Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Graphene and gallium arsenide: two perfect partners find each other

PTB has for the first time made graphene visible on gallium arsenide –
A successful com-bination of two unique electronic materials

It is the marriage of two top candidates for the electronics of the future, both excentric and extremely interesting: Graphene, one of the partners, is an extremely thin fellow and besides, very young. Not until 2004 was it possible to specifically produce and investigate the single layer of carbon atoms.

Its electronic properties are remarkable, because, among other things, its electrons can move so tremendously fast. It is a perfect partner for gallium arsenide, the semiconductor that allows tailoring of its electrical properties and which is the starting material of the fastest electrical and opto-electronic components. Besides, it is possible to produce gallium arsenide with an atomic-layer-smooth surface; this should suit well as a support for graphene.

Scientists of the Physikalisch-Technische Bundesanstalt (PTB) have now, with the aid of a special design, succeeded in making graphene visible on gallium arsenide. Previously it has only been possible on silicon oxide. Now that they are able to view with a light optical microscope the graphene layer, which is thinner than one thousandth of a light wavelength, the researchers want to measure the electrical properties of their new material combination. As experts for precision measurements, the PTB physicists are thus especially well equipped to do this.

The normally practically invisible single-carbon-atom layers can be made visible under a normal light (optical) microscope, if the support (layer) is designed as an anti-reflection filter. Single-layer graphene was identified inside the markings. They use the principle of the anti-reflective layer: If on a material one superimposes a very thin, nearly transparent layer of another material, then the reflectivity of the lower layer changes clearly visibly. In order to make their lower layer of gallium arsenide (plus graphene atomic layer) visible, the PTB physicists chose aluminium arsenide (AlAs). However, it is so similar to gallium arsenide (GaAs) in its optical properties that they had to employ a few tricks: They vapour-coated not only one, but rather several wafer-thin layers. "Thus, even with optically similar materials it is possible, in a manner of speaking, to 'grow' interference effects", Dr. Franz-Josef Ahlers, the responsible department head at PTB, explained. "This principle is known from optical interference filters. We have adapted it for our purposes".

First of all, he and his colleagues calculated the optical properties of different GaAs and AlAs layers and optimized the layer sequence such that they could expect a sufficiently good detectability of graphene. Following this recipe, they got down to action and with the molecular beam epitaxial facility of PTB accurately produced a corresponding GaAs/AlAs crystal atom layer. Then in the same procedure as with silicon oxide, it was overlaid with graphite fragments. "Different from silicon but as predicted by the calculation, although single carbon layers are no longer visible at all wavelengths of visible light, it is, however, possible, e.g. with a simple green filter, to limit the wavelength range such that the graphene is easily visible", explained Ahlers. In the photo, all lighter areas of the dark GaAs are covered with graphene. From the degree of lightening it is possible to conclude the number of individual layers of atoms. The marked areas are 'real', that is, single-layer graphene. But next to them, there are also two, three and multiple layers of carbon atoms, which also have interesting properties. This arrangement was confirmed again with another method, Raman spectroscopy.

Following such a simple identification with a normal light optical microscope, the further steps in the manufacture of electrical components from graphene surfaces are now possible without any difficulty. Thus the PTB scientists can now begin to accurately measure the electrical properties of the new material combination.

The original publication:
Graphene on Gallium Arsenide: Engineering the visibility.
M. Friedemann, K. Pierz, R. Stosch, F. J. Ahlers.
Applied Physics Letters, Appl. Phys. Lett. 95,
DOI: 10.1063/1.3224910,
Dr. Franz Josef Ahlers, PTB Department 2.6 Quantum Electrical Metrology,
phone: +49 531 592 2600, e-mail:

Dr. Franz Josef Ahlers | EurekAlert!
Further information:

More articles from Physics and Astronomy:

nachricht Move over, lasers: Scientists can now create holograms from neutrons, too
21.10.2016 | National Institute of Standards and Technology (NIST)

nachricht Finding the lightest superdeformed triaxial atomic nucleus
20.10.2016 | The Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences

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: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>