Terahertz detector and preparation method of terahertz detector

Abstract

The application discloses a ternary transition metal chalcogenide and application thereof in a terahertz detector, and realizes high-speed, high-sensitivity and room-temperature wide-spectrum terahertz detection under the driving of a strong topological surface state of the ternary transition metal chalcogenide.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of micro-nano manufacturing technology, in particular to a ternary transition metal chalcogenide compound and its application in a terahertz detector. BACKGROUND

[0002] Since the discovery of graphene in 2004, two-dimensional materials have been widely used in optoelectronic detection, sensors, lasers, new storage and superconducting due to their unique optical and electrical properties. So far, most of the research on two-dimensional materials is based on unary and binary systems, and gradually tends to be saturated. The ternary system, the most typical representative of which is the ternary transition metal chalcogenide, introduces the freedom of elements, making the crystal structure more diverse.

[0003] In recent years, topological material systems have attracted widespread attention due to their unique band structure, high mobility, nonlinear response, and abnormal Hall effect. Since Professor Sun Dong's research team at Peking University proposed the enhanced mid-infrared photoelectric response of the Berry curvature in TaIrTe4 in 2019, more and more people have begun to pay attention to the application of similar topological enhancement mechanisms in the field of terahertz detection.

[0004] Terahertz waves (0.1-10 THz, wavelength 30 μm-3 mm) are between microwaves and infrared, with unique advantages such as high bandwidth, safety, water absorption, fingerprint spectrum, and high penetration, and have wide application prospects in high-speed communication, security, biomedicine, and non-destructive testing. For a long time, due to the lack of effective terahertz sources, detectors, and modulators, etc., the advantage of this spectrum resource has not been fully utilized, and a high-speed, high-sensitivity, room-temperature-operable terahertz detector is one of the core components of terahertz applications. The commercially available terahertz detector is difficult to achieve a good balance between response speed, response degree, operating temperature, and response spectral range. Therefore, it is urgent to explore new material systems, advantage device structures, and new response mechanisms to realize high-performance wide-spectrum terahertz detection driven by new physical mechanisms at room temperature.

[0005] The information disclosed in this BACKGROUND section is only for the purpose of increasing the understanding of the background of the present application and should not be taken as an acknowledgment or any form of suggestion that this information forms prior art that is publicly known. SUMMARY

[0006] The purpose of the present application is to provide a ternary transition metal chalcogenide compound and its application in a terahertz detector, by constructing a ternary transition metal chalcogenide compound with a strong topological surface state, and loading a high-gain antenna structure, high-speed, high-sensitivity room-temperature wide-spectrum terahertz detection is realized under the driving of the strong topological surface state.

[0007] To achieve the above object, embodiments of the present application provide a ternary transition metal chalcogenide compound synthesized by a chemical vapor transport method with three elements A, B and C, wherein the element A includes tantalum or niobium, the element B includes palladium or platinum, and the element C includes selenium or tellurium.

[0008] In one or more embodiments of the present application, when synthesized by the chemical vapor transport method, the synthesis environment is controlled to be a vacuum environment, the synthesis temperature is 750-850℃, and the synthesis time is seven days.

[0009] Embodiments of the present application also provide a terahertz detector including a substrate, a channel material layer and an electrode. The channel material layer is disposed on the substrate, the channel material in the channel material layer includes the ternary transition metal chalcogenide compound described above, and the electrode is connected to the channel material layer.

[0010] In one or more embodiments of the present application, the terahertz detector further includes an antenna structure formed on the substrate and connected to the channel material layer and the electrode.

[0011] In one or more embodiments of the present application, the antenna structure includes a log-periodic antenna, a bowtie dipole antenna or a spiral antenna.

[0012] In one or more embodiments of the present application, the ternary transition metal chalcogenide compound is a tantalum-palladium-selenium single crystal.

[0013] In one or more embodiments of the present application, the substrate includes silicon, sapphire, quartz or PET.

[0014] Embodiments of the present application also provide a preparation method of a terahertz detector, including: providing a substrate; providing a channel material including the ternary transition metal chalcogenide compound described above, transferring the channel material to the surface of the substrate to form a channel material layer; and forming an electrode on the substrate, the electrode being connected to the channel material layer.

