Van der waals asymmetric thermal resistance structure infrared thermoelectric detector and preparation method

Abstract

The application discloses a van der Waals asymmetric thermal resistance structure infrared thermoelectric detector and a preparation method thereof. The detector adopts a sandwich stacking structure and sequentially comprises, from bottom to top, a silicon nitride film, a middle electrode layer, a first electrode and a second electrode arranged on the silicon nitride film, and a thermoelectric conversion material layer, two ends of the thermoelectric conversion material layer being respectively in ohmic contact with the first electrode and the second electrode to form a suspended thermal bridge structure with the silicon nitride film as a support. The thermoelectric conversion material layer is selected from a low-thermal-conductivity high-Seebeck-coefficient van der Waals material, the contact area of the thermoelectric conversion material layer with the first electrode is greater than the contact area of the thermoelectric conversion material layer with the second electrode, and an asymmetric thermal resistance interface is formed between the first electrode and the second electrode, so that infrared thermoelectric detection is realized without an external bias. The application provides a novel infrared thermoelectric detector with high performance, self-power supply and compact structure.

Description

Technical Field

[0001] This invention belongs to the field of thermoelectric detection technology, specifically relating to an infrared thermoelectric detector with a van der Waals asymmetric thermal resistance structure and its preparation method. Background Technology

[0002] In the field of infrared thermoelectric detection, the currently mature and widely commercialized technologies are radiometric calorimeters and thermopile systems. Radiometric calorimeters detect changes in the resistance of thermistor materials as a function of temperature. While their structure is relatively simple, they must operate under a constant external bias. This operating mode directly leads to significant dark current, increasing device noise levels, limiting detectivity, and causing additional power consumption and thermal management issues. In contrast, thermopile systems, as passive devices, can operate without a bias, but their inherent structure limits further performance improvements. This technology integrates dozens to hundreds of pairs of p-type and n-type thermocouples in series. The core design idea is to centrally arrange the "hot junctions" of all thermocouples in a common light-absorbing region, while fixing all "cold junctions" to a temperature-stable substrate heat sink. When infrared radiation irradiates the light-absorbing region, the hot junction temperature rises, while the cold junctions are kept at a low temperature by the heat sink, thus generating a Seebeck voltage on each thermocouple pair. These voltages are then superimposed in series to obtain a higher output voltage. The complexity of this structure leads to cumbersome fabrication processes and high costs.

[0003] The existing structure has several key objective drawbacks. First, the external bias voltage required for the calorimeter introduces significant dark current, which not only becomes the main noise source of the device, limiting the final detection sensitivity, but also leads to unnecessary static power consumption. Second, the complex processes for precisely fabricating and integrating a large number of pn thermocouple pairs in the thermopile make these technologies difficult to apply on a large scale in low-cost and high-integration scenarios.

[0004] Therefore, how to realize a miniaturized infrared thermoelectric detector with a simple structure, no external bias voltage required, and high sensitivity is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The first objective of this invention is to provide a van der Waals asymmetric thermal resistance infrared thermoelectric detector, addressing the problems in the prior art.

[0006] Therefore, the above-mentioned objectives of the present invention are achieved through the following technical solutions:

[0007] An infrared thermoelectric detector with a van der Waals asymmetric thermal resistance structure, wherein the detector adopts a sandwich stacked structure, comprising, from bottom to top:

[0008] Silicon nitride thin film serves as the underlying support layer;

[0009] An intermediate electrode layer is disposed on a silicon nitride thin film and includes a first electrode and a second electrode disposed at intervals from each other.

[0010] A thermoelectric conversion material layer spans the first electrode and the second electrode, with its two ends forming ohmic contacts with the first electrode and the second electrode respectively, forming a suspended thermal bridge structure supported by a silicon nitride thin film. The gap between the first electrode and the second electrode forms the bridge surface bridging section of the suspended thermal bridge structure, and the thermoelectric conversion material layer connects the two electrodes by bridging this section.

[0011] The thermoelectric conversion material layer is made of a van der Waals material with low thermal conductivity and high Seebeck coefficient. Its contact area with the first electrode is larger than its contact area with the second electrode, forming an asymmetric thermal resistance interface between the first electrode and the second electrode, so as to realize infrared thermoelectric detection without the need for external bias voltage.

