CN111498794B - Suspended graphene field effect transistor acoustic sensor - Google Patents
Suspended graphene field effect transistor acoustic sensor Download PDFInfo
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- CN111498794B CN111498794B CN202010192199.8A CN202010192199A CN111498794B CN 111498794 B CN111498794 B CN 111498794B CN 202010192199 A CN202010192199 A CN 202010192199A CN 111498794 B CN111498794 B CN 111498794B
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- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B—PERFORMING OPERATIONS; TRANSPORTING
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Abstract
The application relates to a suspended graphene field effect transistor acoustic sensor, wherein a graphene film layer covers the surface of a gate structure and covers a plurality of grooves. Thus, each groove and graphene film layer form a first cavity. Because the graphene film layer is relatively thin, vibration can be generated after the graphene film layer is impacted by mechanical sound waves. The graphene film layer, particularly at the first cavity, is more susceptible to vibration. The distance between the suspended part of the graphene film layer and the substrate can be correspondingly changed when the graphene film layer is excited by the acoustic wave pressure. The graphene film layer and the substrate can be equivalent to two electrodes of a grid capacitor, and the second cavity vacuum forms a capacitor dielectric medium. Therefore, when the distance between the graphene film layer and the substrate is changed, the capacitance value of the gate capacitor is changed. The graphene film layer can have dual functions of sensing sound waves and converting electric signals. Therefore, the suspended graphene field effect transistor acoustic sensor is simple in structure, and production cost is reduced.
Description
Technical Field
The application relates to the field of sensing, in particular to a suspended graphene field effect transistor acoustic sensor.
Background
In the prior art, a driving circuit of a suspended graphene field-effect transistor acoustic sensor usually needs complex circuits such as an electric signal generating circuit and a modulating circuit, which increase the cost of the product.
Disclosure of Invention
In view of the above, it is necessary to provide a suspended graphene fet acoustic sensor.
A suspended graphene field effect transistor acoustic sensor, comprising:
a substrate;
the grid structure is arranged on the substrate, and a groove is formed in the surface of the grid structure;
the source electrode layer and the drain electrode layer are arranged on the substrate and are respectively positioned on two sides of the gate structure;
the graphene film layer covers the surface of the groove, the graphene film layer and the groove surround to form a first cavity, and two ends of the graphene film layer are respectively connected with the source electrode layer and the drain electrode layer.
In one embodiment, the graphene film further includes a protection layer disposed on a surface of the substrate close to the graphene film layer, the protection layer and the substrate surround to form a second cavity, the source electrode layer and the drain electrode layer are located in the second cavity, and the first cavity and the second cavity are both in a vacuum state.
In one embodiment, further comprises
A grid direct current power supply electrically connected with the grid structure; and
and the drain direct current power supply is electrically connected with the drain layer.
In one embodiment, further comprising;
the first electrode layer is arranged on the surface, close to the graphene film layer, of the substrate and is positioned on one side, away from the drain electrode layer, of the protection layer, and the first electrode layer is electrically connected with the drain electrode layer;
the second electrode layer is arranged on the surface, close to the graphene film layer, of the substrate and located on one side, away from the source electrode layer, of the protection layer, and the second electrode layer is electrically connected with the source electrode layer.
In one embodiment, the semiconductor device further includes a conductive layer disposed on a side of the substrate close to the drain layer and spaced apart from the gate structure, and the conductive layer is respectively connected to the drain layer and the first electrode layer.
In one embodiment, the dc power supply further comprises a first low pass filter connected to the negative pole of the gate dc power supply and the negative pole of the drain dc power supply, respectively.
In one embodiment, the semiconductor device further comprises a first high-pass filter, wherein the first high-pass filter is respectively connected with the source layer and the gate structure;
and the second low-pass filter is connected between the drain layer and the grounding electrode.
In one embodiment, the grid dc power supply further comprises a third low-pass filter connected between the first high-pass filter and the positive electrode of the grid dc power supply.
In one embodiment, the system further comprises a band-pass filter, a gain adjuster and a phase adjuster, which are connected between the first high-pass filter and the gate structure in sequence.
In one embodiment, a second high pass filter is further included and connected between the phase adjuster and the gate structure.