[0015] In one or more embodiments of the present application, the preparation method of the terahertz detector further includes a step of forming an antenna structure on the substrate, the antenna structure being connected to the channel material layer, and the electrode being connected to the antenna structure.

[0016] In one or more embodiments of the present application, the preparation method of the terahertz detector further includes an annealing process to optimize the contact between the channel material and the electrode.

[0017] In one or more embodiments of the present application, the providing of the channel material, the transferring of the channel material to the substrate surface to form a channel material layer, comprises: preparing the channel material: in a vacuum environment, heating A, B, C three elements in stoichiometric ratio at 750-850°C for seven days, and then reducing the temperature to ambient temperature to obtain a ternary transition metal chalcogenide; cleaving the ternary transition metal chalcogenide into ternary transition metal chalcogenide nanosheets by mechanical exfoliation; and transferring the ternary transition metal chalcogenide nanosheets to the substrate surface by a PDMS dry transfer method.

[0018] Compared with the prior art, the ternary transition metal chalcogenide according to the embodiment of the present application has a strong topological surface state and a high mobility, and based on the band transition near the strong linear dispersion band and the high electron mobility, the ternary transition metal chalcogenide is applied to a terahertz detector to realize high-speed, high-sensitivity, room-temperature wide-spectrum terahertz detection.

[0019] The ternary transition metal chalcogenide according to the embodiment of the present application can be clearly observed to have a very strong pure topological surface state and a theoretical high mobility corresponding to a linear dispersion relationship through basic characterization and band structure characterization, and at the same time, the high mobility is experimentally verified through low-temperature Hall transport testing, which is conducive to the preparation of high-speed devices and the participation of quasi-particles in detection to help improve the response sensitivity of the device. The ternary transition metal chalcogenide is applied to a terahertz detector to realize high-speed, high-sensitivity, room-temperature wide-spectrum terahertz detection. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is an optical microscope image of a ternary transition metal chalcogenide tantalum-palladium-selenium single crystal according to an embodiment of the present application;

[0021] Figure 2 is an X-ray diffraction spectrum of a ternary transition metal chalcogenide tantalum-palladium-selenium single crystal according to an embodiment of the present application;

[0022] Figure 3 is a band structure diagram of a ternary transition metal chalcogenide tantalum-palladium-selenium single crystal according to an embodiment of the present application;

[0023] Figure 4 is a diagram of the carrier mobility of a ternary transition metal chalcogenide tantalum-palladium-selenium single crystal according to an embodiment of the present application, which is obtained by transport fitting and changes with temperature;

[0024] Figure 5 is a device structure diagram of a terahertz detector according to an embodiment of the present application;

[0025] Figure 6 is a response spectrum diagram of a tantalum-palladium-selenium-based terahertz detector according to an embodiment of the present application in the range of 0.02-0.3 THz.

[0026] Figure 7 Waveform of a tantalum-palladium-selenium-based terahertz detector under different bias according to an embodiment of the present application;

[0027] Figure 8 Response time graph of a tantalum-palladium-selenium-based terahertz detector according to an embodiment of the present application (extracted from the response waveform of zero bias). DETAILED DESCRIPTION

[0028] The specific embodiments of the present application will be described in detail below with reference to the accompanying drawings, but it should be understood that the scope of protection of the present application is not limited by the specific embodiments.

[0029] Unless otherwise clearly indicated, in the entire specification and claims, the term "comprising" or its variants such as "contain" or "comprise" and the like are understood to encompass the stated elements or components, without excluding the presence of other elements or components.

[0030] As described in the background, two-dimensional materials have a wide range of applications in optoelectronic detection, sensors, lasers, new storage and superconductivity due to their unique optical and electrical properties. Most of the research on two-dimensional materials is based on unary and binary systems, and is gradually saturated. The ternary system, the most typical representative of which is ternary transition metal chalcogenide, introduces the freedom of elements, making the crystal structure more diverse.