[0012] While adopting the above technical solutions, the present invention may also adopt or combine the following technical solutions:

[0013] As a preferred technical solution of the present invention: the contact area between the thermoelectric conversion material layer and the first electrode is at least twice the contact area between the thermoelectric conversion material layer and the second electrode, the thermoelectric conversion material layer forms a large-area contact with the first electrode to form a cold junction with low thermal resistance, and forms a small-area contact with the second electrode to form a hot junction with high thermal resistance.

[0014] As a preferred embodiment of the present invention, the low thermal conductivity and high Seebeck coefficient van der Waals material is Nb3I8.

[0015] As a preferred embodiment of the present invention, the first electrode and the second electrode are gold electrodes.

[0016] The second objective of this invention is to provide a method for fabricating an infrared thermoelectric detector with a van der Waals asymmetric thermal resistance structure, addressing the problems in the prior art.

[0017] Therefore, the above-mentioned objectives of the present invention are achieved through the following technical solutions:

[0018] The fabrication method of a van der Waals asymmetric thermal resistance structure infrared thermoelectric detector includes the following steps:

[0019] S1, Thermal bridge substrate preparation: Prepare a silicon nitride thin film, and prepare a first electrode and a second electrode on the silicon nitride thin film;

[0020] S2, Nb3I8 nanosheet exfoliation: Nb3I8 nanosheets were grown and mechanically exfoliated on a SiO2 / Si substrate, using polypropylene carbonate (PPC) as the transfer medium.

[0021] S3, Preparation of transfer sheet: The Nb3I8 nanosheets peeled off in step S2 are transferred onto a glass slide coated with polydimethylsiloxane PDMS to form a transfer sheet;

[0022] S4, Micro-area alignment and transfer: The Nb3I8 nanosheets on the transfer sheet in step S3 are transferred to the first electrode and the second electrode in step S1 by micro-area alignment, so that the Nb3I8 nanosheets span the first electrode and the second electrode.

[0023] S5, Asymmetric Contact: The Nb3I8 nanosheet is biased such that one end of the Nb3I8 nanosheet forms a first contact area with the first electrode and the other end forms a second contact area with the second electrode. The first contact area is larger than the second contact area, thereby forming an asymmetric thermal resistance interface between the first electrode and the second electrode.

[0024] S6, PPC Removal: Remove polypropylene carbonate from the surface of the Nb3I8 nanosheets to complete the fabrication of the van der Waals asymmetric thermal resistance structure infrared thermoelectric detector.

[0025] While adopting the above technical solutions, the present invention may also adopt or combine the following technical solutions:

[0026] As a preferred technical solution of the present invention: In step S4, the micro-area alignment and transfer is performed using a micromanipulation platform to align the preset position of the Nb3I8 nanosheets carried on the glass slide to the first electrode and the second electrode.

[0027] Compared with existing technologies, the van der Waals asymmetric thermal resistance structure infrared thermoelectric detector and its fabrication method of the present invention have the following beneficial effects: In the present invention, Nb3I8 van der Waals material, which has both low thermal conductivity and high Seebeck coefficient, is used as a single thermoelectric conversion unit and integrated on a silicon nitride suspended thermal bridge structure to achieve efficient thermal isolation; on this basis, the contact area between the van der Waals material and the same metal electrodes at both ends is precisely controlled by dry transfer technology, actively constructing an asymmetric thermal resistance interface—that is, a large-area "cold junction" is formed at one end and a small-area "hot junction" is formed at the other end, so that the detector can achieve self-powered operation without external bias voltage, greatly reducing power consumption; at the same time, the design of a single material and symmetrical electrodes simplifies the device structure and fabrication process; and the efficient temperature difference construction capability achieved by the synergy of asymmetric contact and suspended structure ultimately ensures the high sensitivity and excellent detection performance of the detector to infrared radiation, providing a new technical path for the next generation of low-power micro infrared detection systems.

[0028] This invention innovatively proposes a novel van der Waals asymmetric thermal resistance structure. By constructing different thermal resistances at both ends of a single van der Waals semiconductor material (Nb3I8) with low thermal conductivity and a high Seebeck coefficient, it directly forms an efficient lateral temperature gradient and infrared thermoelectric response. The Nb3I8 ends form ohmic contacts with gold electrodes, with no dangling bonds on the surface, effectively reducing interfacial heat loss and electrical noise. This invention aims to simultaneously solve the dual challenges of complex thermopile structures and low detectivity in calorimeters. It achieves a very long-wave infrared response up to 20 micrometers, with a room-temperature blackbody detectivity of approximately 2.5 × 10⁻⁶. 9 cmHz 1 / 2 W -1 . Attached Figure Description

[0029] Figure 1 This is a schematic diagram illustrating the fabrication of the van der Waals asymmetric thermal resistance structure infrared thermoelectric detector of the present invention.