According to the acoustic sensor of the suspended graphene field effect transistor, the graphene film layer covers the surface of the gate structure, and the groove covers the graphene film layer. Thus, the groove and the graphene film layer constitute the first cavity. Because the graphene film layer is small in thickness, vibration can be generated after the graphene film layer is impacted by mechanical sound waves. The graphene film layer, particularly at the first cavity, is more susceptible to vibration. At the groove, the distance between the suspended part of the graphene film layer and the substrate can be correspondingly changed when the graphene film layer is excited by the acoustic pressure. The graphene film layer and the substrate can be equivalent to a gate capacitor C gate The vacuum state of the first cavity constitutes a capacitive dielectric. Therefore, when the distance between the graphene film layer and the substrate is changed, the grid capacitance C is changed gate Will change in capacitance value. Further, the graphene film layer is a semiconductor material, and thus can convert an electric signal. The graphene film layer can have dual functions of sensing acoustic waves and converting electric signals. Therefore, the suspended graphene field effect transistor acoustic sensor is simple in structure, and production cost is reduced. Further, the graphene film layer has a wider acoustic response passband than other acoustic sensitive materials.
Drawings
Fig. 1 is a cross-sectional view of a suspended graphene fet acoustic sensor according to an embodiment of the present disclosure;
FIG. 2 is a circuit diagram provided by one embodiment of the present application;
FIG. 3 is a graph of gate voltage versus conductivity provided by one embodiment of the present application;
FIG. 4 is a circuit diagram provided by one embodiment of the present application;
FIG. 5 is a graph of AC output waveform versus time provided by one embodiment of the present application;
FIG. 6 is a graph of the AC output frequency versus gate voltage provided by one embodiment of the present application;
FIG. 7 is a circuit diagram provided by an embodiment of the present application;
FIG. 8 is a graph of signal versus frequency provided by one embodiment of the present application;
FIG. 9 is a graph of output signal versus frequency provided by one embodiment of the present application;
fig. 10 is a graph of normalized sensitivity versus frequency provided by an embodiment of the present application.
Description of the reference numerals
Suspended graphene fet acoustic sensor 10
Gate dielectric layer 112
Gate electrode layer 114
Groove 120
Graphene film layer 150
Grid DC power supply 170
Drain dc power supply 180
The second electrode layer 230
First low pass filter 250
First high pass filter 260
Second low pass filter 270
Third low pass filter 280
Second high pass filter 330
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is further described in detail below by way of embodiments and with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.
The numbering scheme used herein for the components, such as "first", "second", etc., is used solely to distinguish between the items depicted and not to imply any order or technical meaning. The term "connected" and "coupled" when used in this application, unless otherwise indicated, includes both direct and indirect connections (couplings). In the description of the present application, it is to be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "level", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are used only for convenience in describing the present application and for simplicity in description, and do not indicate or imply that the devices or elements being referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, are not to be considered as limiting the present application.
In this application, unless expressly stated or limited otherwise, a first feature is "on" or "under" a second feature such that the first and second features are in direct contact, or the first and second features are in indirect contact via an intermediary. Also, a first feature "on," "over," and "above" a second feature may be directly or obliquely above the second feature, or may simply mean that the first feature is at a higher elevation than the second feature. A first feature "under," "below," and "beneath" a second feature may be directly or obliquely under the first feature or may simply mean that the first feature is at a lesser elevation than the second feature.
Referring to fig. 1 and fig. 2, an embodiment of the present application provides a suspended graphene fet acoustic sensor 10. The suspended graphene fet acoustic sensor 10 may be a graphene fet sensor. The suspended graphene fet acoustic sensor 10 includes a substrate 100, a gate structure 110, a source layer 130, a drain layer 140, and a graphene film layer 150. The gate structure 110 is disposed on the substrate 100. The surface of the gate structure 110 is provided with a groove 120. The source layer 130 and the drain layer 140 are disposed on the surface of the substrate 100 at an interval and located at two sides of the gate structure 110. The graphene film layer 150 is disposed on the surface of the gate structure 110 close to the groove 120. The graphene film layer 150 is electrically connected to the source layer 130 and the drain layer 140, respectively. The graphene film layer 150 and the groove 120 surround to form a first cavity 160. The graphene film layer 150 may constitute a graphene channel layer. The number of the grooves 120 may be multiple, and the plurality of grooves 120 may be disposed on the surface of the gate structure 110 in an array.
