JP6907323B2 - Multilayer thin film and its preparation - Google Patents

Description

Field of Invention The present invention relates to a multilayer thermoelectric structure, a method for preparing the same, and its use. The multilayer thermoelectric structure according to the present invention is also referred to as a "multilayer thin film" in the present specification, for example, as a heat recovery system of a thermoelectric generator (TEG) that converts thermal energy into electrical energy, or a seat heater. It can be used as a humidity controller or a Perche cooling / heating module that can be used in small refrigerators.

Over the last decade, there has been increasing interest in the field of thermoelectrics. This is because more efficient power generation materials are needed. The thermoelectric system is an environmentally friendly energy conversion technology, and has the advantages of being compact, highly stable, emitting no pollutants, and being able to be used in a wide temperature range. Due to the need for alternative energy technologies to reduce reliance on fossil fuels, important research programs are being implemented in some technical areas.

For example, in the automobile industry, power generation applications are currently under research. For example, in next-generation automobiles, there is research to use it as a means to generate electric power from engine exhaust heat discharged from radiators and exhaust systems. In thermoelectric cooling applications, research is being conducted on seat coolers that pursue comfort and cooling of electronic components.

Among various thermoelectric materials over the past 30 years, _Bi 2 Te ₃ system _{[(Bi 1-x Sb x} ) 2 (Te1 -x Se x) 3] and _{Si 1-y} Ge y based alloys widely studied As a thermoelectric material, it has been optimized for use in a variety of solid thermoelectric cooling and power generation applications.

The crystalline Bi ₂ Te ₃ has an orthorhombic hexagonal hexagonal symmetric layer structure (FIG. 1). Each layer is laminated along the c-axis (... Te _1- Bi-Te ₂ -Bi-Te ₁ ...), and the Bi layer and the Te layer are bonded by a strong covalent bond, and the adjacent Te layers are van der. It is connected by a Waals bond.

The main purpose of research in the thermoelectric field is to increase the performance index ZT of materials, which is directly related to the conversion efficiency between thermal energy and electrical energy.

ZT = S ² GT / (K _e + K _l ) (1)
In the formula, S is the Seebeck coefficient, G is the electrical conductivity, T is the temperature, _Ke is the electron thermal conductivity, and K _l is the lattice thermal conductivity.

J. Massen and M.M. Lundstrom is a computer-simulated Bi ₂ Te ₃ system with a thickness of one five-layer (ie, Te _1- Bi-Te ₂ -Bi-Te ₁ ) and is more thermoelectric than _{bulk Bi 2} Te _3. Discloses that is excellent (Non-Patent Document [1]).

However, when the thermoelectric material is used for, for example, a thermoelectric module, a superconducting cable, a secondary battery, or a nonlinear optical element, the thermoelectric layer may be thicker than 100 μm in order to reduce the electric resistance in the case of the thermoelectric module. desirable.

By using a single crystal as a base material, an arbitrary crystal orientation and thickness can be obtained. This is disclosed in Non-Patent Document [2], and in Non-Patent Document [2], for example, single crystal Si, quartz, ZnO, KCl, BaF ₂ , and MgO can be used as the base material.

However, these methods are not suitable for industrial scale manufacturing.
In Non-Patent Document [2], Venkatas Bramanian et al. Disclose a single crystal substrate. This single crystal substrate gives good TE performance, but is not suitable for mass production on an industrial scale.

The "2D nanosheet" is a multi-layer structure in which several unit layers are laminated. The individual unit layers are separated from each other by a van der Waals gap and are less than 1 μm thick. 2D nanosheets generally have good thermoelectric properties, but when using 2D nanosheets, it is necessary to stack several layers of 2D nanosheets in order to achieve the desired thickness of more than 100 μm. However, it is difficult to maintain the crystal orientation by simply laminating the 2D materials, so that a bond interaction occurs between adjacent layers. As a result, the laminated 2D nanosheets become a common bulk material instead of the 2D nanosheets, and thus the thermoelectric properties of the 2D nanosheets are lost.

Non-Patent Document [1] J. Massen and M.M. Lundstrom: Appl. Phys. Lett. , Vol. 102,093103 (2013)
[2] E. Venkatas Bramanian, E. et al. Siivola, T. et al. Colpitts and B. O'Quinn: Nature 413, 597-602 (2001)
Due to the above circumstances, there is still a need for thermoelectric materials / structures that have high energy conversion efficiency, sufficient thickness, and can be manufactured on an industrial scale.

