阅读说明：本技术 一种层状硅锗热电材料 (Layered silicon-germanium thermoelectric material ) 是由 刘英光 韩中合 于 2019-10-23 设计创作，主要内容包括：本发明公开了一种层状硅锗热电材料,包括：锗基板和设置在锗基板上的超薄GeO<Sub>2</Sub>薄膜层；在超薄GeO<Sub>2</Sub>薄膜层上形成微型阵列孔,微型阵列孔的孔径为0.8nm～1.2nm,间距为3nm～5nm；7～66层硅原子在设置有微型阵列孔的超薄GeO<Sub>2</Sub>薄膜层沉积、长大,形成球形纳米晶体,相邻的球形纳米晶体在交界处达到接触状态,形成纳米硅球层；纳米硅球层上沉积有13～123层的外延锗层,外延锗层上设置超薄GeO<Sub>2</Sub>薄膜层,超薄GeO<Sub>2</Sub>薄膜层上设置纳米硅球层,逐次累计,形成层状硅锗热电材料,热电转化效率高,结构稳定性好。(The invention discloses a layered silicon germanium thermoelectric material, comprising: germanium substrate and ultra-thin GeO disposed thereon 2 A thin film layer; in ultra-thin GeO 2 Forming a micro array hole on the thin film layer, wherein the aperture of the micro array hole is 0.8-1.2 nm, and the distance is 3-5 nm; ultrathin GeO with 7-66 layers of silicon atoms provided with micro array holes 2 The thin film layer is deposited and grown to form spherical nanocrystals, and the adjacent spherical nanocrystals reach a contact state at the junction to form a nano silicon sphere layer; depositing 13-123 epitaxial germanium layers on the nano silicon ball layer, and arranging ultrathin GeO on the epitaxial germanium layers 2 Thin film layer, ultra-thin GeO 2 The nano silicon ball layer is arranged on the thin film layer and is gradually accumulated to form the layered silicon germanium thermoelectric material, the thermoelectric conversion efficiency is high, and the structural stability is good.)

1. A layered silicon germanium thermoelectric material, comprising: germanium substrate (1) and ultra-thin GeO disposed on germanium substrate (1)₂A thin film layer (2);

in the ultra-thin GeO₂Forming a micro array hole on the thin film layer (2), wherein the aperture of the micro array hole is 0.8-1.2 nm, and the distance is 3-5 nm;

7-66 layers of silicon atoms are in the ultrathin GeO provided with the micro array holes₂The thin film layer (2) is deposited and grows to form spherical nano crystals (3), and adjacent spherical nano crystals (3) reach a contact state at the junction to form a nano silicon spherical layer (30).

2. The layered silicon germanium thermoelectric material according to claim 1, wherein 13 to 123 epitaxial germanium layers (4) are deposited on the nanosilicon sphere layer (30).

3. The layered silicon germanium thermoelectric material according to claim 2, wherein adjacent spherical nanocrystals (3) are provided with micro-cavities at the interface; part of germanium atoms of the epitaxial germanium layer (4) penetrate through the micro-pores to fill the gaps between the adjacent spherical nanocrystals (3).

4. The layered silicon germanium thermoelectric material as claimed in claim 3, wherein germanium atoms penetrating through the micro-pores wrap around and fill the surface of the spherical nanocrystals (3) to ensure relative independence of the spherical nanocrystals (3).

5. The layered silicon germanium thermoelectric material as claimed in claim 3, wherein the spherical nanocrystals (3) have a grain size of 3nm to 5nm, which ensures mutual activation, maximum heat absorption, and transformation into ordered electron flow, and high thermoelectric efficiency.

6. The layered sige thermoelectric material as claimed in claim 2, wherein the upper surface of the epitaxial ge layer (4) is formed with a second ultra-thin GeO₂A thin film layer;

second ultra-thin GeO₂The thin film layer is provided with a second layer of nano silicon ball layer.

