CN110320678A - Terahertz wave modulator and preparation method thereof based on strontium titanates all dielectric Meta Materials - Google Patents

Abstract

The invention relates to a terahertz wave modulator based on a strontium titanate all-dielectric metamaterial and a preparation method thereof. The terahertz wave modulator includes: a polymer flexible substrate layer; a doped semiconductor epitaxial layer: grown on the surface of the polymer flexible substrate layer; SiO ₂ insulating-strontium titanate microstructure composite layer grown on semiconductor silicon epitaxial layer: it includes SiO ₂ insulating layer located below, and strontium titanate microstructure layer grown on SiO ₂ insulating layer. Compared with the prior art, the prepared modulator of the present invention has high quality factor, good adjustability and large modulation depth, and the preparation process is relatively simple, which is suitable for large-scale production application.

Description

Terahertz wave modulator based on strontium titanate all-dielectric metamaterial and its preparation method

technical field

The invention belongs to the technical field of semiconductor photoelectric materials and devices, and relates to a terahertz wave modulator based on strontium titanate all-dielectric metamaterial and a preparation method thereof.

Background technique

Terahertz (THz) waves are between microwave and infrared radiation in the electromagnetic spectrum, and are in the transition zone from macroscopic electromagnetic theory to microscopic quantum theory. It has broad prospects in both basic research and practical application. For example, compared with the microwave band, THz wave has the characteristics of high frequency, large signal bandwidth and high resolution, which is suitable for ultra-wideband and ultra-high-speed 5G communication technology. communication. Modulation technology and devices are the key components of THz communication systems. The development of modulators that work at room temperature, have a compact structure and excellent performance is of great significance to promote the application and development of THz technology. In recent years, people have conducted extensive research on THz modulation devices, but there are still many technical bottlenecks to be solved. For example, the quantum well modulator needs to work at low temperature, while the liquid crystal modulator is sensitive to temperature, has a large loss, a slow modulation speed (KHz), and a small frequency adjustment range (the liquid crystal material has a low birefringence in the THz band) .

Metamaterials (MMs), also known as "superstructure", "heterotropic medium" or "specific electromagnetic medium", are composite material structural systems with periodic or quasi-periodic structures and specific electromagnetic properties through artificial processing or synthesis. MMs use artificial resonant cells (unit cell, meta-molecular) to form a new electromagnetic response medium, which has abnormal physical properties that natural materials do not have, such as negative magnetic permeability and negative electrical conductivity. The properties and functions of metamaterials mainly depend on the geometry and spatial distribution of subwavelength structural units, and functional material devices with different physical properties from natural media can be designed according to actual needs. Metamaterial modulation devices are usually composed of metal materials, and the loss mainly comes from the ohmic loss of the material and the radiation loss of the resonant unit; in addition, the wavelength of the terahertz wave is long, and it is difficult for the sub-wavelength structural unit to effectively restrain the THz wave. Therefore, the quality factor (Q-factor) value of THz band modulators is generally not high (<5), which largely limits the development and application of THz metamaterial modulators in many fields, such as the sensing ability of sensors, Filtering characteristics and resolving power of the filter, etc. In order to meet the needs of many practical applications such as waveform control, biological sample analysis and wireless communication, it is urgent to develop tunable THz modulation devices with large modulation depth, fast modulation speed and high quality factor.

At present, most metamaterials are designed and processed by metal materials. Although they have the advantages of easy processing and forming, they have many problems such as high temperature ablation, high frequency loss and low power carrying capacity. Metal MMs mainly rely on the conduction current on the surface to control the frequency-selective characteristics of electromagnetic waves, but according to Maxwell's equations, the displacement current also has a similar function under the action of incident waves. If the incident wavelength matches the structure size, all-dielectric metamaterials (ADMs) with high dielectric constant (Si, Ge) can excite a strong resonance displacement current under the action of an external electromagnetic wave, forming the so-called Mie resonance. Similar to the LC resonance and dipole resonance in metallic metamaterials, the Mie resonance in ADMs can also generate equivalent electric dipoles and magnetic dipoles, and can avoid the dispersion absorption and energy loss of metals, which contributes to Improvement of the quality factor. The all-dielectric material is also easier to process a thicker microstructure, and its phase control ability in the propagation direction is higher than that of a metal structure, and it is easy to achieve 2π phase modulation and high-efficiency wavefront control. In conclusion, compared with metal metamaterial structures, the displacement current loss in ADMs is small, which is beneficial to obtain narrow-band, high-quality factor resonance lines, and can also support electric dipole, magnetic dipole, and multipole resonances, etc. A variety of resonance modes provide a good design platform and flexible and diverse adjustment methods for the development of THz tunable devices.

