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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 ...
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.
The transmittance or reflectance value for each wavelength of the test sample is then compared with the transmission or reflectance values from the reference sample. Most instruments will apply a logarithmic function to the linear transmittance ratio to calculate the 'absorbency' of the sample, a value which is proportional to the ...
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 ...
Typical materials for ATR crystals include germanium, KRS-5 and zinc selenide, while silicon is ideal for use in the Far-IR region of the electromagnetic spectrum. The excellent mechanical properties of diamond make it an ideal material for ATR, particularly when studying very hard solids, although the broad diamond phonon band between 2600 and ...
Photo-reflectance has been particularly important in basic research on semiconductors due to its ability to precisely determine semiconductor bandstructures (even at room temperature). As an optical technique, photo-reflectance would appear suited to industrial applications because it is non-contact, and because it has good spatial resolution.
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and 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 ...