Nanomechanical resonator coupled to a surface acoustic wave device and method of fabrication thereof

Abstract

The application relates to the field of acoustic wave device manufacturing, in particular to a nanomechanical resonator and surface acoustic wave coupling device and a preparation method thereof. The device comprises a surface acoustic wave device electrode arranged on the surface of a substrate and used for generating a surface acoustic wave through voltage excitation. The surface acoustic wave device electrode comprises an interdigital transducer electrode arranged at the middle part of the substrate; mirror electrodes are arranged on the two sides of the interdigital transducer electrode; a nanomechanical resonator is arranged between the interdigital transducer electrode and the mirror electrodes, and the nanomechanical resonator comprises a two-dimensional material arranged at the output end of the nanomechanical resonator and used for exciting or adjusting a vibration wave through direct current voltage or surface acoustic wave excitation; a gate electrode is used for connecting the direct current voltage to the two-dimensional material, so as to change the resonance frequency of the two-dimensional material; and source-drain electrodes are arranged on the two sides of the gate electrode and used for applying a microwave voltage signal with a modulated frequency or for reading a mixed current.

Description

Technical Field

[0001] This invention relates to the field of acoustic device manufacturing, specifically to a nanomechanical oscillator coupled with a surface acoustic wave and its preparation method. Background Technology

[0002] Surface acoustic waves (SAWs) are elastic waves that propagate on solid surfaces. They are characterized by low loss, high information density, and strong resistance to electromagnetic interference. Based on these elastic waves, practical SAW devices can be fabricated using interdigital transducer electrodes that can excite and receive SAW signals on piezoelectric substrates. Currently, SAW-based filters, sensors, and other devices are small in size and lightweight, capable of performing a variety of complex functions. Acoustic platforms developed using SAWs fully utilize these characteristics, enabling fully acoustic information processing, which further expands the application prospects of SAWs.

[0003] Since the discovery of graphene, a material with a thickness of only one atom layer, the unique structural characteristics and excellent physicochemical properties of two-dimensional materials have demonstrated broad potential applications in various optical, electrical, and acoustic devices. Among them, nanomechanical oscillators made from two-dimensional materials have advantages such as small size, high sensitivity, strong stability, and high quality factor, and have wide applications in wireless communication and mass detection.

[0004] Currently, the vibration localization of nanomechanical oscillators based on two-dimensional materials is within a very small range, and their driving and control methods usually rely on electromagnetic signals, which to some extent limits their application. Summary of the Invention

[0005] Based on this, the present invention proposes a nanomechanical oscillator coupled with surface acoustic wave and its preparation method, which can drive and detect the vibration of the nanomechanical oscillator in a non-contact manner using surface acoustic waves.

[0006] According to one aspect of the present invention, a nanomechanical oscillator coupled to a surface acoustic wave is provided, comprising:

[0007] Substrate;

[0008] A surface acoustic wave (SAW) device electrode, disposed on the surface of the substrate, is used to generate a SAW by voltage excitation. The SAW device electrode includes:

[0009] Interdigitated transducer electrodes are disposed in the middle of the substrate.

[0010] The reflector electrodes are disposed on both sides of the interdigital transducer electrodes mentioned above;

[0011] A nanomechanical oscillator, the output end of which is disposed between the interdigital transducer electrode and the reflector electrode, the nanomechanical oscillator comprising:

[0012] A two-dimensional material is disposed at the output end of the aforementioned nanomechanical oscillator, which is used to excite or modulate the aforementioned vibration wave by DC voltage or the aforementioned surface acoustic wave.

[0013] The gate electrode is used to apply a DC voltage to the two-dimensional material, thereby changing the resonant frequency of the two-dimensional material.

[0014] Source and drain electrodes are disposed on both sides of the gate electrode and are used to apply a microwave voltage signal that can be modulated in frequency, or to read the mixing current.

[0015] Wherein, the source / drain electrode is higher than the gate electrode, the two-dimensional material covers the output terminals of the source / drain electrode and the gate electrode, and the two-dimensional material is in contact with the source / drain electrode but not with the gate electrode.

[0016] According to an embodiment of the present invention, the substrate is a piezoelectric material;

[0017] The aforementioned two-dimensional material is a heterostructure formed from graphene, molybdenum disulfide, tungsten selenide, molybdenum selenide, or the above materials.