Chinese patent ZL201310547214.6 discloses a terahertz modulator based on a ferroelectric thin film and its fabrication method. The terahertz modulator includes: a dielectric substrate, which has a high transmittance to terahertz waves; a plurality of ferroelectric thin film units arranged in an array on the dielectric substrate; a terahertz filter structure, arranged on the on the dielectric substrate and the plurality of ferroelectric thin film units. This patent uses the whole piece of strontium titanate as the adjustment medium, and realizes the modulation of the incident THz through the electronic control method. When the external bias voltage is adjusted within the range of 0-10V, the amplitude modulation depth is 21%, and the frequency modulation depth is about 3.8%, amplitude modulation depth and frequency modulation depth are shallow.

Contents of the invention

The object of the present invention is to provide a terahertz wave modulator based on strontium titanate all-dielectric metamaterial and a preparation method thereof in order to overcome the above-mentioned defects in the prior art.

The purpose of the present invention can be achieved through the following technical solutions:

One of the technical solutions of the present invention is to provide a terahertz wave modulator based on strontium titanate all-dielectric metamaterial, including:

polymer flexible substrate layer;

Doped semiconductor epitaxial layer: grown on the surface of the polymer flexible substrate layer;

_SiO2 insulation-strontium titanate microstructure composite layer grown on semiconductor silicon epitaxial layer: it includes _SiO2 insulation layer located below, and strontium titanate microstructure layer grown on _SiO2 insulation layer.

Further, the polymer flexible substrate layer is made of a plastic flexible substrate solution, and its thickness is 1-50 μm. Furthermore, the thickness of the polymer flexible substrate layer is 2-10 μm.

Further, the doped semiconductor epitaxial layer is a Si layer with a thickness of 1-10 μm, a carrier doping concentration of 10 ¹⁵ -10 ¹⁸ cm ^-3 , and an electrical conductivity of 1-10Ω·cm. Furthermore, the thickness of the doped semiconductor epitaxial layer is 1-5 μm, and the doping concentration is 1×10 ¹⁶ -5×10 ¹⁶ cm ^-3 .

Further, the thickness of the SiO ₂ insulating layer is 10-100 nm, and the thickness of the strontium titanate microstructure layer is 1-5 μm. Furthermore, the thickness is 10-50nm.

Further, the strontium titanate microstructure layer is oval. The polarization direction of the incident wave is along the direction of the semi-major axis of the ellipse.

Further, the preparation method of the strontium titanate microstructure layer can refer to the sol-gel method in the second technical solution.

The second technical solution of the present invention is to provide a method for preparing a THz modulator based on strontium titanate microstructure, comprising the following steps:

(1) Make polymer flexible substrate layer:

Using ordinary Si as a sacrificial layer, spraying a solution containing a plastic flexible substrate on the sacrificial layer, drying and curing, to obtain a polymer flexible substrate layer;

(2) Making doped semiconductor epitaxial layer:

Forming a doped semiconductor epitaxial layer on a polymer flexible substrate layer by an epitaxial growth method;

(3) Making SiO ₂ insulation-strontium titanate microstructure composite layer:

(3-1) Atomic layer deposition of SiO ₂ on the doped semiconductor epitaxial layer, rinsed to obtain a SiO ₂ insulating layer;

(3-2) Deposit a strontium titanate thin film on the _SiO2 insulating layer, then heat and anneal to complete the crystallization process and eliminate defects;

(3-3) removing excess strontium titanate to form a strontium titanate microstructure layer;

(4) The sacrificial layer is peeled off, that is, the strontium titanate microstructure THz modulator on the polymer flexible substrate layer is obtained.

Further, in step (1), the drying process conditions are: drying at 150-200° C. for 20-40 minutes, and the curing process conditions are: heating to 300-400° C. under the protection of an inert gas.