In one embodiment, the graphene film layer 150 is a single-layer graphene thin film. Therefore, the volume of the suspended graphene fet acoustic sensor 10 can be reduced, and the sensitivity of the graphene film layer 150 to sound wave vibration can be improved. The single-layer graphene film may have a thickness of 0.3 to 0.4 nanometers. In one embodiment the graphene thin film has a thickness of 0.33 nanometers.
In one embodiment, the suspended graphene fet acoustic sensor 10 further includes the protective layer 190. The protection layer 190 is disposed on the surface of the substrate 100 close to the graphene film layer 150. The protective layer 190 and the substrate 100 surround to form a second cavity 210. The source layer 130 and the drain layer 140 are located within the second cavity 210. It is understood that the second cavity 210 may have a vacuum therein. Therefore, the first cavity 160 may also be in a vacuum state, which may improve the sensitivity of the suspended graphene fet acoustic sensor 10. The source layer 130 and the drain layer 140 are located within the second cavity 210. The first cavity 160 and the second cavity 210 are both in a vacuum state.
In one embodiment, the suspended graphene fet acoustic sensor 10 further includes a gate dc power supply 170 and a drain dc power supply 180. The gate dc power supply 170 is connected to the gate structure 110. The drain dc power supply 180 is electrically connected to the drain layer 140.
The substrate 100 may be a silicon substrate 100 or a semiconductor formed of other materials, such as germaniumA substrate 100. The substrate 100 may be a doped semiconductor substrate 100. The doped semiconductor substrate 100 may be an n-type doped semiconductor substrate 100 or a p-type doped semiconductor substrate 100. Typical doping concentration of p-type silicon is 10 16 cm -3 And (4) horizontal. The complementary n + type heavily doped gate structure 110 and drain layer 140 regions are formed by photolithography and localized ion implantation operations. In one embodiment, the substrate 100110 is a p-type doped silicon substrate 100. When the p-type silicon substrate 100 is held at ground (0V), the positive gate structure 110 is at a voltage (V) gs >0, max not more than 8V to prevent punch through) and a positive drain layer 140 voltage (V) ds >0, typically very low, 10 mV) can achieve reliable electrical isolation by the pn junction reverse bias principle.
The shape of the groove 120 is not limited, and may be any shape of the groove 120, for example, a cylinder, a rectangular parallelepiped, a cube, a sphere, a cone, and the like. The shape and size of the grooves 120 and the spacing between the grooves 120 affect the carrier mobility of the graphene fet.
In one embodiment, the groove 120 is cylindrical, and the diameter of the groove 120 may be 500nm. The grooves 120 may be arranged in a square array. In each row and each column, the center-to-center spacing of adjacent grooves 120 is 1 μm.
In one embodiment, the diameter of the cylindrical recess 120 is 400nm to 600nm, and the depth of the cylindrical recess 120 is 50nm to 150nm. The distance between the centers of the adjacent grooves 120 is 0.5 to 2 μm. The spacing between adjacent grooves 120 is the same.
In one embodiment, every adjacent four of the grooves 120 are arranged in a square shape. In order to obtain better carrier mobility, the ratio of the total area of the grooves 120 to the area of the graphene conductive channel layer is greater than or equal to pi/16.
In one embodiment, the graphene film layer 150 may be at least one of single-layer graphene, double-layer graphene, and multi-layer graphene. In one embodiment, the graphene film layer 150 may be disposed vertically above the gate structure 110. In one embodiment, the graphene film layer 150 is sized 40 μm by 40 μm.
In one embodiment, a chemical vapor deposition method may be used to form the graphene thin film, and then the graphene thin film is transferred onto the gate structure 110 to form the graphene film layer 150.
The source layer 130 and the drain layer 140 may be formed of any suitable material. For example, the material of the source layer 130 and the drain layer 140 may include at least one of Ti, pt, cr, au, al, ni, cu, ag, ITO, and the like. The source layer 130 and the drain layer 140 may be the same material. The source layer 130 and the drain layer 140 may be simultaneously formed in the same process.
The gate structure 110 may be formed of any suitable material. In one embodiment, the gate structure 110 may include a metal material. An insulating layer (e.g., a SiO2 insulating layer) may also be formed between the gate structure 110 and the substrate 100. The metal material may be at least one of Ti, pt, cr, au, al, ni, cu, ag, and the like. In one embodiment, the substrate 100 is a doped semiconductor substrate 100, and the doped semiconductor substrate 100 may be directly subjected to a local complementary doping to form the gate structure 110. For example, the p-doped silicon substrate 100 may be locally heavily doped n-type to form a conductive portion of the gate structure 110.
