In a new type of terahertz (THz)-to-infrared converter for the visualization of THz radiation sources, nanoparticles are embedded in a THz-transparent matrix material. The nanoparticles are made of a metal or an alloy having a partially filled peak of the electron density of states at the Fermi energy. The converter is designed to operate with the THz objective forming a source's image on the matrix, wherein the irradiated nanoparticles convert THz energy to thermal energy, whose spatial distribution is captured by an infrared camera. Nickel nanoparticles are very appropriate for high-frequency THz radiation and can find application in real-time passive imaging of biomedical objects at room temperature. Nanoparticles of compounds with heavy fermions are suitable for low-frequency THz radiation, which could be used to image concealed objects carried by a human being.
In recent years studies of II-group and rare-earth fluoride layers on semiconductors have been quite active. The fluorides have a number of features that make them attractive for epitaxial growth on the most important semiconductors for both practical applications and basic studies. Among other fluorides, ZnF2 is known for its unusual features which are of special interest. The rutile structure of ZnF2 is similar to the MnF2 structure. Moderate (Δα/α = -3.34%, Δc/c = -5.38%) lattice mismatch allows MnF2 epitaxial growth on ZnF2. Zinc fluoride is diamagnetic, and magnetically ordered epitaxial films separated by thin diamagnetic layers are of interest in terms of low-dimensional effects. Polymorphous structural transitions at high pressures and temperatures (100 - 400°C, 30 - 160 KBar) have been found in ZnF2. Electronic properties of ZnF2 differ from those of II a-group metal fluorides. So, after doping by some trivalent impurities, zinc fluorite, being a wide band gap insulator, converses into an n-type semiconductor with the binding energy of shallow donors of about 0.07 - 0.25 eV. Other attractive feature is an effective electroluminescence in rare-earth doped bulk crystals and polycrystalline films. Depending on the impurity, the radiation wavelength changes from IR to UV. Efficient luminescence, in addition to high free electron concentrations, makes zinc fluorite a promising compound for electroluminescent device applications. In this work, we studied the epitaxial growth and structural properties of zinc fluoride films grown on silicon using fluorite buffer layer.