Conductive polymers are a new group of materials that are finding applications in all type of electronic devices. Prototypical flat displays, infrared sensors, strain gauges and memory devices have already been produced. Polymers were discovered to have semi-conductive properties late in the last century (I always wanted to say that), but it hasn't been until very recently that their usefulness are being explored fully. Conductive polymers are a group of polymers that, of course, conduct electricity. What we are studying, ion implanted polymers, are a subclass of conductive polymers.
Why Do We Need Electrically Conducting Polymers?
Polymers have advantages over traditional inorganic conductors and semi-conductors:
- easier to process
- cheaper and safer to fabricate
- more readily available
- better performance in some cases
Main Research Trends
Naturally Conductive Polymers
The main focus of current research into conductive polymers is geared towards naturally conductive and semi-conductive species. The methods used to change their characteristics are: the control of their growth, and with in melt and/or post melt doping. Now, knowing this, you may ask:
There are already conductive polymers out there, why investigate ion implanted polymers?
Good question. With ion implantation, we can change key properties of many common, insulating polymers. These include: electrical properties, increasing resistance to solvents, increasing it’s adhesiveness, or mixing other materials into the polymer. Ion implanted polymers can be a bridging technology between current device fabrication techniques and developing polymer technology.
Polymers Used in This Research
The aims of our research are to take inherently insulating polymers, change their electrical conductivity through ion implantation, and to also develop a model explaining how the implant parameters affect the conductivity mechanism (also known as the charge transport mechanism).
The Implantation Process
Ion implantation occurs within a large instrument called, you guessed it, an ion implanter. During ion implantation, a beam of high energy ions is fired at a sample. These ions interact with the sample, changing its properties. Ion implanters are already widely used in the semi-conductor industry for implanting silicon.
Ion Implanter in Use at SMSU
Upon collision with the sample, there are several processes that can occur. One is the substitution of a sample atom with an implanted one. Another, is the creation of a cascade damage region (a region where the order is changed). Sputtering of the surface can also occur (where the topmost layers are removed). Finally, if there is another material on top of the sample (i.e. surface contamination, oxide layer, etc.), then blending of the two materials occurs.
Modifying and Understanding Electrical Conductivity
There is no clear picture as to how ion implantation modifies electrical conductivity. We plan to establish the conditions necessary for “tuning” the electrical conductivity of common polymers, and, additionally, establish a mechanism for explaining the conductivity modifications. Many of the facilities required for this research are available at the University of Queensland (e.g. the Center for Microscopy and Microanalysis, the Center for Magnetic Resonance, the Brisbane Surface Analysis Facility, etc.)
The ultimate goal of this research is to produce viable devices. In particular, we feel that ion implanted polymers could make a substantial contribution to the development of integrated soft electronics, and by providing an inorganic/organic bridging technology. In addition, ion implanted polymers could find applications in:
- infrared sensors (already in development at SMSU)
- photovoltaics (solar cells)
- interconnects for soft electronics