[0030] Figure 2 This is a schematic diagram of the structure of the van der Waals asymmetric thermal resistance infrared thermoelectric detector of the present invention.

[0031] Figure 3 The noise current power spectral density curve and detectivity curve of the van der Waals asymmetric thermal resistance structure infrared thermoelectric detector of the present invention are shown.

[0032] Figure 4 This is a thermal image of a soldering iron formed by the van der Waals asymmetric thermal resistance infrared thermoelectric detector of this invention. Detailed Implementation

[0033] The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

[0034] An infrared thermoelectric detector with a van der Waals asymmetric thermal resistance structure, wherein the detector adopts a sandwich stacked structure, comprising, from bottom to top:

[0035] Silicon nitride thin film serves as the underlying support layer;

[0036] An intermediate electrode layer is disposed on the upper surface of the silicon nitride thin film, and includes a first electrode and a second electrode spaced apart in the same horizontal plane;

[0037] A thermoelectric conversion material layer spans the first electrode and the second electrode, with its two ends forming ohmic contacts with the first electrode and the second electrode respectively, forming a suspended thermal bridge structure supported by a silicon nitride thin film. The horizontal interval between the first electrode and the second electrode forms the bridge surface bridging section of the suspended thermal bridge structure, and the thermoelectric conversion material layer connects the two electrodes by bridging this section.

[0038] The thermoelectric conversion material layer is made of a van der Waals material with low thermal conductivity and high Seebeck coefficient. Its contact area with the first electrode is larger than its contact area with the second electrode, forming an asymmetric thermal resistance interface between the first electrode and the second electrode, so as to realize infrared thermoelectric detection without the need for external bias voltage.

[0039] The present invention may also employ or combine the following technical solutions:

[0040] The contact area between the thermoelectric conversion material layer and the first electrode is at least twice the contact area between the thermoelectric conversion material layer and the second electrode. The thermoelectric conversion material layer forms a large-area contact with the first electrode to form a cold junction with low thermal resistance, and forms a small-area contact with the second electrode to form a hot junction with high thermal resistance.

[0041] The low thermal conductivity, high Seebeck coefficient van der Waals material is Nb3I8.

[0042] The first electrode and the second electrode are gold electrodes.

[0043] The method for fabricating the van der Waals asymmetric thermal resistance structure infrared thermoelectric detector of the present invention includes the following steps:

[0044] S1, Thermal bridge substrate preparation: Prepare a silicon nitride thin film, and prepare a first electrode and a second electrode on the silicon nitride thin film;

[0045] S2, Nb3I8 nanosheet exfoliation: Nb3I8 nanosheets were grown and mechanically exfoliated on a SiO2 / Si substrate, using polypropylene carbonate (PPC) as the transfer medium.

[0046] S3, Preparation of transfer sheet: The Nb3I8 nanosheets peeled off in step S2 are transferred onto a glass slide coated with polydimethylsiloxane PDMS to form a transfer sheet;

[0047] S4, Micro-area alignment and transfer: The Nb3I8 nanosheets on the transfer sheet in step S3 are transferred to the first electrode and the second electrode in step S1 by micro-area alignment, so that the Nb3I8 nanosheets span the first electrode and the second electrode.

[0048] S5, Asymmetric Contact: The Nb3I8 nanosheet is biased such that one end of the Nb3I8 nanosheet forms a first contact area with the first electrode and the other end forms a second contact area with the second electrode. The first contact area is larger than the second contact area, thereby forming an asymmetric thermal resistance interface between the first electrode and the second electrode.

[0049] S6, PPC Removal: Remove polypropylene carbonate from the surface of the Nb3I8 nanosheets to complete the fabrication of the van der Waals asymmetric thermal resistance structure infrared thermoelectric detector.

[0050] In step S4, the micro-area alignment and transfer is performed using a micromanipulation platform to align the preset positions of the Nb3I8 nanosheets supported on the glass slide to the first electrode and the second electrode.

