TWI412223B - Piezoelectric transducer - Google Patents

Abstract

A Piezoelectric transducer comprises a flexible substrate, a piezoelectric layer having a first surface and a second surface opposite to the first surface, a first conducting layer mounted on the first surface of the piezoelectric layer and a second conducting layer mounted on the second surface of the piezoelectric layer. The first conductive layer or the second conductive layer combines with the substrate. An ohmic contact exists between the first conductive layer and the piezoelectric layer and a schottky contact exists between the second conducting layer and the piezoelectric layer. The Piezoelectric transducer is given the function of rectification through the schottky contact.

Description

Piezoelectric transducer

The present invention relates to a piezoelectric transducer, and more particularly to a piezoelectric transducer having a rectifying function.

Piezoelectricity is a phenomenon of electromechanical energy exchange, first discovered by Pierre Curie and Jacques Curie in 1880; it was found that if a mechanical pressure was applied to the tourmaline, it would be able to obtain a charge on its surface due to mechanical deformation of the material. The resulting polarization phenomenon was named piezoelectric by WG Hankel. The following year, Pierre Curie and Jacques Curie used M. G. Lippmann's thermodynamic theory to confirm the existence of the inverse effect of piezoelectricity, that is, the applied electric field can cause mechanical deformation of the crystal. Since the discovery of piezoelectric materials, it has been widely used in various applications such as communication components, sensing components, microactuators, and power generation components.

Lead zirconate titanate (PZT) and zinc oxide (ZnO) are the most commonly used piezoelectric materials. As shown in Figures 1a, 1b and 1c, a piezoelectric element 91 is composed of a non-conductive material and its interior. There is no free electron to help conduct, but if a stress (for example, a stress 92 or a compressive stress 93) is applied to the piezoelectric element 91, causing internal crystal deformation, it will cause the electron 94 to move, making the piezoelectric element The force surface of 91 accumulates a charge (voltage) proportional to the magnitude of the stress. When the stress direction is opposite, the polarity of the charge (voltage) is also reversed. Therefore, when the piezoelectric material is deformed by vibration, the upper and lower sides are respectively subjected to the tensile stress and the compressive stress to collect different charges, and therefore, an alternating current can be output, as shown in FIG. However, the power supply requirements of general electronic components are mostly DC power. Therefore, when the piezoelectric material is vibrated to supply power to an electronic component, an external rectifier circuit is required to convert the output alternating current into direct current. The rectifier circuit is divided into half-wave rectification and full-wave rectification. The half-wave rectification will cut off the negative half cycle. The rectification mode is composed of diodes. The full-wave rectification turns the negative half cycle into a positive value. Kind: The first type uses a center-tapped transformer and two diodes to form a rectifier circuit, and the second uses four diode designs, the circuit structure is similar to that of a bridge, especially called a bridge rectifier circuit, such as As shown in Fig. 3, it is a bridge rectifier circuit diagram of a conventional piezoelectric transducer.

For example, in the case of full-wave bridge rectification, if the bridge rectifier circuit composed of the 矽 diode is used to perform the output rectification of the conventional piezoelectric transducer, the conventional piezoelectric transducer can be lost by about 1.4. Volt voltage, and the internal resistance of the four diodes also cause energy consumption; if the bridge rectifier circuit composed of 锗 diodes, it will lose about 0.5 to 0.8 volts, while four The internal resistance of the polar body also causes energy consumption; if the 1N5711 diode with a small forward cut-in voltage is used for rectification, it will lose 0.46 volts, and its internal resistance will also cause energy consumption, and because the diode is special Diode, so the unit price is higher.

Therefore, if the piezoelectric transducer can have a rectifying function and directly output direct current, the power loss of the piezoelectric transducer caused by a rectifier circuit can be removed, and the volume and cost of the rectifier circuit can be reduced.

It is an object of the present invention to improve the above disadvantages to provide a piezoelectric transducer capable of generating the alternating current by vibration and utilizing a potential barrier formed by the contact of the piezoelectric material with the metallic material. Perform rectification. Therefore, the power loss of the external rectifier circuit can improve the piezoelectric transducing efficiency.

A second object of the present invention is to provide a piezoelectric transducer capable of generating the alternating current by vibration and rectifying the potential barrier by using a piezoelectric material in contact with the metal material. . Therefore, the cost of the external rectifier circuit can be reduced, and the cost of constructing the piezoelectric transducer system can be reduced.

Still another object of the present invention is to provide a piezoelectric transducer capable of generating the alternating current by vibration and rectifying a potential barrier by using a piezoelectric material in contact with a metal material. . Therefore, the volume required for the external rectification circuit can reduce the number of devices that use space and increase the unit volume.

