WO2020013191A1

WO2020013191A1 - High-purity chalcogenide material and method for producing same

Info

Publication number: WO2020013191A1
Application number: PCT/JP2019/027172
Authority: WO
Inventors: 嘉太郎野瀬; 友輝武村; 涼司勝部
Original assignee: 国立大学法人京都大学
Priority date: 2018-07-10
Filing date: 2019-07-09
Publication date: 2020-01-16
Also published as: JPWO2020013191A1

Abstract

The present invention enables the provision of a high-purity chalcogenide material, which was difficult before. The high-purity chalcogenide material contains, as a high-purity chalcogenide compound containing an element belonging to Group 14 and an element belonging to Group 16 on the periodic table at a ratio of about 1:1, a chalcogenide compound represented by general formula (1): M1M2 x [wherein M1 represents an element belonging to Group 14 on the periodic table; M2 represents an element belonging to Group 16 on the periodic table; and x represents a numerical value of 0.9 to 1.1], wherein the content of the chalcogenide compound is 90 mol% or more as measured by an X-ray diffraction measurement.

Description

High purity chalcogenide material and method for producing the same

The present invention relates to a high-purity chalcogenide material and a method for producing the same.

Tin sulfide SnS, which is a p-type semiconductor composed of inexpensive and safe elements, has a band gap of about 1.3 eV and has a light absorption coefficient of about 10 ⁵ cm ^{-1 in the} visible light region. It is expected as a high-efficiency solar cell material or a two-dimensional material for an electronic device. When used as a solar cell material, the theoretical conversion efficiency is expected to be 30% or more. SnS solar cells are currently reported with a maximum conversion efficiency of 4.36%. Similarly, other 1: 1 chalcogenide compounds of Group 14 and Group 16 elements are also expected to be highly efficient solar cell materials.

In such devices and basic research, it is important to use single-phase crystals, but it is not easy to obtain single-phase crystals. For example, taking a commercially available SnS crystal as an example, even if it is high purity grade (99.9% purity) SnS, the indicated purity indicates that the impurity concentration other than Sn and S is 0.1%. However, impurities containing Sn or S are not taken into account. In this commercially available SnS sample, not only SnS but also impurities such as Sn ₂ S ₃ and SnO ₂ are mixed, so that purity of 99.9% means that SnS, Sn ₂ S ₃ , SnO ₂ etc. And 99.9% in total, and the net SnS purity is only about 50%. In addition, even if it is attempted to directly produce a SnS single-phase crystal, as can be understood from the S-Sn binary phase diagram shown in FIG. 1, the stable region of the SnS single-phase crystal is extremely narrow, and the SnS single-phase crystal is directly produced. It is extremely difficult to do. In this case, from the Sn-S ₂ chemical potential diagram, it is necessary to control the vapor pressure of sulfur to be extremely low (specifically, p _S2 < ^10-8.8 atm) to significantly lower the chemical potential. From this viewpoint, it cannot be easily manufactured. When pure sulfur used as a raw material is used as a raw material, the vapor pressure of pure sulfur is extremely high, and there is a possibility that the reaction vessel may be broken during the heat treatment. The above-mentioned problem is the same not only for SnS but also for other chalcogenide compounds of about 1: 1 of Group 14 elements and Group 16 elements.

The present invention is intended to solve the above-described problems, and has been difficult in the past, a chalcogenide compound having a high purity of about 1: 1 of Group 14 and Group 16 elements of the periodic table and its production. The aim is to provide a method.

The present inventors have conducted intensive studies to solve the above problems, and as a result, instead of directly producing chalcogenide compounds from Group 14 molecules of the periodic table and molecules of Group 16 of the periodic table, the objective chalcogenide compounds After once producing a two-phase coexisting material of the periodic table group 14 molecules, by isolating the target chalcogenide compound using the vapor pressure difference, about 1 of the periodic table group 14 element and the group 16 element: It has been found that a high-purity chalcogenide compound of 1 can be obtained. Based on these findings, the present inventors have further studied and completed the present invention. That is, the present invention includes the following embodiments.
Item 1. General formula (1):
M ¹ M ² _x (1)
Wherein, M ¹ is shows a periodic table group 14 element. M ² represents a Group 16 element in the periodic table. x represents 0.9 to 1.1. ]
Containing a chalcogenide compound represented by
A high-purity chalcogenide material, wherein the amount of the chalcogenide compound is 90 mol% or more in X-ray diffraction measurement.
Item 2. Item 2. The high-purity chalcogenide material according to Item 1, which is in the form of a bulk or a thin film.
Item 3. A method for producing a high-purity chalcogenide material according to

