A stacked atomic layer thermopile heat flow sensor and preparation method thereof

Abstract

The present invention belongs to the technical field of heat flow sensors, and relates to a laminated atomic layer thermopile heat flow sensor and a preparation method thereof. The present invention adopts a laminated structure, and by connecting two ALTP materials with opposite polarities of thermoelectric potential signals in series in three-dimensional space, the effective length of the ALTP film is increased, and the ALTP film is innovatively transformed from a two-dimensional layout to a three-dimensional space architecture. The series connection of the ALTP films will not occupy the plane position of the substrate, which provides a new idea for the miniaturization of the ALTP heat flow sensor, and improves the sensitivity of the ALTP heat flow sensor while ensuring miniaturization.

Description

Technical Field

[0001] The invention belongs to the technical field of heat flow sensors and relates to a stacked structure atomic layer thermopile heat flow sensor and a preparation method thereof. Background Art

[0002] Atomic layer thermopile (ALTP) refers to a material with lateral Seebeck effect, that is, when there is a temperature difference between the upper and lower surfaces of the inclined epitaxial film, a thermoelectric potential is generated perpendicular to the temperature gradient due to the anisotropy of the material's carrier transport. Since the material is anisotropic, when the inclined epitaxial film is under the action of the temperature gradient, the carrier conduction is like that in two materials, so it is called an atomic layer thermopile.

[0003] It is generally believed that the output potential direction of ALTP is determined by the conductivity type of the material. If the majority carriers of the material are holes, the output potential points to one end of the tilt direction (Kouhei Takahashi et al., "Influence of interband transition on the laser-induced voltage in thermoelectric Ca x CoO2thin films”); if the majority carriers of the material are electrons, the output potential is opposite. The potential output of ALTP is proportional to the tilt angle and length of the film, and the potential output of ALTP first increases and then stabilizes as the thickness of the film increases (the article published by Kouhei Takahashi et al., “The off-diagonal thermoelectric effect in inclinedly oriented thin films of layered cobaltite CaxCoO2”). At present, ALTP heat flow sensors have become the main means of capturing high-frequency pulsating heat flow signals due to their fast response characteristics, and have great application prospects in wind tunnel tests. In order to minimize the interference of the sensor on the flow field, its size should be as small as possible. However, the sensitivity of the ALTP heat flow sensor is proportional to the length of the ALTP film, so the reduction in the size of the sensor will inevitably lead to a decrease in sensitivity.

[0004] Based on this, researchers have proposed a method to improve the sensitivity of ALTP heat flow sensors by using a multi-line structure. However, in this method, the number of atomic layer thermopile lines still depends on the size of the sensor, that is, increasing the number of lines to obtain a high-sensitivity ALTP heat flow sensor will inevitably increase the size of the sensor. Therefore, reducing the size of the sensor while ensuring sensitivity through the existing multi-line structure still has certain limitations. Summary of the invention

[0005] In view of the above-mentioned problems or shortcomings, in order to solve the shortcomings of the existing ALTP heat flow sensor in terms of both miniaturization and sensitivity, the present invention provides a stacked atomic layer thermopile heat flow sensor and a preparation method thereof.

[0006] A laminated atomic layer thermopile heat flow sensor comprises: an inclined single crystal substrate, two thermopile lines, an insulating layer, a lead gold film and an external wire.

[0007] The two thermopile lines are two materials with opposite polarities of thermoelectric potential signals, namely n-type and p-type ALTP thin film materials. The two thermopile lines are arranged on an inclined single crystal substrate and are alternately stacked in the thickness direction of three-dimensional space along the inclination direction of the single crystal substrate. An insulating layer film is loaded between two adjacent layers of thermopile lines so that the two are only partially overlapped to ensure that the two thermopile lines are alternately connected in series in the thickness direction of three-dimensional space. The thickness of a thermopile line is 20nm-1000nm, and the total thickness of all thermopile lines does not exceed 10um; when the length of a single thermopile line exceeds 3mm, the length of the overlapping part of the two thermopile lines does not exceed 20% of the length of the single thermopile line; when the length of a single thermopile line is less than 3mm, the length of the overlapping part is 0.01mm-1mm.

[0008] The insulating layer is made of a material that matches the lattice of the thermopile lines to ensure that the thermopile lines can be epitaxially grown on the insulating layer. The thickness of the insulating layer is 10nm-100nm.

[0009] The lead gold film has two locations, which are respectively connected to the first and last two thermopile lines after being connected in series, and then connected to external wires.

[0010] There are two external wires, which are respectively connected to two lead gold films and serve as terminals for external connection of the sensor.

[0011] Furthermore, the single crystal substrate is a LaAlO3, SrTiO3 or MgO single crystal substrate inclined at 5°-45° along the c-axis.

[0012] Furthermore, the two thermopile lines are made of the same material and modulated into n-type and p-type respectively, so as to optimize the problem of reduced device stability due to different thermal stability or thermal expansion coefficients of different materials at high temperatures.