The piezoelectric transducer device of the present invention is mainly composed of a substrate having flexibility; a piezoelectric layer having a first surface and a second surface; and a first conductive layer disposed on the piezoelectric layer a first surface of the layer; a second conductive layer disposed on the second surface of the piezoelectric layer; wherein the first conductive layer or the second conductive layer is bonded to the substrate; the first conductive layer and the The piezoelectric layers are an ohmic contact; the second conductive layer and the piezoelectric layer are in a Schottky contact. A piezoelectric transducer having a rectifying function is formed by the Schottky contact.

The above and other objects, features, and advantages of the present invention will become more apparent from the description of the appended claims. It is a first embodiment of the piezoelectric transducer device of the present invention. The piezoelectric transducer device comprises a substrate 1, a first conductive layer 2, a piezoelectric layer 3 and a second conductive layer 4. The first conductive layer 2 is formed on the substrate 1 , and the piezoelectric layer 3 is disposed between the first conductive layer 2 and the second conductive layer 4 . The first conductive layer 2 and the piezoelectric layer 3 are in an ohmic contact; the second conductive layer 4 and the piezoelectric layer 3 are in a Schottky contact. Therefore, the alternating current generated by the piezoelectric transducer of the piezoelectric transducer can be rectified by the Schottky contact.

In detail, the substrate 1 is preferably made of a flexible substrate such as plastic, and the substrate 1 can be electrically conductive or non-conductive, and the substrate 1 can be used to grow other material layers. The first conductive layer 2 is preferably formed of a conductive metal material, and the first conductive layer 2 is disposed on one surface of the substrate 1. The piezoelectric layer 3 is preferably made of lead zirconate titanate or zinc oxide, by radio frequency sputtering, direct current sputtering, sol-gel method, hot pressing method, screen printing method, chemical vapor deposition method, electron It is composed of a beam evaporation method, a laser deposition method or an atomic layer deposition method. The piezoelectric layer 3 has a first surface 31 and a second surface 32. The first surface 31 is bonded to the first conductive layer 2, and the first surface 31 and the first conductive layer 2 are The ohmic contact. The second conductive layer 4 is preferably made of a metal material such as gold, platinum, silver or copper by radio frequency sputtering, direct current sputtering, thermal evaporation, screen printing, chemical vapor deposition, or electron beam evaporation. It is made by plating, laser deposition, atomic layer deposition or coating. The second conductive layer 4 is bonded to the second surface 32 of the piezoelectric layer 3, and the Schottky contact is between the second conductive layer 4 and the second surface 32 of the piezoelectric layer 3.

The operation of the piezoelectric transducer of the present invention is as follows. In the following, since the substrate 1 has flexibility, when one end of the substrate 1 is vibrated (for example, repeatedly oscillated), it can be disposed on the substrate. The layers of material on 1 are also deformed as they vibrate. As shown in FIG. 5a, when the substrate 1 is swung upward, the first surface 31 and the second surface 32 of the piezoelectric layer 3 are respectively subjected to a stress and a compressive stress, and thus are concentrated on the first surface 31. And charging a positive charge on the second surface 32; conversely, as shown in FIG. 5b, when the substrate 1 is swung downward, the first surface 31 and the second surface 32 of the piezoelectric layer 3 are respectively collected. Positive and negative charges.

In addition, the ohmic contact is a metal semiconductor junction, which can be turned in both directions, and the contact resistance value is much smaller than the series resistance of a semiconductor. When the current passes, the voltage drop is negligible; the Schottky contact is another a metal semiconductor junction, when the metal and semiconductor forming the junction of the metal semiconductor are in contact, the electron affinity of the semiconductor and the work function of the metal will form a Schottky barrier, the Schottky barrier By subtracting the potential difference between a Fermi Level and the conduction conduction band, a built-in potential barrier is obtained, and the built-in potential barrier is an electron in the semiconductor conduction band that attempts to move into the metal. The obstacles you see when you see it. In the case of forward bias, the barrier from the metal to the semiconductor is unchanged, but the barrier from the semiconductor to the metal is reduced; conversely, in the case of reverse bias, the barrier from the metal to the semiconductor It does not change, but the barrier from the semiconductor to the metal increases.

In summary, since the ohmic contact is between the first conductive layer 2 and the piezoelectric layer 3, and the Schottky contact is between the second conductive layer 4 and the piezoelectric layer 3, when the pressure is When the electrical layer 3 swings upward, the first surface 31 collects a negative charge and the second surface 32 collects a positive charge. If the first conductive layer 2 having the ohmic contact is grounded, the first conductive layer 2 and the second conductive layer The layer 4 is forward biased, and the barrier from the semiconductor to the metal is reduced, and the second conductive layer 4 having the Schottky contact can output a positive voltage; otherwise, when the piezoelectric layer 3 is swung downward The first surface 31 collects a positive charge and the second surface 32 collects a negative charge. If the first conductive layer 2 having the ohmic contact is grounded, the first conductive layer 2 and the second conductive layer 4 are reversely biased. The voltage increases from the semiconductor to the metal, and the voltage value of the output of the second conductive layer 4 having the Schottky contact is zero. Please refer to FIG. 6, which is an ideal output voltage waveform diagram of the piezoelectric transducer of the present invention. Therefore, the piezoelectric transducer disclosed in the present invention can directly provide rectified power without passing through any rectifier circuit.