item

1 or 2,
(1) A raw material containing a periodic table group 14 molecule and a periodic table group 16 molecule is heated, and a two-phase coexisting material of the chalcogenide compound represented by the general formula (1) and the periodic table group 14 molecule is removed. The process of making,
(2) A production method comprising a step of heating the two-phase coexisting material obtained in the step (1).
Item 4. Item 4. The production method according to Item 3, wherein the heating temperature in the step (2) is 300 to 900 ° C.
Item 5. Item 5. The production method according to

item

3 or 4, wherein the pressure at the time of heating in the step (2) is 10 ⁻⁶ to 10 Pa.

According to the present invention, it is possible to obtain a high-purity chalcogenide compound having a ratio of about 1: 1 of Group 14 and Group 16 elements of the periodic table.

The S-Sn binary phase diagram is shown. Sn, shows a vapor pressure curve of SnS and S _2. 3 shows a heat treatment profile of Production Example 1. 3 shows an SEM image of the surface of the Sn—SnS two-phase sample obtained in Production Example 1. 1 shows an X-ray diffraction profile of a Sn—SnS two-phase sample obtained in Production Example 1. The lower part shows the literature values of SnS for reference. In Example 1, a temperature profile inside the Bridgman furnace after completion of the temperature rise is shown. 1 shows a powder X-ray diffraction profile of the SnS single-phase bulk crystal obtained in Example 1. The lower part shows the literature values of SnS for reference. 2 shows a photograph of the SnS single-phase bulk crystal obtained in Example 1 after cleavage. 3 shows an SEM image of a cleavage plane of the SnS single-phase bulk crystal obtained in Example 1. 2 shows an X-ray diffraction profile of a cleavage plane of the SnS single-phase bulk crystal obtained in Example 1. The first row from the top shows the results for the front side, and the second row shows the results for the back side. The third row shows SnS literature values. 4 shows an X-ray diffraction profile of the SnS single-phase thin film obtained in Example 2. The lower part shows the literature values of SnS for reference. 3 shows a stereograph and a surface SEM image of the SnS single-phase thin film (substrate temperature: room temperature, upper stage) and SnS single-phase thin film (substrate temperature: 300 ° C., lower stage) obtained in Example 2. 2 shows an X-ray diffraction profile of Comparative Example 1. The first row from the top shows the results for the powder reagent, and the second row shows the results for the granular reagent. The third row shows the literature value of SnS, the fourth row shows the literature value of Sn ₂ S ₃ , and the fifth row shows the literature value of SnO ₂ . 4 shows a stereoscopic photograph and a surface SEM image of the thin film (substrate temperature room temperature) obtained in Comparative Example 2. 1 shows a Ge-S binary phase diagram. 3 shows vapor pressure curves of Ge and GeS. 4 shows X-ray diffraction profiles of a GeS single-phase bulk crystal (top) and a Ge—GeS two-phase sample (bottom) obtained in Example 3. The third column also shows the literature values of GeS, and the fourth column also shows the literature values of Ge.

において In this specification, when the numerical range is indicated by “A to B”, it means A or more and B or less. In addition, “contain” includes any of “comprise”, “consist essentially” of “consist” and “consist of”.

1. High Purity Chalcogenide Material The high purity chalcogenide material of the present invention has a general formula (1):
M ¹ M ² _x (1)
Wherein, M ¹ is shows a periodic table group 14 element. M ² represents a Group 16 element in the periodic table. x represents 0.9 to 1.1. ]
Containing a chalcogenide compound represented by
In the X-ray diffraction measurement, the amount of the chalcogenide compound is 90 mol% or more.

In the general formula (1), M ¹ represents a Group 14 element of the periodic table, and includes Sn, Si, Ge, Pb, and the like. From the viewpoint of easily obtaining a high-purity chalcogenide material, Sn, Ge, and the like are preferable, and Sn is preferably More preferred.

In the general formula (1), M ² represents a Group 16 element of the periodic table, and includes S, Se, Te, and the like. From the viewpoint of easily obtaining a high-purity chalcogenide material, S, Se, and the like are preferable, and S is more preferable. .

