Subscribe free to our newsletters via your
. Space Industry and Business News .




CHIP TECH
Piezotronics and piezo-phototronics leading to unprecedented active electronics and optoelectronics
by Staff Writers
Beijing, China (SPX) Apr 28, 2014


This is a schematic diagram showing the prospects of utilizing piezotronic effect, which couples piezoelectric and semiconducting properties of piezoelectric semiconductor materials, for implementing many novel applications in tunable electronics, optoelectronics, spintronics, artificial photosynthesis and many other areas. Image courtesy Science China Press. For a larger version of this image please go here.

New technologies for developing electronics and optoelectronics with tunable/adaptive functionalities and performance are critical to emerging applications in wearable technology, communication, pervasive computing, human-machine interfacing and biomedical diagnostics, in which the active and adaptive interactions between devices and stimuli from the ambient/host (e. g. human body) are essential.

Mechanical stimuli are ubiquitous and abundant in the environment for interacting with or controlling these electronics/optoelectronics. This is, however, not facile to implement using the state-of-the-art technology using semiconductor materials such as silicon, which rely on electrically-gated modulation of charge carriers by externally-applied voltage to perform intelligence-bearing operations.

Piezoelectric effect has been widely utilized for electromechanical sensing, actuating and energy harvesting, which produces polarization charges in response to mechanical deformation in materials lacking inversion symmetry. Conventional piezoelectric materials such as Pb(ZrxTi1-x)O3 (PZT) and polyvinylidene fluoride (PVDF) are insulators and hence not feasible for constructing functional electronics/optoelectronics.

The effect of mechanically-induced polarization on charge carriers in piezoelectric materials has consequently been long overlooked. Semiconductor materials such as ZnO, GaN and CdS also possess piezoelectric properties but are not as extensively utilized in piezoelectric sensors and actuators due to their relatively small piezoelectric coefficients.

The coupling of piezoelectric polarization with semiconductor properties in these materials has resulted in both novel fundamental phenomenon and unprecedented device applications, leading to the increasing research interests in the emerging field of piezotronics since its first discovery in 2006.

Piezotronic effect is the modulation of charge carrier transport across metal-semiconductor (M-S) barrier or p-n junction by mechanical deformation, which results from the redistribution of free carriers and modification of band structure near the interface due to the existence of strain-induced polarization charges.

Strain-induced polarization charges can hence effectively modulate the local interfacial band structure and charge carrier transport. Electronic devices fabricated by utilizing these interfacial piezoelectric polarization charges as "gate" controlling signal is piezotronics, which is fundamentally different from electrically-gated field effect transistor (FET). By replacing the external gating voltage with strain-induced polarization charges for controlling the charge transport, two-terminal strain-gated piezotronic transistors have been presented.

More complex functionalities have also been developed following these preliminary demonstrations, such as strain-gated piezotronic logic nanodevices for performing mechanical action modulated electronic logic operation and piezotronic strain memory devices with write/read access of the memory cell programmed via electromechanical modulation for electrically recording and reading out the logical levels of applied strain.

The sensitivity of Schottky-contact based sensors for detecting chemicals and biomolecules can also be significantly enhanced by piezoelectric polarization via the piezotronic effect.

By replacing the traditional gate voltage with self-induced piezoelectric polarization in semiconductor nanomaterials, piezotronic nanodevices present a much simpler design with superior performance compared to conventional devices, which may offer new strategy for 3D structuring.

Using the piezoelectric polarization charges created at M-S interface to modulate transport process of local charge carriers, piezotronic effect has be applied to design independently addressable two-terminal transistor arrays, which convert mechanical stimuli applied on the devices into local electronic controlling signals.

Based on this concept, large-scale 3D integration of vertical ZnO nanowire (NW) transistors circuitry (92 + 92 tactile pixels in 1 cm2) as flexible force/pressure-sensor matrix for artificial skin has been designed and developed, which exhibits performance comparable to human skins and superior to any nanodevices previously demonstrated for tactile sensing, in terms of integration complexity, spatial resolution and response.

