Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Inside a quantum dot: Tracking electrons at trillionths of a second

24.11.2005


Researchers at the EPFL (Ecole Polytechnique Federale de Lausanne) have developed a new machine that can reveal how electrons behave inside a single nano-object. The results from initial tests on pyramidal gallium-arsenide quantum dots are presented in an article in the November 24 issue of Nature.

Hiding in the lab behind a dramatic black curtain, the hardware setup is not particularly imposing. It doesn’t look expensive. Nonetheless, this machine in EPFL’s Laboratory of quantum optoelectronics took four years to perfect and represents an equipment investment of more than a million Swiss francs.

It is an ingenious combination of technologies onto a single powerful platform. It will improve our understanding of the dynamics that rule the nanoscale world, perhaps opening doors to exploiting the physics of nanoscale phenomena for practical ends.



Even the most sophisticated methods used to explore material properties and dynamics run into limits when applied at the nanoscale. Current techniques either have good spatial resolution (down to tens of nanometers or below) or an ultrafast time resolution (down to picoseconds), but not both.

At least not until now. The machine developed by Professor Benoit Deveaud-Pledran and his EPFL colleagues is the first tool that can track the passage of an electron in a nanostructure – at a time scale of ten picoseconds and a spatial resolution of 50 nanometers.

The EPFL researchers replaced the standard electron gun filament on an off-the-shelf electron microscope with a 20 nanometer-thick gold photocathode. The gold is illuminated by an ultraviolet mode-locked laser, generating an electron beam that pulses 80 million times per second. Each pulse contains fewer than 10 electrons. The electrons excite the sample, causing it to emit light. The spectroscopic information is collected and analyzed to recreate the surface morphology and to trace the path the electrons follow through the sample.

Deveaud-Pledran and his colleagues tested their new machine on pyramidal quantum dots. These 2-micron-high nano-objects, specially synthesized in the lab of EPFL professor Eli Kapon, contain several different nanostructures, making them ideal test objects. When the electron beam impacts the pyramid, the electrons diffuse towards the closest nanostructure. From there, the diffusion continues until the point of lowest energy is reached -- the quantum dot at the tip of the pyramid. The time traces corresponding to each of these nanostructures reveal just how critical that 10- picosecond time resolution is; with even a 100-picosecond resolution, important information would be lost.

The machine will not only give us a glimpse into nanoscale dynamics, but because it will work on any semiconductor, it will also allow researchers to study previously intractable materials. The wide energy range of the electrons in the beam can excite materials that won’t luminesce with laser techniques, explains Deveaud-Pledran. "With a laser, you can’t get a short enough wavelength to excite diamond or silicon, for example. This machine will."

Nanotechnology is widely heralded as the key to the technology of the future -- everything from quantum computing to ultra-dense data storage to quantum cryptography depends on the behavior and control of materials at the nanoscale.

"Remember the first portable CD-players?" says Deveaud. "They consumed 4 AA batteries reading a single disk. We improved our understanding of the physics of materials, and now they consume 50 times less energy. As far as the nanoworld is concerned, we still don’t understand the dynamics of materials at the nanoscale. I can’t tell you exactly what this machine will lead to because that depends on who uses it and what we find. But there’s no question that it will help us make progress, and that the potential applications are exciting."

Benoit Deveaud-Pledran | EurekAlert!
Further information:
http://www.epfl.ch

More articles from Physics and Astronomy:

nachricht From the cosmos to fusion plasmas, PPPL presents findings at global APS gathering
13.11.2018 | DOE/Princeton Plasma Physics Laboratory

nachricht A two-atom quantum duet
12.11.2018 | Institute for Basic Science

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A Chip with Blood Vessels

Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.

Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...

Im Focus: A Leap Into Quantum Technology

Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.

In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...

Im Focus: Research icebreaker Polarstern begins the Antarctic season

What does it look like below the ice shelf of the calved massive iceberg A68?

On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.

Im Focus: Penn engineers develop ultrathin, ultralight 'nanocardboard'

When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure

Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...

Im Focus: Coping with errors in the quantum age

Physicists at ETH Zurich demonstrate how errors that occur during the manipulation of quantum system can be monitored and corrected on the fly

The field of quantum computation has seen tremendous progress in recent years. Bit by bit, quantum devices start to challenge conventional computers, at least...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

“3rd Conference on Laser Polishing – LaP 2018” Attracts International Experts and Users

09.11.2018 | Event News

On the brain’s ability to find the right direction

06.11.2018 | Event News

European Space Talks: Weltraumschrott – eine Gefahr für die Gesellschaft?

23.10.2018 | Event News

 
Latest News

Epoxy compound gets a graphene bump

14.11.2018 | Materials Sciences

Microgel powder fights infection and helps wounds heal

14.11.2018 | Health and Medicine

How algae and carbon fibers could sustainably reduce the athmospheric carbon dioxide concentration

14.11.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>