Piezotronics effect is using the piezoelectric potential (piezopotential) created in materials with

piezoelectricity Piezoelectricity (, ) is the electric charge that accumulates in certain solid materials—such as crystals, certain ceramics, and biological matter such as bone, DNA, and various proteins—in response to applied mechanical stress. The word ''p ...

as a “gate” voltage to tune/control the charge carrier transport properties for fabricating new devices. Neil A Downie showed how simple it was to build simple demonstrations on a macro-scale using a sandwich of piezoelectric material and carbon piezoresistive material to make an FET-like amplifying device and put it in a book of science projects for students in 2006. The fundamental principle of piezotronics was introduced by Prof. Zhong Lin Wang at Georgia Institute of Technology in 2007. A series of electronic devices have been demonstrated based on this effect, including piezopotential gated

field-effect transistor The field-effect transistor (FET) is a type of transistor that uses an electric field to control the flow of current in a semiconductor. FETs ( JFETs or MOSFETs) are devices with three terminals: ''source'', ''gate'', and ''drain''. FETs cont ...

, piezopotential gated diode, strain

sensors A sensor is a device that produces an output signal for the purpose of sensing a physical phenomenon. In the broadest definition, a sensor is a device, module, machine, or subsystem that detects events or changes in its environment and sends ...

, force/flow sensors, hybrid

, piezotronic logic gates, electromechanical

memories Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remembered, ...

, etc. Piezotronic devices are regarded as a new semiconductor-device category. Piezotronics is likely to have important applications in sensor, human-silicon technology interfacing,

MEMS Microelectromechanical systems (MEMS), also written as micro-electro-mechanical systems (or microelectronic and microelectromechanical systems) and the related micromechatronics and microsystems constitute the technology of microscopic devices, ...

, nanorobotics and active flexible electronics.

Mechanism

Due to the non-central symmetry in materials such as the

wurtzite Wurtzite is a zinc and iron sulfide mineral with the chemical formula , a less frequently encountered structural polymorph form of sphalerite. The iron content is variable up to eight percent.Palache, Charles, Harry Berman & Clifford Frondel (19 ...

structured ZnO,

GaN The word Gan or the initials GAN may refer to: Places *Gan, a component of Hebrew placenames literally meaning "garden" China * Gan River (Jiangxi) * Gan River (Inner Mongolia), * Gan County, in Jiangxi province * Gansu, abbreviated ''Gā ...

and

InN Inns are generally establishments or buildings where travelers can seek lodging, and usually, food and drink. Inns are typically located in the country or along a highway; before the advent of motorized transportation they also provided accommo ...

, a piezopotential is created in the

crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macro ...

by applying a

stress Stress may refer to: Science and medicine * Stress (biology), an organism's response to a stressor such as an environmental condition * Stress (linguistics), relative emphasis or prominence given to a syllable in a word, or to a word in a phrase ...

. Owing to the simultaneous possession of

and

semiconductor A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way. ...

properties, the piezopotential created in the crystal has a strong effect on the carrier transport process. Generally, the construction of the basic piezotronic devices can be divided into two categories. Here we use the nanowires as the example. The first kind is that the piezoelectric nanowire was put on a flexible substrate with two ends fixed by the electrodes. In this case, when the substrate is bended, the nanowire will be purely stretched or compressed. Piezopotential will be introduced along its axis. It will modify the electric field or the

Schottky barrier A Schottky barrier, named after Walter H. Schottky, is a potential energy barrier for electrons formed at a metal–semiconductor junction. Schottky barriers have rectifying characteristics, suitable for use as a diode. One of the primary ...

(SB) height at the contact area. The induced positive piezopotential at one end will reduce the SB height, while the negative piezopotential at the other end will increase it. Thus the electric transport properties will be changed. The second kind of the piezotronic device is that one end of the nanowire is fixed with electrode, while the other end is free. In this case, when a force is applied at the free end of the nanowire to bend it, the piezopotential distribution will be perpendicular to the axis of the nanowire. The introduced piezoelectric field is perpendicular to electron transport direction, just like applying a gate voltage in the traditional

. Thus the electron transport properties will also be changed. The materials for piezotronics should be piezoelectric semiconductors, such as ZnO, GaN and InN. Three-way coupling among

, photoexcitation and semiconductor is the basis of piezotronics (piezoelectricity-semiconductor coupling), piezophotonics (piezoelectric-photon excitation coupling),

optoelectronics Optoelectronics (or optronics) is the study and application of electronic devices and systems that find, detect and control light, usually considered a sub-field of photonics. In this context, ''light'' often includes invisible forms of radiat ...

, and piezophototronics (piezoelectricity-semiconductor-photoexcitation). The core of these coupling relies on the piezopotential created by the piezoelectric materials.
Zhong Lin Wang “Piezopotential Gated Nanowire Devices: Piezotronics and Piezo-phototronics”, Nano Today, 5 (2010) 540-552.

References

{{Electronic systems Microtechnology Nanoelectronics Semiconductor devices

Mechanism

See also

References