In the general formula (1), x represents 0.9 to 1.1, preferably 0.95 to 1.05, and more preferably 0.95 to 1.05, from the viewpoint of easily obtaining a high-purity chalcogenide material having a ratio of about 1: 1 of Group 14 and Group 16 elements. ～ 1.02 is more preferred.

In the high-purity chalcogenide material of the present invention, the abundance of the chalcogenide compound represented by the general formula (1) as described above is 90 mol% or more in X-ray diffraction measurement, and a higher-purity chalcogenide material is obtained. From the viewpoint, 95 mol% or more is preferable, and 98 mol% or more is more preferable. The amount of the chalcogenide compound represented by the general formula (1) is most preferably 100 mol%. More specifically, when the X-ray diffraction measurement is performed, the ratio of the peak intensity determined to be derived from the chalcogenide compound phase represented by the general formula (1) among the clearly observed X-ray diffraction peaks It is preferable that the estimated amount of the chalcogenide compound phase be within the above range.

The high-purity chalcogenide material of the present invention can be obtained as a bulk or a thin film. When obtained as a bulk, for example, a high-purity chalcogenide material having an average diameter of about 5 to 10 mm can be obtained. When obtained as a thin film, for example, a high-purity chalcogenide material having an average thickness of about 1 to 10 μm can be obtained. Obtainable. The size in the case of obtaining a bulk shape can be appropriately adjusted depending on the size of a quartz tube or the like to be used, and the average thickness in the case of obtaining a thin film is, for example, temperature or time when obtaining by a manufacturing method described later. Can be adjusted appropriately.

2. Method for producing a high-purity chalcogenide materialA method for producing a high-purity chalcogenide material of the present invention comprises:
(1) A raw material containing a periodic table group 14 molecule and a periodic table group 16 molecule is heated, and a two-phase coexisting material of the chalcogenide compound represented by the general formula (1) and the periodic table group 14 molecule is removed. The process of making,
(2) a step of heating the two-phase coexisting material obtained in the step (1).

(2-1) Step (1): Preparation of Two-Phase Coexisting Material In the step (1), a raw material containing a molecule of Group 14 of the periodic table and a molecule of Group 16 of the periodic table is heated, and A biphasic coexisting material of the chalcogenide compound represented and the periodic table group 14 molecule is prepared.

In the step (1), a raw material containing a Group 14 molecule of the periodic table and a Group 16 molecule of the periodic table is used as a raw material. Specifically, the group 14 molecules of the periodic table include tin, silicon, germanium, lead, and the like. From the viewpoint of easily obtaining a high-purity chalcogenide material, tin, germanium, and the like are preferable, and tin is more preferable. Examples of the group 16 molecules of the periodic table include sulfur, selenium, and tellurium. From the viewpoint of easily obtaining a high-purity chalcogenide material, sulfur, selenium, and the like are preferable, and sulfur is more preferable.

Regarding the composition ratio between the periodic table group 14 molecules and the periodic table group 16 molecules in the raw materials, as long as the two-phase coexisting material of the chalcogenide compound represented by the general formula (1) and the periodic table group 14 molecules can be prepared. There is no particular limitation. As can be understood from the S-Sn binary phase diagram shown in FIG. 1, when the Sn content is 100 mol% or in the immediate vicinity, it is a Sn stable region, and the Sn content is 50 mol%. In the case of or in the immediate vicinity of this, it is a stable region of SnS. This example is an example of the S-Sn binary phase diagram, but the same tendency is observed in other binary phase diagrams of elements of Group 14 of the periodic table to elements of Group 16 of the periodic table. From such a viewpoint, when the content of the group 14 molecules of the periodic table is about 51 to 99 mol%, a two-phase coexisting material of the group 14 molecules of the periodic table and the target chalcogenide compound is prepared at a predetermined temperature. obtain. However, since the target chalcogenide compound is a material having a molar ratio of the Group 14 element of the Periodic Table and the Group 16 element of the periodic table of 1: 1, the periodic table Group 14 molecules and the Periodic Table Group The composition ratio with the group 16 molecule is also preferably as close as possible to 1: 1 in molar ratio. However, if the composition ratio between the Group 14 molecules of the periodic table and the Group 16 molecules in the raw material is completely 1: 原料 1, a two-phase coexisting material cannot be produced, so the periodic table in the raw material cannot be produced. The content of Group 14 molecules is preferably 51 to 99 mol% (particularly 52 to 90 mol%, more preferably 53 to 80 mol%), and the content of Group 16 molecules of the periodic table in the raw material is 1 to 49 mol% ( In particular, 10 to 48 mol%, and more preferably 20 to 47 mol%).