[0031] In addition, the high mobility, nonlinear absorption, magnetism, anisotropy and topological state transition in ternary transition metal chalcogenides provide a new platform for the study of high-performance terahertz detection, magnetic transition, superconductivity and non-trivial topological phase. At the same time, the rich crystal structure and unique properties of ternary transition metal chalcogenides promote the construction of novel optoelectronic devices, which have great application potential in the field of high-performance optoelectronic detection in the future.

[0032] Current commercial terahertz detectors are difficult to achieve a good balance between response speed, sensitivity, operating temperature and response spectral range. Terahertz detection driven by new states in topological quantum materials is a major research focus in recent years, but the correlation between the detection mechanism and the intrinsic properties of the material is not clear. On the other hand, the study of adjusting the working state of the device by regulating the quantum state is also relatively scarce.

[0033] Therefore, it is urgent to explore new material systems, advantageous device structures and new response mechanisms to realize high-performance wide-spectrum terahertz detection driven by new physical mechanisms at room temperature.

[0034] Based on this, the high-speed, high-sensitivity room-temperature wide-spectrum terahertz detector is realized by constructing the high-quality crystal ternary transition metal chalcogenide with strong topological surface state and high mobility, preferably tantalum palladium selenium, combining the device structure and high-gain terahertz antenna, which is a good supplement to the existing terahertz detector. The basic physical properties and terahertz response mechanism are related through band structure analysis and transport testing. At the same time, by applying the ternary transition metal chalcogenide tantalum palladium selenium to the terahertz detector and adjusting the Fermi level position through simple means such as gate voltage control or doping, the device can work in an optimal state.

[0035] An embodiment of the present application provides a ternary transition metal chalcogenide synthesized by a chemical vapor transport method with three elements A, B and C; wherein the A element includes tantalum or niobium, the B element includes palladium or platinum, and the C element includes selenium or tellurium.

[0036] The preparation method of the ternary transition metal chalcogenide tantalum palladium selenium single crystal is described in detail below with the A element being tantalum, the B element being palladium, and the C element being selenium.

[0037] For example, first, put 1.0 g of tantalum, palladium and selenium powders (Alfa aesar, 99.99%) with a total weight of 1.0 g into a quartz tube according to the stoichiometric ratio, select an appropriate amount of iodine as a transport agent (3mg / ml), and then vacuum seal. Next, place the quartz tube in a double-temperature zone tube furnace, and raise the temperature of the low-temperature end and the high-temperature end to 750 DEG C and 850 DEG C respectively. After heating and growing for seven days, slowly reduce the temperature of the quartz tube to room temperature, and obtain high-quality needle-shaped tantalum palladium selenium crystals with obvious metallic luster in the low-temperature zone (growth zone), as shown in the accompanying Figure 1 .

[0038] The crystal phase, element composition and crystal structure of the tantalum palladium selenium single crystal are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), spherical aberration-corrected transmission electron microscopy (STEM), etc. The XRD characterization is shown in the accompanying Figure 2 , Figure 2 , wherein the abscissa represents the 2θ angle (degree), and the ordinate represents the intensity. By comparing with the standard PDF card, the crystal phase of the synthesized single crystal can be confirmed, and it is confirmed that the component and structure required for construction are obtained. Figure 2

[0039] The band structure of the synthesized tantalum palladium selenium single crystal is analyzed by angle-resolved photoelectron spectroscopy (ARPES), and the strong topological surface state and linear dispersion relationship are observed, and the results are shown in the accompanying Figure 3 . Figure 3 ​In the figure, the abscissa represents the x-direction wave vector (Angstroms), and the ordinate represents the energy (electron volts), TSS represents a topological surface state (TSS), a topological surface state, BVB: bulk valence band structure (BVB), a bulk valence band. Figure 3 The band structure diagram in the figure can intuitively reflect the strong topological surface state existing in the tantalum-palladium-selenium single crystal, and lay a foundation for construction of a high-performance terahertz detector.