7. The layered silicon germanium thermoelectric material of claim 1, wherein said ultra-thin GeO is₂The thin film layer (2) has 1-5 GeO layers₂A molecular layer.

8. The layered silicon germanium thermoelectric material of claim 1, wherein said ultra-thin GeO is₂The thin film layer (2) has 2-3 GeO layers₂A molecular layer.

Technical Field

The invention relates to the technical field of thermoelectric conversion, in particular to a layered silicon-germanium thermoelectric material.

Background

Energy is the fundamental power and important material basis for the development of the human economic society.

The energy of China presents the structural current situation of more coal, less oil and less gas, and the improvement of the energy structure and the improvement of the energy utilization rate are not slow at all. And the utilization efficiency of the energy is lower at present, and the improved space is larger.

The thermoelectric material is a novel energy material which can realize direct interconversion of heat energy and electric energy by utilizing the Seebeck effect and the Peltier effect of the materials, and has wide application prospect in the aspects of industrial waste heat, automobile exhaust waste heat recycling, thermoelectric refrigeration and the like. The device has the advantages of simple structure, no mechanical transmission part, small volume, long service life, high reliability, no noise in work, environmental friendliness and the like.

The performance of a thermoelectric material is mainly determined by the thermoelectric figure of merit ZT, which can be expressed as ZT ═ σ S²A T/κ, wherein: s is Seebeck coefficient, sigma is electric conductivity, kappa is heat conductivity, and T is absolute temperature.

The current situation that the thermal conductivity of the current thermoelectric material is higher is still outstanding, and the thermoelectric material provided by the invention can greatly reduce the thermal conductivity of the material and improve the thermoelectric performance of the material.

Disclosure of Invention

In view of the foregoing, the present invention provides a layered silicon germanium thermoelectric material.

A layered silicon germanium thermoelectric material comprising: germanium substrate and ultra-thin GeO disposed thereon₂A thin film layer;

in ultra-thin GeO₂Forming a micro array hole on the thin film layer, wherein the aperture of the micro array hole is 0.8-1.2 nm, and the distance is 3-5 nm;

ultrathin GeO with 7-66 layers of silicon atoms provided with micro array holes₂The thin film layer is deposited and grown to form spherical nanocrystals, and the adjacent spherical nanocrystals reach a contact state at the junction to form a nano silicon sphere layer.

Preferably, 13-123 epitaxial germanium layers are deposited on the nano silicon sphere layer.

Preferably, the adjacent spherical nanocrystals are provided with micro-pores at the interface; part of germanium atoms of the epitaxial germanium layer penetrate through the micro-pores to fill the gaps between the adjacent spherical nanocrystals.

Preferably, germanium atoms penetrating through the micro-pores are wrapped and filled on the surface of the spherical nanocrystals, so as to ensure the relative independence of the spherical nanocrystals.

Preferably, the grain size of the spherical nano-crystal is 3 nm-5 nm, so that the spherical nano-crystal can be ensured to be in an active state, can absorb heat to the maximum extent and is converted into ordered electron flow, and the thermoelectric efficiency is high.

It is preferable thatThe upper surface of the epitaxial Ge layer is formed with a second ultra-thin GeO layer₂A thin film layer;

second ultra-thin GeO₂The thin film layer is provided with a second layer of nano silicon ball layer.

Preferably, ultra-thin GeO₂The thin film layer has 1-5 GeO layers₂A molecular layer.

Preferably, ultra-thin GeO₂The thin film layer has 2-3 GeO layers₂A molecular layer.

The invention also provides a preparation method of the layered silicon-germanium thermoelectric material.

