Terahertz wave emitter and method of manufacturing the same

Abstract

The application discloses a terahertz wave emitter and a manufacturing method thereof. The manufacturing method comprises the following steps: providing a substrate with a first surface and a second surface opposite to each other; forming a functional layer on the first surface; and forming a ferromagnetic metal layer on the side of the functional layer away from the substrate; wherein the functional layer is used for improving the resistance and spin Hall angle of the terahertz wave emitter. In the manufacturing method of the terahertz wave emitter, the functional layer is formed on the first surface, and the functional layer can improve the resistance and spin Hall angle of the terahertz wave emitter when the terahertz wave is formed, so that the intensity of the terahertz wave generated by the terahertz wave emitter can be improved.

Description

Technical Field

[0001] This invention relates to the field of terahertz optoelectronic devices, and more specifically, to a terahertz wave transmitter and its manufacturing method. Background Technology

[0002] Existing terahertz wave transmitters are typically heterostructures of ferromagnetic and non-ferromagnetic metals, utilizing the inverse spin Hall effect of the non-ferromagnetic metal to generate terahertz waves. Current research on this system mainly focuses on the selection of ferromagnetic and non-ferromagnetic materials, the design of the number and thickness of layers, and interface improvements to enhance the intensity and bandwidth of terahertz waves. However, in these studies, selecting traditional heavy metals and heavy metal alloys as non-ferromagnetic layers has proven insufficient to further increase terahertz wave intensity. Summary of the Invention

[0003] In view of the above, this application provides a terahertz wave transmitter and a method for manufacturing the same, as follows: A method for manufacturing a terahertz wave transmitter, the method comprising:

[0004] A substrate is provided having opposing first and second surfaces;

[0005] A functional layer is formed on the first surface;

[0006] A ferromagnetic metal layer is formed on the side of the functional layer opposite to the substrate;

[0007] The functional layer is used to improve the resistance and spin Hall angle of the terahertz wave transmitter.

[0008] Preferably, in the above manufacturing method, the method of forming the functional layer includes: forming a non-ferromagnetic metal layer on the first surface;

[0009] The non-ferromagnetic metal layer is doped to form the functional layer.

[0010] Preferably, in the above manufacturing method, the doping material in the non-ferromagnetic metal layer includes: insulating material and / or semiconductor material.

[0011] Preferably, in the above manufacturing method, the material used to form the non-ferromagnetic metal layer includes one or more of Au, Ag, Pt, Pd, W, Ta, Cr, and Ir.

[0012] Preferably, in the above manufacturing method, multi-target co-sputtering technology is used to dope the non-ferromagnetic metal layer.

[0013] Preferably, in the above manufacturing method, the thickness of the functional layer ranges from 1 to 15 nm.

[0014] Preferably, in the above manufacturing method, the manufacturing method further includes: forming a protective layer on the side of the ferromagnetic metal layer opposite to the functional layer;

[0015] A magnetic field device is provided on the side of the protective layer opposite to the ferromagnetic metal layer;

[0016] The protective layer is used to protect the ferromagnetic metal layer to prevent oxidation; the magnetic field device is used to regulate the polarization of the terahertz waves generated by the terahertz wave transmitter.

[0017] Based on the above manufacturing method, this application proposes a terahertz wave transmitter, the transmitter comprising: a substrate having opposing first and second surfaces;

[0018] A functional layer located on the first surface, the functional layer being used to improve the resistance and spin Hall angle of the terahertz wave transmitter;

[0019] A ferromagnetic metal layer located on the side of the functional layer opposite to the substrate.

[0020] Preferably, in the above-described transmitter, the functional layer includes: a doped material and a non-ferromagnetic metal layer.

[0021] Preferably, in the above-described transmitter, the transmitter further includes: a protective layer located on the side of the ferromagnetic metal layer opposite to the functional layer;

[0022] A magnetic field device located on the side of the protective layer away from the ferromagnetic metal layer.