In one embodiment, the graphene film layer 150 may be in contact with the source layer 130 and the drain layer 140 for electrical connection. The gate dc power supply 170 may provide a dc voltage to the gate structure 110. The drain dc power supply 180 may provide a dc voltage to the drain layer 140.
The material of the protection layer 190 is an insulating material, and in one embodiment, the protection layer 190 is silicon oxide. The protective layer 190 is disposed to prevent the graphene from being contaminated by external contaminants and affecting the stability of the carrier mobility of the graphene. Further, the inside of the second cavity 210 may be in a vacuum state, so that the graphene film layer 150 is prevented from being affected by air damping when vibrating, and the resonance effect is improved. It is understood that the source layer 130 and the drain layer 140 may be in contact with the inner wall of the second cavity 210.
It is understood that the graphene film layer 150 covers the surface of the gate structure 110 and covers the groove 120. Thus, the groove 120 and the graphene film layer 150 constitute the first cavity 160. Since the graphene film layer 150 has a small thickness, it may vibrate after being impacted by mechanical sound waves. The graphene film layer 150, particularly at the first cavity 160, is more susceptible to vibration. At the groove 120, the distance between the suspended portion of the graphene film layer 150 and the substrate 100 may change correspondingly when excited by the acoustic pressure. The graphene film layer 150 and the substrate 100 may be equivalent to a gate capacitor C gate The vacuum state of the first cavity 160 constitutes a capacitive dielectric. Therefore, when the distance between the graphene film layer 150 and the substrate 100 changes, the gate capacitance C gate Will change in capacitance value. Further, the graphene film layer 150 is a semiconductor material, and thus can convert the function of an electrical signal. The graphene film layer 150 may have dual functions of sensing acoustic waves and converting electrical signals. Therefore, the suspended graphene field effect transistor acoustic sensor is simple in structure and reduces production cost. Further, the graphene film layer 150 has a wider acoustic response passband than other acoustic sensitive materials.
The gate capacitance C gate I.e., the variable capacitance, which is affected by the vibration of the graphene film layer 150. The electrical constraint relationship of the graphene film layer 150 can be expressed by the law of conservation of charge as: v ch C Q -V gs [C gate C Q /(C gate +C Q )]= qn, wherein n represents graphene internal carrier density; q represents a unit charge amount; v ch The chemical potential of the graphene is expressed, and the special energy band structure of the graphene film layer 150 as a zero band gap semiconductor has an approximate relation V ch C Q 2qn. Accordingly, the aforementioned conservation of charge equation can be simplified approximately as: v gs C gate Qn, which is just in line with the general description of the electrical characteristics of field effect devices. Due to the fact thatThe gate capacitance change Δ C caused by acoustic wave excitation gate The resulting electrical signal response of the fet, in relation to the change in carrier density of the graphene film layer 150, can be expressed as follows according to the Drude model (σ = μ qn, σ is the semiconductor conductivity; μ is the carrier mobility):
that is, under the condition that the carrier mobility mu is high and the change is not large, the acoustic wave excitation generates the device conductivity (proportional to the drain current) with the approximately linear change of the electric signal response, and the sensitivity is high. That is, the output electrical signal of the suspended graphene fet acoustic sensor 10 that can be directly measured is the current I flowing through the drain ds It has a direct relationship with the conductivity σ:
wherein L is the length of the graphene conduction channel, and W is the width of the graphene conduction channel (
Defined as the aspect ratio, which does not occur if the graphene conductive channel is square); v ds Is the drain voltage, which may be a small dc voltage of 10mV or tens of millivolts. Thus, the current I through the drain ds The output electrical signal of the suspended graphene fet acoustic sensor 10 can be obtained. Experiments prove that the response gain of the graphene film layer 150 is almost flat in the range of 1-210kHz, and covers sound waves and low-frequency ultrasonic frequency bands. And the carrier wave emitted by the graphene film layer 150 has a certain tunability.