[0018] According to an embodiment of the present invention, it further includes overlay marks for positioning the aforementioned nanomechanical oscillator and for detecting the positioning accuracy of the aforementioned nanomechanical oscillator.

[0019] According to an embodiment of the present invention, the surface acoustic wave device electrode and the overlay mark are made of a metallic material, and the thickness of the surface acoustic wave device electrode and the overlay mark is 30-200 nanometers.

[0020] According to an embodiment of the present invention, both the gate electrode and the source / drain electrode include overlapping first metal electrodes and second metal electrodes;

[0021] The first metal electrode material is titanium or chromium, and the thickness of the first metal electrode is 3-10 nanometers.

[0022] The material of the second metal electrode is gold or palladium, and the thickness of the second metal electrode is 20-70 nanometers.

[0023] According to an embodiment of the present invention, the source and drain electrodes each include overlapping third and fourth metal electrodes;

[0024] The aforementioned third metal electrode material is titanium or chromium, and the thickness of the aforementioned third metal electrode is 30-40 nanometers;

[0025] The material of the fourth metal electrode is gold or palladium, and the thickness of the fourth metal electrode is 210-280 nanometers.

[0026] According to an embodiment of the present invention, the closest distance between the source / drain electrode and the interdigital transducer electrode is a half-integer multiple of the surface acoustic wave wavelength.

[0027] According to an embodiment of the present invention, the period length of the interdigital transducer electrode is obtained based on the ratio of the wave velocity of the surface acoustic wave to be excited on the substrate to its frequency.

[0028] The period length of the aforementioned mirror electrode is half the period length of the aforementioned interdigital transducer electrode.

[0029] According to another aspect of the present invention, a method for fabricating the above-described nanomechanical oscillator coupled to a surface acoustic wave (SAW) device is provided, comprising:

[0030] Fabricate interdigitated transducer electrodes and mirror electrodes on a substrate;

[0031] Fabrication of the gate electrode;

[0032] Fabrication of source and drain electrodes;

[0033] A dry transfer process was used to prepare transferable two-dimensional materials, which were then used to cover the output end of a nanomechanical oscillator.

[0034] In this configuration, the source and drain electrodes are higher than the gate electrode, and the two-dimensional material is in contact with the source and drain electrodes but not with the gate electrode.

[0035] According to an embodiment of the present invention, the preparation of the transfer two-dimensional material using a dry transfer process, wherein the two-dimensional material covers the output end of the nanomechanical oscillator, includes:

[0036] A thin film with the aforementioned two-dimensional material is fixed onto a glass slide;

[0037] The glass slide was inverted, and the two-dimensional material was aligned with the output end of the nanomechanical oscillator under an optical microscope.

[0038] After attaching the two-dimensional material to the output end of the nanomechanical oscillator, heat it to 50-120℃.

[0039] The glass plate is lifted, and the two-dimensional material separates from the thin film, remaining at the output end of the nanomechanical oscillator.

[0040] As can be seen from the above technical solutions, the nanomechanical oscillator and surface acoustic wave coupling device and its fabrication method provided by the present invention have the following beneficial effects:

[0041] This invention and its solution are applicable to the design and fabrication of single or even multiple nanomechanical oscillators coupled to surface acoustic waves based on various two-dimensional materials and their heterojunctions.

[0042] Nanomechanical oscillators are coupled with surface acoustic waves (SAWs). On the one hand, SAWs can be used to drive and detect the vibration of nanomechanical oscillators non-contactly; on the other hand, nanomechanical oscillators can be used to modulate the propagation of SAWs.

[0043] By coupling surface acoustic wave (SAW) devices with nanomechanical oscillators based on two-dimensional materials through a specific design, the nanomechanical oscillators can be driven and controlled by SAW, and the SAW will be influenced by the nanomechanical oscillators, thus transmitting the vibration information of the nanomechanical oscillators in the form of traveling waves. This design expands the control methods of nanomechanical oscillators based on two-dimensional materials, and at the same time provides a reliable "component" for acoustic platforms built with SAW, improving the diversity and operability of acoustic platforms. Attached Figure Description

[0044] Figure 1 This is a top view of the nanomechanical oscillator and surface acoustic wave coupling device according to an embodiment of the present invention;

[0045] Figure 2 This is a top view schematic diagram of a two-dimensional material according to an embodiment of the present invention;

[0046] Figure 3 for Figure 2 A front view schematic diagram of a two-dimensional material according to an embodiment of the present invention;

[0047] Figure 4 This is a flowchart illustrating the fabrication process of the nanomechanical oscillator and surface acoustic wave coupling device according to an embodiment of the present invention.