Further, in step (3-1), the temperature of atomic layer deposition SiO ₂ is 180-220°C.

Further, in step (3-2): the annealing temperature of the strontium titanate thin film is 600-1200° C., and the time is 2-4 hours.

Furthermore, in step (3-2): the annealing temperature of the strontium titanate thin film is 800-1000°C.

Further, the deposition method of the strontium titanate thin film is a sol-gel method or a magnetron sputtering method, wherein the process of the sol-gel method is specifically:

(a) Dissolve strontium acetate in acetic acid solution, heat to boiling, keep warm for 15 minutes, then cool to room temperature, then add tetrabutyl titanate solution dissolved in 2,4-pentanedione, stir evenly, then add Adjust with acetic acid and save for later use;

(b) taking the solution prepared in step (a) and depositing it on the surface of the doped semiconductor epitaxial layer by spin spraying, drying and heating to obtain a strontium titanate film from which organic impurities have been removed;

Furthermore, in the sol-gel method, in step (a), the molar ratio of the added amount of barium acetate to tetrabutyl titanate is 1:1, and the concentrations of strontium acetate and tetrabutyl titanate are both 0.3M;

In step (b), the drying temperature is 250°C, the drying time is 5 minutes, the heating temperature is 500°C, and the heating time is 10 minutes;

Compared with the conduction current in the metal, the displacement current in the strontium titanate dielectric layer is weak, so a thicker scale (the thickness of the metal layer is generally 100 nanometers) is required to excite obvious resonance, but if the strontium titanate thickness is too large Large, it will not only bring difficulties in preparation, but also increase the loss, so we choose 1-5μm. If the thickness of the _SiO2 insulating layer is too large, it is unfavorable for the transmissive modulator, and will reduce the transmittance and modulation performance. The reason why the elliptical microstructure is selected is that, on the one hand, it is difficult to realize the circular microstructure due to errors in the actual processing process; on the other hand, the microstructure scale along the polarization direction of the incident wave that really plays a major role uses The type microstructure can obtain better excitation effect under the same sample area, and the resonance line is more obvious.

The working principle of the THz modulation based on the strontium titanate elliptical microstructure obtained by the present invention is as follows:

After the incident THz wave and the strontium titanate elliptical microstructure modulator, due to the high dielectric constant of strontium titanate, a strong displacement current is formed and obvious resonance lines are generated. Among them, the photoelectric properties of the strontium titanate microstructure can be adjusted by changing the temperature. When the temperature is low, such as 70K, the dielectric constant of strontium titanate is high, and the resonance response is strong; as the temperature increases, such as 300K, the dielectric constant of strontium titanate decreases, the resonance response decreases, and the resonance frequency of the spectral line and amplitudes vary with temperature.

Compared with the prior art, the present invention has the following advantages:

(1) Compared with the traditional whole piece of strontium titanate, the present invention adopts strontium titanate elliptical microstructure, when the polarization direction of the incident wave is along the semi-major axis, it can form obvious resonance spectral lines, through Properly adjusting the temperature can change the waveform of the resonance line;

(2) The present invention adopts the strontium titanate metamaterial structure, based on the asymmetric microstructure of ellipse, by changing the polarization direction of the incident wave, the adjustment of the resonance spectrum line waveform and amplitude can be easily realized;

(3) The present invention can also select and optimize the material size of the flexible substrate, the thickness of the back electrode semiconductor layer, etc., thereby further obtaining larger modulation depth and lower loss;

(4) The final modulator has high quality factor, good tunability and large modulation depth (amplitude modulation depth greater than 90%).

(5) The preparation process is relatively simple and suitable for large-scale production applications.

