Guided growth of nanowires leads to self-integrated nanoelectronics circuits

QDOTS imagesCAKXSY1K 8(Nanowerk News) Researchers working with tiny  components in nanoelectronics face a challenge similar to that of parents of  small children: teaching them to manage on their own. The nano-components are so  small that arranging them with external tools is impossible. The only solution  is to create conditions in which they can be “trusted” to assemble themselves.
Much effort has gone into facilitating the self-assembly of  semiconductors, the basic building blocks of electronics, but until recently,  success has been limited. Scientists had developed methods for growing  semiconductor nanowires vertically on a surface, but the resultant structures  were short and disorganized. After growing, such nanowires need to be  “harvested” and aligned horizontally; since such placement is random, scientists  need to determine their location and only then integrate them into electric  circuits.
A team led by Prof. Ernesto Joselevich of the Weizmann  Institute’s Materials and Interfaces Department has managed to overcome these  limitations. For the first time, the scientists have created self-integrating  nanowires whose position, length and direction can be fully controlled.
This is a SEM image of a logic circuit based on 14 nanowires
This  is a SEM image of a logic circuit based on 14 nanowires.
The achievement, reported today in the Proceedings of the  National Academy of Sciences (“Self-integration of nanowires into circuits via  guided growth”), was based on a method developed by Joselevich two years ago  for growing nanowires horizontally in an orderly manner. In the present study —  conducted by Joselevich with Dr. Mark Schvartzman and David Tsivion of his lab,  and Olga Raslin and Dr. Diana Mahalu of the Physics of Condensed Matter  Department — the scientists went further, creating self-integrated electronic  circuits from the nanowires.
First, the scientists prepared a surface with tiny, atom-sized  grooves and then added to the middle of the grooves catalyst particles that  served as nuclei for the growth of nanowires. This setup defined the position,  length and direction of the nanowires. They then succeeded in creating a  transistor from each nanowire on the surface, producing hundreds of such  transistors simultaneously. The nanowires were also used to create a more  complex electronic component — a functioning logic circuit called an Address  Decoder, an essential constituent of computers. These ideas and findings have  earned Joselevich a prestigious European Research Council Advanced Grant.
“Our method makes it possible, for the first time, to determine  the arrangement of the nanowires in advance to suit the desired electronic  circuit,” Joselevich explains. The ability to efficiently produce circuits from  self-integrating semiconductors opens the door to a variety of technological  applications, including the development of improved LED devices, lasers and  solar cells.
Source: Weizmann Institute of Science 

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New process to make nanospheres could enable advances across multiple industries

QDOTS imagesCAKXSY1K 8(Nanowerk News) A patent-pending technology to produce  nanospheres developed by a research team at North Dakota State University,  Fargo, could enable advances across multiple industries, including electronics,  manufacturing, and biomedical sectors.


The environmentally-friendly process produces polymer-based  nanospheres (tiny microscopic particles) that are uniform in size and shape,  while being low-cost and easily reproducible. The process developed at NDSU  allows scale-up of operation to high production levels, without requiring  specialized manufacturing equipment.

The environmentally-friendly process oxidizes ozone in water to produce  polymer-based nanospheres, ranging from 70 to 400 nanometers in diameter, that  are uniform in size and shape, stay suspended in solution, and are easily  removed using a centrifuge. The scanning electron microscopy image depicts the  uniform spherical morphology of these nanospheres.

A 3 a.m. Eureka! moment

Dr. Victoria Gelling, associate professor in the Department of  Coatings and Polymeric Materials at NDSU, had a “Eureka!” moment when she woke  early one morning – 3 a.m., to be precise, an hour when most of us are still  sleeping. Dr. Gelling used early morning creativity to imagine a new way to  oxidize monomers, which are relatively small and simple molecules, into  polymers, which are larger, more complex molecules that can be used to create  synthetic materials. Dr. Gelling hypothesized that oxidizing ozone in water  might accomplish this task.

Later that day in the lab, Dr. Gelling and her team tested the  hypothesis. On the first try, they created a suspension of nearly perfectly  rounded, uniformly-sized nanospheres, ranging from 70 to 400 nanometers in  diameter. In addition to their uniform size, the nanospheres stay suspended in  the solution, and are easily removed using a centrifuge.

“The synthesis of the nanospheres is rather simple, with no  other chemicals required other than water, ozone, and the small molecules which  will become the polymers,” said Dr. Gelling. “We also have tight control of the  size, as they are beautiful, perfect marbles.”

Given their uniform size and shape, the nanospheres could have  uses across multiple industries. According to Dr. Gelling, such nanospheres  could be used to:

  • Produce  high-performance electronic devices and energy-efficient digital displays
  • Create  materials with high conductivity and smaller parts for consumer electronics
  • Deliver  medicine directly to diseased cells in the body
  • Provide  antibacterial coating on dressing for wounds
  • Develop  nanosensors to aid in early disease detection
  • Create  coatings that provide increased protection against corrosion and  abrasion

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