A method of making a layered silicon germanium thermoelectric material, comprising:

A. at a temperature of 330-430 ℃ and an oxygen partial pressure of (1.8-2.2) × 10^-4Under the environment of Pa, carrying out surface oxidation on a clean germanium substrate for 10-20 min to form ultrathin GeO₂A thin film layer;

B. heating to 550-650 deg.C, the silicon impacts the ultra-thin GeO in the form of ion beam₂On the upper surface of the thin film layer, the following chemical reactions occur:

Si+GeO₂→SiO↑+GeO↑；

in ultra-thin GeO₂Forming a micro array hole on the thin film layer, wherein the aperture of the micro array hole is 0.8-1.2 nm, and the distance is 3-5 nm;

C. depositing 7-11 layers of silicon atoms on the ultrathin GeO provided with the micro array holes at the deposition rate of (1-1.4) ML/min by using a silicon electrodeposition method in the temperature environment of 550-650 DEG C₂A thin film layer of electrodeposited silicon sufficient to fill the micro-array holes;

D. under the temperature environment of 550-650 ℃, silicon is continuously deposited with 26-66 layers of silicon atoms in the ultrathin GeO provided with the micro array holes at the deposition rate of (1-1.4) ML/min by an electrodeposition method₂And the film layer, the silicon atoms which are continuously deposited are trapped in the micro array holes, so that the spherical nano crystals are formed and continuously deposited, the spherical nano crystals grow, and the adjacent spherical nano crystals reach a contact state at the junction to form a nano silicon sphere layer.

Preferably, D is followed by:

E. and reducing the temperature to 450-500 ℃ and continuously depositing 13-123 epitaxial germanium layers on the nano silicon sphere layer at the deposition rate of (1.5-1.8) ML/min.

Preferably, the adjacent spherical nanocrystals are provided with micro-pores at the interface; part of germanium atoms of the epitaxial germanium layer penetrate through the micro-pores to fill the gaps between the adjacent spherical nanocrystals.

Preferably, germanium atoms penetrating through the micro-pores are wrapped and filled on the surface of the spherical nanocrystals, so as to ensure the relative independence of the spherical nanocrystals.

Preferably, the grain size of the spherical nano-crystal is 3 nm-5 nm, so that the spherical nano-crystal can be ensured to be in an active state, can absorb heat to the maximum extent and is converted into ordered electron flow, and the thermoelectric efficiency is high.

Preferably, E is followed by:

F. at a temperature of 330-430 ℃ and an oxygen partial pressure of (1.8-2.2) × 10^-4Under the Pa environment, carrying out surface oxidation on the epitaxial germanium layer for 10-20 min to form ultrathin GeO₂A thin film layer;

G. b, C and D are repeated to obtain a second layer of nano-silicon spheres.

Preferably, a is preceded by:

A1. conventionally cleaning a non-doped germanium substrate by adopting a dilute solution of a sulfuric acid-hydrogen peroxide mixed solution and a hydrofluoric acid solution;

A2. the germanium substrate after being cleaned conventionally is subjected to basic pressure of (2.8-3.2) × 10^-8Introducing the substrate into a molecular beam epitaxy chamber in a Pa environment, heating to 350-410 ℃, degassing for 3-5 hours, and growing a (80-120) nm germanium buffer layer on the germanium substrate to form a clean germanium surface.

Preferably, after a2, a is preceded by:

A3. and (3) observing the germanium surface by using a high-energy electron diffraction device (RHEED) to determine the cleanliness of the germanium surface.

Preferably, ultra-thin GeO₂The thin film layer has 1-5 GeO layers₂A molecular layer.

Preferably, the first and second liquid crystal materials are,ultra-thin GeO₂The thin film layer has 2-3 GeO layers₂A molecular layer.