The piezoelectric polarization charges can also effectively modulate the optoelectronic processes, such as the generation, separation, diffusion and recombination, of charge carriers, which is the piezo-phototronic effect. This effect has been used to enhance the performance of photocells, the sensitivity of photodetectors and the external efficiency of an LED.

Furthermore, it has recently demonstrated that strain-controlled LED emission can be used to directly 'image' the force/pressure distribution on the device with micrometer-resolution, based on the tuning of local light-emitting intensity from individual NW-LEDs by strain-induced polarization charges.

The two-dimensional distribution of light-emission intensity then becomes a map of the pressure distribution on the surface. This approach is scientifically new because it relies on the piezoelectric polarization charges for designing a stable, fast response and parallel-detection strain-sensor arrays.

The output signal is electroluminescence light, which is easy to integrate with photonic technologies for fast data transmission, processing and recording, and may enable the development of highly intelligent human-machine interfaces. This may represent a major step towards on-chip recording of mechanical signals by optical means.

The essence of the emerging research and applications in piezotronics and piezo-phototronics relies on the coupling between strain-induced polarization and semiconductor properties in piezoelectric semiconductor materials.

These concepts provide the novel approach for modulating device characteristics by tuning the junction/contact properties, which has been unavailable in conventional technologies without modifying the interface structure or chemistry.

It is prospected that piezotronics and piezo-phototronics will enable technology advances in sensing, human-electronics interfacing, robotics, biomedical therapy, prosthetics, bio-imaging and optical MEMS.

See the article: Wang ZL, Wu WZ. Piezotronics and piezo-phototronics: fundamentals and applications. National Science Review, 2014 Vol. 1 (1): 62-90

.


Related Links
Science China Press
Computer Chip Architecture, Technology and Manufacture
Nano Technology News From SpaceMart.com






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





CHIP TECH
Superconducting Qubit Array Points the Way to Quantum Computers
Santa Barbara CA (SPX) Apr 28, 2014
A fully functional quantum computer is one of the holy grails of physics. Unlike conventional computers, the quantum version uses qubits (quantum bits), which make direct use of the multiple states of quantum phenomena. When realized, a quantum computer will be millions of times more powerful at certain computations than today's supercomputers. A group of UC Santa Barbara physicists has mo ... read more


CHIP TECH
Thinnest feasible membrane produced

When things get glassy, molecules go fractal

How Productive are the Ore Factories in the Deep Sea?

Vacuum Ultraviolet Lamp of the Future Created in Japan

CHIP TECH
Radio terminals for MUOS satellite communications have testing facility

High Gain Amplifiers for Commercial and Military Radar Released by Pasternack

Tactical radios tested with MUOS waveform

Harris supplying more communications terminals to Navy

CHIP TECH
Vega for third Arianespace mission, carrying Earth observation spacecraft

It's a "go" for Arianespace's Vega launch with Kazakhstan's first Earth observation satellite

Russia sends two satellites into space

SpaceX sues US Air Force over satellite contracts

CHIP TECH
Glonass Failure Caused by Faulty Software

Homegrown high-precision positioning system put to use

Russia eyes building Glonass stations in 36 countries

Turn your satnav ideas into business

CHIP TECH
Air Force enhancing mission capability to its remotely piloted aircraft

Northrop Grumman Awarded US Navy Contract for Next-Gen Mission Computer

Middle East country getting air combat training support from Cubic

Alenia Aermacchi, ATK MC-27J in flight test

CHIP TECH
Progress made in developing nanoscale electronics

Piezotronics and piezo-phototronics leading to unprecedented active electronics and optoelectronics

Superconducting Qubit Array Points the Way to Quantum Computers

Stanford bioengineers create circuit board modeled on the human brain

CHIP TECH
When next Earth's magnetic field reverse begins and what consequences for mankind will it have?

Ball Aerospace Moving Ahead on TEMPO and GEMS Air Quality Sensors

UV-radiation data to help ecological research

EO May Increase Survival Of 'Uncontacted' Tribes

CHIP TECH
China toughens environment law to target polluters

The result of slow degradation

MEPs back plans to slash use of plastic shopping bags

Oil company blamed for toxic tap water in China: Xinhua




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.