Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Gold surfaces repair themselves at room temperature

Micromechanical systems and electric switches are based on smallest sliding contacts. They only work without loss of energy or material, if the surfaces are very smooth and without any defects.

So far, little has been understood about the underlying atomic-scale principles. In cooperation with researchers at the universities of Münster and Gießen as well as the Fraunhofer Institute for Mechanics of Materials IWM in Freiburg, scientists at the INM – Leibniz Institute for New Materials were able to show that on atomic scale gold surfaces smoothen out by themselves at room temperature. In their publication in Physical Review Letters, they reveal that this effect disappears at low temperatures.

So far, it has been assumed that perfect sliding works the better the more rigid the surface is. On the atomic scale this could mean freezing lattice vibrations in the crystal at low temperatures below -100°C; where the atoms hardly move. Against expectation, smooth sliding on gold surfaces is not quite possible at these temperatures, but, however, at room temperature. The scientists explain this phenomenon with the diffusion of the gold atoms: If they are able to move freely on the surface, the gold atoms migrate into defects on the surfaces and remove holes and bumps. The diffusion effectively stops below -100°C.

"Imagine a record player whose needle made from rubber moves over a wax plate. If the wax is hard, wax pieces will be scratched out and, after a while, the needle pushes a pile of wax, which can only be surmounted by the needle after it bends strongly", explains Roland Bennewitz, Head of the Program Division "Nanotribology". If the temperature rises, the wax melts and the needle leaves no more traces in the wax. In fact, the liquid wax removes holes and bumps at once, and the needle slides uniformly through the wax.

A similar process occurs on the gold surfaces. Although they do not melt at room temperature, the diffusion of the gold atoms is so strong that smallest asperities on the nanoscale are removed at once. The regular structure of the surface is preserved.

Experiments were performed by atomic force microscopy (AFM). A thin needle slides forth and back on the gold surface. The measured signal shows how strong the needle bends in contact. On a crystalline surface, the needle "jumps" regularly from atom group to atom group – the scientists measure a stable so-called stick-slip pattern. In the event of defects, such as the accumulated gold atoms, the needle bends stronger and the stick-slip pattern will be broken.

In their research, the scientists also employed atomistic modelling on the computer. Here, they were able to reproduce the stick-slip pattern for the scanning of the gold surface with gold and nickel needles. With a 3D simulation, they were also able to show how gold atoms accumulate at low temperatures. The accumulated gold atoms are attracted by the needle like a liquid into a capillary.

Original publication:
Nitya Nand Gosvami, Michael Feldmann, Joël Peguiron, Michael Moseler, André Schirmeisen, and Roland Bennewitz:
„Ageing of a Microscopic Sliding Gold Contact at Low Temperatures“
Physical Review Letters 107, 144303 (2011)
DOI: 10.1103/PhysRevLett.107.144303
Prof. Dr. Roland Bennewitz
INM - Leibniz-Institut für Neue Materialien gGmbH
Phone: (+49) 681 9300 213
INM is focused on the research and development of materials – for today, tomorrow and the future. Chemists, physicists, biologists, materials and engineering scientists shape the work at INM. From molecule to pilot production, they follow the recurring questions: Which material properties are new, how can they be investigated and how can they be used in the future?

INM – Leibniz Institute for New Materials, situated in Saarbrücken/Germany, is an internationally leading centre for materials research. It is a scientific partner to national and international institutes and a provider of research and development for companies throughout the world. INM is an institute of the Scientific Association Gottfried Wilhelm Leibniz and employs around 190 collaborators. Its main research fields are Chemical Nanotechnology, Interface Materials, and Materials in Biology.

Dr. Carola Jung | idw
Further information:

More articles from Materials Sciences:

nachricht From ancient fossils to future cars
21.10.2016 | University of California - Riverside

nachricht Study explains strength gap between graphene, carbon fiber
20.10.2016 | Rice University

All articles from Materials Sciences >>>

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 >>>