Versatile Applications of Ion Implanted Polymers
- PDF / 1,003,739 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 46 Downloads / 175 Views
M. G. MOSS-*-, AND J. KAUFMANN...
*Dept. of Physics and Astronomy, Southwest Missouri State University, Springfield, Mo. 65804, [email protected] **Acadiana Research Laboratory, University of Northwestern La., La Fayette, La., 70504 ***Brewer Science Inc., Rolla, Mo., 65401
ABSTRACT Ion beam implantation of polymers has been shown to modify electrical and mechanical properties near the surface of the material. A complete understanding of the mechanism of modification and type of microstructure remaining as a result of this process has not yet been achieved. In this paper, we will discuss how recent advances in our understanding of these fundamental mechanisms and material processing techniques has led to a number of prototypical applications. Specifically, the fundamentals of using ion implanted polymers as high value, small geometry resistors, temperature, strain, and vacuum sensing materials and as protective surfaces in chemically reactive environments.
INTRODUCTION An ion implanted polymer is a type of composite material whose components consist of at least two forms of dense carbon near the surface, and the original polymer beyond the mean range of the ion. The implantation process, consisting of collisions followed by rapid quenching in the vicinity of the ion track, create many non-equilibrium structures. As a result, the mechanical and electronic properties are quite distinct from other carbonization processes. The unique electronic behavior of these materials has led to the development of applications based on some of the more unusual properties. Figure 1. shows one of the most measured unusual properties of ion implanted polymers: the resistance versus temperature curve. Of course this general behavior is not unusual and is typically semiconductive. However, the rate of increase, six orders of magnitude in 250 degrees C, is very high. As a result of these R-T characteristics, the use of ion unimplanted polymers as temperature sensors has been speculated[l]. Unfortunately, this relative improvement over current technologies is not sufficient to justify its use as a discrete temperature sensor. The primary concern of most discrete, high precision, temperature sensors is not the TCR (temperature coefficient of resistance) but the repeatability and uniformity between devices. Also shown in the figure is the identical sample measured a number of times. Although some repeatability is demonstrated, the graph is logarithmic, and long term stability is always a problem in these materials. An unusual characteristic of ion implanted polymers is the high resistivity per square[2]. This feature combined with the development of efficient processing techniques can be applied in the manufacture of high value, small geometry resistor network devices. At a beam dose of 1016 ions/cm 2 , and energy of 50 keV the sheet resistance is around 109 Q/DE. While this is quite high compared to the maximum sheet resistance of 5 x 104 0/0I in tin oxide, or 10'Q/0 in amorphous carbon, or 105 (l/EI in cermet (Cr-SiO), it is not as
Data Loading...