The present invention is a multi-layer thermoelectric structure.
(A) A layer of crystalline thermoelectric material and
(B) Containing a plurality of alternating layers with a layer of a separating material, which is a material different from (A).
At least one of the two end layers is the layer (B).
The crystalline thermoelectric material (A) is Bi ₂ Te ₃ , GaTe, Bi ₂ S ₃ , Bi ₂ Se ₃ , MoS ₂ , TiS ₃ , TiSe ₃ , TiTe ₃ , MnPS ₃ , CdPS ₃ , CdPS ₃ , NiPS ₃ . _{ZnPS 3, Mn 0.5 Fe 0.5 PS} 3, GaS, GaSe, InS, InSe, InTe, TiS 2, MnS, MnTe, ZnS, ZnSe, GaSb, GeSb, GeTe, CdS, CdSe, CdTe, In 2 S _{3, In 2 Se 3, InSb} , Sb 2 Te 3, and _Ge 2 _Sb 2 Te ₅ is selected from the group consisting of, a multilayer-type thermoelectric structure.

The present invention also relates to the use of the multilayer thermoelectric structure in a thermoelectric module, a superconducting cable, a secondary battery, or a nonlinear optical element.

It is the schematic which shows the crystal structure of Bi ₂ Te _3. It is the schematic which shows the non-limiting example of the multilayer thermoelectric structure which concerns on this invention. It is the schematic which shows the non-limiting example of the multilayer thermoelectric structure which concerns on this invention. It is the schematic which shows the non-limiting example of the multilayer thermoelectric structure which concerns on this invention. It is the schematic which shows the non-limiting example of the multilayer thermoelectric structure which concerns on this invention. It is an X-ray diffraction pattern of one of the Examples, References, and Comparative Examples of a multilayer thermoelectric material. It is an X-ray diffraction pattern of one of the Examples, References, and Comparative Examples of a multilayer thermoelectric material. It is an X-ray diffraction pattern of one of the Examples, References, and Comparative Examples of a multilayer thermoelectric material. It is an X-ray diffraction pattern of one of the Examples, References, and Comparative Examples of a multilayer thermoelectric material. It is an X-ray diffraction pattern of one of the Examples, References, and Comparative Examples of a multilayer thermoelectric material. It is an X-ray diffraction pattern of one of the Examples, References, and Comparative Examples of a multilayer thermoelectric material. 9 is a transmission electron microscope (TEM) image of the multilayer thermoelectric material of Example 1. It is an enlarged view of the Bi ₂ Te _{3 layer of FIG. 9A.} An example of a thermoelectric device using the multilayer thermoelectric structure according to the present invention is shown.

Detailed description of the invention <Definition>
The term "thermoelectric material" as used herein refers to a semiconductor capable of converting heat into electricity and electricity into heat. This definition includes not only well-known inorganic materials such as _{Bi 2} Te _{3 but also polymeric materials.}

The term "amorphous" as used herein refers to having neither a true crystalline form nor an apparent crystalline form.

The term "unit layer", as used herein, refers to a composite layer consisting of several atomic layers. The unit layer is separated from the unit layers adjacent to both sides by a van der Waals gap.

The c-plane is represented by (00 l) and is perpendicular to the c-axis [001] of the crystal. That is, the direction in which the (00l) planes overlap is parallel to the stacking direction of the multilayer thermoelectric structure. In other words, the (00 l) plane is parallel to the layer for separation use. The (00l) plane can be detected by a diffraction technique such as electron diffraction using XRD or TEM. According to XRD, the c-plane growth can be identified from the (00 l) reflection, for example (006). For crystals that are not c-plane oriented, other reflections such as (015) are given. Preferred c-plane growth can be defined by the following conditions. The condition is that the peak intensity ratio (006) / (015) is greater than 1 when the diffraction plane is perpendicular to the stacking direction of the multilayer thermoelectric structure.

The "stacking direction", as used herein, corresponds to the direction perpendicular to the plane of the multilayer thermoelectric structure.

In the case of the crystal layer according to the advantageous embodiment of the present invention, the c-plane is parallel to the unit layer and separated by a van der Waals gap. Electrons or holes are transported much faster when transported within the c-plane than when transported across the c-plane.