Applying a positive gate voltage V to the gate structure 110 via the gate DC power supply 170 gs In addition, a smaller drain voltage V is applied to the drain layer 140 via the drain DC power supply 180 ds . In one embodiment, the drain voltage V ds May be 10mV. Then passing electricityFlow table 350 measures the drain current output of the device. And then obtaining a conductivity output signal through the drain current. Since the graphene film layer 150 has a dangling portion at the groove 120, a positive gate voltage V is applied gs In this case, the graphene film layer 150 is bound to increase the electron density or decrease the hole density due to the electric field effect. Thus, coulomb force between the gate layer and the graphene film layer 150 will cause the graphene film layer 150 at the suspension part to generate tensile deformation (the equivalent distance becomes smaller), and the gate capacitance C is gate It becomes large. The coulomb force acts similar to the pressure created by the acoustic signal. Therefore, by continuously adjusting the DC gate voltage V gs Namely, the effect of the force can be verified, so that the suspended graphene field effect transistor can generate conductivity change.
Referring to fig. 3, when the acoustic pressure is applied to the graphene film layer 150 to deform the graphene film layer 150, the carrier density and conductivity of the graphene film layer 150 should be changed similarly, so as to generate an output electrical signal.
In one embodiment, the suspended graphene fet acoustic sensor 10 further includes a first electrode layer 220 and a second electrode layer 230. The first electrode layer 220 is disposed on the surface of the substrate 100 close to the graphene film layer 150, and is located on a side of the protection layer 190 away from the source layer 130. The first electrode layer 220 is electrically connected to the drain electrode layer 140. The second electrode layer 230 is disposed on the surface of the substrate 100 close to the graphene film layer 150, and is located outside the second cavity 210. The second electrode layer 230 is electrically connected to the source layer 130. Therefore, the drain layer 140 may be connected to an external circuit through the first electrode layer 220, and the source layer 130 may be connected to an external circuit through the second electrode layer 230. In one embodiment, the source layer 130 may be connected to the first electrode through the substrate 100.
In one embodiment, the suspended graphene field effect transistor acoustic sensor 10 further includes a conductive layer 240. The conductive layer 240 is disposed on a side of the substrate 100 close to the drain layer 140. The conductive layer 240 is spaced apart from the gate structure 110. The conductive layer 240 is connected to the drain layer 140 and the first electrode layer 220, respectively. The conductive layer 240 may be a heavily n + doped drain region in the substrate 100. The drain layer 140 is electrically connected to the first electrode layer 220 through the conductive layer 240.
In one embodiment, the gate structure 110 includes a gate dielectric layer 112 and a gate electrode layer 114, which are stacked, and the gate dielectric layer 112 is disposed adjacent to the graphene film layer 150. The gate dielectric layer 112 may be a thin layer of high dielectric constant solid dielectric deposited by photolithography and localized atomic layer evaporation over the heavily doped n + type gate region. In one embodiment the thin high-k solid dielectric layer may be HfO 2 、ZrO 2 And Al 2 O 3 At least one of (1). In one embodiment, the gate dielectric layer 112124 is made of hafnium aluminum oxide (Hf) compound x Al y O 2 From HfO 2 With Al 2 O 3 Composite formation). The thickness of the gate dielectric layer 112124 can be 1nm to 100nm. Preferably, the thickness of the gate dielectric layer 112124 is10nm to 15nmThis thickness range does not induce the risk of pinhole breakdown. The gate dielectric layer 112124 can be prepared by atomic layer evaporation deposition, and the gate dielectric layer 112 prepared by the method is better in uniformity and coverage. In one embodiment, a dry oxygen oxidation process (using O) may be employed 3 Precursor) to avoid the pinhole breakdown risk of vapor oxidation. The gate dielectric may serve as a gate capacitance layer of the device.
The gate electrode layer 114 may be formed of any suitable material. In one embodiment, the gate electrode layer 114 may be formed of a metal material. An insulating layer (e.g., siO) may be formed between the gate electrode layer 114 and the substrate 100 2 An insulating layer). The metal material may be at least one of Ti, pt, cr, au, al, ni, cu, ag, and the like. In one embodiment, the substrate 100110 is a doped semiconductor substrate 100, and the doped semiconductor substrate 100 can be directly doped with a local complementary dopant to form the gate electrode layer 114. For example, the p-type doped silicon substrate 100 may be doped withThe rows are partially heavily n-doped to form the gate electrode layer 114, which is conductive.
In one embodiment, the suspended graphene field effect transistor acoustic sensor 10 further includes a first low pass filter 250. The first low pass filter 250 is connected to the negative electrode of the gate dc power supply 170 and the negative electrode of the drain dc power supply 180, respectively. The gate dc power supply 170 and the drain dc power supply 180 may be prevented from interfering with each other by the first low pass filter 250. In one embodiment, the first low pass filter 250 may be an isolated bead.