The invention has the beneficial effects that: a layered silicon germanium thermoelectric material comprising: germanium substrate and ultra-thin GeO disposed thereon₂A thin film layer; in ultra-thin GeO₂Forming a micro array hole on the thin film layer, wherein the aperture of the micro array hole is 0.8-1.2 nm, and the distance is 3-5 nm; ultrathin GeO with 7-66 layers of silicon atoms provided with micro array holes₂The thin film layer is deposited and grown to form spherical nanocrystals, and the adjacent spherical nanocrystals reach a contact state at the junction to form a nano silicon sphere layer; depositing 13-123 epitaxial germanium layers on the nano silicon ball layer, and arranging ultrathin GeO on the epitaxial germanium layers₂Thin film layer, ultra-thin GeO₂The nano silicon ball layer is arranged on the thin film layer and is gradually accumulated to form the layered silicon germanium thermoelectric material, the thermoelectric conversion efficiency is high, and the structural stability is good.

The invention aims to: a layered silicon germanium thermoelectric material comprising: A. at a temperature of 330-430 ℃ and an oxygen partial pressure of (1.8-2.2) × 10^-4Under the environment of Pa, carrying out surface oxidation on a clean germanium substrate for 10-20 min to form ultrathin GeO₂A thin film layer; B. heating to 550-650 deg.C, the silicon impacts the ultra-thin GeO in the form of ion beam₂The upper surface of the thin film layer generates chemical reaction: si + GeO₂→ SiO ≈ ≈ SiO ≈ GeO ≠; in ultra-thin GeO₂Forming a micro array hole on the thin film layer, wherein the aperture of the micro array hole is 0.8-1.2 nm, and the distance is 3-5 nm; C. depositing 7-11 layers of silicon atoms on the ultrathin GeO provided with the micro array holes at the deposition rate of (1-1.4) ML/min by using a silicon electrodeposition method in the temperature environment of 550-650 DEG C₂A thin film layer of electrodeposited silicon sufficient to fill the micro-array holes; D. under the temperature environment of 550-650 ℃, silicon is continuously deposited with 26-66 layers of silicon atoms in the ultrathin GeO provided with the micro array holes at the deposition rate of (1-1.4) ML/min by an electrodeposition method₂The film layer, the silicon atoms which are continuously deposited are trapped in the micro array holes, so that the spherical nano crystals are formed and continuously deposited, the spherical nano crystals grow, and the adjacent spherical nano crystals reach a contact state at the junction, so that the shape of the spherical nano crystals is changedForming a nano silicon ball layer. E. And reducing the temperature to 450-500 ℃ and continuously depositing 13-123 epitaxial germanium layers on the nano silicon sphere layer at the deposition rate of (1.5-1.8) ML/min. F. At a temperature of 330-430 ℃ and an oxygen partial pressure of (1.8-2.2) × 10^-4Under the Pa environment, carrying out surface oxidation on the epitaxial germanium layer for 10-20 min to form ultrathin GeO₂A thin film layer; G. b, C and D are repeated to obtain a second layer of nano-silicon spheres. And (3) repeating B, C, D, E and F to obtain a third nano silicon ball layer, … … and an Nth nano silicon ball layer, wherein N is a natural number and is more than or equal to 3. The process is simple, the aperture of the micro array hole is 0.8-1.2 nm, the distance is 3-5 nm, the grain size of the spherical nanocrystal is 3-5 nm, the spherical nanocrystal and the micro array hole can be combined and atom exchanged through a crystal boundary junction, the mutual independence can be guaranteed, and the structural stability is good.

The invention provides a preparation method of a thermoelectric material with simple process to promote the scientific development of the thermoelectric material, the thermoelectric material which takes germanium as a substrate and contains epitaxial silicon nano-dots and a preparation scheme thereof, and the thermoelectric material which takes germanium as the substrate to grow the composite nano-structure of the epitaxial silicon nano-dots can respectively and effectively control the thermal conductivity and the electric conductivity of the material and improve the thermoelectric figure of merit of the material.