Description of drawings

Figure 1 is a schematic diagram of the principle of the tunable temperature-controlled high-quality factor THz modulator based on the ferroelectric material strontium titanate elliptical microstructure of the present invention;

Fig. 2 is the top view of the structure diagram of the THz modulator based on the ferroelectric material strontium titanate elliptical microstructure of the present invention;

3 is a schematic diagram of the temperature control principle of the present invention based on the ferroelectric material strontium titanate elliptical microstructure modulator;

Fig. 4 is the simulation result figure of the ferroelectric material strontium titanate elliptical microstructure THz modulation device based on the present invention, the influence of temperature on the resonant spectrum line;

Fig. 5 is the simulation result diagram of the ferroelectric material strontium titanate elliptical microstructure THz modulation device based on the present invention, the influence of different polarization angles of the incident wave on the resonant spectral line waveform;

Fig. 6 is the simulation result of the resonance spectral line quality factor and optimization factor of the THz modulation device based on the strontium titanate elliptical microstructure;

In the figure, 1-polymer flexible substrate layer, 2-doped semiconductor epitaxial layer, 3-SiO ₂ insulating layer, 4-strontium titanate microstructure layer.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is carried out on the premise of the technical solution of the present invention, and detailed implementation and specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.

In one of the technical solutions of the present invention, a terahertz wave modulator based on strontium titanate all-dielectric metamaterial is proposed, including:

polymer flexible substrate layer 1;

Doped semiconductor epitaxial layer 2: grown on the surface of the polymer flexible substrate layer, with better insulation to achieve the purpose of reducing loss;

SiO ₂ insulation-strontium titanate microstructure composite layer grown on semiconductor silicon epitaxial layer: it includes SiO ₂ insulation layer 3 located below, and strontium titanate microstructure layer 4 grown on SiO ₂ insulation layer 3 .

In a specific embodiment of the present invention, the polymer flexible substrate layer is made of a plastic flexible substrate solution, and its thickness is 1-50 μm, preferably 2-10 μm.

In a specific embodiment of the present invention, the doped semiconductor epitaxial layer is a Si layer with a thickness of 1-10 μm, a carrier doping concentration of 10 ¹⁵ -10 ¹⁸ cm ^-3 , and an electrical conductivity of 1-10Ω·cm. Furthermore, the thickness of the doped semiconductor epitaxial layer is 1-5 μm, and the doping concentration is 10 ¹⁶ -5×10 ¹⁶ cm ^-3 .

In a specific embodiment of the present invention, the thickness of the SiO ₂ insulating layer is 10-100 nm, and the thickness of the strontium titanate microstructure layer is 1-5 μm. Furthermore, the thickness is 10-50nm.

In a specific embodiment of the present invention, the strontium titanate microstructure layer is oval.

In a specific embodiment of the present invention, the preparation method of the strontium titanate microstructure layer can refer to the following sol-gel method.

In the second technical solution of the present invention, a method for preparing a THz modulator based on a strontium titanate microstructure is provided, comprising the following steps:

(1) Make polymer flexible substrate layer:

Using ordinary Si as a sacrificial layer, spraying a solution containing a plastic flexible substrate on the sacrificial layer, drying and curing, to obtain a polymer flexible substrate layer;

(2) Making doped semiconductor epitaxial layer:

Forming a doped semiconductor epitaxial layer on a polymer flexible substrate layer by an epitaxial growth method;

(3) Making SiO ₂ insulation-strontium titanate microstructure composite layer:

(3-1) Atomic layer deposition of SiO ₂ on the doped semiconductor epitaxial layer, rinsed to obtain a SiO ₂ insulating layer;

(3-2) Deposit a strontium titanate thin film on the _SiO2 insulating layer, then heat and anneal to complete the crystallization process and eliminate defects;

(3-3) removing excess strontium titanate to form a strontium titanate microstructure layer;

(4) The sacrificial layer is peeled off, that is, the strontium titanate microstructure THz modulator on the polymer flexible substrate layer is obtained.

In one specific embodiment, in step (1), the drying process conditions are: drying at 150-200°C for 20-40min, and the curing process conditions are: heating to 300-400°C under the protection of an inert gas .

In another specific embodiment, in step (3-1), the temperature of atomic layer deposition SiO ₂ is 180-220°C.

In another specific embodiment, in step (3-2): the annealing temperature of the strontium titanate thin film is 600-1200° C., and the time is 2-4 hours.

Furthermore, in step (3-2): the annealing temperature of the strontium titanate thin film is 800-1000°C.

