Optical properties of nanostructured GaSb

TL;DR

This study investigates how nanostructured GaSb surfaces, composed of densely packed cones, alter optical responses, using Mueller Matrix Ellipsometry and spectroscopic ellipsometry to reveal anisotropic effects and low scattering.

Contribution

It demonstrates the significant impact of nanostructuring on GaSb optical properties and applies Mueller matrix techniques for detailed analysis of anisotropic and depolarization effects.

Findings

Nanostructured GaSb surfaces modify optical responses significantly.

Low off-specular scattering and depolarization observed.

Mueller matrix elements oscillate with sample rotation, indicating anisotropy.

Abstract

Optical measurements of nanostructured GaSb prepared by sputtering is presented. The optical response is studied by Mueller Matrix Ellipsometry (MME) in the visible range (430--850nm), and by spectroscopic ellipsometry in the range 0.6--6.5eV. The nano-structured surfaces reported in this work, consist of densely packed GaSb cones approximately 50nm high, on bulk GaSb. The nanostructured surfaces are here shown to considerably modify the optical response of the surface, hence giving a strong sensitivity to the far field spectroscopic (Mueller matrix) ellipsometric measurements. The off-specular scattering and the depolarization is found to be low. The anisotropic response is particularly emphasized by studying nano-structured GaSb cones approximately 45 degrees tilted with respect to the surface normal. In the latter case, one observes upon rotating the sample around the surface normal, that the Mueller matrix elements $m_{13}$ and $m_{14}$ oscillate as a function of the rotation angle. Finally, Mueller matrix techniques have been applied to the measured data, in order to analyze the acquired Mueller matrix in terms of physical realizability and noise.