[0051] Example 1

[0052] This invention provides an infrared thermoelectric detector with a van der Waals asymmetric thermal resistance structure. The detector employs a sandwich stacked structure, using a suspended thermal bridge structure supported by a low thermal conductivity silicon nitride thin film. Its core innovation lies in fabricating gold electrodes at both ends of the thermal bridge. A van der Waals material (Nb3I8) with low thermal conductivity and a high Seebeck coefficient is precisely transferred to the thermal bridge region using a dry transfer technique. This results in asymmetrical van der Waals contacts between the two ends of the material and the gold electrodes, thus constructing an inherently asymmetric thermal resistance structure. Specifically, the contact between the two-dimensional material and the gold electrode at one end is designed to overlap over a large area, forming a low thermal resistance "cold junction"; while the contact with the gold electrode at the other end is precisely controlled to have a small area, forming a high thermal resistance "hot junction".

[0053] The technological advantages of this structure are mainly reflected in three aspects: First, due to the significant difference in thermal resistance at the contact points of the two electrodes, the "hot junction" temperature rises rapidly under infrared radiation, while the "cold junction" remains at a relatively low temperature, thus spontaneously forming an efficient lateral temperature gradient within the van der Waals material. Second, this single-junction structure avoids the complex multi-junction alignment process of thermopile, simplifying the fabrication process. Furthermore, it eliminates the need for an external bias voltage for the calorimeter, fundamentally reducing dark current noise. The device's noise current power spectral density is as low as 2.7 × 10⁻⁶. -30 A 2 / Hz, enabling very long-wave infrared responses up to 20 micrometers, with a room-temperature blackbody detectivity of approximately 2.2 × 10⁻⁶. 9 cmHz 1 / 2 W -1 .

[0054] The method for fabricating the van der Waals asymmetric thermal resistance structure infrared thermoelectric detector described in this invention is as follows: Figure 1 The steps shown are performed in sequence:

[0055] S1, a low-stress silicon nitride thin film is grown on a silicon substrate by low-pressure chemical vapor deposition. A thermal bridge structure supported by a silicon nitride thin film with low thermal conductivity is prepared by photolithography, electron beam evaporation and wet etching processes.

[0056] S2, Nb3I8 nanosheets are peeled onto the surface of a polypropylene carbonate (PPC) film using Nitto tape;

[0057] S3, the composite film is attached to the polydimethylsiloxane (PDMS) support layer to complete the preparation of the transfer sheet;

[0058] S4. With the aid of a microscope, a dry transfer platform was used to perform micro-area alignment and transfer, and the obtained Nb3I8 van der Waals material was accurately transferred to the thermal bridge region.

[0059] S5, bias the Nb3I8 nanosheet so that the two ends of the Nb3I8 nanosheet form asymmetrical area contact with the two gold electrodes respectively, and heat the substrate to 120°C to cause the polypropylene carbonate film to detach from the polydimethylsiloxane PDMS support layer.

[0060] S6, remove the PPC polymer to complete the fabrication of the asymmetric thermal resistance structure van der Waals infrared thermoelectric detector.

[0061] Figure 2 This is a top view schematic diagram of the device structure of the van der Waals asymmetric thermal resistance infrared thermoelectric detector of the present invention, wherein: a silicon nitride thin film 1, a first electrode 201, a second electrode 202, and a thermoelectric conversion material layer 3 are present. The silicon nitride thin film 1 has low thermal conductivity and serves as a support for the suspended thermal bridge structure. The thermoelectric conversion material layer 3 is a van der Waals material Nb3I8 with low thermal conductivity and high Seebeck coefficient, which spans and connects the first electrode 201 and the second electrode 202, and forms ohmic contacts with the first electrode 201 and the second electrode 202 respectively. The contact area between the thermoelectric conversion material layer 3 and the first electrode 201 is at least twice the contact area between the thermoelectric conversion material layer and the second electrode 202, forming an asymmetric thermal resistance interface between the first electrode 201 and the second electrode 202 to achieve infrared thermoelectric detection without the need for an external bias voltage.

[0062] Figure 3 In the figure, 'a' represents the noise current power spectral density curve of the fabricated asymmetric thermal resistance structure van der Waals infrared thermoelectric detector, and... Figure 3 In the figure, b represents the detectivity curve of the fabricated asymmetric thermal resistance structure van der Waals infrared thermoelectric detector under 800 K blackbody irradiation. The measured device noise current power spectral density is as low as 2.7 × 10⁻⁶. -30 A 2 It exhibits superior room-temperature blackbody detection capabilities at / Hz, with a detection wavelength up to 20 micrometers and a room-temperature blackbody detectivity of approximately 2.2 × 10⁶. 9 cmHz 1 / 2 W -1 .

