Calcium Fluoride Substrates Research Articles

Porous fluoride antireflective coatings

Quarterwave antireflective coatings of CaF(2) and MgF(2) have been prepared on fused silica and calcium fluoride substrates from colloidal suspensions of the relevant fluorides in methanol. These coatings have high optical efficiency and laser damage thresholds at 350 nm in the 6-8-J/cm(2) range for single shots of 0.6-ns pulse length and 20-25 J/cm(2) for 25-Hz multishots of 25-ns pulse length.

Étude de la cinétique de croissance de couches ZnSe ET ZnS épitaxiées sur fluorine par transport en phase vapeur

Epitaxial layers of ZnSe and ZnS were grown on (111) calcium fluoride (CaF 2) substrates in an open tube system by reaction of hydrogen with the compounds in powdered form. Typical growth rates of 1–2 μm h −1 for ZnSe and 3–5 μm h −1 for ZnS have been obtained. The parameters investigated were source temperature, substrate temperature and hydrogen flow rate. The experimental results were compared with theoretical growth rates calculated from the partial pressures of the components. In this case, the growth rate is proportional to the concentration difference between the source and the substrate and contains one adjustable parameter which depends on the substrate temperature and vapour phase composition.

Optical property of bovine plasma albumin between 2 and 82 eV.

AbstractThe optical constants of bovine plasma albumin in the form of a dry solid film have been determined in the 2–82 eV region of photon energy. The extinction coefficient k was obtained by transmission measurements on thin films on a calcium fluoride substrate and on ultrathin films of polystyrene supported by mesh screen. The refractive index n was determined by a Kramers–Kronig analysis using the measured values of k. The complex dielectric function ε and the energy‐loss function −Im(1/ε) for charged particles were derived from the data of n and k. The result for k exhibit, in addition to the well‐known absorptions at 4.4, 5.5, and 6.4 eV, a small peak at 7.6 eV, a shoulder around 9.7 eV, and a strong peak at 14.0 eV. A prominent peak at 22.7 eV in the energy‐loss function exhibits a large degree of collective nature.

The influence of substrate properties on microwave losses in thin films of semiconductors

A method is presented for the contactless measurement at microwave frequencies of the resistivity of thin films of semiconductors deposited on insulating substrates. The resistivity is determined through a measurement of the change in the power loss or Q of a microwave cavity upon insertion of the sample. In addition to the intended application, knowledge can be obtained about microwave power losses in supported thin films. Calculated microwave losses in the semiconductor films are presented in a normalized form as a function of the thickness and electrical properties of both the film and the supporting substrate at 9.0 GHz (X band) and 23.0 GHz (K band). These calculations were made for germanium on calcium fluoride and sapphire substrates. The power losses are normalized on a unit surface area and a unit surface field intensity basis. Limited experimental data are presented for germanium on calcium fluoride. The computed curves show that a maximum in power dissipation for a fixed substrate thickness and frequency is reached at higher and higher film resistivities as the film thickness increases. A very strong dependence of power loss on substrate thickness is demonstrated.

Changes in epitaxy produced by electron bombardment

The growth of evaporated lead telluride layers on calcium fluoride substrates has been studied by use of electron microscopy and diffraction techniques. It has been found that deposition simultaneously with low energy electron bombardment leads to differences in orientation and growth behaviour compared with otherwise similar depositions without electron bombardment. The results are considered in terms of current speculations regarding the effects of electron bombardment on ionic substrates.

Role of surface states in contributing to p-type carrier concentration of vacuum deposited thin germanium films

Germanium films were deposited by evaporation on to heated single crystal calcium fluoride substrates, which were cleaved either in air or inside the vacuum system. Results indicate that structural defects and impurities probably are not responsible for the high concentration of acceptors (≈ 10 18/cm 3) typically found in deposited germanium films. It is therefore believed that surface states and the associated space charge layer completely dominate the electrical characteristics of thin (< 3000 Å) deposited germanium films.