[0040] Low-temperature transport research on carrier dynamics in the tantalum-palladium-selenium single crystal; the electron and hole mobilities in the tantalum-palladium-selenium single crystal are calculated by fitting the results of six-terminal Hall test combined with a double-band model, and the results are shown in the figure. Figure 4 Figure 4 In the figure, the abscissa represents temperature (Kelvin), and the ordinate represents mobility (square centimeters per volt-second). Figure 4 The carrier mobility fitting results in the figure show that the tantalum-palladium-selenium single crystal has the excellent characteristic of high mobility, which provides a material basis for preparation of a high-speed terahertz detector.

[0041] Based on this, the application synthesizes a high-quality single crystal Ta2PdSe6, and first characterizes the band structure of the material through experimental means, and a very strong pure topological surface state and a theoretical high mobility corresponding to a linear dispersion relationship can be clearly observed; at the same time, through low-temperature Hall transport test, it is experimentally proved that it has high mobility, which is conducive to the preparation of high-speed devices, and the participation of quasi-fermions in detection also helps to improve the response sensitivity of the device.

[0042] Reference Figure 5 As shown in the figure, the application further provides a terahertz detector, which comprises a substrate 10, a channel material layer 20, an antenna structure 30 and an electrode 40. The channel material layer 20 is arranged on the substrate 10, and the channel material in the channel material layer 20 comprises the ternary transition metal chalcogenide compound described above. The antenna structure 30 is formed on the substrate 10 and connected with the channel material layer 20 and the electrode 40. The electrode 40 is connected with the channel material layer 20 through the antenna structure 30. The ternary transition metal chalcogenide compound is synthesized by a chemical vapor transport method with three elements A, B and C; the element A comprises tantalum, the element B comprises palladium or platinum, and the element C comprises selenium or tellurium. Preferably, the ternary transition metal chalcogenide compound is tantalum-palladium-selenium. The substrate 10 comprises silicon, sapphire, quartz or a flexible substrate such as PET. The antenna structure 30 comprises a logarithmic-periodic antenna, a bowtie dipole antenna or a spiral antenna, and the like high-gain broadband antenna.

[0043] ​The application further provides a preparation method of a terahertz detector, comprising: providing a substrate; providing a channel material, the channel material comprising the ternary transition metal chalcogenide compound; transferring the channel material to a surface of the substrate to form a channel material layer; forming an antenna structure on the substrate, the antenna structure being connected with the channel material layer; and forming an electrode on the substrate, the electrode being connected with the antenna structure and the channel material layer through the antenna structure. The ternary transition metal chalcogenide compound is synthesized by a chemical vapor transport method using three elements A, B and C; the element A comprises tantalum or niobium, the element B comprises palladium or platinum, and the element C comprises selenium or tellurium. Preferably, the ternary transition metal chalcogenide compound is tantalum-palladium-selenium.

[0044] The preparation method of the terahertz detector based on the ternary transition metal chalcogenide-tantalum-palladium-selenium single crystal is specifically introduced as follows:

[0045] Firstly, an antenna structure suitable for a terahertz frequency band to be tested is designed by using an electromagnetic simulation software HFSS, and a logarithmic periodic antenna is preferably used. The designed antenna structure is drawn into a layout as shown in FIG. 2. Figure 5

[0046] Secondly, a laser direct writing or electron beam lithography device is used to etch various structures required, including the antenna structure and a square electrode structure for a lead wire. The device structure required is prepared on an intrinsic silicon substrate (resistivity p>20000 Ω·cm) by combining subsequent film plating, etching and stripping processes. In this step, in order to reduce the influence of the substrate effect, high-resistivity intrinsic silicon is used as the substrate to reduce the loss of terahertz waves and enhance the coupling.

[0047] Then, the tantalum-palladium-selenium single crystal prepared is mechanically peeled off by using blue glue or white glue with strong viscosity, and cleaved into tantalum-palladium-selenium single crystal nanosheets. Subsequently, the PDMS is used to pick up the material on the adhesive tape, and the nanosheet with a required thickness is transferred to a suitable position of the channel material layer of the device by using a fine transfer platform. The PDMS dry transfer is a full-dry transfer method based on polydimethylsiloxane (PDMS). The square electrode structure for the lead wire is arranged at a certain distance from the channel material-tantalum-palladium-selenium single crystal nanosheet, so as to avoid micro-damage to the channel material during the lead wire process.

