Light Scattering by Submicron Spherical Particles on Semiconductor Surfaces

Abstract

In this work we report on the angle resolved light scattering characteristics of individual polystyrene spheres on silicon surfaces. A He-Ne laser (632.8 nm) focused to a 15 μm 1/e² diameter was employed to illuminate 4.10 and 0.804 μm. diameter spheres on optically smooth (σ«λ) silicon. Scattering was measured as a function of incident beam polarization for incident angles of 30, 45, and 75.3 degrees (Brewster’s Angle). A ring/wedge photodetector array centered on the specular beam was employed for the scattering measurements. The detector intercepted light scattered up to 45 degrees from the specular beam. The results obtained are qualitatively explained with reference to the silicon surface reflectance which varies significantly as beam incident angle and polarization are changed. Conditions associated with high surface reflectance result in larger values for sphere scattering cross section. We propose that the scattering measurements can be modeled in terms of a first order theoretical model developed previously by one of the authors (Hirleman). Initial results show that the theory is useful for understanding trends and predicts the correct order of magnitude for the scattering cross section. Possible improvements to the model are discussed.