Total external reflection

About: Total external reflection is a research topic. Over the lifetime, 829 publications have been published within this topic receiving 22213 citations.

Refractive index monitor for deposition of gradient-index films

Abstract: A method is provided for monitoring the refractive index of an optical film as it is being deposited on a substrate. The film is illuminated by a source of light at a wavelength that is outside and less than the reflectance band of the coating. If the refractive index of the film is initially matched to the refractive index of the substrate and has no abrupt changes in its gradient-index profile, reflectance from the surface of the film can be detected and measured. In the absence of interference fringing from internal reflections, surface reflectance of the interface of the film with the surrounding air or vacuum is closely related to the refractive index of the film at its surface. Thus, surface reflection is monitored to provide a control signal to the deposition apparatus to conform the refractive index of material being deposited to a predetermined refractive index profile specified for the desired optical film.

Time modulation of an x‐ray beam by surface acoustic waves

Abstract: X‐ray time modulation was investigated in the total external reflection conditions in the process of x‐ray diffraction on the surface of the YX cut of a LiNbO3 crystal modulated by the rectangular pulses of the surface acoustic waves. It is shown that the period and the width of the x‐ray pulses are determined by the period and the width of the rectangular surface acoustic waves pulses. Through the use of surface acoustic waves pulses it is possible to form the x‐ray pulses with special forms of x‐ray beam control, for investigation of time modulated process in microelectronic materials, and also for x‐ray/acoustic microscopy, which can be based on thermal or thermoelastically generated acoustic waves by x‐ray pulses at the depth of x‐ray penetration in investigating materials. These experiments have been made at CNRS (Grenoble, France) using a rotating copper anode.

A facile method for the density determination of ceramic thin films using X-ray reflectivity

Abstract: A fast and non-destructive method based on X-ray reflectivity was developed to determine the density of sol–gel derived ceramic thin films, without prior assumptions on the microstructure of the system. The thin film density is calculated from the critical angle θc, i.e. the maximum angle at which total external reflection is still observed, which becomes increasingly difficult for imperfect films. We propose a simple numerical approach, instead of laborious fitting procedures, to determine the thin film density. A pseudo-critical angle, θpc, was defined by the first minimum in the 3rd derivative of the reflectivity curves. The measured samples were compared with calibration curves obtained from simulations with changing film densities. Although the absolute positions of θc and θpc are different, similar shifts are observed with changing density. The accuracy of the described method was validated by determining the density of single crystal substrates (ρrel = 100 %) and by Rutherford backscattering spectroscopy in combination with scanning electron microscopy. Varying sample size, film thickness, and film/interface roughness of yttria-stabilized zirconia films were found to have no influence on the final calculated density.

Supersmooth and modified surface of sapphire crystals: Formation, characterization, and applications in nanotechnologies

Abstract: The results of studying the state of the surface of sapphire crystals by a complex of methods in different stages of crystal treatment are considered by an example of preparing sapphire substrates with a supersmooth surface. The possibility of purposefully forming regular micro- and nanoreliefs and thin transition layers using thermal and thermochemical impacts are considered. The advantages of sapphire substrates with a modified surface for forming heteroepitaxial CdTe and ZnO semiconductor films and ordered ensembles of gold nanoparticles are described. The results of the experiments on the application of crystalline sapphire as a material for X-ray optical elements are reported. These elements include total external reflection mirrors and substrates for multilayer mirrors, output windows for synchrotron radiation, and monochromators working in the reflection geometry in X-ray spectrometers. In the latter case, the problems of the defect structure of bulk crystals sapphire and the choice of a method for growing sapphire crystals of the highest structural quality are considered.

Visualization of the complex refractive index of a conductor by frustrated total internal reflection

Abstract: A simple imaging geometry in which total internal reflection in a glass prism is frustrated by the proximity of a metal surface is implemented for observation of surface plasmon resonance. At a certain angle of incidence, the total internal reflection is completely suppressed at a certain distance between the metal and the prism surfaces. Using planar metal and spherical prism surfaces, the distance parameter is sampled in a single image. This allows a direct determination of the complex refractive index in bulk samples as well as in thin films. Our experimental data are in good agreement with previously published data.