[0023] As described above, this application proposes a terahertz wave transmitter and its fabrication method. The fabrication method includes: providing a substrate having opposing first and second surfaces; forming a functional layer on the first surface; and forming a ferromagnetic metal layer on the side of the functional layer facing away from the substrate. The functional layer is used to improve the resistance and spin Hall angle of the terahertz wave transmitter when generating terahertz waves. In the fabrication method of the terahertz transmitter, the functional layer is formed on the first surface, and the functional layer can improve the resistance and spin Hall angle of the terahertz wave transmitter, thereby increasing the intensity of the terahertz waves generated by the terahertz wave transmitter. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0025] The structures, proportions, sizes, etc., shown in the accompanying drawings are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the implementation conditions of this application. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size should still fall within the scope of the technical content disclosed in this application, provided that they do not affect the effects and purposes that this application can produce.

[0026] Figure 1 This is a flowchart illustrating a method for manufacturing a terahertz wave transmitter according to an embodiment of this application;

[0027] Figure 2 This is a flowchart illustrating another method for manufacturing a terahertz wave transmitter according to an embodiment of this application;

[0028] Figure 3 This is a flowchart illustrating another method for manufacturing a terahertz wave transmitter according to an embodiment of this application;

[0029] Figure 4 This is a schematic diagram of the structure of a terahertz wave transmitter according to another embodiment of this application;

[0030] Figure 5 This is a schematic diagram of the structure of the functional layer described in another embodiment of this application;

[0031] Figure 6 This is a schematic diagram of another terahertz wave transmitter in another embodiment of this application;

[0032] Figure 7 This is a comparison diagram of the terahertz waves generated by a doped and an undoped terahertz wave transmitter according to another embodiment of this application.

[0033] Figure 8 This is a schematic diagram of the structure of another terahertz wave transmitter in another embodiment of this application. Detailed Implementation

[0034] The embodiments of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0035] Terahertz waves are generally defined as electromagnetic waves with frequencies ranging from 0.1 to 10 THz. Because the terahertz wave band lies between microwaves and infrared light, it is difficult to generate and detect using traditional electronic and photonic methods. Therefore, for many years, research on this band of electromagnetic waves was minimal, and the region covered by terahertz waves was known as the "Terahertz gap." In recent years, advancements in ultrafast laser technology and high-precision circuit fabrication have led to the rapid development of terahertz technology. Due to its unique frequency band, terahertz waves possess many excellent properties, such as penetrability, security, and fingerprint-like characteristics, making them significant in materials science and physical science research.

[0036] Terahertz wave generation and detection are crucial aspects of terahertz technology; therefore, terahertz wave transmitters are key components of terahertz systems. Traditional photonic methods generate terahertz waves using the optical rectification effect of nonlinear optical crystals and photoconductive antennas. However, in photoconductive antenna technology, the inherent phonon absorption of the material limits the intensity and bandwidth of the generated terahertz waves, and photoconductive antennas are expensive. In optical rectification, terahertz pulse waves are generated through the nonlinear effect of nonlinear crystals. In this technology, the phase matching of the excitation light and the terahertz light within the crystal significantly affects the bandwidth and terahertz intensity.

[0037] Currently, terahertz wave transmitters based on spintronics have effectively solved the problems of narrow bandwidth and high cost. Terahertz wave transmitters are usually heterostructures of ferromagnetic metals and non-ferromagnetic metals. They utilize the inverse spin Hall effect of non-ferromagnetic metals to generate terahertz waves. However, for heterostructures of ferromagnetic metals and non-ferromagnetic metals, it is necessary to find materials with larger spin Hall angles to make the non-ferromagnetic metal layers, or to improve the spin Hall angle of traditional metals through certain means, so as to improve the intensity of terahertz waves.