In another specific embodiment wherein, the deposition method of the strontium titanate thin film is a sol-gel method or a magnetron sputtering method, wherein the process of the sol-gel method is specifically:

(a) Dissolve strontium acetate in acetic acid solution, heat to boiling, keep warm for 15 minutes, then cool to room temperature, then add tetrabutyl titanate solution dissolved in 2,4-pentanedione, stir evenly, then add Acetic acid is adjusted to (the total concentration of strontium acetate and tetrabutyl titanate is 0.3M, keep for later use;

(b) taking the solution prepared in step (a) and depositing it on the surface of the doped semiconductor epitaxial layer by spin spraying, drying and heating to obtain a strontium titanate film from which organic impurities have been removed;

The specific process _of the magnetron sputtering method is as follows: SrTiO3 is used as the target material for magnetron sputtering, and a mixed gas composed of inert gas Ar and _O2 is introduced into the sputtering process.

Furthermore, in the sol-gel method, in step (a), the ratio of the added amount of barium acetate to tetrabutyl titanate is (please add the specific range of added amount, and specify whether it is mass ratio, molar ratio or other ratio ),

In step (b), the drying temperature is 250° C., the drying time is 5 minutes, the heating temperature is 500° C., and the heating time is 10 minutes.

The above-mentioned implementation manners of the present invention will be further described in detail below in conjunction with specific examples.

Example 1:

A THz modulator based on strontium titanate-based elliptical microstructure, including:

polymer flexible substrate layer;

Semiconductor epitaxial layer: a doped semiconductor Si layer formed by epitaxial growth method, with good insulation to achieve the purpose of reducing loss;

SiO ₂ insulation-strontium titanate microstructure composite layer: grown on the semiconductor Si epitaxial layer, composed of a structural unit of SiO ₂ insulation-strontium titanate microstructure layer, which specifically includes the SiO ₂ insulation layer located below, and the growth Strontium titanate microstructure layer on _SiO2 insulating layer.

In this embodiment, the polymer flexible substrate layer is made of a plastic flexible substrate solution, such as polyimide, and its thickness is 50 μm; the doped semiconductor epitaxial layer is a doped Si layer, its thickness is 10 μm, and the carrier doped The concentration is 10 ¹⁸ cm ^-3 , and the conductivity is 10Ω·cm. The carrier concentration in the doped Si layer can be realized and determined by common semiconductor doping methods such as diffusion and ion implantation.

The SiO ₂ insulation-strontium titanate microstructure composite layer is composed of the SiO ₂ insulation-strontium titanate elliptical microstructure layer. The _SiO2 insulation-active region structure composite layer of this structure can improve the modulation depth and speed of the modulation waveform. The thickness of the SiO ₂ insulating layer is about 30nm, and the strontium titanate microstructure layer is oval, and its thickness is about 2-5μm.

Example 2

This embodiment provides a preparation process of a high quality factor THz modulator with a strontium titanate-based elliptical microstructure, which specifically includes the following steps:

(1) Fabrication of polymer flexible substrate layer: ordinary Si sheet is used as a sacrificial layer, and the solution containing plastic polymer flexible substrate layer is sprayed on it by spincoating method, and then dried in an oven for about 30 minutes , the temperature range is about 150-200°C (preferably about 180°C), and then heated to 300-400°C (preferably 350°C) in a high-temperature furnace in a protective atmosphere of inert gas (or N ₂ ) to form a uniform polymer Flexible substrate layer;

(2) Making a doped semiconductor epitaxial layer: Form a semiconductor Si epitaxial layer with a thickness of 1-10 μm (which can be 1 μm, 5 μm or 10 μm, preferably about 5 μm in this embodiment) by epitaxial growth method, with a doping concentration of 3×10 ¹⁶ cm ^-3 , the electrical conductivity of the Si layer is 1-10Ω·cm, and the insulation is good to achieve the purpose of reducing loss;

(3) Form a SiO ₂ insulating layer on the Si buffer layer by atomic layer deposition technology, the optimum thickness is about 60-80nm, the forming temperature is 200°C, and then rinse with distilled water;

(4) Prepare strontium titanate solution by sol-gel method: dissolve strontium acetate (Sr(CH ₃ COO) ₂ ) in acetic acid solution, control its molar concentration to 0.6mol/L, heat to boiling, and keep warm for 15 Cool to room temperature after minutes;