[0048] Figure 5 This is a schematic diagram illustrating the relationship between gate voltage and resonant frequency in an embodiment of the present invention;

[0049] Figure 6 The surface acoustic wave resonator prepared in the network analyzer measurement embodiment of this invention. Parameter diagram;

[0050] Figure 7 This is a schematic diagram of the model in Embodiment 3 of the present invention;

[0051] Figure 8 This is a displacement diagram of the entire nanomechanical oscillator in the model of Embodiment 3 of the present invention in the range of 100 MHz to 105 MHz;

[0052] Figure 9 This is a displacement diagram of the entire nanomechanical oscillator in the model of Embodiment 3 of the present invention at 102 MHz;

[0053] Figure 10 This diagram illustrates the modulation effect of the nanomechanical oscillator on surface acoustic waves in Embodiment 3 of the present invention.

[0054] In the picture:

[0055] 101-substrate

[0056] 201-Interdigital transducer electrode;

[0057] 202 - Mirror electrode;

[0058] 301 - Gate electrode;

[0059] 302 - Source / drain electrodes;

[0060] 401-overlay mark

[0061] 501-Two-dimensional materials Detailed Implementation

[0062] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0063] Figure 1 This is a top view of the nanomechanical oscillator and surface acoustic wave coupling device according to an embodiment of the present invention.

[0064] According to one aspect of the general inventive concept of the present invention, a nanomechanical oscillator coupled to a surface acoustic wave is provided, such as... Figure 1 As shown, it includes a substrate 101, surface acoustic wave device electrodes, nanomechanical oscillators, and two-dimensional material 501.

[0065] The surface acoustic wave device electrodes are disposed on the surface of the substrate 101 and are used to generate surface acoustic waves by voltage excitation. The surface acoustic wave device electrodes include interdigital transducer electrodes 201 and mirror electrodes 202.

[0066] The interdigitated transducer electrode 201 is disposed in the middle of the substrate 101.

[0067] The mirror electrode 202 is disposed on both sides of the interdigital transducer electrode 201.

[0068] The nanomechanical oscillator has its output end located between the interdigital transducer electrode 201 and the mirror electrode 202. The nanomechanical oscillator includes a two-dimensional material 501, a gate electrode 301, and source / drain electrodes 302.

[0069] Two-dimensional material 501 is placed at the output end of the nanomechanical oscillator to excite or modulate vibration waves by DC voltage or surface acoustic waves.

[0070] The gate electrode 301 is used to connect a DC voltage to the two-dimensional material 501, thereby changing the resonant frequency of the two-dimensional material 501.

[0071] The source and drain electrodes 302 are disposed on both sides of the gate electrode 301 and are used to apply a microwave voltage signal that can be modulated in frequency, or to read the mixing current.

[0072] In this configuration, the source / drain electrode 302 is higher than the gate electrode 301, and the two-dimensional material 501 covers the output terminals of the source / drain electrode 302 and the gate electrode 301. The two-dimensional material 501 is in contact with the source / drain electrode 302 but not with the gate electrode 301.

[0073] The electrodes of the surface acoustic wave (SAW) device and the nanomechanical oscillator can be excited and measured independently. Combining these two systems allows for more excitation and measurement methods. A microwave signal can be applied to the interdigital transducer electrode 201 of the SAW device to generate a SAW wave. When the SAW wave propagates to the nanomechanical oscillator, it excites the nanomechanical oscillator to vibrate, even without a frequency-modulated microwave voltage signal applied. Alternatively, both can be excited, and the response at one end can be measured to provide feedback on the overall system state.

[0074] By coupling surface acoustic wave (SAW) devices with nanomechanical oscillators based on two-dimensional material 501 through a specific design, the nanomechanical oscillators can be driven and controlled by SAW, and conversely, SAW will also be influenced by the nanomechanical oscillators, thus transmitting the vibration information of the nanomechanical oscillators in the form of traveling waves. This design expands the control methods of nanomechanical oscillators based on two-dimensional material 501, while providing a reliable "component" for acoustic platforms built with SAW, improving the diversity and operability of acoustic platforms.

[0075] According to an embodiment of the present invention, the substrate 101 is a piezoelectric material.

