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Ex. 1: Reflectance spectra collected over 190–1000nm wavelength range for an amorphous silicon film (a-Si) on an oxidized silicon substrate (SiO 2 /Si-Sub) plus the n(λ) and k(λ) spectra of the a-Si film. The film thickness was found to be 1147nm.
Dielectric mirrors are also used to produce ultra-high reflectivity mirrors: values of 99.999% or better over a narrow range of wavelengths can be produced using special techniques. Alternatively, they can be made to reflect a broad spectrum of light, such as the entire visible range or the spectrum of the Ti-sapphire laser.
Refraction at interface. Many materials have a well-characterized refractive index, but these indices often depend strongly upon the frequency of light, causing optical dispersion.
For layered and finite media, according to the CIE, [citation needed] reflectivity is distinguished from reflectance by the fact that reflectivity is a value that applies to thick reflecting objects. [6] When reflection occurs from thin layers of material, internal reflection effects can cause the reflectance to vary with surface thickness.
An illustration of geometrical parameters in the visible-near Infrared (VNIR) reflectance spectrum of montmorillonite, a clay mineral. Modified from Clark et al., 2007. [15] The analysis of absorption features in a reflectance spectrum typically looks into the position (P), depth (D), and width (W) of absorption bands across a certain ...
The effects of thin-film interference can also be seen in oil slicks and soap bubbles. The reflectance spectrum of a thin-film features distinct oscillations and the extrema of the spectrum can be used to calculate the thickness of the thin-film. [1] Ellipsometry is a technique that is often used to measure properties of thin films. In a ...
If R 1 represents a clean freshly prepared surface (e.g., after a cleavage in vacuum) and R 2 the same sample after the exposure to hydrogen or oxygen contaminants, the ΔR/R spectrum can be related to features of the clean surface (e.g., surface states); [2] if R 1 is the reflectivity spectrum of a sample covered by an organic film (even if ...
The metal used determines the reflection characteristics of the mirror; aluminium is the cheapest and most common coating, and yields a reflectivity of around 88%-92% over the visible spectrum. More expensive is silver , which has a reflectivity of 95%-99% even into the far infrared , but suffers from decreasing reflectivity (<90%) in the blue ...