Oct 7 2015
It has been discovered that that electronic properties found at the edges of organic molecular systems vary from those found in the bulk of the material.
Sarah Burke, Katherine Cochrane and Tanya Roussy in UBC’s Laboratory for Atomic Imaging Research.
With the increasingly large demand for faster and smaller electronic gadgets this new discovery could pave the way for novel designs of advanced gadgets. It is hoped that these gadgets will be both more effective and more cost-effective.
Manufacturers of LEDs, transistors and solar panels are looking towards using organic materials in their designs. This is because plastics are lightweight, cheap and consume lower energy to produce than conventional silicon.
In such gadgets an important role is played by the interfaces between two different types of material.
We found that the polarization-induced energy level shifts from the edge of these materials to the interior are significant, and can't be neglected when designing components.
Katherine Cochrane - UBC
The University of British Columbia’s (UBC) team focused on nano-islands’ of clustered organic molecules. These molecules were placed on a silver crystal, which was coated with a very thin layer of salt measuring just two-atoms deep. The salt acts as an insulator by preventing electrons in the organic molecules from mixing with electrons in the silver. This helped the researchers to isolate the molecular interactions.
While we were expecting some differences, we were surprised by the size of the effect and that it occurred on the scale of a single molecule
Compared to the middle region of the nano-islands, the molecules at the edge of the nano-islands possessed very different properties. This difference in the properties was based on the orientation and position of other molecules in close proximity.
With the aid of a simple, analytical model, the team illustrated the differences. The same method can be applied to determine interface properties in highly complex systems, such as real-world devices.
“Herbert Kroemer said in his Nobel Lecture that ‘The interface is the device’ and it’s equally true for organic materials. The differences we’ve seen at the edges of molecular clusters highlights one effect that we’ll need to consider as we design new materials for these devices, but likely they are many more surprises waiting to be discovered.
Sarah Burke - UBC
Going forward, Cochrane and colleagues will study the interfaces in these materials. They will collaborate with materials chemists to create the design rules for the electronic properties and structure of next-generation gadgets.
Methods
The experiments were performed at UBC’s Laboratory for Atomic Imaging Research, which has state-of-the-art ultra-quiet rooms. These specially designed rooms allow the instruments to operate in total silence without any disturbances in order to conduct the intricate measurements, thus enabling the researchers to collect dense data sets with a scanning tunneling microscope, which helped to reveal energy levels on a single atom scale in real space.
The UBC research findings were published in the Nature Communications journal.