[0076] According to an embodiment of the present invention, the substrate 101 is preferably one of gallium arsenide, lithium niobate, lithium tantalate, zinc oxide, and quartz.

[0077] According to an embodiment of the present invention, the thickness of the substrate 101 is 500-800 micrometers.

[0078] According to embodiments of the present invention, for example, the thickness of the substrate 101 can be 500 micrometers, 550 micrometers, 600 micrometers, 650 micrometers, 700 micrometers, 750 micrometers or 800 micrometers, preferably 625 micrometers.

[0079] When stress is applied to the piezoelectric substrate 101, the internal polarization of the material is enhanced, thereby accumulating charge on the surface and forming a voltage or current, which is called the piezoelectric effect. This process is reversible; when a voltage is applied, the material undergoes elastic deformation, which is called the inverse piezoelectric effect. When a high-frequency electrical signal is applied to both ends of the interdigital transducer electrode 201, the surface of the piezoelectric material will generate mechanical vibration and simultaneously excite surface acoustic waves with the same frequency as the applied electrical signal. These surface acoustic waves will propagate along the surface of the substrate material.

[0080] According to an embodiment of the present invention, the two-dimensional material 501 is a heterostructure formed of graphene, molybdenum disulfide, tungsten selenide, molybdenum selenide, or the above materials.

[0081] According to an embodiment of the present invention, it further includes an overlay mark 401 for positioning the nanomechanical oscillator and detecting the positioning accuracy of the nanomechanical oscillator.

[0082] According to an embodiment of the present invention, the surface acoustic wave device electrode and the overlay mark 401 are made of a metallic material, and the thickness of the surface acoustic wave device electrode and the overlay mark 401 is 30-200 nanometers.

[0083] According to an embodiment of the present invention, the thickness of the electrode and the overlay mark 401 of the surface acoustic wave device can be 30 nanometers, 50 nanometers, 100 nanometers, 150 nanometers or 200 nanometers, preferably 200 nanometers.

[0084] Figure 2 This is a top view schematic diagram of a two-dimensional material according to an embodiment of the present invention.

[0085] Figure 3 for Figure 2 A frontal view of a two-dimensional material according to an embodiment of the present invention.

[0086] According to embodiments of the present invention, such as Figure 2 and Figure 3 As shown, the gate electrode 301 and the source / drain electrode 302 both include overlapping first metal electrodes and second metal electrodes. The material of the first metal electrode is titanium or chromium, and the thickness of the first metal electrode is 3-10 nanometers.

[0087] The second metal electrode is made of gold or palladium and has a thickness of 20-70 nanometers.

[0088] According to embodiments of the present invention, for example, the thickness of the first metal electrode can be 3 nanometers, 4 nanometers, 5 nanometers, 6 nanometers, 7 nanometers, 8 nanometers, 9 nanometers or 10 nanometers.

[0089] According to embodiments of the present invention, for example, the thickness of the second metal electrode can be 20 nanometers, 30 nanometers, 40 nanometers, 50 nanometers, 60 nanometers or 70 nanometers.

[0090] According to an embodiment of the present invention, both the source and drain electrodes 302 include overlapping third metal electrodes and fourth metal electrodes, wherein the material of the third metal electrode is titanium or chromium, and the thickness of the third metal electrode is 30-40 nanometers.

[0091] The fourth metal electrode is made of gold or palladium and has a thickness of 210-280 nanometers.

[0092] According to embodiments of the present invention, for example, the thickness of the third metal electrode can be 30 nanometers, 31 nanometers, 32 nanometers, 33 nanometers, 34 nanometers, 35 nanometers, 36 nanometers, 37 nanometers, 38 nanometers, 39 nanometers or 40 nanometers.

[0093] According to embodiments of the present invention, for example, the thickness of the fourth metal electrode can be 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, 260 nm, 270 nm or 280 nm.

[0094] According to an embodiment of the present invention, the interdigital transducer electrode 201 also has an input terminal, which can lead the internal circuitry to the measurement circuit / device for electrical excitation and measurement.

[0095] According to an embodiment of the present invention, the DC voltage applied to the gate electrode 301 is used to adjust the stress of the two-dimensional material 501, thereby changing its resonant frequency.

[0096] According to an embodiment of the present invention, the source and drain electrodes 302 include two identical electrodes, one of which can be used as the source electrode and the other as the drain electrode.