Referring to FIG. 7, which is a second embodiment of the present invention, the second embodiment is different from the first embodiment in that the second conductive layer 4 can be formed on the substrate 1 first. The piezoelectric layer 3 and the first conductive layer 2 are sequentially formed on the second conductive layer 4. Wherein, the Schottky contact is between the second conductive layer 4 and the piezoelectric layer 3, and the ohmic contact is between the first conductive layer 2 and the piezoelectric layer 3, so when the piezoelectric layer 3 swings upward When the first conductive layer 2 having the ohmic contact is grounded, the first conductive layer 2 and the second conductive layer 4 are reversely biased, and the voltage of the second conductive layer 4 having the Schottky contact is output. The value is zero; conversely, when the piezoelectric layer 3 is swung downward, if the first conductive layer 2 having the ohmic contact is grounded, the first conductive layer 2 and the second conductive layer 4 are forward biased. The second conductive layer 4 having the Schottky contact outputs a positive voltage.

Therefore, the piezoelectric transducer device disclosed in the present invention can selectively combine the first conductive layer 2 or the second conductive layer 4 on the substrate, and directly provide rectified power without passing through any rectifier circuit.

In the piezoelectric transducer device of the present invention, the alternating current can be generated by vibration, and the potential barrier formed by the piezoelectric material in contact with the metal material can be rectified. Therefore, there is no power loss of the external rectifying circuit, which has the effect of improving the piezoelectric transducing efficiency.

In the piezoelectric transducer device of the present invention, the alternating current can be generated by vibration, and the potential barrier formed by the piezoelectric material in contact with the metal material can be rectified. Therefore, the cost required for the external rectification circuit has the effect of reducing the cost of constructing the piezoelectric transducing system.

In the piezoelectric transducer device of the present invention, the alternating current can be generated by vibration, and the potential barrier formed by the piezoelectric material in contact with the metal material can be rectified. Therefore, the volume required for the external rectification circuit has the effect of reducing the space of use and increasing the number of devices per unit volume.

While the invention has been described in connection with the preferred embodiments described above, it is not intended to limit the scope of the invention. The technical scope of the invention is protected, and therefore the scope of the invention is defined by the scope of the appended claims.

[this invention]

1. . . Substrate

2. . . First conductive layer

3. . . Piezoelectric layer

31. . . First surface

32. . . Second surface

4. . . Second conductive layer

[知知]

91. . . Piezoelectric element

92. . . Tensile stress

93. . . Compressive stress

94. . . electronic

Figure 1a: Schematic diagram of a conventional piezoelectric transducer that is unstressed.

Figure 1b: Schematic diagram of the tensile stress experienced by a conventional piezoelectric transducer.

Figure 1c: Schematic diagram of a conventional piezoelectric transducer that is subjected to compressive stress.

Figure 2: Voltage waveform diagram after power generation by a conventional piezoelectric transducer.

Figure 3: Bridge rectifier circuit diagram of a conventional piezoelectric transducer.

Fig. 4 is a perspective view showing the combination of the first embodiment of the piezoelectric transducer of the present invention.

Fig. 5a is a schematic view showing the upward swing power generation of the first embodiment of the piezoelectric transducer device of the present invention.

Fig. 5b is a schematic view showing the first embodiment of the piezoelectric transducer device of the present invention which swings downward to generate electricity.

Fig. 6 is a view showing voltage waveforms of self-rectification after power generation in the first embodiment of the piezoelectric transducer device of the present invention.

Figure 7 is a perspective view showing the combination of the second embodiment of the piezoelectric transducer of the present invention.

1. . . Substrate

2. . . First conductive layer

3. . . Piezoelectric layer

31. . . First surface

32. . . Second surface

4. . . Second conductive layer

Claims (4)

A piezoelectric transducer device comprising: a substrate having flexibility; a piezoelectric layer having a first surface and a second surface; and a first conductive layer disposed on the piezoelectric layer a first surface; a second conductive layer disposed on the second surface of the piezoelectric layer; wherein the first conductive layer or the second conductive layer is bonded to the substrate; the first conductive layer and the piezoelectric layer An ohmic contact between the layers; the second conductive layer and the piezoelectric layer are in a Schottky contact, and the first conductive layer, the piezoelectric layer and the second conductive layer on the substrate are when the substrate is stressed and vibrated Deformation. The piezoelectric transducer device of claim 1, wherein the first conductive layer is a conductive film. The piezoelectric transducer according to claim 1, wherein the material of the second conductive layer is one of gold, platinum, silver and copper. The piezoelectric transducer according to claim 1, wherein the substrate is electrically conductive.