<Multi-layer thermoelectric structure>
The present invention is a multi-layer thermoelectric structure.
(A) A layer of crystalline thermoelectric material and
(B) Containing a plurality of alternating layers with a layer of a separating material, which is a material different from (A).
At least one of the two end layers is the layer (B).
The crystalline thermoelectric material (B) is Bi ₂ Te ₃ , GaTe, Bi ₂ S ₃ , Bi ₂ Se ₃ , MoS ₂ , TiS ₃ , TiSe ₃ , TiTe ₃ , MnPS ₃ , CdPS ₃ , CdPS ₃ , NiPS ₃ . _{ZnPS 3, Mn 0.5 Fe 0.5 PS} 3, GaS, GaSe, InS, InSe, InTe, TiS 2, MnS, MnTe, ZnS, ZnSe, GaSb, GeSb, GeTe, CdS, CdSe, CdTe, In 2 S _{3, In 2 Se 3, InSb} , Sb 2 Te 3, and _Ge 2 _Sb 2 Te ₅ is selected from the group consisting of, a multilayer-type thermoelectric structure.

(A) Thermoelectric Materials The thermoelectric materials used herein are Bi ₂ Te ₃ , Bi ₂ S ₃ , Bi ₂ Se ₃ , transition metal dicalcogenides (eg MoS ₂ ), transition metal tricalcogenides (eg TiS _3). , TiSe ₃ , TiTe ₃ ), metal lintrical cogenides (eg MnPS ₃ , CdPS ₃ , CdPS ₃ , NiPS ₃ , ZnPS ₃ , Mn _0.5 Fe _0.5 PS ₃ ), and III-VI layered semiconductors (eg GaS). , GaSe, GaTe, InS, InSe, and InTe). Alternatively, the thermoelectric materials in the present invention include TiS ₂ , MnS, MnTe, ZnSe, GaSb, GeSb, GeTe, CdS, CdSe, CdTe, In ₂ S ₃ , In ₂ Se ₃ , In Sb, and Sb ₂ Te _3. , Ge ₂ Sb ₂ Te ₅ can also be used. The thermoelectric material used in the present specification is not particularly limited, but is preferably selected in consideration of reactivity with the layer for separation.

Preferably, the thermoelectric material used in the present invention is Bi ₂ Te ₃ or Ge Te. Most preferably, the thermoelectric material used in the present invention is Bi ₂ Te ₃ .

For Bi ₂ Te ₃ , when depositing a layer of thermoelectric material by ALD (atomic layer deposition), for example, BiCl ₃ and (Et ₃ Si) ₂ Te or (Me ₃ Si) ₂ Te are used as precursors. can.

Precursors that can be used to deposit other thermoelectric materials are listed in Table 1.

The thickness of one layer is advantageously selected from the standpoint of performance.
The minimum thickness of the thermoelectric material layer is preferably half the thickness of one unit layer, and preferably the thickness of one unit layer.

The maximum thickness of the thermoelectric material layer is preferably 20 times the thickness of the unit layer, and preferably 3 times the thickness of one unit layer.

Preferably, the thickness of the thermoelectric material is at least half the thickness of one unit layer and at least 20 times the thickness of the unit layer.

Even more preferably, the thickness of the thermoelectric material is at least the thickness of one unit layer and at least three times the thickness of the unit layer.

When the thickness is within the above range, the mobility of carriers can be high and the lattice thermal conductivity can be low, so that a higher ZT value can be obtained.

Preferably, for a layer of thermoelectric material in the present invention, eg, a layer of Bi ₂ Te ₃ , the thickness of the thermoelectric material layer is at least 0.5 nm and at most 50 nm, preferably in order to obtain a higher ZT value. The minimum is 0.5 nm and the maximum is 30 nm, more preferably the minimum is 0.5 nm and the maximum is 20 nm, and most preferably the minimum is 1 nm and the maximum is 10 nm.

(B) Separation Material The separation layer used herein may be any material different from the thermoelectric material used in (A). Suitable materials include, for example, solid organics, solid polymers, and amorphous inorganics.

The solid organic substance may be, for example, pentacene.
The solid polymer may be, for example, polyimide, poly (p-phenylene terephthalamide), polyimide-amide, and PET.

The amorphous inorganic substance may be, for example, MgO, Al ₂ O ₃ , SiO ₂ , CaF ₂ , TiO ₂ , Y ₂ O ₃ , ZrO ₂ , and Sb ₂ O ₅ .