[0097] A frequency-modulated microwave signal can be applied through the source electrode, and the mixing current can be read through the drain electrode, thereby detecting the vibration state of the nanomechanical oscillator and thus the state of the entire composite system.

[0098] According to an embodiment of the present invention, the closest distance between the source / drain electrode 302 and the interdigital transducer electrode 201 is a half-integer multiple of the wavelength of the surface acoustic wave.

[0099] According to an embodiment of the present invention, the period length of the interdigital transducer electrode 201 is obtained based on the ratio of the wave velocity of the surface acoustic wave to be excited on the substrate 101 to its frequency.

[0100] The period length of the mirror electrode 202 is half the period length of the interdigital transducer electrode 201.

[0101] The period length of the interdigital transducer electrode 201 corresponds to the wavelength of the surface acoustic wave.

[0102] According to an embodiment of the present invention, the period length of the electrodes of the surface acoustic wave device can be adjusted according to the desired surface acoustic wave frequency, satisfying the formula... .in To design the period length of the interdigital transducer electrode 201, / 2 represents the period length of the reflector electrode 202. The surface acoustic wave velocity on substrate 101, The frequency of the surface acoustic wave to be excited.

[0103] Theoretically, surface acoustic waves (SAWs) can be generated using the piezoelectric effect by applying a signal of a certain frequency to a pair of electrodes. However, the resulting SAWs are very weak. To generate stronger SAW signals at frequency f, an interference enhancement method is needed, employing multiple periodic electrodes such that the SAWs generated by these electrodes have the same phase at any point along the propagation path. Assuming the wave velocity on a piezoelectric substrate 101 is v, the electrode period must satisfy λ = v / f. For the mirror electrode 202, since a single electrode has a very weak reflection effect on SAWs, this leads to significant SAW leakage, thus requiring an electrode array. Similarly, using the interference enhancement method, when the electrode period is v / (2f), the SAWs reflected back by each electrode have the same phase at any point.

[0104] According to an embodiment of the present invention, the array shape of the electrodes of the surface acoustic wave device can be rectangular or arc-shaped.

[0105] Figure 4 This is a flowchart illustrating the fabrication process of the nanomechanical oscillator and surface acoustic wave coupling device according to an embodiment of the present invention.

[0106] According to another aspect of the present invention, a method for fabricating a nanomechanical oscillator coupled to a surface acoustic wave (SAW) device is provided, comprising:

[0107] S1: Fabricate interdigitated transducer electrode 201 and mirror electrode 202 on substrate 101;

[0108] S2: Fabrication of gate electrode 301;

[0109] S3: Fabricate source / drain electrodes 302;

[0110] S4: A dry transfer process is used to prepare two-dimensional material 501, which is then used to cover the output end of the nanomechanical oscillator.

[0111] In this configuration, the source / drain electrode 302 is higher than the gate electrode 301, and the two-dimensional material 501 is in contact with the source / drain electrode 302 but not with the gate electrode 301.

[0112] According to an embodiment of the present invention, S1 specifically includes the following steps S11 to S13:

[0113] Step S11: Clean the surface of substrate 101 using the standard sample cleaning process;

[0114] Step S12: Using ultraviolet lithography, electron beam evaporation coating, and metal lift-off techniques, interdigitated transducer electrodes 201, mirror electrodes 202, and overlay marks 401 are fabricated on the surface of substrate 101.

[0115] According to an embodiment of the present invention, the overlay mark 401 in step S12 specifically includes the simultaneous preparation of the overlay mark 401, the interdigital transducer electrode 201, and the mirror electrode 202.

[0116] According to an embodiment of the present invention, since the two-dimensional material 501 needs to be in contact with the source / drain electrode 302 and suspended directly above the gate electrode 301, there is a height difference between the source / drain electrode 302 and the gate electrode 301. Therefore, the source / drain electrode 302 and the gate electrode 301 need to be prepared separately.

[0117] According to an embodiment of the present invention, S2 specifically includes the following steps S21 to S22:

[0118] Step S21: Clean the substrate 101, on which the interdigitated transducer electrode 201 and the mirror electrode 202 are prepared, using a standard sample cleaning process;

[0119] Step S22: The gate electrode 301 is fabricated on the surface of the substrate 101 using ultraviolet lithography, electron beam evaporation coating, and metal stripping techniques.

