Reflectance difference spectroscopy

Reflectance difference spectroscopy (RDS) is a spectroscopic technique which measures the difference in reflectance of two beams of light that are shone in normal incident on a surface with different linear polarizations.[1] It is also known as reflectance anisotropy spectroscopy (RAS).[2]

It is calculated as:

${\displaystyle RDS=2{\frac {r_{\alpha }-r_{\beta }}{r_{\alpha }+r_{\beta }}},r\in \mathbb {C} }$

${\displaystyle r_{\alpha }}$ and ${\displaystyle r_{\beta }}$ are the reflectance in two different polarizations.

The method was introduced in 1985 for the study optical properties of the cubic semiconductors silicon and germanium.[3] Due to its high surface sensitivity and independence of ultra-high vacuum, its use has been expanded to in situ monitoring of epitaxial growth[4] or the interaction of surfaces with adsorbates.[5] To assign specific features in the signal to their origin in morphology and electronic structure, theoretical modelling by density functional theory is required.