Ultra fast photodetectors out of carbon nanotubes

March 7, 2011

Ultra fast photodetectors out of carbon nanotubes

Enlarge

Single-walled carbon nanotubes are promising building blocks for future optoelectronic devices. With this measurement set-up physicists led by Professor Alexander Holleitner (Technische Universitaet Muenchen) can resolve the ultra fast optoelectronic dynamics of carbon-nanotubes. A first laser exites electrons in the carbon-nanotubes spanning the gap between two gold electrodes while a second laser measures the resulting photo-current. Credit: Prof. Dr. A. Holleitner, TUM

Single-walled carbon nanotubes are promising building blocks for future optoelectronic devices. But conventional electronic measurements were not able to resolve the ultra fast optoelectronic dynamics of the nanotubes. Now German scientists led by Professor Alexander Holleitner, physicist at the Technische Universitaet Muenchen, have found a way to directly measure the dynamics of photo-excited electrons in nanoscale photodetectors.

Carbon nanotubes have a multitude of unusual properties which make them promising candidates for optoelectronic components. However, so far it has proven extremely difficult to analyze or influence their optic and electronic properties. A team of researchers headed by Professor Alexander Holleitner, a physicist at the Technische Universitaet Muenchen and member of the Cluster of Excellence Nanosystems Munich (NIM), has now succeeded in developing a measurement method allowing a time-based resolution of the so-called photocurrent in photodetectors with picosecond precision.

"A picosecond is a very small time interval," explains Alexander Holleitner. "If electrons traveled at the speed of light, they would make it almost all the way to the moon in one second. In a picosecond they would only cover about a third of a millimeter." This new is about a hundred times faster than any existing method. It allowed the scientists headed by Professor Alexander Holleitner to measure the precise speed of electrons. In the carbon nanotubes the electrons only cover a distance of about 8 ten-thousandths of a millimeter or 800 nanometers in one picosecond.

At the heart of the photodetectors in question are carbon tubes with a diameter of about one nanometer spanning a tiny gap between two gold detectors. The physicists measured the speed of the electrons by means of a special time-resolved process – the pump-probe technique. It works by exciting electrons in the by means of a laser pulse and observing the dynamics of the process using a second laser.

The insights and analytic opportunities made possible by the presented technique are relevant to a whole range of applications. These include, most notably, the further development of optoelectronic components such as nanoscale photodetectors, photo-switches and solar cells.

More information: Time-Resolved Picosecond Photocurrents in Contacted Carbon Nanotubes, Leonhard Prechtel, Li Song, Stephan Manus, Dieter Schuh, Werner Wegscheider, Alexander W. Holleitner, Nano Letters 2011, 11 (1), pp 269, DOI:10.1021/nl1036897

Provided by Technische Universitaet Muenchen


Rank 5 /5 (3 votes)
Relevant PhysicsForums posts
  • Writing a book so im learning about things, i have some general questions please read
    created2 hours ago
  • Question about induced E field.
    created3 hours ago
  • Charging a capacitor in a tesla coil
    created3 hours ago
  • Water Rocket
    created7 hours ago
  • why do trucks have bigger brakes?
    created11 hours ago
  • Solar Sail Physics - Do they work on a large scale?
    created12 hours ago
  • More from Physics Forums - General Physics

More news stories

Dopant gives graphene solar cells highest efficiency yet

(Phys.org) -- By taking advantage of graphene’s favorable electrical and optical properties, and then adding an organic dopant, researchers have achieved the highest power conversion efficiency yet for ...

Nanotechnology / Nanophysics

created May 21, 2012 | popularity 5 / 5 (10) | comments 14 | with audio podcast feature

Nanomedicine: Quantum dots appear safe in pioneering study on primates

A pioneering study to gauge the toxicity of quantum dots in primates has found the tiny crystals to be safe over a one-year period, a hopeful outcome for doctors and scientists seeking new ways to battle diseases ...

Nanotechnology / Bio & Medicine

created May 20, 2012 | popularity 4.3 / 5 (3) | comments 8 | with audio podcast

In nanorod crystal growth, nanoparticles seen as artificial atoms

In the growth of crystals, do nanoparticles act as "artificial atoms" forming molecular-type building blocks that can assemble into complex structures? This is the contention of a major but controversial theory ...

Nanotechnology / Nanophysics

created May 24, 2012 | popularity 4.8 / 5 (6) | comments 0 | with audio podcast

First direct observation of oriented attachment in nanocrystal growth

Berkeley Lab researchers have reported the first direct observation of nanoparticles undergoing oriented attachment, the critical step in biomineralization and the growth of nanocrystals. A better understanding ...

Nanotechnology / Nanophysics

created May 24, 2012 | popularity 4.7 / 5 (3) | comments 0 | with audio podcast

Synthetic nano-waste does not disappear

(Phys.org) -- Tiny particles of cerium oxide do not burn or change in the heat of a waste incineration plant. They remain intact on combustion residues or in the incineration system, as a new study by Swiss ...

Nanotechnology / Bio & Medicine

created May 25, 2012 | popularity 5 / 5 (2) | comments 1 | with audio podcast


Scientist: Evolution debate will soon be history

(AP) -- Richard Leakey predicts skepticism over evolution will soon be history. Not that the avowed atheist has any doubts himself.

Dell tablet leak: 10.1-inch display, two-battery choice

(Phys.org) -- Headline after headline talks about vendors’ tablets in the wings as likely number-one contenders for the iPad. Such claims have justifiably been taken with a grain of salt, considering ...

SpotterRF debuts Radar Backpack Kit (w/ Video)

(Phys.org) -- SpotterRF has announced a special radar backpack kit designed to enhance situational awareness for soldiers on the ground. The company says its special radar is designed for warfighters as part ...

SpaceX capsule has 'new car' smell, astronauts say (Update)

SpaceX's Dragon cargo vessel smells like a new car, said astronauts at the International Space Station after opening the hatches Saturday following the spacecraft's landmark mission to the orbiting lab.

Thousands of shellfish found dead in Peru

Thousands of crustaceans were found dead off the coast of Lima following the mystery mass death of dolphins and pelicans, the Peruvian Navy said Friday.

Astronomers seize last chance in lifetime for Venus Transit

Astronomers are gearing for one the rarest events in the Solar System: an alignment of Earth, Venus and the Sun that will not be seen for another 105 years.