The beneficial effects are that: the thermal conductivity in the material is controlled by phonons, and the electrical conductivity is controlled by electrons, so that compared with the thermoelectric material with the prior structure, the thermoelectric material can respectively control the thermal conductivity and the electrical conductivity; phonons are scattered when passing through spherical nanocrystals (nano-dots) grown by epitaxy, so that the phonon transport resistance is increased, and the thermal conductivity of the material is reduced; the structure has small influence on the resistance of electron transportation, so that the thermoelectric figure of merit can be improved by reducing the thermal conductivity of the material and improving the electrical conductivity according to the formula of the thermoelectric figure of merit, and the thermoelectric performance of the material is further improved. Silicon and germanium are good semiconductor materials, but the simple substances of the silicon and the germanium have higher thermal conductivity, and the thermal conductivity of the germanium can be obviously reduced after the silicon is doped in the germanium.

Drawings

The invention relates to a layered silicon germanium thermoelectric material, which is combined with the attached drawings.

Fig. 1 is a flow chart illustrating a method for fabricating a layered sige thermoelectric material in accordance with the present invention.

Fig. 2 is a schematic structural diagram of a layered sige thermoelectric material of the present invention.

Fig. 3 is a partial enlarged view of a portion a of fig. 2 illustrating a structure of a layered sige thermoelectric material according to the present invention.

In the figure:

1-a germanium substrate; 2-ultrathin GeO₂A thin film layer; 3-spherical nanocrystals; 30-a layer of nano-silicon spheres; 4-epitaxial germanium layer.

Detailed Description

The present invention will be further described with reference to fig. 1 to 3.

A layered silicon germanium thermoelectric material comprising: germanium substrate 1 and ultra-thin GeO disposed on germanium substrate 1₂A thin film layer 2;

in ultra-thin GeO₂Forming a micro array hole on the thin film layer 2, wherein the aperture of the micro array hole is 0.8-1.2 nm, and the distance is 3-5 nm;

ultrathin GeO with 7-66 layers of silicon atoms provided with micro array holes₂The thin film layer 2 is deposited and grown to form spherical nanocrystals 3, and the adjacent spherical nanocrystals 3 reach a contact state at the junction to form a nano silicon sphere layer 30.

In this embodiment, 13-123 epitaxial germanium layers 4 are deposited on the nano-silicon ball layer 30.

In this embodiment, the adjacent spherical nanocrystals 3 are provided with micro-pores at the interface; part of the germanium atoms of the epitaxial germanium layer 4 penetrate through the micro-pores to fill the gaps between the adjacent spherical nanocrystals 3.

In this embodiment, germanium atoms penetrating through the micro-pores are wrapped and filled on the surface of the spherical nanocrystals 3, thereby ensuring the relative independence of the spherical nanocrystals 3.

In the embodiment, the grain size of the spherical nanocrystals 3 is 3 nm-5 nm, so that the spherical nanocrystals can be ensured to be in an active state, can absorb heat to the maximum extent and can be converted into ordered electron flow, and the thermoelectric efficiency is high.

In this embodiment, a second ultra-thin GeO layer is formed on the upper surface of the epitaxial Ge layer 4₂A thin film layer;

second ultra-thin GeO₂The thin film layer is provided with a second layer of nano silicon ball layer.

In this example, ultra-thin GeO₂The thin film layer 2 has 1-5 GeO layers₂A molecular layer.

In this example, ultra-thin GeO₂The thin film layer 2 has 2-3 GeO layers₂A molecular layer.

A method of making a layered silicon germanium thermoelectric material, comprising:

A. at a temperature of 330-430 ℃ and an oxygen partial pressure of (1.8-2.2) × 10^-4Under the environment of Pa, carrying out surface oxidation on the clean germanium substrate 1 for 10-20 min to form ultrathin GeO₂A thin film layer 2;

B. heating to 550-650 deg.C, the silicon impacts the ultra-thin GeO in the form of ion beam₂On the upper surface of the thin film layer 2, the following chemical reactions occur:

Si+GeO₂→SiO↑+GeO↑；

in ultra-thin GeO₂Forming a micro array hole on the thin film layer, wherein the aperture of the micro array hole is 0.8-1.2 nm, and the distance is 3-5 nm;