市販 As these raw materials, commercially available products (preferably high-purity products) can be used as they are, but when an oxide film is formed on a commercially available product, it is preferable to remove the oxide film by a conventional method.

The heating atmosphere is not particularly limited. However, from the viewpoint of preventing impurities such as oxides from being particularly mixed, under reduced pressure (for example, 10 ⁻⁶ to 10 Pa) or under inert atmosphere (for example, under nitrogen atmosphere, argon atmosphere). Under an atmosphere).

The heating temperature (the maximum temperature during heating) is not particularly limited as long as a two-phase coexisting material can be produced, and is, for example, preferably 500 to 1000 ° C, more preferably 600 to 900 ° C. When the heating temperature is high (860 ° C or higher in the case of Sn-S system), it becomes a liquid phase in that temperature range, but after cooling, the group 14 molecules of the periodic table and the target chalcogenide compound Can be produced. In addition, it is possible to heat up to the maximum temperature at a time, but it is also possible to raise the temperature stepwise to prevent the container from being broken by the vapor pressure of the raw material.

The heating time is not particularly limited as long as a two-phase coexisting material can be produced. For example, the maintenance time at the highest temperature is preferably 1 to 48 hours, more preferably 2 to 24 hours.

二 Thus, a two-phase coexisting material of the periodic table group 14 molecule and the target chalcogenide compound can be produced.

(2-2) Step (2): Chalcogenide Material Preparation In step (2), the two-phase coexisting material obtained in step (1) is heated. In the two-phase coexisting material obtained in step (1), molecules of the 14th group of the periodic table and the target chalcogenide compound are mixed. However, since these two components have significantly different equilibrium vapor pressures, use this vapor pressure difference. Thus, only the target chalcogenide compound can be isolated.

(4) The heating temperature (the highest temperature during heating) is not particularly limited as long as the desired chalcogenide compound can be isolated, and is, for example, preferably 300 to 900 ° C, more preferably 550 to 850 ° C.

In step (2), the pressure during heating and the heating temperature are closely related, and the logarithmic value of the equilibrium vapor pressure of Group 14 molecules and the target chalcogenide compound is almost linear with the reciprocal of temperature. (The logarithmic value of the equilibrium vapor pressure increases with increasing temperature). This can be understood from Sn, steam SnS and S ₂ pressure curve shown in Figure 2. Note that this vapor pressure curve is for obtaining SnS, but the same behavior is shown for obtaining other chalcogenide compounds. From the above, it is preferable to appropriately adjust the pressure and the temperature within a range where the chalcogenide compound evaporates and the group 14 molecule of the periodic table does not evaporate.

The heating time is not particularly limited as long as the objective chalcogenide compound can be isolated. For example, the maintenance time at the highest temperature is preferably 1 to 48 hours, more preferably 2 to 24 hours.

In this way, only the target chalcogenide compound can be isolated. At this time, since the chalcogenide compound is obtained as a gas, the chalcogenide material of the present invention is cooled by, for example, room temperature to 800 ° C. In particular, a single-phase crystal of a chalcogenide compound can be obtained.

Note that the heating and the cooling in the step (2) can be performed in separate vessels, but when a Bridgman furnace is used, the temperature can be changed between the upper part and the lower part. For this reason, the two-phase coexisting material is filled in the lower part of the Bridgman furnace, and only the chalcogenide compound is isolated by heating the lower part, and the chalcogenide compound is cooled and crystallized in the upper part of the Bridgman furnace to obtain the main product. It is also possible to obtain the chalcogenide material of the present invention (particularly, a single-phase crystal of a chalcogenide compound). In this case, it is easy to obtain a bulk chalcogenide material of the present invention (particularly, a single-phase crystal of a chalcogenide compound). On the other hand, without using a Bridgman furnace, soda lime glass (SLG), silicon, etc. are placed as substrates on the heating unit in a heating furnace, and the substrate is heated to 100 to 500 ° C as necessary. It is also possible to obtain a thin-film chalcogenide material of the present invention (particularly, a single-phase crystal of a chalcogenide compound) on the upper substrate by a vacuum evaporation method in which the lower two-phase coexisting material is heated.

Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited to Examples.

