Radiative Properties of Two-Dimensional Random Roughness Surfaces Based on an Electromagnetic Wave Model

Abstract

The radiative properties of engineering surfaces with microscale surface textures (patterned or random roughness and coating) are of fundamental importance and practical interest. In the rapid thermal processing or arc/flash-assisted heating of silicon wafers, the control of energy deposition through thermal radiation and the surface temperature measurement using optical pyrometry require in-depth knowledge of the surface radiative properties. These properties are temperature, wavelength, and surface texture dependent. It is important that these properties can be modeled and predicted with reasonable accuracy. This study solved the Maxwell equations that describe the electromagnetic wave reflection from two-dimensional random roughness surfaces. The surface used in the study has a surface height distribution that is non-Gaussian and anisotropic. The incident electromagnetic wave scattered from the rough surface was computed using the finitedifference time-domain method. The application of this method was described in details. The method accounts for the interference of multiple scattered waves accurately. It allows accurate prediction of the bi-directional reflectivity, from which other properties, for example, transmissivity and absorptivity, can be obtained. The preliminary bi-directional reflectance function predictions were presented and discussed.