[0038] Based on the above problems, this application proposes a terahertz wave transmitter and its manufacturing method. In the manufacturing method, the functional layer is formed, which can improve the resistance and spin Hall angle of the terahertz wave transmitter when generating terahertz waves, thereby improving the intensity of the terahertz waves generated by the terahertz wave transmitter.

[0039] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0040] refer to Figure 1 , Figure 1 This is a flowchart illustrating a method for manufacturing a terahertz wave transmitter according to an embodiment of this application. The method includes:

[0041] Step S11: Provide a substrate 1 having a first surface S1 and a second surface S2 opposite to each other;

[0042] Step S21: Form a functional layer 2 on the first surface S1;

[0043] Step S31: A ferromagnetic metal layer 3 is formed on the side of the functional layer 2 opposite to the substrate 1;

[0044] The functional layer 2 is used to improve the resistance and spin Hall angle of the terahertz wave transmitter. The terahertz wave transmitter fabricated according to the method described in this embodiment mainly comprises three core layers: the substrate 1, the functional layer 2, and the ferromagnetic metal layer 3. Since the terahertz wave transmitter generates terahertz waves dependent on the incident femtosecond laser, the substrate 1 is required to be made of a material that can transmit visible or near-infrared femtosecond lasers. This material includes, but is not limited to, MgO and SiO2, and the thickness of the substrate 1 is required to be between 0.2 mm and 1 mm. The functional layer 2 can improve the resistance and spin Hall angle of the terahertz wave transmitter, thereby increasing the intensity of the generated terahertz wave. An external magnetic field is applied to the ferromagnetic metal layer 3, with the direction of the magnetic field parallel to the plane of the ferromagnetic metal layer 3, and the polarization of the generated terahertz wave can be controlled by the magnetic field. As can be seen from the above, the implementation of this invention also requires an external femtosecond laser source. The femtosecond laser is incident on the second surface S2 of the substrate 1 in a direction perpendicular to the substrate 1, and sequentially passes through the substrate 1, the functional layer 2, and the ferromagnetic metal layer 3, radiating terahertz waves outward. The ferromagnetic metal layer 3 is formed on the side of the functional layer 2 opposite to the substrate 1 by techniques such as magnetron sputtering or electron beam evaporation.

[0045] refer to Figure 2 , Figure 2 This is a flowchart illustrating another method for manufacturing a terahertz wave transmitter according to an embodiment of this application. In the above manufacturing method, the method for forming the functional layer 2 includes:

[0046] Step S211: Form a non-ferromagnetic metal layer 21 on the first surface S1;

[0047] Step S212: Doping the non-ferromagnetic metal layer 21 to form the functional layer 2.

[0048] refer to Figure 2As described above, the manufacturing method of this application forms the functional layer 2 to improve the resistance and spin Hall angle of the terahertz wave emitter when generating terahertz waves. The formation of the functional layer 2 includes: growing the non-ferromagnetic metal layer 21 on the first surface S1 using techniques such as magnetron sputtering or electron beam evaporation, and then doping the non-ferromagnetic metal layer 21 to form the functional layer 2. When doping the non-ferromagnetic metal layer 21, the doping concentration needs to be determined based on the material of the non-ferromagnetic metal layer 21 and the atomic ratio of the dopant material 22. For example, if the non-ferromagnetic metal layer 21 is Pt and the dopant material 22 is MgO, the doping concentration will be used. 1-x (MgO) x In this context, 'x' represents the atomic percentage. A larger 'x' results in higher electrical resistance, but also a significantly reduced spin diffusion length, which is detrimental to terahertz wave generation. When 'x' is between 0.5 and 2.0, a larger self-selected Hall angle and a suitable spin diffusion length can be obtained, leading to stronger terahertz waves. Of course, the atomic ratio required to obtain a larger terahertz wave varies considerably depending on the material and the impurities used.

[0049] In the above manufacturing method, the doped material 22 in the non-ferromagnetic metal layer 21 includes insulating material and / or semiconductor material, which are used to improve barrier properties and adjust the self-selected Hall angle and spin diffusion length.