[0013] The potential output of ALTP increases first and then stabilizes as the film thickness increases. Therefore, when the film thickness reaches a certain value, further increasing the film thickness will not help improve the sensitivity. If two or more layers of ALTP films of a certain thickness are connected in series in the thickness direction, their potential outputs can be superimposed. Figure 1When the surface of the ALTP heat flow sensor of the present invention is irradiated by a heat source, a temperature gradient will appear in the film on the substrate 1 along the thickness direction. The directions of the thermoelectric potentials generated by the ALTP lines 2 and ALTP lines 4 are opposite, and there is an insulating layer film 3 between the ALTP lines 2 and ALTP lines 4 so that the two are only partially overlapped. Therefore, the ALTP lines 2 and ALTP lines 4 are connected in series in three-dimensional space, thereby improving the sensitivity of the ALTP heat flow sensor. Different from the existing two-dimensional multi-line structure, the mutual series connection of the ALTP lines in the present invention is based on stacking in the thickness direction of three-dimensional space. The increase in the number of effective lines does not depend on the substrate size, which is more conducive to the miniaturization of the ALTP heat flow sensor.

[0014] like Figure 2 As shown, the process flow of preparing the above-mentioned stacked structure atomic layer thermopile heat flow sensor is as follows:

[0015] Step 1: epitaxially grow n-type (p-type) thermopile lines (ALTP thin film lines) on an inclined single crystal substrate using a metal mask by sputtering, metal organic chemical vapor deposition or pulsed laser deposition.

[0016] Step 2: epitaxially grow an insulating layer on the n-type (p-type) ALTP thin film lines using a metal mask by sputtering, metal organic chemical vapor deposition or pulsed laser deposition.

[0017] Step 3: epitaxially grow p-type (n-type) ALTP thin film lines on the insulating layer by using a metal mask through sputtering, metal organic chemical vapor deposition or pulsed laser deposition.

[0018] Step 4: Continue to repeatedly prepare the insulating layer n-type (p-type) thermopile line-insulating layer-p-type (n-type) thermopile line upward in the thickness direction until all the thermopile lines are stacked, and keep the two adjacent thermopile lines stacked and connected in series.

[0019] Step 5: After the stacking is completed and the first and last thermopile lines are connected in series, lead gold films are prepared respectively, and then two external wires (for external testing of the sensor) are connected to the two lead gold films respectively.

[0020] In summary, the present invention connects two ALTP materials with opposite polarities of thermoelectric potential signals in series in three-dimensional space, which not only increases the effective length of the ALTP film, but also innovatively transforms the ALTP film from a two-dimensional layout to a three-dimensional space architecture. The series connection of the ALTP films will not occupy the planar position of the substrate, which provides a new idea for the miniaturization of the ALTP heat flow sensor and improves the sensitivity of the ALTP heat flow sensor while ensuring miniaturization. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the structure and principle of the ALTP heat flow sensor;

[0022] Figure 2 Schematic diagram of the preparation process of ALTP heat flow sensor;

[0023] Figure 3 The structural diagram of the example sample is shown in FIG.

[0024] Figure 4 is the test curve of the example sample;

[0025] Reference numerals: 1-single crystal substrate, 2-n-type LaCaMnO3 line, 3-LaMnO3 insulating layer, 4-p-type YBa2Cu3O 7-δ Lines, 5-lead gold film, 6-external wires. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings and embodiments.

[0027] Example:

[0028] Step 1: epitaxially grow a LaCaMnO3 functional layer film using metal organic vapor deposition.

[0029] First, La source, Ca source, and Mn source were dissolved in tetrahydrofuran at concentrations of 0.0138 mol / L, 0.0320 mol / L, and 0.0344 mol / L, and the precursor solution was obtained after sufficient stirring. The surface-cleaned strontium titanate substrate was placed in the deposition chamber, and a metal mask was used to reserve a position for depositing the LaCaMnO3 film. The vacuum was pumped to 2 Pa, and the substrate heating temperature was adjusted to 830°C, the oxygen flow rate was 500 mL / min, the argon flow rate was 700 mL / min, the nitrous oxide flow rate was 500 mL / min, and the liquid intake was 40 ml. The LaCaMnO3 film was about 200 nm.

[0030] Step 2: epitaxially grow a LaMnO3 insulating layer film on the LaCaMnO3 functional layer film by metal organic vapor deposition.

[0031] First, La source and Mn source were dissolved in tetrahydrofuran at concentrations of 0.0460 mol / L and 0.0344 mol / L, and the precursor solution was obtained after sufficient stirring. The strontium titanate substrate on which LaCaMnO3 had been deposited was placed in the deposition chamber, and a position for depositing the LaMnO3 film was reserved using a metal mask. The vacuum was pumped to 2 Pa, and the substrate heating temperature was adjusted to 830°C, the oxygen flow rate was 500 mL / min, the argon flow rate was 700 mL / min, the nitrous oxide flow rate was 500 mL / min, and the liquid volume was 10 ml. The LaMnO3 film was about 50 nm.