Production Example 1: Pure tin (manufactured by Kojundo Chemical Laboratory , granular, 4N) and pure sulfur (manufactured by Kojundo Chemical Laboratory, powdered, 4N) ) Was used. Pure tin is etched for 30 seconds by immersing it for 30 seconds in a solution obtained by diluting HCl (manufactured by Nacalai Tesque, 35% by mass) with ultrapure water for 30 seconds. After ultrasonic cleaning, the substrate was subjected to ultrasonic cleaning in 2-propanol for 5 minutes and then dried with nitrogen gas.

The raw material reagents were weighed so as to have a molar ratio of Sn: S = 60: 40 and a total amount of about 5.0 g. The sample was vacuum-sealed in a quartz tube having an outer diameter of 9 mm and an inner diameter of 7 mm. The evacuation was performed by an oil diffusion pump. When the degree of vacuum reached about 10 ^-2 Pa, the quartz tube was heated with a burner and sealed by welding. Thereafter, heat treatment was performed using a horizontal tubular electric furnace with a profile shown in FIG. The temperature was raised stepwise to prevent the ampoule from bursting due to unreacted sulfur vapor pressure.

一部分 A part of the obtained sample was cut out with a diamond wheel saw and taken out. The removed sample was observed using a sample scanning electron microscope (SEM, JCM-6000 電子 Plus, manufactured by JEOL Ltd.) and an energy dispersive X-ray analyzer (EDX, manufactured by JEOL Ltd., JED- 2300 Series). In the quantitative analysis, the acceleration voltage was set to 15 kV, and point analysis was performed at five points. The error was twice the standard deviation. FIG. 4 shows the results. As a result, it can be understood that Sn is distributed using SnS as a matrix.

In addition, a part of the sample was powdered using an agate mortar and an agate pestle, and phase identification was performed using an X-ray diffractometer (X'pert PRO Alpha-1 manufactured by PANalytical). Monochromatic Cu Kα ₁ rays (λ = 1.5406 °) were used as incident X-rays, and the tube voltage was set to 45 kV and the tube current was set to 40 mA. The goniometer scanning method used the θ-2θ method, the step angle was 0.00836 ° step ⁻¹ , the integration time was 59.7 s step ^−1, and the scanning angle was between 10 ° and 70 °. FIG. 5 shows the results. As a result, it can be understood that only SnS and Sn were detected, and Sn ₂ S ₃ and SnO ₂ were not detected at all.

Example 1: Preparation of SnS single-phase bulk crystal A Sn-SnS two-phase sample prepared in Production Example 1 was used as a raw material. The raw material was weighed to about 10 g and vacuum-sealed in a quartz tube having an outer diameter of 9 mm and an inner diameter of 7 mm. The evacuation was performed by an oil diffusion pump. When the degree of vacuum reached about 10 ^-2 Pa, the quartz tube was heated with a burner and sealed by welding. The tip of the ampoule was narrowed to promote crystal precipitation at the upper end.

The ampoule was fixed such that the top was 18 cm from the bottom of the Bridgman furnace. The final temperatures of the three heaters constituting the Bridgman furnace were set to 725 ° C in the upper part, 870 ° C in the middle part, and 870 ° C in the lower part, and the temperature was raised from room temperature to the target temperature over two hours. FIG. 6 shows the temperature profile inside the Bridgman furnace after the completion of the temperature rise. After completion of the temperature rise, the temperature was kept isothermal for 8 hours, and then the heater was lowered by about 160 mm at a moving speed of 7 mm day ^-1 using a motor, and then the furnace was cooled for 10 hours.

A part of the sample formed at the upper end of the ampoule was powdered using an agate mortar and an agate pestle, and phase identification was performed using an X-ray diffraction apparatus (X'pert PRO Alpha-1 manufactured by PANalytical). Monochromatic Cu Kα ₁ rays (λ = 1.5406 °) were used as incident X-rays, and the tube voltage was set to 45 kV and the tube current was set to 40 mA. The goniometer scanning method used the θ-2θ method, the step angle was 0.00836 ° step ⁻¹ , the integration time was 59.7 s step ^−1, and the scanning angle was between 10 ° and 70 °. FIG. 7 shows the results. As a result, only SnS was detected, and it can be understood that a single-phase bulk crystal of 100% SnS was obtained.