[0050] As described above, when forming the functional layer 2, the non-ferromagnetic metal layer 21 needs to be doped. The dopant material in the non-ferromagnetic metal layer 21 includes insulating materials and / or semiconductor materials. Insulating materials and / or semiconductor materials are used as dopant materials because of their poor conductivity. As described above, the terahertz wave emitter generates electromagnetic waves by a femtosecond laser incident from the second surface S2 of the substrate, exciting an ultrafast spin current within the ferromagnetic metal layer 3. This spin current enters the functional layer 2 from the ferromagnetic metal layer 3, generating a transient charge current in the functional layer 2 through the inverse spin Hall effect, thereby radiating terahertz waves. This requires the functional layer 2 to have low conductivity, i.e., the dopant material 22 forming the functional layer 2 must have low conductivity to avoid the loss of the instantaneous charge generated in the functional layer.

[0051] In the above manufacturing method, the material used to form the non-ferromagnetic metal layer includes one or more of Au, Ag, Pt, Pd, W, Ta, Cr, and Ir.

[0052] As can be seen from the above, forming the functional layer 2 includes forming the non-ferromagnetic metal layer 21 on the first surface S1, wherein the material forming the non-ferromagnetic metal layer includes one or more of Au, Ag, Pt, Pd, W, Ta, Cr and Ir, or a composite material based on the above materials and the doping material 22.

[0053] In the above manufacturing method, multi-target co-sputtering technology is used to dope the non-ferromagnetic metal layer 21.

[0054] Multi-target co-sputtering is a process technology that uses multiple targets to simultaneously sputter composite materials, belonging to physical vapor deposition. Its advantages include ease of adjusting material composition and high effectiveness in material composition screening. The atomic ratio of the thin film obtained by doping the non-ferromagnetic metal layer 21 using multi-target co-sputtering technology is better controlled, and the atomic ratio of the thin film obtained by multi-target sputtering technology can be determined by detection techniques.

[0055] In the above manufacturing method, the thickness of the functional layer 2 ranges from 1 to 15 nm.

[0056] When fabricating the terahertz wave transmitter, the functional layer 2 needs to be grown on the first surface. The thickness of the functional layer 2 is limited during its growth. In this embodiment, the thickness of the functional layer 2 is 1-15 nm, which is the same as the thickness of the ferromagnetic metal layer 3.

[0057] refer to Figure 3 , Figure 3 This is a flowchart illustrating a method for manufacturing a terahertz wave transmitter according to another embodiment of this application. The manufacturing method further includes:

[0058] Step S41: A protective layer 4 is formed on the side of the ferromagnetic metal layer 3 that is away from the functional layer 2;

[0059] Step S51: A magnetic field device is provided on the side of the protective layer 4 away from the ferromagnetic metal layer 3; wherein, the protective layer is used to protect the ferromagnetic metal layer to prevent oxidation; the magnetic field device is used to regulate the polarization of the terahertz wave generated by the terahertz wave transmitter.

[0060] Based on the above, in addition to the three core layers forming the terahertz wave transmitter, a protective layer 4 is also formed on the side of the ferromagnetic metal layer 3 facing away from the functional layer 2 to protect the ferromagnetic metal layer 3 and prevent oxidation. The material forming the protective layer 4 includes, but is not limited to, MgO, SiO2, Al2O3, etc. Furthermore, a magnetic field device is provided on the side of the protective layer 4 facing away from the ferromagnetic metal layer 3. The magnetic field device can be a permanent magnet fixed on a rotating support or an electromagnet. By controlling the magnitude of the current on the two poles, the magnetic field is rotated, thereby regulating the direction of the magnetic field in the plane, and thus regulating the polarization of the terahertz wave generated by the terahertz wave transmitter.

[0061] Based on the above manufacturing method, this application proposes a terahertz wave transmitter.