Preferably, the separation layer may be made of solid organics, solid polymers, and amorphous inorganics. This is because these materials more effectively reduce the interaction between the thermoelectric material layers, thus enhancing thermoelectric performance.

Even more preferably, the separation layer is _{formed of Al 2} O ₃ or polyimide.
When depositing a layer of Al ₂ O _{3 , for example, Me 3} Al and H ₂ O, or O ₂ or O ₃ can be used as precursors.

When depositing the polyimide layer, for example, DAH (diaminohexane) and PMDA (pyromellitic dianhydride) can be used as precursors.

Examples of precursors that can be used for other separation materials are shown in Table 2.

The thickness of the separation layer is a minimum of 1 nm and a maximum of 100 nm, preferably a minimum of 2 nm and a maximum of 50 nm, more preferably a minimum of 4 nm and a maximum of 20 nm, and most preferably a minimum of 4 nm and a maximum of 10 nm. ..

When the thickness of the separation layer is within the above range, each 2D nanosheet is separated by the separation layer, and as a result, a high ZT value can be obtained.

(C) Base material The multilayer thermoelectric structure according to the present invention optionally includes a base material.

The base material is not particularly limited and may be made of any material suitable for depositing a thermoelectric material. Suitable substrates are, for example, single crystal Si, quartz, natural oxide Si, single crystal Si, soda-lime glass, SiO ₂ / Si, ZnO, KCl, BaF ₂ , MgO, polyethylene terephthalate (PET), or photolithography. It may be a mask for use.

Preferably, the substrate is a SiO ₂ / Si substrate.
Structure The multilayer thermoelectric structure according to the present invention includes a plurality of alternating layers (A) and (B), and at least one of the two end layers is the layer (B).

Here, the term "alternate" means that any two adjacent layers are not of the same type. That is, in the multilayer structure according to the present invention, it means that the layer (A) is not adjacent to each other by two layers and the layer (B) is not adjacent to each other by two layers.

Here, the term "end layer" means the uppermost layer and the lowest layer in the stacking direction of the multilayer structure. One surface of each end layer is not in contact with the surface of the adjacent layer. The edge layers are indicated by arrows in FIG.

In the present invention, any one of the above-mentioned thermoelectric materials (A) can be combined with any one of the above-mentioned separation materials (B), and the above-mentioned preferable thickness of the thermoelectric material (A) can be combined. Can be applied to any one of the above-mentioned thermoelectric materials, and the above-mentioned preferred thickness range for the separation material (A) can be applied to any one of the above-mentioned separation materials. Can be applied. In the present invention, any one of the above-mentioned thermoelectric materials (A) having a length included in any one of the above-mentioned preferable thickness ranges for the thermoelectric material (A) can be separated from the material (A). Regarding B), it can be used in combination with any of the above-mentioned separation materials (B) having a length included in any of the above-mentioned preferable thickness ranges.

3 (a) to 3 (c) are schematic views showing some examples of the multilayer thermoelectric structure according to the present invention.

In FIG. 3A, an undercoat layer (2') made of an amorphous material for separation is deposited on the base material (1), and the same amorphous material is used on the undercoat layer (2'). Two sets of layers consisting of the formed separation layer (2) and the thermoelectric material layer (3) are deposited.

In FIG. 3 (b), two sets of layers consisting of an amorphous layer (2) for separation and a layer (3) of a thermoelectric material are directly deposited on the base material (1). ..

In FIG. 3C, an undercoat layer (2') made of an amorphous material is deposited on the base material (1), and the same amorphous material is formed on the undercoat layer (2'). Five pairs of layers consisting of the separated layer for separation (2) and the layer of thermoelectric material (3) are deposited.

The thickness of the separation layer is preferably as thin as long as the c-plane growth can be maintained. That is, the thickness ratio of the thermoelectric layer to the separation layer (ie, (thickness of layer of thermoelectric material) :( thickness of layer for separation)) is preferably 70%: 30% or greater. More preferably 80%: 20% or greater, most preferably 90%: 10% or greater.

The multilayer structure according to the present invention can realize a thickness of more than 100 μm, which is desired in industrial applications such as thermoelectric modules, superconducting cables, secondary batteries, and nonlinear optical elements, without losing the thermoelectricity of 2D nanosheets. ..

Here, the lamination of the alternating layers may be carried out by the deposition process described below. Stacking of alternating layers may be carried out so that the two adjacent layers are joined, rather than the other simply resting on one of the two adjacent layers and the two layers do not interact.