[0032] Step 3: Epitaxial growth of YBa2Cu3O on the long LaMnO3 insulating layer film by metal organic vapor deposition 7-δ Functional layer film.

[0033] First, the Y source, Ba source, and Cu source were dissolved in tetrahydrofuran at concentrations of 0.08 mol / L, 0.145 mol / L, and 0.16 mol / L, and the precursor solution was obtained after sufficient stirring. The strontium titanate substrate on which the LaMnO3 insulating layer had been deposited was placed in the deposition chamber, and a metal mask was used to reserve a space for depositing YBa2Cu3O 7-δ The film was placed in a vacuum chamber at 2 Pa, and the substrate heating temperature was adjusted to 850 °C, the oxygen flow rate was 840 mL / min, the argon flow rate was 1080 mL / min, the nitrous oxide flow rate was 340 mL / min, and the liquid volume was 5 ml. 7-δ The film is about 200nm.

[0034] Step 4: Preparation of lead gold film.

[0035] The sample was placed in the chamber and the vacuum was drawn to 2.13×10 -3 Pa, adjust the oxygen partial pressure to 0.5Pa, the sputtering current to 0.15A, and time for 20s; then turn off the oxygen, and after the gas pressure drops and stabilizes, adjust the argon partial pressure to 0.7Pa, the sputtering current to 0.2A, and time for 3.5min. At this time, the thickness of the gold film is about 300nm.

[0036] Step 5: Use welding technology to connect the external wires to the lead gold film. At this point, the stacked atomic layer thermopile heat flow sensor is completed.

[0037] In this example, the samples were prepared as Figure 3 The samples prepared above were subjected to heat flow test, and the results are as follows:

[0038] Figure 4 The heat flow test curve of the example sample shows the potential output curve of a typical ALTP heat flow sensor at 45.32kW / m 2 The output voltage under heat flow is 485μV, which is 400μV higher than the output voltage of YBCO with the same thickness.

[0039] In summary, the present invention adopts a laminated structure to connect the ALTP thin films in series in the thickness direction of the thin films, thereby improving the sensitivity of the ALTP heat flow sensor. Moreover, unlike the existing multi-line structure, the present invention uses a laminated structure to connect the ALTP thin films in series without occupying the substrate position, which is more conducive to the miniaturization of the ALTP heat flow sensor.

Claims

1. A stacked atomic layer thermopile heat flow sensor, characterized in that: It includes a tilted single crystal substrate, two types of thermopile lines, an insulating layer, a lead gold film and an external wire; The two thermopile lines are two materials with opposite polarities of thermoelectric potential signals, namely n-type and p-type ALTP thin film materials. The two thermopile lines are arranged on an inclined single crystal substrate and are alternately stacked in the thickness direction of three-dimensional space along the inclination direction of the single crystal substrate; an insulating layer film is loaded between two adjacent layers of thermopile lines so that the two are only partially overlapped, so as to ensure that the two thermopile lines are alternately connected in series in the thickness direction of three-dimensional space; the thickness of a thermopile line is 20nm-1000nm, and the total thickness of all thermopile lines does not exceed 10um; when the length of a single thermopile line exceeds 3mm, the length of the overlapping part of the two thermopile lines does not exceed 20% of the length of the single thermopile line; when the length of a single thermopile line is less than 3mm, the length of the overlapping part is 0.01mm-1mm; The insulating layer is made of a material that matches the thermopile line lattice and has a thickness of 10nm-100nm; The lead gold film has two locations, which are respectively connected to the first and last two thermopile lines after being connected in series, and then connected to external wires; There are two external wires, which are respectively connected to two lead gold films and serve as terminals for external connection of the sensor.

2. The stacked atomic layer thermopile heat flow sensor according to claim 1, characterized in that: The single crystal substrate is a LaAlO3, SrTiO3 or MgO single crystal substrate inclined by 5°-45° along the c-axis.

3. The stacked atomic layer thermopile heat flow sensor according to claim 1, characterized in that: The two thermopile lines are made of the same material and modulated into n-type and p-type respectively.

4. The method for preparing the stacked structure atomic layer thermopile heat flow sensor according to claim 1, characterized in that: The following steps are involved: Step 1: epitaxially growing n-type or p-type thermopile lines on an inclined single crystal substrate by sputtering, metal organic chemical vapor deposition or pulsed laser deposition using a metal mask; Step 2: epitaxially growing an insulating layer on the n-type or p-type thermopile lines by sputtering, metal organic chemical vapor deposition or pulsed laser deposition using a metal mask; Step 3, epitaxially growing p-type or n-type thermopile lines on the insulating layer by sputtering, metal organic chemical vapor deposition or pulsed laser deposition using a metal mask; Step 4, then continue to repeatedly prepare the insulating layer n-type or p-type thermopile line-insulating layer-p-type or n-type thermopile line upward in the thickness direction until all the thermopile lines are stacked, and the adjacent two thermopile lines are kept stacked and connected in series; Step 5: After the stacking is completed and the first and last thermopile lines are connected in series, lead gold films are prepared respectively, and then two external wires are connected to the two lead gold films respectively.

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