[0062] refer to Figure 4 , Figure 4 This is a schematic diagram of the structure of a terahertz wave transmitter according to another embodiment of this application. The terahertz wave transmitter includes:

[0063] Substrate 1 has a first surface S1 and a second surface S2 that are opposite to each other;

[0064] A functional layer 2 located on the first surface S1 is used to improve the resistance and spin Hall angle of the terahertz wave transmitter.

[0065] The ferromagnetic metal layer 3 is located on the side of the functional layer 2 facing away from the substrate 1.

[0066] Based on the above manufacturing method, this application also proposes a terahertz wave transmitter, the transmitter comprising: the substrate 1, the functional layer 2 and the ferromagnetic and metallic layer 3, wherein the functional layer 2 can improve the resistance and spin Hall angle of the terahertz wave transmitter when forming terahertz waves, thereby improving the intensity of the terahertz waves generated by the terahertz wave transmitter.

[0067] refer to Figure 5 , Figure 5 The diagram below shows the structure of the functional layer in another embodiment of this application. In the transmitter described above, the functional layer 2 includes: a doped material 22 and a non-ferromagnetic metal layer 21.

[0068] As can be seen from the above, the transmitter includes the functional layer 2, which includes a doped material 22 and a non-ferromagnetic metal layer 21. Doping the non-ferromagnetic metal layer 21 with the doped material 22 can effectively improve the intensity of the terahertz wave generated by the terahertz wave transmitter.

[0069] refer to Figure 6 , Figure 6This is a schematic diagram of another terahertz wave transmitter in another embodiment of this application. The transmitter further includes a protective layer 4 located on the side of the ferromagnetic metal layer 3 facing away from the functional layer 2.

[0070] A magnetic field device located on the side of the protective layer 4 away from the ferromagnetic metal layer 3.

[0071] refer to Figure 6 The transmitter also includes the protective layer 4 and the magnetic field device. The protective layer 4 is provided on the side of the ferromagnetic metal layer 3 away from the functional layer 2 to protect the ferromagnetic metal layer 3 from oxidation. The magnetic field device is provided on the side of the protective layer 4 away from the ferromagnetic metal layer 3 to regulate the direction of the magnetic field in the plane, thereby regulating the polarization of the terahertz wave generated by the terahertz wave transmitter.

[0072] refer to Figure 7 , Figure 7 This is a comparison diagram of the terahertz waves generated by a doped and an undoped terahertz wave emitter according to another embodiment of this application. Figure 7 The illustration uses MgO doping in a SiO2 / Pt / CoFeB structure as an example. Figure 7 The horizontal axis represents the delay time, and the vertical axis represents the intensity of the terahertz wave. As can be seen from the figure, the intensity of the terahertz wave generated by the terahertz wave transmitter formed by the doped non-ferromagnetic metal layer 21 is significantly greater than that generated by the terahertz wave transmitter formed by the undoped non-ferromagnetic metal layer 21.

[0073] refer to Figure 8 , Figure 8 This is a schematic diagram of another terahertz wave emitter according to another embodiment of this application, wherein 1 is a substrate, 2 is a functional layer, 3 is a ferromagnetic metal layer, 5 is an external magnetic field, 6 is an external femtosecond laser, and 7 is the emitted terahertz wave. The process of generating the terahertz wave in the terahertz wave emitter includes: a femtosecond laser 6 is incident from one side of the substrate 1, irradiates the ferromagnetic metal layer 3, and generates an ultrafast spin current within the ferromagnetic metal layer 3. The spin current enters the functional layer 2 from the ferromagnetic metal layer 3, where the ultrafast spin current is converted into a transient charge current through the inverse spin Hall effect, thereby radiating the terahertz wave 7. The intensity of the terahertz wave generated by the inverse spin Hall effect depends on the spin Hall angle of the functional layer 2, and the polarization depends on the magnetization direction of the ferromagnetic metal layer 3. By doping the non-ferromagnetic layer material 21 with insulating materials and / or semiconductor materials, the resistivity and spin Hall angle of the functional layer 2 can be increased, thereby significantly improving the intensity of the terahertz wave. The polarization of the generated terahertz wave can be controlled by changing the direction of the magnetic field applied to the ferromagnetic metal layer 3. Furthermore, the terahertz wave transmitter manufactured using the method of this application has low production costs.