(5) Dissolve tetrabutyl titanate (Ti(OC ₄ H ₉ ) ₄ ) in 2,4-pentanedione (CH ₃ COCH ₂ COCH ₃ ) solution, control its molar concentration to 0.6mol/L, add In the solution in step (4), reaction occurs to obtain strontium titanate solution (i.e. STO solution);

(6) Preparation of strontium titanate thin film by spin spraying method: add acetic acid to the STO solution obtained in the above step (5) until the solute strontium acetate and tetrabutyl titanate are diluted to 0.3mol/L, The method of spin spraying is deposited on the epitaxial Si surface, the spin spraying speed is 3000rpm, and the time is 20s;

(7) Dry the STO film obtained in step (6) at 250° C. for 5 minutes; heat to 500° C. and hold for 10 minutes to remove residual organic matter.

(8) Repeat the above two processes (6) and (7) to obtain the STO film until the film thickness is about 2-5 μm.

(9) Heating and annealing the STO film at a temperature of 600-1200° C. and keeping it warm for 3-5 hours to complete the crystallization process of the STO and reduce the internal defects of the film.

(10) Removing excess strontium titanate by photolithography or plasma etching to obtain an elliptical strontium titanate microstructure layer.

(11) Clean the terahertz strontium titanate microstructure modulator obtained in the above process with distilled water for more than 3-5 times, and then blow it and dry it in a protective atmosphere (Ar or N ₂ ).

(12) The terahertz modulator based on the strontium titanate elliptical microstructure was peeled off from the Si substrate to obtain a strontium titanate thin film tunable device on the polymer flexible substrate layer.

Figure 1 is a schematic diagram of the principle of the THz modulator based on the strontium titanate elliptical microstructure of the present invention. The incident THz wave interacts with the strontium titanate elliptical microstructure unit modulator to form strong resonance lines. Among them, the strontium titanate microstructure layer 4 is used as a tunable dielectric layer, and its dielectric constant can be adjusted by changing the temperature. As shown in Figure 1, when the temperature is low, such as 70K, strontium titanate has a high dielectric constant, and the resonance characteristics of the strontium titanate layer generated by the displacement current are remarkable; on the contrary, when the temperature is high, the strontium titanate dielectric constant The electrical constant is low, the resonance characteristics are weak, and the position of the resonance valley will also vary with temperature.

Fig. 2 is the top view of the THz modulator structure schematic diagram based on the strontium titanate elliptical microstructure of the present invention, wherein a _x and a _y are the semi-minor axis and the semi-major axis of the strontium titanate elliptical microstructure, p _x and _py is the period length of the strontium titanate elliptical microstructure along the x direction and the y direction, Hx indicates that the magnetic field direction of the incident wave is the x direction, and Ey is the electric field direction of the incident wave is the y direction.

3 is a schematic diagram of the temperature control principle of the strontium titanate elliptical microstructure terahertz modulator of the present invention, and the heater is placed on the surface of the strontium titanate. The external circuit closes the switch, the heating indicator lights up, and the temperature of the strontium titanate microstructure is changed under the heater. The total resistance in the circuit is adjusted through the sliding rheostat and the rheostat box, thereby changing the current in the circuit and realizing heating work under different powers. At the same time, the real-time temperature value of strontium titanate can be monitored through the temperature display. For example, when the resistance is small (such as R ₁ ), the current in the circuit is large and the heating power is large, at this time the temperature of strontium titanate is high (such as T ₁ ), and the dielectric constant ε ₁ is low; on the contrary, when the resistance is high When it is large (such as R ₂ ), the current in the circuit is small, and the heating power is small. At this time, the temperature of strontium titanate is low (such as T ₂ ), and the dielectric constant ε ₂ is low.

Fig. 4 is the simulation result of the THz modulation device based on the strontium titanate elliptical microstructure prepared in Example 2 of the present invention; in the figure, the lengths of the semi-minor axis and the semi-major axis of the elliptical microstructure are 15 μm and 60 μm, respectively. When the temperature is adjusted between 70K and 300K (in the figure, along the initial position to the right, the five curves respectively represent the temperature is 70K-300K), the frequency modulation depth of the resonance valley is 21.9%, and the amplitude modulation depth is 95.6 %, where the amplitude modulation depth is defined as (T _max -T _min )/T _max , where T _max and T _min are the maximum and minimum values of the resonance valley of the transmission spectrum, respectively. The frequency modulation depth is defined as: (f _max -f _min )/f _max , where f _max and f _min are the maximum and minimum values of the resonant frequency of the transmission line, respectively.

