Thickness and the optical constants

The exact optical model describing multiple internal reflections, which are important for thin films where the penetration depth of the light 8 is larger than the layer thickness. Because of this part, iph depends on the layer thickness and the optical constants of both substrate and layer. This optical part mainly explains the observed variation in iph(df) found in the photocurrent spectra. 

The main advantage of this method is that the absolute value of 0 can be determined directly. Howevei supplementary information such as the surface concentration, the angle of incidence, the thin-cavity thickness, and the optical constants of the film have to be determined from independent measurements. Below, we show several examples of how to apply this method. 

Microscopic roughness on solid surfaces can affect ellipso-metric measurements and thus the optical constants of a bulk material determined from the ellipsometric measurements. If thin surface films are studied by ellipsometric measurements that assume a smooth boundary between the substrate and film, the thickness and the optical constants thus obtained are in error if the substrate surface had microscopic roughness. The other side of... 

By fitting the parameters of an optical model to the experimental values of A and tan xp, the layer thickness and the optical constants of the sample can be obtained [64,65,67,68]. 

The starting point is to determine the J-V characteristics of the two single junction cells as a function of layer thickness and the optical constants [n, k) of the photoactive layers. Using optical modeling of the layer stack of the single junctions, it is then possible to calculate the IQE as the ratio... 

The simplest case for ellipsometric data analysis is the case of an isotropic optically thick homogeneous bulk sample with a flat surface, i.e. a sample constituted by one single homogeneous material, which is thick enough so light can t reach the back surface of the sample. In this simple ideal case, no fit is necessary, and the optical constants can be directly calculated from the experimental ellipsometric parameters. Most opaque bulk samples will have a thin oxide overlayer, which will contribute significantly to the measured ellipsometric parameters, and render the direct calculation of optical constants for the bulk material from T and A inaccurate. A very thorough review of several techniques for... 

Thickness (x) and the Optical Constants (it, k) of Anodic Films on Metab Determined by Three-Parameter Ellipsometry... 

Quaternary Ga In j.As jPj, grown on InP is of major importance to fibre-optic communications. In quaternary compounds, both the gap and the lattice constant can be tailored by changing the chemical composition. In thick layers, in order to avoid the generation of strain-induced defects, care must be taken in adjusting the ratio of x and v to maintain the lattice-matched composition x = 2.2v. The available gaps range from 1.34 eV in InP to -0.75 eV in... 

Determination of the optical constants and the thickness is affected by the problem of calculating three results from two ellipsometric values. This problem can be solved by use of the oscillator fit in a suitable wavenumber range or by using the fact that ranges free from absorption always occur in the infrared. In these circumstances the thickness and the refractive index outside the resonances can be determined - by the algorithm of Reinberg [4.317], for example. With this result only two data have to be calculated. 

Manifacier JC, Gasiot J, Fillard JP (1976) A simple method for the determination of the optical constants n, k and the thickness of a weakly ahsorhine thin film. J Phys E 9 1002-1004... 

Fig. 4. Reflectivity of parallel- and perpendicular-polarized light at 1600 cm for the system Ge/Pt/ vacuum determined for platinum films of various thicknesses. In the calculations, the optical constants of bulk platinum were used nce = 4.0, npt = 5.71 + Z23.35. The angle of incidence was 45°. Calculations were performed according to the matrix formalism described in the text.

In general for a highly reflective sample, 50 to 60 percent of the energy is lost through the reflection optics. If the optical constants of the film are known, the thickness of the film can be calculated based on optical theory 134-144>. Studies have been made of thin films of poly(methyl methacrylate) depolymerization on gold, nickel and zinc surfaces using ERS 135) and FT-IR. 

Thin films of silicates have been produced by pressing powders in a diamond anvil cell (Hofmeister 1997), by cutting grain samples to submicron thick slices with an ultra-microtome (Bradley et al 1999), by electron-beam evaporation (Djouadi et al. 2005), and by laser deposition in a vacuum (Brucato et al. 2004). On one hand, powders produced in a laboratory are directly measured in transmittance when they are embedded in a matrix of transparent materials (e.g. KBr or polyethylene). On the other hand, reflectance measurements do not require the use of matrices powders of selected-size grains are directly measured with an appropriate optical accessory. Through measurements in both transmittance and reflectance, it is possible to evaluate the optical constants of a material. These are certainly the physical parameters... 

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