[0074] The various embodiments in this specification are described in a progressive, parallel, or combined manner. Each embodiment focuses on its differences from other embodiments, and similar or identical parts between embodiments can be referred to interchangeably. For the apparatuses disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple, and relevant parts can be referred to the method section.

[0075] It should be noted that, in the description of this application, the drawings and embodiments are illustrative rather than restrictive. The same reference numerals throughout the embodiments identify the same structures. Additionally, for ease of understanding and description, the thicknesses of some layers, films, panels, regions, etc., may be exaggerated in the drawings. It is also understood that when an element such as a layer, film, region, or substrate is referred to as being "on" another element, the element may be directly on the other element or there may be intermediate elements. Furthermore, "on" means positioning an element on or below another element, but does not inherently mean positioning it above another element according to the direction of gravity.

[0076] The terms "upper," "lower," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. When a component is considered to be "connected" to another component, it can be directly connected to the other component or there may be a component positioned centrally in the middle.

[0077] It should also be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or apparatus comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or apparatus that includes the aforementioned element.

[0078] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for manufacturing a terahertz wave transmitter, characterized in that, The manufacturing method includes: A substrate is provided having opposing first and second surfaces; A non-ferromagnetic metal layer is formed on the first surface, wherein the doping material in the non-ferromagnetic metal layer includes: insulating material and / or semiconductor material; A multi-target co-sputtering technique is used to dope the non-ferromagnetic metal layer to form a functional layer. The doping concentration is determined based on the material of the non-ferromagnetic metal layer and the atomic ratio of the dopant material. Specifically, the non-ferromagnetic metal layer is made of Pt, the dopant material is MgO, and the functional layer is made of Pt. 1-x (MgO) x Where x represents the atomic percentage, and x ranges from 0.5 to 2.0; A ferromagnetic metal layer is formed on the side of the functional layer opposite to the substrate; The functional layer is used to improve the resistance and spin Hall angle of the terahertz wave transmitter.

2. The manufacturing method according to claim 1, characterized in that, The thickness range of the functional layer is 1-15 nm.

3. The manufacturing method according to claim 1, characterized in that, The manufacturing method further includes: forming a protective layer on the side of the ferromagnetic metal layer opposite to the functional layer; A magnetic field device is provided on the side of the protective layer opposite to the ferromagnetic metal layer; The protective layer is used to protect the ferromagnetic metal layer to prevent oxidation; the magnetic field device is used to regulate the polarization of the terahertz waves generated by the terahertz wave transmitter.

4. A terahertz wave transmitter, characterized in that, The transmitter includes: A substrate having opposing first and second surfaces; A functional layer located on the first surface, used to improve the resistance and spin Hall angle of the terahertz wave transmitter, comprises: a doped material and a non-ferromagnetic metal layer. The functional layer is obtained by doping the non-ferromagnetic metal layer using multi-target co-sputtering technology. The doped material includes: an insulating material and / or a semiconductor material. The doping concentration is determined based on the material of the non-ferromagnetic metal layer and the atomic ratio of the doped material. Specifically, the material of the non-ferromagnetic metal layer is Pt, the doped material is MgO, and the functional layer is Pt. 1-x (MgO) x Where x represents the atomic percentage, and x ranges from 0.5 to 2.0; A ferromagnetic metal layer located on the side of the functional layer opposite to the substrate.

5. The transmitter according to claim 4, characterized in that, The transmitter further includes a protective layer located on the side of the ferromagnetic metal layer opposite to the functional layer; A magnetic field device located on the side of the protective layer away from the ferromagnetic metal layer.

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