Three-Dimensional Finite-Difference Time-Domain Simulation of Optical Absorption Properties of Al-N Films with Mesoscopic Surface Roughness

摘要

Incompletely nitrided sputtered aluminum (Al-N) films with mesoscopic surface roughness have a promising function of high solar absorptance [T. Ishiguro et al: Jpn. J. Appl. Phys. 41 (2002) 292]. In this paper, we present an application by three-dimensional finite-difference time-domain (FDTD) method to the simulation of the optical properties of Al-N films. From the observed data, the optical and structural parameters of the specimen are determined. The simulation reproduces the systematic changes in the surface roughness dependences of absorptance and reflectance. The evaluated distribution of the local Poynting vector shows the refraction effect at the slope of protuberances on a rough surface. Additionally, energy absorption mainly takes place at the surface skin depth. As a result, it is confirmed that the FDTD method is useful for understanding local optical behavior in specimens with mesoscopic surface roughness.