[0048] Then, annealing treatment is performed to form better contact between the material and the electrode.

[0049] Finally, mature semiconductor packaging technology is used to package the prepared terahertz detector with a lead wire, so as to facilitate subsequent testing.

[0050] ​In order to test the performance of the terahertz detector of the present application, the above-mentioned chemical vapor transport method can be used to synthesize a unary or binary transition metal chalcogenide compound, and the above-mentioned preparation method of the terahertz detector can be used to prepare the unary or binary transition metal chalcogenide compound into a terahertz detector, wherein the various parameter conditions (thickness, size, etc.) are consistent with the above-mentioned embodiments.

[0051] The performance of the terahertz detector prepared by using the ternary transition metal chalcogenide compound as the channel material and the terahertz detector prepared by using other binary or unary transition metal chalcogenide compound as the channel material is tested by using the self-built terahertz test system. Under the same test conditions, by comparing the response photocurrent and response time of the two, it can be obtained that the application of the ternary transition metal chalcogenide compound in the terahertz detector greatly improves the responsivity and response speed of the terahertz detector. Among them, the self-built terahertz test system uses a microwave source to carry a VDI frequency multiplier to realize the terahertz test requirement of 0.02-0.3 THz. The terahertz beam is converged by a pair of off-axis mirrors and then hits the detector. The signal is amplified by a preamplifier, and then the signal is read by a lock-in amplifier. At the same time, the preamplifier can be connected to an oscilloscope to read the response waveform.

[0052] The results are shown in Figure 6 , Figure 7 and Figure 8 . Figure 6 is the response spectrum diagram of the tantalum-palladium-selenium-based terahertz detector according to an embodiment of the present application at 0.02-0.3 THz, wherein the abscissa represents the frequency (terahertz), and the ordinate represents the photocurrent (microampere); Figure 7 is the waveform diagram of the tantalum-palladium-selenium-based terahertz detector according to an embodiment of the present application under different biases, wherein the abscissa represents the time (millisecond), and the ordinate represents the normalized photocurrent; Figure 8 is the response time diagram of the tantalum-palladium-selenium-based terahertz detector according to an embodiment of the present application (extracted from the response waveform of zero bias), wherein the abscissa represents the time (microsecond), and the ordinate represents the normalized photocurrent. Figure 6-8 It is proved that the terahertz detector based on the tantalum-palladium-selenium single crystal has the room temperature detection capability of high speed, high sensitivity and wide spectrum.

[0053] The present application synthesizes high-quality ternary transition metal chalcogenide compounds, especially single crystal Ta2PdSe6, and for the first time characterizes the band structure of the material by experimental means. The very strong pure topological surface state and the theoretical high mobility corresponding to the linear dispersion relationship can be clearly observed. At the same time, the high mobility is proved by low-temperature Hall transport test, which is beneficial to the preparation of high-speed devices, and the participation of quasi-fermions in detection also helps to improve the response sensitivity of the device.

[0054] In addition, studies have shown that Ta2PdSe6 itself is also a thermoelectric material with excellent thermoelectric performance. However, devices based on photothermoelectric effect usually need to be constructed asymmetrically to enhance the thermoelectric response of the device. The asymmetry can be the intrinsic asymmetry of the crystal structure, the asymmetry of the device structure or the asymmetry of the external excitation. The Ta2PdSe6 material belongs to the monoclinic system, and has low symmetry in the crystal structure. Even without additional external asymmetry, the photothermoelectric effect can also work. Finally, on the basis of the material, in order to compensate for the weak coupling caused by the mismatch between the terahertz detector and the terahertz wavelength, the coupling between light and matter is enhanced by combining the terahertz antenna structure, and the terahertz detector is constructed through the traditional micro-nano processing technology. Under the synergistic driving of the photothermoelectric effect and the strong topological surface state, the device realizes high-speed and high-sensitivity terahertz detection.

[0055] It can be understood that the trench material in the terahertz detector can also be doped, and the material can be Ta2PdSe6 to further increase the electron mobility; or the position of the Fermi level is adjusted by an external voltage (gate voltage adjustment) to adjust the operating point of the device, thereby further improving the performance of the detector.