When the multilayer thermoelectric structure according to the present invention is used, it is preferable that the layer for separation is exposed to the outside.

The optionally included layer of substrate may be removed prior to use.
Number of layers The number of layers is not particularly limited. The thickness of one layer for separation and the thickness of one layer of thermoelectric material may be appropriately selected from the viewpoint of performance.

<Preparation method of thermoelectric material>
The present invention is also a method for preparing a thermoelectric material.
1) The process of providing the base material and
2) The process of depositing a layer of thermoelectric material on the base material,
3) Including a step of depositing a layer for separation on the thermoelectric layer deposited in step 2).
Steps 2) and 3) are performed at least once and
4) It also relates to a preparation method that optionally includes a step of removing the base material.

1) Preparation of base material The first step of the method for preparing a multilayer thermoelectric material is to prepare a base material. The substrate is not particularly limited, and for example, single crystal Si, quartz, natural oxide Si, single crystal Si, soda-lime glass, SiO ₂ / Si, ZnO, KCl, BaF ₂ , MgO, polyethylene terephthalate (PET), or A mask for photolithography can be used.

When a substrate with a very flat substrate is used, a layer of thermoelectric material with a smoother surface and higher mobility can be obtained.

2) Depositing a layer of thermoelectric material on a substrate The second step of the above method is to deposit a thermoelectric layer. Any method can be used when depositing the first thermoelectric layer, for example, atomic layer deposition (ALD), metalorganic vapor phase growth (MOCVD), or sputtering.

First of all, in the case of ALD, control of layer thickness can be carried out by adjusting the number of deposition cycles. In the case of ALD, thickness control can also be performed, for example, by adjusting the precursor charge time, purge time, and substrate temperature.

When depositing a layer of Bi ₂ Te _{3 , for example, BiCl 3} and (Et ₃ Si) ₂ Te or (Me ₃ Si) ₂ Te can be used as precursors.

Precursors that can be used to deposit other thermoelectric materials are listed in Table 1 above.
3) Accumulation of separation layer on the thermoelectric layer deposited in step 2) The third step of the above method is to deposit the separation layer. Any method can be used when depositing the thermoelectric layer, for example atomic layer deposition, MOCVD, or sputtering.

First of all, in the case of ALD, control of layer thickness can be carried out by adjusting the number of deposition cycles. In the case of ALD, thickness control can also be performed, for example, by adjusting the precursor charge time, purge time, and substrate temperature.

When depositing a layer of Al ₂ O _{3 , for example, Me 3} Al and H ₂ O, or O ₂ or O ₃ can be used as precursors.

When depositing the polyimide layer, for example, DAH (diaminohexane) and PMDA (pyromellitic dianhydride) can be used as precursors.

Precursors that can be used to deposit other thermoelectric materials are listed in Table 2 above.
Steps 2) and 3) are repeated several times to obtain a thicker multilayer structure. Preferably, steps 2) and 3) are repeated 3 or more times, more preferably 5 times or more.

Here, the number of cycles corresponds to the number of repeating units of the layer.
4) Removal of base material Optionally, the base material is removed before use.

<Use of thermoelectric materials>
The multilayer thermoelectric structure according to the present invention can be used in, for example, a thermoelectric module, a superconducting cable, a secondary battery, and a nonlinear optical element. Further, the multilayer thermoelectric structure according to the present invention can be used, for example, as a heat recovery system for a thermoelectric generator (TEG) that converts thermal energy into electrical energy, or for a seat heater, a humidity controller, or a small refrigerator. It can also be used as a Perche cooling / heating module.

FIG. 11 shows an example of a thermoelectric device using the multilayer thermoelectric structure according to the present invention.
When the multilayer thermoelectric structure according to the present invention is used in, for example, a thermoelectric module, a superconducting cable, a secondary battery, or a nonlinear optical element, the thickness of the thermoelectric layer is increased to more than 100 μm without losing the thermoelectric characteristics of the 2D nanosheet. can do.

Appropriately, the semiconductor material may be contained in more than 50% by volume in the material used in the thermoelectric module. In automotive applications, the operating temperature is limited to the range of −40 ° C. to 1000 ° C.

In the following examples, nitrogen was used as the carrier and purge gas in the flow-through ALD reactor, and a thin film was deposited at an operating pressure of less than 10 mbar. As a base material, 5 × 5 cm ² natural SiO ₂ / Si or soda-lime glass was used.