Fig. 5 is the simulation result of the resonant spectrum line of the THz modulation device based on the strontium titanate elliptical microstructure obtained in Example 2 of the present invention; the lengths of the semi-minor axis and the semi-major axis of the elliptical microstructure in the figure are respectively 15 μm and 60 μm. As shown in the small picture in the box in Figure 5, θ is the angle of the incident wave vector k ₀ relative to the surface normal direction (in the figure, along the initial position to the right, the five curves represent the angle θ is 0-89degree), φ is the angle between the incident wave polarization direction and the y-axis. In the case of normal incidence, if the polarization angle φ varies between 0-90 degrees, the amplitude modulation depth of the resonance valley can reach 89.2%. It can be seen from Figure 5 that when the incident wave angle is changed, the resonance frequency does not change much, but it can have a great impact on the waveform, and the amplitude modulation depth can reach 89%. Without changing the structural parameters of the sample, by changing The polarization direction of the incident wave can realize the regulation of the incident wave waveform.

Figure 6 shows the simulation results of the resonance line quality factor and optimization factor of the THz modulation device based on the strontium titanate elliptical microstructure; the lengths of the semi-minor axis and the semi-major axis of the elliptical microstructure in the figure are 15 μm and 60 μm, respectively. As shown in the small picture in the box in Figure 5, θ is the angle of the incident wave vector k ₀ relative to the surface normal direction (in the figure, along the initial position to the right, the five curves represent the angle φ is 0-89 degrees) , φ is the angle between the incident wave polarization direction and the y-axis. In the case of normal incidence, when the polarization angle φ is 0 degrees, 30 degrees, 60 degrees and 75 degrees, the quality factors of the resonance lines are 5.575, 6.514, 13.36 and 20.39, respectively, as shown in Figure 6 , the quality factor Q is defined as: Q=fres/ _FWHW , where fres is the resonant frequency, and _FWHW (full width at half maximum) is the full width at half maximum of the spectral line.

In the above embodiment, each structural layer and process conditions can be adjusted arbitrarily within the following range, which will not affect the acquisition of the terahertz wave modulator based on strontium titanate all-dielectric metamaterial of the present invention, specifically:

The process conditions for plastic flexible substrate solution drying can be arbitrarily selected within the following range: drying at 150-200°C for 20-40 minutes; similarly, the curing process conditions can also be arbitrarily selected within the following range: under the protection of inert gas Heating to 300-400°C;

The temperature of ALD _SiO2 can be replaced by 180°C, 220°C, etc., respectively.

The annealing temperature of the strontium titanate film can be arbitrarily selected in the following range: 600-1200 ℃ (such as 600, 800, 900, 1000, 1200), preferably arbitrarily selected in the following range: 800-1000 ℃, the holding time is 2- 4 hours or so.

In addition, the thickness of the finally obtained polymer flexible substrate layer can be arbitrarily selected within the following range of 1-50 μm;

The doped semiconductor epitaxial layer can be arbitrarily selected within the following specifications: thickness 1-10 μm, carrier doping concentration 10 ¹⁵ -10 ¹⁸ cm ^-3 , conductivity 1-10Ω·cm.

The thickness of the SiO ₂ insulating layer can be arbitrarily selected within the following specification range: 10-100nm, and the thickness of the strontium titanate microstructure layer can be arbitrarily selected within the following specification range: 1-5μm.

The above descriptions of the embodiments are for those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments, and apply the general principles described here to other embodiments without creative efforts. Therefore, the present invention is not limited to the above-mentioned embodiments. Improvements and modifications made by those skilled in the art according to the disclosure of the present invention without departing from the scope of the present invention should fall within the protection scope of the present invention.

Claims (10)

1. a kind of terahertz wave modulator based on strontium titanates all dielectric Meta Materials characterized by comprising

Polymer flexibility substrate layer；

Doped semiconductor epitaxial layer: it is grown in polymer flexibility substrate layer surface；

The SiO being grown on semiconductor silicon epitaxial layer₂Insulation-strontium titanates micro-structure composite layer: it includes underlying SiO₂Absolutely Edge layer, and it is grown in SiO₂Strontium titanates microstructured layers on insulating layer.

