David Kirkpatrick

November 2, 2010

Cool nanotech image — growing nanowires

Cool image and interesting process

nanotechnology image
In the growth of sapphire nanowires using the vapor-liquid-solid method, scientists have observed that a facet at the liquid-solid interface alternately grows and shrinks, which promotes nanowire growth. These images are from the video below. Image credit: Sang Ho Oh, et al.

From the link:

Nanowires can be grown in many ways, but one of the lesser-understood growth processes is vapor-liquid-solid (VLS) growth. In VLS, a vapor adsorbs onto a liquid droplet, and the droplet transports the vapor and deposits it as a crystal at a liquid-solid interface. As the process repeats, a nanowire is built one crystal at a time. One advantage of the VLS process is that it allows scientists to control the nanowire’s growth in terms of size, shape, orientation, and composition, although this requires understanding the growth mechanisms on the atomic scale. In a new study, scientists have investigated the steps involved in VLS growth, and have observed a new oscillatory behavior that could lead to better controlled nanowire growth.

Hit the link for a video of the process.

August 23, 2010

Making graphene electronics friendly

Electronics is a very attractive application for both carbon nanotubes and graphene, but graphene is proving fairly stubborn to working out in real world deployment. This news out of the Oak Ridge National Laboratory sounds very promising.

From the link:

Structural loops that sometimes form during a graphene cleaning process can render the material unsuitable for electronic applications. Overcoming these types of problems is of great interest to the electronics industry.

“Graphene is a rising star in the materials world, given its potential for use in precise electronic components like transistors or other semiconductors,” said Bobby Sumpter, a staff scientist at ORNL.

The team used quantum  to simulate an experimental graphene cleaning process, as discussed in a paper published in . Calculations performed on ORNL supercomputers pointed the researchers to an overlooked intermediate step during processing.

Imaging with a transmission electron microscope, or TEM, subjected the graphene to electron irradiation, which ultimately prevented loop formation. The ORNL simulations showed that by injecting  to collect an image, the electrons were simultaneously changing the material’s structure.

Scientists help explain graphene mystery

ORNL simulations demonstrate how loops (seen above in blue) between graphene layers can be minimized using electron irradiation (bottom).

June 11, 2010

Friday video fun — graphene into fullerene

This time it’s fun with science watching graphene turn into buckyballs.

PhysOrg has an article covering this video with additional images.

From the link:

Peering through a transmission electron microscope (TEM), researchers from Germany, Spain, and the UK have observed graphene sheets transforming into spherical fullerenes, better known as buckyballs, for the first time. The experiment could shed light on the process of how fullerenes are formed, which has so far remained mysterious on the atomic scale.

“This is the first time that anyone has directly observed the mechanism of fullerene formation,” Andrei Khlobystov of the University of Nottingham toldPhysOrg.com. “Shortly after the discovery of fullerene (exactly 25 years ago), the ‘top down’ mechanism of fullerene assembly was proposed. However, it was soon rejected in favor of a multitude of different ‘bottom up’ mechanisms, mainly because people could not understand how a flake of  could form a fullerene and because they did not have means to observe the fullerene formation in situ.”