<Sedimentation conditions>
The deposition conditions were as follows.

Polyamide amorphous layer DAH (1,6-diaminohexane) and PMDA (1,2,3,5-benzenetetracarboxylic acid anhydride) were evaporated at 35 ° C and 150 ° C, respectively, and DAH / purge / PMDA / purge was performed. The polyamide amorphous layer was deposited under the deposition conditions of 2/3 / 2.5 / 3 seconds.

_{Precursors, namely BiCl 3} and (Et ₃ Si) ₂ Te, are evaporated from the open glass vessel placed in the Bi ₂ Te _3- layer reactor at 140 ° C and 43 ° C, respectively, and the inert gas is pulsed by valving. By releasing, a Bi ₂ Te ₃ layer was deposited. For the duration of pulse emission, BiCl ₃ / purge / (Et ₃ Si) ₂ Te / purge was performed at 0.5 / 2/2/2 seconds. The substrate temperature was 165 ° C.

For Al ₂ O ₃ amorphous layer Al ₂ O ₃ , Me ₃ Al / purge / H ₂ O / purge was performed in 0.5 / 1/1/2 seconds. The precursor was evaporated at room temperature.

Example 1
A multilayer structure including one layer of a polyimide undercoat layer and five layers of _{Bi 2} Te ₃ layers in which each layer is separated by an amorphous polyimide layer _{is deposited on a natural SiO 2} / Si substrate. , Prepared by the following method.

The natural SiO ₂ / Si is single crystal Si, and its surface is converted to SiO ₂ by natural oxidation.

1) A 6 nm amorphous polyimide undercoat layer was deposited on a _{natural SiO 2 / Si substrate.}

_{2) A 14 nm Bi 2} Te ₃ layer was deposited on the amorphous polyimide undercoat layer deposited in step 1).

3) A 6 nm amorphous polyimide layer was deposited on the _{Bi 2} Te ₃ layer deposited in step 2).

4) Step 2) and step 3) were repeated 5 times to form a multi-layer structure.
Reference example 1
A multi-layer structure containing a Bi ₂ Te ₃ layer and an amorphous polyimide layer _{deposited on a natural SiO 2} / Si substrate was prepared by the following method.

1) A 6.5 nm Bi ₂ Te ₃ layer was deposited on a _{natural SiO 2 / Si substrate.}
2) A 100 nm amorphous polyimide layer was deposited on the _{Bi 2} Te ₃ layer deposited in step 1).

Comparative Example 1
A multilayer structure containing a polyamide undercoat layer and Bi ₂ Te ₃ deposited on a natural SiO ₂ / Si substrate was prepared by the following method.

1) A 6 nm amorphous polyimide undercoat layer was deposited on a _{natural SiO 2 / Si substrate.}

_{2) A 65 nm Bi 2} Te ₃ layer was deposited on the amorphous polyimide undercoat deposited in step 1).

Example 2
A multilayer structure including a polyamide undercoat layer and a _{Bi 2} Te ₃ layer 2 layer in which _{each layer is separated by an amorphous Al 2} O ₃ layer, which is _{deposited on a natural SiO 2 / Si substrate.} Was prepared by the following method.

1) A 6 nm amorphous Al ₂ O ₃ undercoat layer was deposited on a _{natural SiO 2 / Si substrate.}

2) A 14 nm Bi ₂ Te ₃ layer was deposited on _{the amorphous Al 2} O ₃ undercoat layer deposited in step 1).

3) A 6 nm amorphous Al ₂ O ₃ layer was deposited on _{the Bi 2} Te ₃ layer deposited in step 2).

4) Step 2) and step 3) were repeated twice to form a multi-layer structure.
Example 3
A multi-layer structure containing a Bi ₂ Te ₃ layer and an amorphous Al ₂ O ₃ layer deposited on a natural SiO ₂ / Si substrate was prepared by the following method.

1) A 14 nm Bi ₂ Te ₃ layer was deposited on a _{natural SiO 2 / Si substrate.}
2) A 6 nm amorphous Al ₂ O ₃ layer was deposited on _{the Bi 2} Te ₃ layer deposited in the step 1).

3) Step 2) and step 3) were repeated twice to form a multi-layer structure.
Comparative Example 2
A multilayer structure containing an Al ₂ O ₃ undercoat layer and a Bi ₂ Te ₃ layer deposited on a natural SiO ₂ / Si substrate was prepared by the following method.