[0056] The above description uses tantalum-palladium-selenium single crystal as a specific example of ternary transition metal chalcogenide compounds applied to a terahertz detector, but it can be understood that other ternary transition metal chalcogenide compounds with strong topological surface states similar to tantalum-palladium-selenium single crystal, such as tantalum-palladium-tellurium and tantalum-platinum-tellurium, can also be used as channel materials to improve the performance of the terahertz detector.

[0057] Compared with the prior art, the ternary transition metal chalcogenide compound according to the embodiment of the present application has a strong topological surface state and high mobility. Based on the interband transition near the strong linear dispersion band and the high electron mobility, it is applied to a terahertz detector to realize high-speed, high-sensitivity and room-temperature wide-spectrum terahertz detection.

[0058] The ternary transition metal chalcogenide compound according to the embodiment of the present application can be clearly observed to have a strong pure topological surface state and a theoretical high mobility corresponding to the linear dispersion relationship through basic characterization and band structure characterization. At the same time, the high mobility is experimentally verified through low-temperature Hall transport testing, which is beneficial to the preparation of high-speed devices, and the participation of quasi-particles in detection also helps to improve the response sensitivity of the device. When it is applied to a terahertz detector, high-speed, high-sensitivity and room-temperature wide-spectrum terahertz detection is realized.

[0059] The terahertz detector according to the embodiment of the present application, by analyzing and transporting testing the band structure of ternary transition metal chalcogenide, especially tantalum-palladium-selenium, the basic physical properties and the terahertz response mechanism are disassociated, the change of the intrinsic property of the material is associated with the change of the terahertz performance, and a new detection mechanism possibly existing in the new material system is explored.

[0060] The foregoing description of specific exemplary embodiments of the application has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the application to the precise forms disclosed, and various modifications and variations are possible in light of the above teachings. It is intended that the embodiments be chosen and / or described to best explain the principles of the application and its practical application, and to thereby enable one skilled in the art to best utilize the application and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the application be defined by the claims and their equivalents.

Claims

1. A terahertz detector, characterized by, The application relates to a substrate, a channel material layer arranged on the substrate, and an electrode connected to the channel material layer. The channel material in the channel material layer comprises ternary transition metal chalcogenide with strong topological surface state and high mobility. The ternary transition metal chalcogenide is synthesized by a chemical vapor transport method with three elements A, B and C. The element A comprises tantalum or niobium, the element B comprises palladium or platinum, and the element C comprises selenium or tellurium. The synthesis is performed in a vacuum environment at a temperature of 750-850 DEG C for seven days.

2. The terahertz detector of claim 1, wherein, The antenna structure comprises a logarithmic-periodic antenna, a bowtie dipole antenna or a spiral antenna.

3. The terahertz detector of claim 2, wherein, The ternary transition metal chalcogenide is a tantalum-palladium-selenium single crystal.

4. The terahertz detector of claim 1, wherein, The substrate comprises silicon, sapphire, quartz or PET.

5. A method of fabricating a terahertz detector, comprising: The application also relates to a method for manufacturing a transistor. The method comprises the following steps. The channel material is transferred to the surface of the substrate to form a channel material layer. An electrode is formed on the substrate and connected to the channel material layer. The method further comprises the step of forming an antenna structure on the substrate.

6. The method of claim 5, wherein the substrate is a silicon substrate. The antenna structure is connected to the channel material layer.

7. The method of claim 5, wherein the method further comprises forming a passivation layer on the surface of the substrate. The electrode is connected to the antenna structure.

8. The method of claim 5, wherein the substrate is a silicon substrate. The method further comprises an annealing process to optimize the contact between the channel material and the electrode. The method for providing the channel material and transferring the channel material to the surface of the substrate to form a channel material layer comprises the following steps. The channel material is prepared by heating the three elements A, B and C in a stoichiometric ratio at 750-850 DEG C for seven days in a vacuum environment. The ternary transition metal chalcogenide is cleaved into ternary transition metal chalcogenide nanosheets by mechanical exfoliation. The ternary transition metal chalcogenide nanosheets are dry-transferred to the surface of the substrate by using PDMS.

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