[0063] Figure 4This is a thermal image of a soldering iron formed by a device. The heated soldering iron is used as the infrared thermal imaging target, and its emitted infrared radiation signal is focused onto a detector through an optical lens group. A two-dimensional electrically controlled displacement stage moves the detector point-by-point to scan, simultaneously acquiring the thermoelectric response signals corresponding to each spatial position, ultimately obtaining an infrared thermal image of the soldering iron under test.

[0064] The above specific embodiments are used to explain and illustrate the present invention, and are only preferred embodiments of the present invention, not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

Claims

1. An infrared thermoelectric detector with a van der Waals asymmetric thermal resistance structure, characterized in that: The detector adopts a sandwich stacked structure, which includes, from bottom to top: Silicon nitride thin film serves as the underlying support layer; An intermediate electrode layer is disposed on a silicon nitride thin film and includes a first electrode and a second electrode disposed at intervals from each other. A thermoelectric conversion material layer spans the first electrode and the second electrode, with its two ends forming ohmic contacts with the first electrode and the second electrode respectively, forming a suspended thermal bridge structure supported by a silicon nitride thin film. The gap between the first electrode and the second electrode forms the bridge surface bridging section of the suspended thermal bridge structure, and the thermoelectric conversion material layer connects the two electrodes by bridging this section. The thermoelectric conversion material layer is made of a van der Waals material with low thermal conductivity and high Seebeck coefficient. Its contact area with the first electrode is larger than its contact area with the second electrode, forming an asymmetric thermal resistance interface between the first electrode and the second electrode, so as to realize infrared thermoelectric detection without the need for external bias voltage.

2. The van der Waals asymmetric thermal resistance structure infrared thermoelectric detector as described in claim 1, characterized in that: The low thermal conductivity, high Seebeck coefficient van der Waals material is Nb3I8.

3. The van der Waals asymmetric thermal resistance structure infrared thermoelectric detector as described in claim 1, characterized in that: The contact area between the thermoelectric conversion material layer and the first electrode is at least twice the contact area between the thermoelectric conversion material layer and the second electrode. The thermoelectric conversion material layer forms a large-area contact with the first electrode to form a cold junction with low thermal resistance, and forms a small-area contact with the second electrode to form a hot junction with high thermal resistance.

4. The van der Waals asymmetric thermal resistance structure infrared thermoelectric detector as described in claim 1, characterized in that: The first electrode and the second electrode are gold electrodes.

5. The method for fabricating the van der Waals asymmetric thermal resistance structure infrared thermoelectric detector according to any one of claims 1-4, characterized in that: Includes the following steps: S1, Thermal bridge substrate preparation: Prepare a silicon nitride thin film, and prepare a first electrode and a second electrode on the silicon nitride thin film; S2, Nb3I8 nanosheet exfoliation: Nb3I8 nanosheets were grown and mechanically exfoliated on a SiO2 / Si substrate, using polypropylene carbonate (PPC) as the transfer medium. S3, Preparation of transfer sheet: The Nb3I8 nanosheets peeled off in step S2 are transferred onto a glass slide coated with polydimethylsiloxane PDMS to form a transfer sheet; S4, Micro-area alignment and transfer: The Nb3I8 nanosheets on the transfer sheet in step S3 are transferred to the first electrode and the second electrode in step S1 by micro-area alignment, so that the Nb3I8 nanosheets span the first electrode and the second electrode. S5, Asymmetric Contact: The Nb3I8 nanosheet is biased such that one end of the Nb3I8 nanosheet forms a first contact area with the first electrode and the other end forms a second contact area with the second electrode. The first contact area is larger than the second contact area, thereby forming an asymmetric thermal resistance interface between the first electrode and the second electrode. S6, PPC Removal: Remove polypropylene carbonate from the surface of the Nb3I8 nanosheets to complete the fabrication of the van der Waals asymmetric thermal resistance structure infrared thermoelectric detector.

6. The preparation method according to claim 5, characterized in that, In step S4, the micro-area alignment and transfer is performed using a micromanipulation platform to align the Nb3I8 nanosheets supported on the glass slide to the first electrode and the second electrode at a preset position.

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