaluation criteria of the specific resistance measurement shown in Table 2 are as follows.

A: The specific resistance is 4.5×10 ^-4 Ω. cm below.

B: The specific resistance exceeds 4.5×10 ^-4 Ω. cm and is 6.0×10 ^-4 Ω. cm below.

C: The specific resistance exceeds 6.0×10 ^-4 Ω. cm.

The transparent conductive film after the heat treatment contains 90.0 mass % or more of indium in terms of In ₂ O ₃ , 3.5 to 6.5 mass % of niobium in terms of Nb ₂ O ₅ , and 0.5 to 2 mass % in terms of SnO ₂ . By comparing Examples 1 to 7 with tin in mass % and Comparative Examples 1 to 6 in which niobium and tin are not contained at the content ratio, it can be seen that in terms of In ₂ O ₃ , 90.0 mass % or more of indium is contained, and Nb It contains 3.5 to 6.5 mass % of niobium in terms of ₂ O ₅ and 0.5 to 2 mass % of tin in terms of SnO ₂ , so that the transmittance in the ultraviolet region (wavelength 300 nm) is increased to 52% or more.

In addition, in Examples 1 to 7, the transparent conductive films after heat treatment, as shown in Table 2 and Figure 2, not only in the ultraviolet light region, but also in the visible light region (for example, wavelengths of 400 nm to 800 nm) have the same characteristics as those in Comparative Examples 1 to 10. 6 The penetration rate of the same or more. That is, in the embodiment, when the transparent conductive film is applied to a transparent electrode of a solar cell, light incident in a wide wavelength region of the solar cell can be used for power generation.

Therefore, according to the embodiment, the power generation efficiency of the solar cell to which the transparent conductive film is applied can be further improved.

In addition, examples in which 90.0 mass % or more of indium is contained in terms of In ₂ O ₃ , 4.0 to 6.0 mass % of niobium in terms of Nb ₂ O ₅ , and 0.5 to 2 mass % of tin in terms of SnO ₂ are included. 1 to 3, 5, and 6 are compared with those of Examples 4 and 7 that do not contain niobium at this content rate. It can be seen that 90.0 mass % or more of indium is contained in terms of In ₂ O ₃ , and indium is contained in terms of Nb ₂ O ₅ . By containing 4.0 to 6.0 mass % of niobium and 0.5 to 2 mass % of tin in terms of SnO ₂ , the conductivity of the transparent conductive film can be maintained favorably.

In addition, the implementation of 90.0 mass % or more of indium in terms of In ₂ O ₃ , 4.5 to 5.5 mass % of niobium in terms of Nb ₂ O ₅ , and 0.5 to 2 mass % of tin in SnO ₂ conversion Comparing Examples 1 to 3 with Examples 4 to 7 that do not contain niobium at the content ratio, it is found that 90.0 mass % or more of indium is contained in terms of In ₂ O ₃ , and 4.5 to 4.5 mass % of indium is contained in terms of Nb ₂ O ₅ . 5.5 mass % of niobium and 0.5 to 2 mass % of tin in SnO ₂ conversion can improve the transmittance in the purple region (wavelength 400nm) to 93.2% or more.

In addition, it contains 90.0 mass % or more of indium in terms of In ₂ O ₃ , 4.8 to 5.2 mass % of niobium in terms of Nb ₂ O ₅ , and 0.8 to 1.2 mass % of tin in terms of SnO ₂ . Example 2 was compared with Examples 1, 3 to 7 which did not contain niobium and tin at the content ratios, and it was found that 4.8 to 5.2 mass % of niobium was contained in terms of Nb ₂ O ₅ and 4.8 to 5.2 mass % in terms of SnO ₂ . 0.8 to 1.2 mass % of tin increases the transmittance in the ultraviolet region (wavelength 300nm) to over 61.4% and in the purple region (wavelength 400nm) to over 94.6%.

As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, Various changes are possible in the range which does not deviate from the summary. For example, in the embodiment, the example in which the transparent conductive film is applied to the solar cell is disclosed, but the device to which the transparent conductive film of the embodiment can be applied is not limited to the solar cell.

For example, when the transparent conductive film of the embodiment is applied to a transparent electrode of an image display device such as liquid crystal or organic EL (electro-luminescence), since the transmittance of the short wavelength region such as the ultraviolet region and the violet region is high, it can be Improves luminous efficiency in the short wavelength region.

Furthermore, by applying the transparent conductive film of the embodiment to an antistatic film of an optical system of an ultraviolet light source such as an ultraviolet lamp, the luminous efficiency in the ultraviolet region can be improved, and ultraviolet light can be stably emitted without generating static electricity.

In addition, in the embodiment, although the example in which the sputtering target was produced using the oxide sintered body in a plate shape was disclosed, the shape of the oxide sintered body is not limited to the plate shape, and may be various shapes such as a cylindrical shape.

More effects and modifications can be easily derived by manufacturers. Therefore, the broader aspect of the present invention is not limited to the specific details and representative embodiments shown and described above. Therefore, various modifications can be made without departing from the spirit or scope of the overall inventive concept defined by the appended claims and their equivalents.

Claims (7)

An oxide sintered body containing indium, niobium, tin and oxygen, and 90.0 mass % or more of the aforementioned indium in terms of In ₂ O ₃ and 4.8 to 6.5 mass % of the aforementioned niobium in terms of Nb ₂ O ₅ , The aforementioned tin is contained in an amount of 0.5 to 2 mass % in terms of SnO ₂ . The oxide sintered body described in claim 1 of the claimed scope contains the aforementioned niobium in an amount of 4.8 to 6.0 mass % in terms of Nb ₂ O ₅ . The oxide sintered body as described in item 1 or 2 of the scope of the application has a specific resistance of 7.0×10 ^-4 Ω. cm below. According to the oxide sintered body described in claim 1 or 2, the relative density is 95% or more. A sputtering target using the oxide sintered body described in claim 1 or 2 as a target material. A transparent conductive film containing indium, niobium, tin and oxygen, and containing 90.0 mass % or more of the aforementioned indium in terms of In ₂ O ₃ conversion, 4.8 to 6.5 mass % of the aforementioned niobium in terms of Nb ₂ O ₅ conversion, and The aforementioned tin is contained in an amount of 0.5 to 2 mass % in terms of SnO ₂ . The transparent conductive film as described in item 6 of the patent application scope has a transmittance of more than 52% at a wavelength of 300 nm.

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