Referring to fig. 4, in an embodiment, the suspended graphene fet acoustic sensor 10 further includes a first high-pass filter 260 and a second low-pass filter 270. The first high pass filter 260 is connected to the source layer 130 and the gate structure 110, respectively. The second low pass filter 270 is connected between the drain layer 140 and the ground 360. Therefore, the source layer 130, the first high pass filter 260, and the gate structure 110 form a high pass network, and output an alternating current. The source layer 130, the second low pass filter 270, and the ground electrode 360 form a low pass network, and output a direct current. It is understood that the first high pass filter 260 may be a capacitor. The second low pass filter 270 may be an isolated bead.
In one embodiment, the suspended graphene fet acoustic sensor 10 further includes a third low pass filter 280. The third low pass filter 280 is connected between the first high pass filter 260 and the positive electrode of the gate dc power supply 170. The third low pass filter 280 may be an isolated bead. The third low pass filter 280 may function as a lattice dc. The gate dc power supply 170 is prevented from interfering with the loop formed by the high-pass network.
In one embodiment, the suspended graphene fet acoustic sensor 10 further includes a band pass filter 290, a gain adjuster 310, and a phase adjuster 320, which are connected in sequence. Wherein the band pass filter 290 is connected to the first high pass filter 260. The phase adjuster 320 is connected to the gate structure 110.
In one embodiment, the suspended graphene field effect transistor acoustic sensor 10 further includes a second high pass filter 330. The second high pass filter 330 is connected between the phase adjuster 320 and the gate structure 110. The influence of the direct current on the loop formed by the high-pass network can be further reduced by the second high-pass filter 330.
The output current of the low-pass network is the same as that of the above embodiment, and is not described herein again.
For the high-pass network, when the temperature is higher than absolute zero, any device is in the presence of thermal noise, so the output signal necessarily contains a tiny ac ripple component. The alternating current can be partially fed back to the gate structure 110 of the suspended graphene fet acoustic sensor 10 through a feedback loop formed by the high-pass network. The alternating current part and the gate voltage V gs And superposing carrier waves which can generate self-excitation and form high-frequency oscillation.
Referring to FIG. 5, therefore, when the gate voltage V is applied gs When the high-frequency resonant circuit is locked at different direct-current voltage values, a high-frequency resonant signal with the frequency of tens of megahertz can be generated through closed-loop positive feedback of the high-pass network, the waveform is very close to a sine wave, and the high-frequency resonant circuit has a high quality factor (Q value). High-frequency resonant frequency f OSC And a DC gate voltage V gs Showing a positive correlation.
As shown in fig. 6, when the gate voltage V is applied gs With =1.5V, the resonance frequency is approximately 38MHz. The gate voltage V gs Increasing to 4V, the resonant frequency rises to around 43 MHz. This phenomenon may be due to the gate dc voltage V as described gs The static coulomb force generated is different from the pulling force. The change in static coulomb force pull can result in a change in the stress properties of the graphene film layer 150. Because the high-frequency resonance waveform of tens of megahertz level has directly been used as the carrier and modulates the baseband signal to realize the wireless communication of signal of telecommunication, consequently the embodiment of this application provides unsettled graphite alkene field effect transistor acoustic sensor 10 does not need additionally to design high-frequency oscillation circuit, has practicality moreAnd the method has the advantages of simplicity and rapidness. The adjustable high-frequency carrier is also favorable for selecting the proper grid voltage V gs Different carrier frequencies are selected to achieve frequency division multiplexing of the radio signal when multiple devices are used together.
Referring to fig. 7, in an embodiment, the suspended graphene fet acoustic sensor 10 further includes an acoustic wave generator 340. The acoustic wave generator is configured to emit an acoustic wave to the graphene film layer 150. The acoustic wave generator 340 may be a programmable acoustic wave generator 340. The acoustic signal emitted by the acoustic generator 340 acts as a known excitation signal. The baseband signal generated by the acoustic wave excitation can perform a modulation action on the high-frequency carrier formed by the high-pass network, so as to generate a conventional Amplitude Modulation (AM) signal. Since the carrier frequency is measurable, a coherent demodulation method may be used to extract the baseband response signal of the suspended graphene fet acoustic sensor 10, and the sensing performance of the suspended graphene fet acoustic sensor 10 may be analyzed by comparing the known acoustic excitation signal with the graphene baseband response signal.