The sample was cleaved by lightly tapping it with the blade of a cutter knife. FIG. 8 shows a photograph of the sample after cleavage. The cleavage plane is observed using a scanning electron microscope (SEM, JCM-6000 Plus, manufactured by JEOL Ltd.) and an energy dispersive X-ray analyzer (EDX, JED-2300 Series, manufactured by JEOL Ltd.) Quantitative analysis of the composition was performed using In the quantitative analysis, the acceleration voltage was set to 15 kV, and point analysis was performed at 10 points. The error was twice the standard deviation. FIG. 9 shows the obtained surface SEM image. Further, the cleavage plane was subjected to X-ray diffraction measurement using an X-ray diffraction apparatus (X'pert PRO Alpha-1 manufactured by PANalytical). Monochromatic Cu Kα ₁ rays (λ = 1.5406 °) were used as incident X-rays, and the tube voltage was set to 45 kV and the tube current was set to 40 mA. The goniometer was scanned using the θ-2θ method, with a step angle of 0.00836 ° step ⁻¹ , an integration time of 59.7 s step ⁻¹ and a scan angle between 10 ° and 90 °. The results are shown in FIG. As a result of quantitative analysis of the composition by EDX, Sn was 50.2 ± 0.5 mol% and S was 49.8 ± 0.5 mol%. This indicates that single crystal SnS was obtained.

Further, the electrical characteristics were evaluated using a resistivity / Hall measurement system (Resitest 8300, manufactured by Toyo Technica Co., Ltd.). As a result, the conductivity type was p-type, the specific resistance was 8.7 × 10 ⁻² Ωcm, the carrier density was 6.7 × 10 ¹⁷ cm ⁻³ , and the carrier mobility was 107 cm ² V ⁻¹ s ⁻¹ .

Example 2: Soda-lime glass (SLG) was used for the substrate of the SnS single-phase thin film production thin film. The SLG was cut into 10 mm × 10 mm × 0.5 mm using a diamond pen, washed with a neutral detergent, and then subjected to ultrasonic cleaning for 5 minutes for acetone, 2-propanol and ultrapure water in this order. The washed SLG was dried using nitrogen gas. Note that the substrate temperature of SLG was room temperature or 300 ° C. The Sn-SnS two-phase sample prepared in Production Example 1 was used as the evaporation source. The sample was cut to a width of about 3 mm using a diamond wheel saw. The cut sample was placed on a tungsten boat and evaporated by resistance heating the boat. The degree of vacuum at the time of vapor deposition was 4 × 10 ^-2 Pa, and the current value was about 16 A, and vapor deposition was performed for 2.5 minutes. As a result, the heating temperature of the sample was about 900 to 1000 ° C.

The sample was subjected to phase identification using an X-ray diffractometer (X'pert PRO Alpha-1 manufactured by PANalytical). Monochromatic Cu Kα ₁ rays (λ = 1.5406 °) were used as incident X-rays, and the tube voltage was set to 45 kV and the tube current was set to 40 mA. The goniometer was scanned using the θ-2θ method, with a step angle of 0.00836 ° step ⁻¹ , an integration time of 59.7 s step ⁻¹ and a scan angle of 10 ° -70 °. The results are shown in FIG. As a result, only SnS was detected, and it can be understood that a single-phase thin film of 100% SnS was obtained.

Further, the surface and cross section of the sample were observed using a sample scanning electron microscope (SEM, manufactured by JEOL Ltd., JCM-6000 Plus), and an energy dispersive X-ray analyzer (EDX, manufactured by JEOL Ltd.) The composition was quantitatively analyzed using JED-2300 Series. In the structure observation, the accelerating voltage was 10 kV. In the quantitative analysis, the acceleration voltage was set to 15 kV, and the analysis was performed at five locations. The error was twice the standard deviation. A stereogram and a surface SEM image of the obtained thin film (substrate temperature at room temperature) are shown in the upper part of FIG. 12, and a solid photograph and a surface SEM image of the obtained thin film (substrate temperature of 300 ° C.) are shown in the lower part of FIG. As a result of quantitative analysis of the composition by EDX, Sn was 50.1 ± 0.3 mol% and S was 49.9 ± 0.3 mol%. This indicates that the composition of the obtained thin film is SnS.

(4) Diffuse reflectance was measured using a spectrophotometer (UV-2600, manufactured by Shimadzu Corporation). Conversion using the Kubelka-Munk function was performed on the allowable and direct transition (n = 2), and a Tauc plot was created to evaluate the band gap.

SThe SnS single-phase thin film obtained in this way can be applied to solar cells and various devices.