1) A 6 nm amorphous Al ₂ O ₃ undercoat layer was deposited on a _{natural SiO 2 / Si substrate.}

_{A 130 nm Bi 2} Te ₃ layer was deposited on the amorphous polyamide undercoat deposited in step 1).

Table 3 shows an outline of the structures of Examples 1 to 4 and Comparative Examples 1 and 2.

<Confirmation of c-plane growth>
It was confirmed by X-ray diffraction (XRD) that the samples prepared according to Examples 1 to 3, Reference Examples 1 and Comparative Examples 1 and 2 had a preferable c-plane orientation. The diffraction surface is perpendicular to the stacking direction of the multilayer thermoelectric structure. That is, the direction in which the (00l) planes overlap is perpendicular to the stacking direction of the multilayer thermoelectric structure. In other words, the (00 l) plane is parallel to the layer for separation use. The preferred c-plane orientation is confirmed by the intensities of the (001) peaks [(003), (006), (0015), and (0018)] with respect to the (015) peak and the like. The higher the ratio of (00 l) to (015), the stronger the c-plane orientation.

In XRD, when the condition that the peak intensity ratio (006) / (015) is larger than 1 when the diffraction plane is perpendicular to the stacking direction of the multilayer thermoelectric structure is satisfied, the c-plane growth is performed. You can check.

If it is difficult to perform XRD on the sample, for example because the sample is small, electron diffraction can also be performed.

<Use>
FIG. 11 shows an example of a thermoelectric device using the multilayer thermoelectric structure according to the present invention.

Claims (16)