Referring to fig. 8, the maximum frequency of the transmitted sound wave signal is 210kHz, and the frequency spectrum completely covers the human threshold (below 20 kHz), and enters the ultrasonic range.
Referring to fig. 9, by demodulation, a response signal spectrum of the suspended graphene fet acoustic sensor 10 to the acoustic wave can be obtained,
referring to fig. 10, comparing fig. 8 and fig. 9, it can be seen that when the acoustic frequency is lower than 210kHz, the response of the sensing device is substantially proportional to the intensity of the excitation signal, so that the suspended graphene fet acoustic sensor 10 is flat for a wide acoustic frequency band (< 210 kHz). Therefore, the graphene field effect transistor acoustic sensor with the suspended graphene field effect transistor has a large detection range.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present patent. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, and these are all within the scope of protection of the present application. Therefore, the protection scope of the present patent application shall be subject to the appended claims.
The present invention is supported by the following studies: china national science fund (61901300), tianjin City science fund (18 JCYBJC 86000), tianjin City textbook scientific research program (2018 KJ 153).
Claims (10)
1. A suspended graphene field effect transistor acoustic sensor, comprising:
a substrate (100);
the grid structure (110) is arranged on the substrate (100), and a groove (120) is arranged on the surface of the grid structure (110);
a source electrode layer (130) and a drain electrode layer (140) disposed on the substrate (100) and respectively located at two sides of the gate structure (110);
the graphene film layer (150) covers the surface of the groove (120), the graphene film layer (150) and the groove (120) surround to form a first cavity (160), and two ends of the graphene film layer (150) are respectively connected with the source electrode layer (130) and the drain electrode layer (140);
the protective layer (190) is arranged on the surface, close to the graphene film layer (150), of the substrate (100), the protective layer (190) and the substrate (100) surround to form a second cavity (210), the source electrode layer (130) and the drain electrode layer (140) are located in the second cavity (210), and the first cavity (160) and the second cavity (210) are both in a vacuum state.
2. The suspended graphene field effect transistor acoustic sensor of claim 1, further comprising
A gate DC power supply (170) electrically connected to the gate structure (110); and
and a drain DC power supply (180) electrically connected to the drain layer (140).
3. The suspended graphene field effect transistor acoustic sensor of claim 1, further comprising;
the first electrode layer (220) is arranged on the surface, close to the graphene film layer (150), of the substrate (100) and is positioned on one side, away from the drain layer (140), of the protective layer (190), and the first electrode layer (220) is electrically connected with the drain layer (140);
and the second electrode layer (230) is arranged on the surface, close to the graphene film layer (150), of the substrate (100) and is positioned on the side, away from the source layer (130), of the protection layer (190), and the second electrode layer (230) is electrically connected with the source layer (130).
4. The suspended graphene fet acoustic sensor of claim 3, further comprising a conductive layer (240) disposed on a side of the substrate (100) adjacent to the drain layer (140) and spaced apart from the gate structure (110), wherein the conductive layer (240) is connected to the drain layer (140) and the first electrode layer (220), respectively.
5. The suspended graphene field effect transistor acoustic sensor of claim 2, further comprising a first low pass filter (250), the first low pass filter (250) being connected to a negative electrode of the gate dc power supply (170) and a negative electrode of the drain dc power supply (180), respectively.
6. The suspended graphene field effect transistor acoustic sensor of claim 5, further comprising a first high pass filter (260), the first high pass filter (260) being connected to the source layer (130) and the gate structure (110), respectively;
and a second low-pass filter (270) connected between the drain layer (140) and a ground electrode (360).
7. The suspended graphene field effect transistor acoustic sensor of claim 6, further comprising a third low pass filter (280) connected between the first high pass filter (260) and the positive pole of the grid DC power supply (170).
8. The suspended graphene field effect transistor acoustic sensor of claim 7, further comprising a band pass filter (290), a gain adjuster (310), and a phase adjuster (320) sequentially connected between the first high pass filter (260) and the gate structure (110).
9. The suspended graphene field effect transistor acoustic sensor of claim 8, further comprising a second high pass filter (330) connected between the phase adjuster (320) and the gate structure (110).
10. The suspended graphene field effect transistor acoustic sensor of claim 1, wherein the graphene film layer (150) is one of single-layer graphene, double-layer graphene, and multi-layer graphene.
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