A new structural view of organic electronic devices

Although still in the qualifying rounds, U.S. researchers are helping manufacturers win the race to develop low-cost ways to commercialize a multitude of products based on inexpensive organic electronic materials -- from large solar-power arrays to electronic newspapers that can be bent and folded.

In the on-line issue of Advanced Materials,* researchers from the National Institute of Standards and Technology (NIST) and the University of California at Berkeley report success in using a non-destructive measurement method to detail three structural properties crucial to making reliable electronic devices with thin films of the carbon-rich (organic) semiconductors. The new capability could help industry clear hurdles responsible for high manufacturing development costs that stand in the way of widespread commercial application of the materials.

With the technique called near-edge X-ray absorption fine-structure spectroscopy, or NEXAFS, the team tracked chemical reactions, molecular reordering and defect formation over a range of processing temperatures.

They then evaluated how process-induced changes in thin-film composition and structure affected the movement of charge carriers (either electrons or electron "holes") in organic field effect transistors, devices basic to electronic circuits. With NEXAFS measurements taken over the range from room temperature to 300 degrees Celsius, the team monitored the conversion of a precursor chemical to an oligothiophene, an organic semiconductor. The molecular organization and composition achieved at 250 degrees Celsius yielded the highest levels of charge carrier movement and, consequently, maximum electric-current flow.

As chemical conversion progressed, the researchers calculated how the molecules arranged themselves on top of an electrical insulator. Top transistor performance corresponded to a vertical alignment of molecules. In addition, they used NEXAFS to determine the angles of chemical bonds and to assess the thickness and uniformity of film coverage, also critical to performance.

NEXAFS has the potential to be the "ideal measurement platform for systematic investigation" of organic electronic materials, says lead investigator Dean DeLongchamp, a NIST materials scientist. "A straightforward means of correlating chemical and physical structure to the electronic performance of organic semiconductor films is a much-needed tool."

* D.M. DeLongchamp, S. Sambasivan, D.A. Fischer, E.K. Lin, P. Chang, A.R. Murphy, J.M.J. Frechet, and V. Subramanian, "Direct Correlation of Organic semiconductor film structure to field-effect mobility," Advanced Materials, published online Aug. 30, 2005, DOI number (10.1002/adma.200500253).

Source: NIST

Related stories:

Printed optical electronics come into view
European researchers have taken a major step towards the goal of developing printable electronics that can be used for creating radio frequency identification tags and flexible watch displays.
A bright future for plastics -- robot 'skin,' flexible laptops and electric posters
WITH market analysts predicting a ten fold increase in the value of the organic light emitting display industry, from £1.5 billion to £15.5 billion, by 2014, it is no wonder that scientists and governments alike are keen to advance research into "plastic electronics".
IMEC, AIXTRON set important step towards low-cost GaN power devices
IMEC, Europe's leading independent research center in the field of nanoelectronics, and AIXTRON, the world leader in metal-organic chemical-vapor deposition (MOCVD) equipment, have demonstrated the growth of high-quality and uniform AlGaN/GaN heterostructures on 200mm silicon wafers. This demonstration is a milestone towards fabricating low-cost GaN power devices for high-efficiency/high-power systems beyond the silicon limits.
Bright sparks make gains towards plastic lasers of the future
Imperial researchers have come one step closer to finding the 'holy grail' in the field of plastic semiconductors by demonstrating a class of material that could make electrically-driven plastic laser diodes a reality.
Nano-designed transistors with disordered materials, but high performance
The Holy Grail for transistor designers has been the requirement to be able to get high performance at reduced costs over very large substrate areas. Transistors on cheap and flexible substrates like glass and plastics are currently unable to deliver such performance and therefore do not lend themselves to seamless monolithic integration of increased electronic functions on human interface devices (displays and sensors).
Nanoengineered barrier invented to protect plastic electronics from water degradation
A breakthrough barrier technology from Singapore A*STAR’s Institute of Materials Research and Engineering (IMRE) protects sensitive devices like organic light emitting diodes (OLEDs) and solar cells from moisture 1000 times more effectively than any other technology available in the market, opening up new opportunities for the up-and-coming plastic electronics sector.
Goodbye, Bunny Ears: Future Antennas May be Flat
The long, wiry antennas that protrude from airplanes, cars, cell phones – and even the bunny ears on some TVs – may one day become novelty items. Researchers are developing a smart-skin antenna that is simply a thin patch of electrical elements, which could contain a variety of antennas for different purposes within its palm-sized surface.
Researchers Make Breakthrough in Nanotechnology by Uncovering Conductive Property of Carbon-based Molecules
University of Pittsburgh researchers have discovered that certain organic—or carbon-based—molecules exhibit the properties of atoms under certain circumstances and, in turn, conduct electricity as well as metal. Detailed in the April 18 edition of Science, the finding is a breakthrough in developing nanotechnology that provides a new strategy for designing electronic materials, including inexpensive and multifunctional organic conductors that have long been considered the key to smaller, cheaper, and faster technologies.

News discussion:

Physics news