C. depositing 7-11 layers of silicon atoms on the ultrathin GeO provided with the micro array holes at the deposition rate of (1-1.4) ML/min by using a silicon electrodeposition method in the temperature environment of 550-650 DEG C₂ A membrane layer 2 of electrodeposited silicon sufficient to fill the micro-array holes;

D. under the temperature environment of 550-650 ℃, silicon is continuously deposited with 26-66 layers of silicon atoms in the ultrathin GeO provided with the micro array holes at the deposition rate of (1-1.4) ML/min by an electrodeposition method₂And the thin film layer 2, the silicon atoms which are continuously deposited are trapped in the micro array holes, so that the spherical nano crystals 3 are formed, the spherical nano crystals 3 are continuously deposited, the adjacent spherical nano crystals 3 reach a contact state at the junction, and the nano silicon sphere layer 30 is formed.

In this embodiment, D is followed by:

E. and reducing the temperature to 450-500 ℃ and continuously depositing 13-123 epitaxial germanium layers 4 on the nano silicon ball layer 30 at the deposition rate of (1.5-1.8) ML/min.

In this embodiment, the adjacent spherical nanocrystals 3 are provided with micro-pores at the interface; part of the germanium atoms of the epitaxial germanium layer 4 penetrate through the micro-pores to fill the gaps between the adjacent spherical nanocrystals 3.

In this embodiment, germanium atoms penetrating through the micro-pores are wrapped and filled on the surface of the spherical nanocrystals 3, thereby ensuring the relative independence of the spherical nanocrystals 3.

In the embodiment, the grain size of the spherical nanocrystals 3 is 3 nm-5 nm, so that the spherical nanocrystals can be ensured to be in an active state, can absorb heat to the maximum extent and can be converted into ordered electron flow, and the thermoelectric efficiency is high.

In this embodiment, E further includes:

F. at a temperature of 330-430 ℃ and an oxygen partial pressure of (1.8-2.2) × 10^-4Under the Pa environment, oxidizing the surface of the epitaxial germanium layer 4 for 10-20 min to form ultrathin GeO₂A thin film layer 2;

G. b, C and D are repeated to obtain a second layer of nanosilicon spheres 30.

In this embodiment, a further includes:

A1. conventionally cleaning a non-doped germanium substrate 1 by adopting a dilute solution of a sulfuric acid-hydrogen peroxide mixed solution and a hydrofluoric acid solution;

A2. the germanium substrate 1 after the conventional cleaning is subjected to a basic pressure of (2.8-3.2) × 10^-8Introducing the substrate into a molecular beam epitaxy chamber in a Pa environment, heating to 350-410 ℃, degassing for 3-5 hours, and growing a (80-120) nm germanium buffer layer on the germanium substrate 1 to form a clean germanium surface.

In this embodiment, after a2, a is preceded by:

A3. and (3) observing the germanium surface by using a high-energy electron diffraction device (RHEED) to determine the cleanliness of the germanium surface.

In this example, ultra-thin GeO₂The thin film layer 2 has 1-5 GeO layers₂MoleculeAnd (3) a layer.

In this example, ultra-thin GeO₂The thin film layer 2 has 2-3 GeO layers₂A molecular layer.

And (3) repeating B, C, D, E and F to obtain a third nano silicon ball layer, … … and an Nth nano silicon ball layer, wherein N is a natural number and is more than or equal to 3.

The process is simple, the aperture of the micro array hole is 0.8-1.2 nm, the distance is 3-5 nm, the grain size of the spherical nanocrystal is 3-5 nm, the spherical nanocrystal and the micro array hole can be combined and atom exchanged through a crystal boundary junction, the mutual independence can be guaranteed, and the structural stability is good.

The foregoing is only a preferred embodiment of this invention and it should be noted that modifications can be made by those skilled in the art without departing from the principle of the invention and these modifications should also be considered as the protection scope of the invention.