[0120] According to an embodiment of the present invention, S3 specifically includes the following step S31:

[0121] Step S31: After a standard sample cleaning process, source and drain electrodes 302 are prepared on the surface of substrate 101 using ultraviolet lithography, electron beam evaporation coating, and metal stripping techniques.

[0122] According to an embodiment of the present invention, in step S4, a dry transfer process is used to prepare a transferable two-dimensional material 501, which covers the output end of the nanomechanical oscillator. Specifically, this includes the following steps S41 to S44:

[0123] Step S41: Fix the film with the two-dimensional material 501 onto the glass slide;

[0124] Step S42: Invert the glass slide and align the two-dimensional material 501 with the output end of the nanomechanical oscillator under an optical microscope;

[0125] Step S43: After attaching the two-dimensional material 501 to the output end of the nanomechanical oscillator, heat it to 50-120℃;

[0126] Step S44: Lift the glass plate, and the two-dimensional material 501 separates from the thin film, remaining at the output end of the nanomechanical oscillator.

[0127] According to an embodiment of the present invention, in S41, the film is a polydimethylsiloxane (PDMS) film.

[0128] According to an embodiment of the present invention, the standard sample cleaning process includes: cleaning the substrate 101 sequentially with acetone (ACE), isopropanol (IPA) and deionized water (DI) for 5 minutes each, with ultrasonic cleaning accompanying each reagent cleaning, and finally drying with high-purity nitrogen gas.

[0129] According to an embodiment of the present invention, the ultraviolet lithography exposure technique includes: using two ultraviolet photoresists, LOR 5B and S1813, as a double-layer photoresist; first, uniformly spin-coating LOR 5B, then uniformly spinning S1813; wherein, when uniformly spinning LOR 5B, the spin coater speed is 4000 rpm for 40 seconds, and the baking stage is 180 degrees Celsius for 5 minutes; when uniformly spinning S1813, the spin coater speed is 4000 rpm for 40 seconds, and the baking stage is 115 degrees Celsius for 2 minutes. The developer selected is AZ300MIF, and development is performed at room temperature for 20 seconds.

[0130] The metal stripping process includes immersion in 1-methyl-2-pyrrolidone (NMP) at a constant temperature of 80 degrees Celsius for 3 hours.

[0131] The technical solution of the present invention will be described in detail below through preferred embodiments. It should be noted that the specific embodiments in the following text are for illustrative purposes only and are not intended to limit the present invention.

[0132] Example 1: Sample preparation.

[0133] The surface of the gallium arsenide substrate 101 was cleaned using a standard sample cleaning process. Then, interdigitated transducer electrodes 201, mirror electrodes 202, and overlay marks 401 for precise overlay in subsequent steps were fabricated on the gallium arsenide surface using ultraviolet lithography, electron beam evaporation, and metal lift-off techniques. The coating metal was aluminum. In this embodiment, a frequency of 102 MHz and the (100) crystal plane of gallium arsenide were selected. With this crystal orientation, the wavelength of the surface acoustic wave is 28 micrometers, and correspondingly, the period of the interdigital transducer electrode 201 is 28 micrometers; the period of the mirror electrode 202 is 14 micrometers.

[0134] The substrate 101 is cleaned using a standard sample cleaning process. Then, a gate electrode 301 is fabricated on the gallium arsenide surface using ultraviolet lithography, electron beam evaporation, and metal lift-off techniques. After another standard sample cleaning process, source and drain electrodes 302 are fabricated on the gallium arsenide surface using ultraviolet lithography, electron beam evaporation, and metal lift-off techniques.

[0135] The gate electrode 301 is coated with two layers of titanium and gold, with thicknesses of 3 nm and 20 nm respectively. The source / drain electrodes 302 are coated with two layers of titanium and gold, with thicknesses of 10 nm and 250 nm respectively.

[0136] Two-dimensional material 501 was peeled off from a glass slide with a polydimethylsiloxane (PDMS) film attached to its surface using a mechanical peeling method.

[0137] Observe the two-dimensional material 501 under an optical microscope, select a strip of two-dimensional material 501 with appropriate size and thickness, and position it.

[0138] To prevent damage to the electrode structure of the surface acoustic wave device during subsequent transfer, the target two-dimensional material 501 was observed under an optical microscope, and PDMS was cut with a blade to remove impurities near the target two-dimensional material 501.

