Effects of Surface Defects on the Local Electric Field in Inhomogeneous Media
- PDF / 352,058 Bytes
- 4 Pages / 420.48 x 639 pts Page_size
- 26 Downloads / 208 Views
EFFECTS OF SURFACE DEFECTS ON THE LOCAL ELECTRIC FIELD IN INHOMOGENEOUS MEDIA KIM F. FERRIS* AND STEVEN M. RISSER"* * Materials Science Department, Pacific Northwest Laboratory, Richland, WA 99352 "**Departmentof Chemistry, University of Pittsburgh, Pittsburgh, PA 15260. ABSTRACT Surface defects both focus the local electric field and enhance its intensity in the vicinity of the defect. Using a finite element model of an inhomogeneous dielectric film, we have examined the relationship between the defect shape and local electric field in the film and defect. We find that raised defect regions that are peaked have the largest local fields while the slope of removed regions has little effect on the field in raised defects. Both peaked and flat surface defects can lead to large enhancements of the local electric field above that predicted by effective medium approximation (EMA) methods. INTRODUCTION While many properties of dielectric films can be adequately described by volume fractions of the film components, others are strongly influenced by the inhomogeneity produced by the film microstructure. Microstructural details, such as the columnar growth seen from CVD processes [1] and the spherical grains in sol-gel generated coatings [2*1, have been shown to affect the accuracy to which we can determine the dielectric properties of films. Previously, the most common methods used to model the dielectric properties of inhomogeneous media, have been based upon scaled macroscopic properties of the medium. The interaction of those characteristics generated by the microstructure are approximated by a surrounding 'effective' medium in these methods. Thus, these theories can provide little information about the microscopic properties of the medium and are not particularly relevant for examining properties relating to the microstructure. In principle, the local electric field in an inhomogencous medium can be directly determined from Maxwell's equations [3], however, the complex boundary conditions imposed by the microstructure prevent analytic solution for the field. To address this question, we developed a method to numerically calculate the static local electric field in an inhomogeneous medium. This method uses the self-consistent solution for both the local field and polarization within a lattice of cubic volume elements, and has been discussed in previous work [4,5]. In this work, we use this model to simulate defects on the surface of a homogeneous dielectric film. We show the effect of defect shape on the local electric field within the film and defect, providing information on the types of defects leading to high electric field intensities.
Mat. Res. Soc. Symp. Proc. Vol. 291. 01993 Materials Research Society
522
RESULTS AND DISCUSSION The large spatial variation of the dielectric function in a film caused by volume defects has been shown to lead to large fluctuations in the local field intensity [4,6]. The presence of defects at the surface of the film can also produce large variations in the local field from the fi
Data Loading...