2. a kind of terahertz wave modulator based on strontium titanates all dielectric Meta Materials according to claim 1, feature exist In the polymer flexibility substrate layer is made of plastic flexible substrate solution, with a thickness of 1-50 μm；

The doped semiconductor epitaxial layer is Si layers, and with a thickness of 1-10 μm, charge-carrier dopant concentration is 10¹⁵-10¹⁸cm^-3, Conductivity is 1-10 Ω cm.

3. a kind of terahertz wave modulator based on strontium titanates all dielectric Meta Materials according to claim 2, feature exist In, the polymer flexibility substrate layer with a thickness of 2-10 μm；

The doped semiconductor epitaxial layer with a thickness of 1-5 μm, doping concentration 10¹⁶-5×10¹⁶cm^-3。

4. a kind of terahertz wave modulator based on strontium titanates all dielectric Meta Materials according to claim 1, feature exist In the SiO₂Insulating layer with a thickness of 10-100nm, strontium titanates microstructured layers with a thickness of 1-5 μm.

5. a kind of terahertz wave modulator based on strontium titanates all dielectric Meta Materials according to claim 1, feature exist In strontium titanates microstructured layers are oval.

6. a kind of preparation method of THz modulator based on strontium titanates micro-structure a method as claimed in any one of claims 1 to 5, feature It is, comprising the following steps:

(1) polymer flexibility substrate layer is made:

Using common Si as sacrificial layer, by the solution spraying containing plastic flexible substrate on sacrificial layer, after baking and curing, obtain Polymer flexibility substrate layer；

(2) doped semiconductor epitaxial layer is made:

Doped semiconductor epitaxial layer is formed on polymer flexibility substrate layer by epitaxial growth method；

(3) SiO is made₂Insulation-strontium titanates micro-structure composite layer:

(3-1) atomic layer deposition SiO on doped semiconductor epitaxial layer₂, rinse well, SiO be made₂Insulating layer；

(3-2) is in SiO₂Strontium titanate film is deposited on insulating layer, then heating anneal completes crystallisation procedure, and eliminates defect；

(3-3) removes the strontium titanates of redundance, forms strontium titanates microstructured layers；

(4) removing sacrificial layer is to get to the strontium titanates micro-structure THz modulator on polymer flexibility substrate layer.

7. a kind of preparation method of THz modulator based on strontium titanates micro-structure according to claim 6, feature exist In, in step (1), the process conditions of drying are as follows: dry 20-40min, cured process conditions are as follows: lazy in 150-200 DEG C 300-400 DEG C is heated under property gas shield；

In step (3-1), atomic layer deposition SiO₂Temperature be 180-220 DEG C；

In step (3-2): the annealing temperature of strontium titanate film is 600-1200 DEG C, and the time is 2-4 hours.

8. a kind of preparation method of THz modulator based on strontium titanates micro-structure according to claim 7, feature exist In in step (3-2): the annealing temperature of strontium titanate film is 800-1000 DEG C.

9. a kind of preparation method of THz modulator based on strontium titanates micro-structure according to claim 6, feature exist In the deposition method of strontium titanate film is sol-gal process or magnetron sputtering method, wherein the process of sol-gal process specifically:

(a) first strontium acetate is taken to be dissolved in acetum, and is heated to boiling, heat preservation is cooled to room temperature after 15 minutes, is added The solution of tetrabutyl titanate being dissolved in 2,4- pentanedione, stirs evenly, and is subsequently added into acetic acid adjusting, retains spare；

(b) it takes the solution of step (a) preparation and doped semiconductor epi-layer surface is deposited to using spin spraying method, dry, After heating, the strontium titanate film of removal organic impurities is obtained.

10. a kind of preparation method of THz modulator based on strontium titanates micro-structure according to claim 9, feature exist In, in sol-gal process, in step (a), the ratio between additive amount of barium acetate and butyl titanate is 1:1,

In step (b), the temperature of drying is 250 DEG C, drying time 5min, and heating temperature is 500 DEG C, and heating time is 10min。