Comparative Example 1: Commercially available SnS reagent A commercially available SnS reagent (3N grade, powder sample and granular sample) was employed as the SnS reagent of Comparative Example 1. As in Examples 1 and 2, phase identification was performed using an X-ray diffractometer (manufactured by PANalytical, X'pert PRO Alpha-1). Monochromatic Cu Kα ₁ rays (λ = 1.5406 °) were used as incident X-rays, and the tube voltage was set to 45 kV and the tube current was set to 40 mA. The goniometer was scanned using the θ-2θ method, with a step angle of 0.00836 ° step ⁻¹ , an integration time of 59.7 s step ⁻¹ and a scan angle of 20 ° -40 °. FIG. 13 shows the results. As a result, unlike Examples 1 and 2, in both the powder sample and the granular sample, Sn ₂ S ₃ and SnO ₂ were mixed in addition to SnS, and the abundance of SnS was only about 50 mol%. I understand that there is no.

Comparative Example 2: Vacuum evaporation using a commercially available SnS reagent Example 2 except that a commercially available SnS reagent (3N grade, powder sample and granular sample) was used instead of the Sn-SnS two-phase sample prepared in Production Example 1 Similarly, vacuum deposition was performed.

サンプル Similar to Example 2, the surface and cross section of the sample were observed using a scanning electron microscope (SEM, manufactured by JEOL Ltd., JCM-6000 Plus). In the structure observation, the accelerating voltage was 10 kV. FIG. 14 shows a stereogram and a surface SEM image of the obtained thin film (substrate temperature: room temperature).

Example 3: GeS single-phase bulk crystal preparation As can be understood from the Ge-S system phase diagram shown in FIG. 15, a Ge-GeS two-phase sample can be prepared in the same manner as the Sn-SnS two-phase sample. Further, as can be understood from the vapor pressure curve shown in FIG. 16, when this Ge—GeS two-phase sample is used as a raw material, a GeS single-phase crystal can be produced.

(4) Pure germanium (granular, 5N grade, manufactured by Furuuchi Chemical Co., Ltd.) and pure sulfur (powder, 4N, manufactured by Kojundo Chemical Laboratory Co., Ltd.) were used as raw material reagents. Otherwise in the same manner as in Production Example 1, a Ge-GeS two-phase sample was obtained. Further, using the Ge-GeS two-phase sample as a raw material, the same procedure as in Example 1 was performed except that the final temperatures of the three heaters constituting the Bridgman furnace were set to upper 600 ° C, middle 700 ° C, and lower 700 ° C, respectively. Thus, a GeS single phase bulk crystal was obtained.

A part of the sample formed at the upper end of the ampoule was powdered using an agate mortar and an agate pestle, and phase identification was performed using an X-ray diffraction apparatus (X'pert PRO Alpha-1 manufactured by PANalytical). Monochromatic Cu Kα ₁ rays (λ = 1.5406 °) were used as incident X-rays, and the tube voltage was set to 45 kV and the tube current was set to 40 mA. The goniometer scanning method used the θ-2θ method, the step angle was 0.00836 ° step ⁻¹ , the integration time was 59.7 s step ^−1, and the scanning angle was between 10 ° and 70 °. The results are shown in FIG. As a result, only GeS was detected from the upper end of the ampoule, and it can be understood that a single-phase bulk crystal of 100% GeS was obtained.

Claims

General formula (1):
M 1 M 2 x (1)
Wherein, M 1 is shows a periodic table group 14 element. M 2 represents a Group 16 element in the periodic table. x represents 0.9 to 1.1. ]
Containing a chalcogenide compound represented by
A high-purity chalcogenide material, wherein the amount of the chalcogenide compound is 90 mol% or more in X-ray diffraction measurement.
The high-purity chalcogenide material according to claim 1, which is in the form of a bulk or a thin film.
A method for producing a high-purity chalcogenide material according to claim 1 or 2,
(1) A raw material containing a periodic table group 14 molecule and a periodic table group 16 molecule is heated, and a two-phase coexisting material of the chalcogenide compound represented by the general formula (1) and the periodic table group 14 molecule is removed. The process of making,
(2) A production method comprising a step of heating the two-phase coexisting material obtained in the step (1).
The production method according to claim 3, wherein the heating temperature in the step (2) is 300 to 900 ° C.
The production method according to claim 3, wherein in the step (2), the pressure at the time of heating is 10 -6 to 10 Pa.