From a bent nanowire to a transistor

In 2007 the Wang group at Georgia Tech published the first piezotronic field-effect transistor: a single ZnO nanowire whose source-drain current was modulated not by an applied gate voltage, but by bending the wire. The bend produced a piezopotential at the metal-semiconductor (Schottky) contact — and that piezopotential played the same role as a gate.

Key Concept

Piezotronics

The field, founded by Z. L. Wang, that uses piezopotentials generated by strain in non-centrosymmetric semiconductors (ZnO, GaN, CdS, …) to gate or modulate carrier transport in electronic and optoelectronic devices.

Key Concept

Piezopotential

The static electric potential that appears across a strained piezoelectric crystal. For ZnO under typical lab strains, hundreds of millivolts to a few volts — well above the threshold of many transistors.

Key Concept

Schottky Barrier

The energy barrier at a metal-semiconductor junction. Its height controls how much current flows. A piezopotential modulates this barrier directly — that is the mechanism behind a piezotronic FET.

Key Concept

Electromechanical Gate

A gate whose 'voltage' arises from a mechanical input (pressure, strain, vibration) rather than from a wired bias. A keyboard you can crush is a literal example; a piezotronic FET is the chip-scale version.

Diagram · Wang lab milestones (2007 → 2024)

interactive

First ZnO piezotronic FET

ZnO nanowire

ON/OFF ratio ~10³

Wang et al. demonstrate that bending a ZnO nanowire creates a piezopotential that gates current — no external gate voltage required.

Click each year to see the device, the metric, and the cross-section.

A piano that plays itself

A normal piano needs your finger on a key (gate voltage) AND a hammer hitting the string (channel current). A piezotronic FET *is* the key — pressing it both writes and reads. The crystal doubles as input device and amplifier.

Checkpoint · +5 XP

In a piezotronic FET, what physically modulates the channel current?

Why this matters for the thesis. If a single bent ZnO nanowire can switch ON/OFF cleanly with mechanical input alone, then a stationary crystal under a dynamic EM-driven strain (pillar 3) should also gate cleanly. Wang's 2007–present work is the experimental backbone of pillar 2.

Devices proven so far: piezotronic FETs, AND/OR/NAND/XOR logic, tactile-imaging sensor matrices, non-volatile memory, piezo-phototronic LEDs, wafer-scale integration (2024).

Try It Yourself

Find ZnO's switching stress

Open the Piezo Engine. Select ZnO. Adjust the stress slider until the generated piezopotential reads exactly 0.5 V — that is the typical threshold for switching a small Schottky-gated transistor.

Open Piezo Engine

Lesson Summary

Professor Zhong Lin Wang (Georgia Tech) coined 'piezotronics' in 2007.
ZnO and GaN nanowires gate transistors purely from mechanical strain — no battery on the gate.
Demonstrated devices: FETs, AND/OR/NAND logic gates, tactile sensors, non-volatile memories, LEDs.
If a stressed crystal can switch a transistor in a lab, it can switch one in a chip — that's the proof of concept for pillar 2.

Test Your Knowledge · +60 XP

Piezotronics was founded by:

A piezopotential is:

In a piezotronic FET, the piezopotential gates the channel by:

Which crystals are most commonly used in Wang-lab piezotronic devices?

Why are these results important to the Crystal-EM thesis?