[0139] Finally, graphene is transferred to the nanomechanical oscillator using a dry transfer technique, so that the two-dimensional material 501 is in contact with the front end of the source / drain electrode 302, thereby obtaining the nanomechanical oscillator and surface acoustic wave coupling device.

[0140] Example 2: Sample characterization.

[0141] Figure 5 This is a schematic diagram showing the relationship between gate voltage and resonant frequency in an embodiment of the present invention.

[0142] Reference Figure 5 As shown, for the nanomechanical oscillator and surface acoustic wave coupling device prepared in Example 1, applying a DC bias to the gate electrode 301 at its bottom changes the resonant frequency. A frequency-modulated microwave voltage signal is applied to the source electrode, and a DC voltage is applied to the gate electrode 301 for modulation. The mixing current is measured on the drain electrode. The resonant frequency can be read from the change of the mixing current with the driving frequency for each gate electrode 301 voltage. . Figure 5 Different gate electrode 301 voltages are given. The resonant frequency below It can be seen that the resonant frequency and the voltage of the gate electrode 301 have a parabolic relationship, indicating that the resonant mode of the graphene two-dimensional material 501 can be adjusted by the voltage of the gate electrode 301, and its tuning rate reaches 0.49 MHz / V.

[0143] Figure 6 The surface acoustic wave resonator prepared in the network analyzer measurement embodiment of this invention. Parameter diagram. (Refer to...) Figure 6 As shown, the resonant frequency of the surface acoustic wave resonator is determined by the wave velocity of the substrate 101 and the electrode period, and therefore can be modified by changing the device structure. The surface acoustic wave resonator fabricated in the embodiment was measured using a network analyzer. Parameters such as Figure 6 As shown. A strong resonant signal appeared at 102.37 MHz.

[0144] Example 3: Model Validation.

[0145] Figure 7 This is a schematic diagram of the model in Embodiment 3 of the present invention. To better verify the feasibility of the coupling device, finite element simulation of this type of device was also performed using COMSOL. The constructed model is as follows. Figure 7 As shown, according to the actual sample design, surface acoustic wave (SAW) electrodes and nanomechanical oscillators are arranged on the surface of the piezoelectric substrate 101. The resonant frequency of the SAW resonator can be adjusted by changing the electrode period. In the nanomechanical oscillator, the two side electrodes are source / drain electrodes 302, the middle electrode is the gate electrode 301, and a layer of two-dimensional material 501 is suspended in contact with the source / drain electrodes 302 and directly above the gate electrode 301. The Young's modulus of this two-dimensional material 501 is set. =1 TPa, Poisson's ratio =0.16, density =1950 kg / m 3 .

[0146] Figure 8 This is a displacement diagram of the nanomechanical oscillator as a whole in the model of Embodiment 3 of the present invention in the range of 100 MHz to 105 MHz. Figure 9 This is a displacement diagram of the entire nanomechanical oscillator in the model of Embodiment 3 of the present invention at 102 MHz.

[0147] After calculating the resonant frequency of the nanomechanical oscillator to be 102 MHz using COMSOL, this model was used to simulate the vibration of the nanomechanical oscillator when surface acoustic waves (SAWs) of different frequencies were excited. SAWs were excited using interdigital transducer electrodes 201 on a piezoelectric substrate 101. The period of the interdigital transducer electrodes 201 was modified according to the frequency of the input microwave signal to excite SAWs of different frequencies. The vibration of the right-hand oscillator was simulated when the SAW frequency was within a 5 MHz bandwidth near the resonant frequency of the nanomechanical oscillator. The overall displacement of the nanomechanical oscillator in the range of 100 MHz to 105 MHz is as follows: Figure 8As shown, when the two resonant frequencies are the same, the nanomechanical oscillator is resonantly excited. Figure 9 The displacement of the nanomechanical oscillator at 102 MHz (the resonant frequency of the nanomechanical oscillator) is given.

[0148] Figure 10 This diagram illustrates the modulation effect of the nanomechanical oscillator on surface acoustic waves in Embodiment 3 of the present invention. The nanomechanical oscillator component was removed from the original simulation model, and surface acoustic waves were excited using 102 MHz microwaves to compare the effect of the presence and absence of the nanomechanical oscillator on the surface displacement of substrate 101. The results are as follows. Figure 10 As shown. In both cases, the difference in the surface displacement phase of substrate 101 reflects the modulation effect of the nanomechanical oscillator on surface acoustic waves.