It is a multi-layer thermoelectric structure
(A) A layer of crystalline thermoelectric material and
(B) A plurality of alternating layers with a layer of a separating material, which is a material different from the above (A), are included.
At least one of the two end layers is the layer (B).
The crystalline thermoelectric material (A) is Bi ₂ Te ₃ , GaTe, Bi ₂ S ₃ , Bi ₂ Se ₃ , MoS ₂ , TiS ₃ , TiSe ₃ , TiTe ₃ , MnPS ₃ , CdPS ₃ , CdPS ₃ , NiPS _3. , ZnPS ₃ , Mn _0.5 Fe _0.5 PS ₃ , GaS, GaSe, InS, InSe, InTe, TiS ₂ , MnS, MnTe, ZnS, ZnSe, GaSb, GeSb, GeTe, CdS, CdSe, CdTe, In _{2 S 3, In 2 Se 3,} InSb, is selected from the group consisting of _Sb 2 Te _3, and _Ge 2 _Sb 2 Te _5,
The thickness of the layer of the crystalline thermoelectric material (A) is 0.5 nm at the minimum and 50 nm at the maximum.
The (00 l) plane of the crystalline thermoelectric material (A) is parallel to the layer (B) for separation use.
The layer (B) is selected from the group consisting of polyimide, poly (p-phenylene terephthalamide), polyimide-amide, and PET.
The layer (B) has a minimum thickness of 1 nm and a maximum thickness of 100 nm, which is a multilayer thermoelectric structure. It is a multi-layer thermoelectric structure
(A) Crystalline thermoelectric material
Layer and
(B) Separation material, which is a material different from (A) above.
Includes multiple alternating layers with
At least one of the two end layers is the layer (B).
The crystalline thermoelectric material (A) is Bi. ₂ Te ₃ , GaTe, Bi ₂ S ₃ , Bi ₂ Se ₃ , MoS ₂ , TiS ₃ , TiSe ₃ , TiTe ₃ , MnPS ₃ , CdPS ₃ , CdPS ₃ , NiPS ₃ , ZnPS ₃ , Mn _0.5 Fe _0.5 PS ₃ , Gas, Gase, InS, InSe, InTe, TiS ₂ , MnS, MnTe, ZnS, ZnSe, GaSb, GeSb, GeTe, CdS, CdSe, CdTe, In ₂ S ₃ , In ₂ Se ₃ , InSb, Sb ₂ Te ₃ , And Ge ₂ Sb ₂ Te ₅ Selected from the group consisting of
The thickness of the layer of the crystalline thermoelectric material (A) is 0.5 nm at the minimum and 50 nm at the maximum.
The (00 l) plane of the crystalline thermoelectric material (A) is parallel to the layer (B) for separation use.
The layer (B) is a solid organic substance and is a solid organic substance.
The layer (B) has a minimum thickness of 1 nm and a maximum thickness of 100 nm, which is a multilayer thermoelectric structure. The multilayer thermoelectric structure according to claim 2, wherein the layer (B) is pentacene. It is a multi-layer thermoelectric structure
(A) Crystalline thermoelectric material
Layer and
(B) Separation material, which is a material different from (A) above.
Includes multiple alternating layers with
At least one of the two end layers is the layer (B).
The crystalline thermoelectric material (A) is Bi. ₂ Te ₃ , GaTe, Bi ₂ S ₃ , Bi ₂ Se ₃ , MoS ₂ , TiS ₃ , TiSe ₃ , TiTe ₃ , MnPS ₃ , CdPS ₃ , CdPS ₃ , NiPS ₃ , ZnPS ₃ , Mn _0.5 Fe _0.5 PS ₃ , Gas, Gase, InS, InSe, InTe, TiS ₂ , MnS, MnTe, ZnS, ZnSe, GaSb, GeSb, GeTe, CdS, CdSe, CdTe, In ₂ S ₃ , In ₂ Se ₃ , InSb, Sb ₂ Te ₃ , And Ge ₂ Sb ₂ Te ₅ Selected from the group consisting of
The thickness of the layer of the crystalline thermoelectric material (A) is 0.5 nm at the minimum and 50 nm at the maximum.
The (00 l) plane of the crystalline thermoelectric material (A) is parallel to the layer (B) for separation use.
The layer (B) is an amorphous inorganic substance, and is composed of MgO and CaF. ₂ , TIO ₂ , Y ₂ O ₃ , ZrO ₂ , And Sb ₂ O ₅ Selected from the group consisting of
The layer (B) has a minimum thickness of 1 nm and a maximum thickness of 100 nm, which is a multilayer thermoelectric structure. The same crystalline thermoelectric material (A) is used for all of the layers (A).
The same separating material (B) is used for all of the layers (B).
The multilayer thermoelectric structure according to any one of claims 1 to 4. In the X-ray diffraction pattern, the condition that the peak intensity ratio (006) / (015) is larger than 1 is satisfied when the diffraction surface is preferentially perpendicular to the stacking direction of the multilayer thermoelectric structure. The multilayer thermoelectric structure according to any one of claims 1 to 4. The multilayer thermoelectric structure according to any one of claims 1 to 6 , wherein the crystalline thermoelectric material (A) is Bi ₂ Te _{3 or Ge Te.} The method according to any one of claims 1 to 7 , wherein the thickness of the layer (A) is at least half the thickness of one unit layer and at least 20 times the thickness of the unit layer. Multi-layer thermoelectric structure. The multilayer thermoelectric structure according to any one of claims 1 to 8 , wherein the layer thickness of the crystalline thermoelectric material (A) is 0.5 nm at the minimum and 30 nm at the maximum. It also contains a base material (C) with a set of main surfaces , including
The alternating layers are deposited only on the main surface of one of the substrates.
The uppermost layer in the stacking direction of the multilayer thermoelectric structure is the layer (B).
The multilayer thermoelectric structure according to any one of claims 1 to 9, wherein the uppermost layer is exposed to the outside. The base material (C) is single crystal Si, quartz, natural oxide Si, single crystal Si, soda-lime glass, SiO ₂ / Si, ZnO, KCl, BaF ₂ , MgO, polyethylene terephthalate (PET), or photolithography. The multilayer thermoelectric structure according to claim 10 , which is selected from the masks for use. The multilayer thermoelectric structure according to claim 10 , wherein the multilayer thermoelectric structure further includes an undercoat between the layers of the base material (C) and the crystalline thermoelectric material (A). The method for preparing a multilayer thermoelectric material according to any one of claims 1 to 12.
1) The process of providing the base material and
2) A step of depositing a layer of the first thermoelectric material on the base material,
3) A step of depositing a second separation layer on the thermoelectric layer deposited in the step 2) is included.
The preparation method, wherein the steps 2) and 3) are carried out at least once. 13. The method of claim 13 , wherein the steps 2) and 3) are repeated three or more times. The method according to claim 13 or 14 , further comprising a step of depositing an undercoat between the steps 1) and 2). Use of the thermoelectric structure according to any one of claims 1 to 12 in any one of a thermoelectric module, a superconducting cable, a secondary battery, or a nonlinear optical element.

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