[0149] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A nanomechanical oscillator coupled to a surface acoustic wave (SAW) device, comprising: Substrate; A surface acoustic wave (SAW) device electrode, disposed on the surface of the substrate, is used to generate a SAW by voltage excitation. The SAW device electrode includes: Interdigitated transducer electrodes are disposed in the middle of the substrate; The reflector electrodes are disposed on both sides of the interdigital transducer electrodes; A nanomechanical oscillator, the output end of which is disposed between the interdigital transducer electrode and the reflector electrode, the nanomechanical oscillator comprising: A two-dimensional material is disposed at the output end of the nanomechanical oscillator for exciting or modulating vibration waves by DC voltage or surface acoustic waves. A gate electrode is used to connect a DC voltage to the two-dimensional material, thereby changing the resonant frequency of the two-dimensional material; Source and drain electrodes are disposed on both sides of the gate electrode and are used to apply a microwave voltage signal with a modulation frequency or to read the mixing current. Wherein, the source / drain electrode is higher than the gate electrode, the two-dimensional material covers the output terminals of the source / drain electrode and the gate electrode, and the two-dimensional material is in contact with the source / drain electrode but not with the gate electrode.

2. The nanomechanical oscillator and surface acoustic wave coupling device according to claim 1, wherein, The substrate is a type of piezoelectric material; The two-dimensional material is a heterostructure formed from graphene, molybdenum disulfide, tungsten selenide, molybdenum selenide, or the above materials.

3. The nanomechanical oscillator and surface acoustic wave coupling device according to claim 1 further includes overlay markings for positioning the nanomechanical oscillator and detecting the positioning accuracy of the nanomechanical oscillator.

4. The nanomechanical oscillator and surface acoustic wave coupling device according to claim 3, wherein the surface acoustic wave device electrode and the overlay mark are made of a metallic material, and the thickness of the surface acoustic wave device electrode and the overlay mark is 30-200 nanometers.

5. The nanomechanical oscillator and surface acoustic wave coupling device according to claim 1, wherein, Both the gate electrode and the source / drain electrode include overlapping first and second metal electrodes; The first metal electrode material is titanium or chromium, and the thickness of the first metal electrode is 3-10 nanometers; The material of the second metal electrode is gold or palladium, and the thickness of the second metal electrode is 20-70 nanometers.

6. The nanomechanical oscillator and surface acoustic wave coupling device according to claim 1, wherein, The source and drain electrodes each include overlapping third and fourth metal electrodes; The third metal electrode material is titanium or chromium, and the thickness of the third metal electrode is 30-40 nanometers; The fourth metal electrode is made of gold or palladium, and its thickness is 210-280 nanometers.

7. The nanomechanical oscillator and surface acoustic wave coupling device according to claim 1, wherein, The closest distance between the source / drain electrodes and the interdigital transducer electrodes is a half-integer multiple of the surface acoustic wave wavelength.

8. The nanomechanical oscillator and surface acoustic wave coupling device according to claim 1, wherein, The period length of the interdigital transducer electrode is obtained based on the ratio of the wave velocity of the surface acoustic wave to be excited on the substrate to its frequency. The period length of the mirror electrode is half the period length of the interdigital transducer electrode.

9. A method for preparing a nanomechanical oscillator coupled to a surface acoustic wave according to any one of claims 1-8, comprising: Fabricate interdigitated transducer electrodes and mirror electrodes on a substrate; Fabrication of the gate electrode; Fabrication of source and drain electrodes; A dry transfer process was used to prepare a transferable two-dimensional material, which was then used to cover the output end of a nanomechanical oscillator. The source / drain electrodes are higher than the gate electrode, and the two-dimensional material is in contact with the source / drain electrodes but not with the gate electrode.

10. The method according to claim 9, wherein, The preparation of the two-dimensional material using a dry transfer process, wherein the two-dimensional material covers the output end of the nanomechanical oscillator, includes: A thin film with the two-dimensional material attached is fixed onto a glass slide; The glass slide was inverted, and the two-dimensional material was aligned with the output end of the nanomechanical oscillator under an optical microscope; After attaching the two-dimensional material to the output end of the nanomechanical oscillator, heat it to 50-120℃. The glass plate is lifted, and the two-dimensional material separates from the thin film, remaining at the output end of the nanomechanical oscillator.

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