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Luminescence spectroscopic and temporal dynamic properties of high energy elementary excitations in CdF2-CaF2 superlattices have been studied utilising excitation with vacuum ultraviolet and X-ray synchrotron radiation while comparing the results with those obtained for CdF2 and CaF2 bulk crystals. It is shown that the optical properties of the superlattice structures are determined by exciton emission in the CdF2 monolayers. The experimental manifestations of exciton confinement phenomena are discussed. [ABSTRACT FROM AUTHOR]

Pulsed laser deposition has been used to grow thin (10–84 nm) epitaxial layers of Yttrium Iron Garnet Y3Fe5O12 (YIG) on (111)–oriented Gadolinium Gallium Garnet substrates at different growth conditions. Atomic force microscopy showed flat surface morphology both on micrometer and nanometer scales. X-ray diffraction measurements revealed that the films are coherent with the substrate in the interface plane. The interplane distance in the [111] direction was found to be by 1.2% larger than expected for YIG stoichiometric pseudomorphic film indicating presence of rhombohedral distortion in this direction. Polar Kerr effect and ferromagnetic resonance measurements showed existence of additional magnetic anisotropy, which adds to the demagnetizing field to keep magnetization vector in the film plane. The origin of the magnetic anisotropy is related to the strain in YIG films observed by XRD. Magneto-optical Kerr effect measurements revealed important role of magnetization rotation during magnetization reversal. An unusual fine structure of microwave magnetic resonance spectra has been observed in the film grown at reduced (0.5 mTorr) oxygen pressure. Surface spin wave propagation has been demonstrated in the in-plane magnetized films. [ABSTRACT FROM AUTHOR]

Metal/CaF2/p-Si(111) capacitors with the improved-quality several-nanometer-thick epitaxial fluorite films are examined, aiming at solidifying a candidacy of this material for barrier layers in silicon devices. Structural and transport properties of a thin crystalline dielectric are characterized by different experimental techniques. The measured current-voltage characteristics accompanied with simulation results demonstrate that the elastic tunneling electron injection takes place in the considered structures. The same result follows from the behavior of hot-electron-injection-related electroluminescence within the selected spectral intervals. The result is important considering a perspective of using the epitaxial fluorides as barrier layers in resonant tunneling diodes. [ABSTRACT FROM AUTHOR]

Au/CaF2/nSi(111) structures with 4–5 monolayers of epitaxial fluoride are fabricated and electrically tested. The leakage current in these structures was substantially smaller than in similar samples reported previously. Simulations adopting a Franz-type dispersion relation with Franz mass of mF∼1.2m0 for carriers in the forbidden band of CaF2 reproduced the measured current-voltage curves quite satisfactorily. Roughly, these curves could also be reproduced using the parabolic dispersion law with the electron mass of me=1.0m0, which is a material constant rather than a fitting parameter. Experimental facts and their comparison to modeling results allow qualification of the crystalline quality of fabricated structures as sufficient for device applications. [ABSTRACT FROM AUTHOR]

The growth of MnF2 and ZnF2 layers on Si(001) and Si(111) substrates was studied by molecular-beam epitaxy. Calcium fluoride buffer layers with (001), (110), and (111) orientations were used to prevent chemical interaction of MnF2 and ZnF2 molecules with the Si substrate. The analysis of x-ray and reflection high-energy electron-diffraction (RHEED) patterns showed that MnF2 layers grow on all of these planes in the orthorhombic α-PbO2-type crystal phase observed earlier only at high pressures and temperatures. Atomic force microscopy revealed a strong dependence of the surface morphology on the buffer orientation and growth temperature. The best-ordered MnF2 growth occurred at 500 °C on a CaF2 (110) buffer layer. The diffraction analysis enabled us to find the epitaxial relations at the MnF2/CaF2 interface. A careful analysis of the RHEED patterns of the films grown on CaF2(001) showed a similarity in the structure and growth modes between MnF2 and ZnF2 layers, with ZnF2 tending to form multiphase layers. These findings are in agreement with the x-ray diffraction measurements. [ABSTRACT FROM AUTHOR]

Synthesis of nanosized yttrium iron garnet (Y3Fe5O12, YIG) films followed by the study of ferromagnetic resonance (FMR) and spin wave propagation in these films is reported. The YIG films were grown on gadolinium gallium garnet substrates by laser molecular beam epitaxy. It has been shown that spin waves propagating in YIG deposited at 700 °C have low damping. At the frequency of 3.29 GHz, the spin-wave damping parameter is less than 3.6Γ10–5. Magnetic inhomogeneities of the YIG films give the main contribution to the FMR linewidth. The contribution of the relaxation processes to the FMR linewidth is as low as 1.2%. [ABSTRACT FROM AUTHOR]

Current-voltage characteristics of epitaxially grown Au/CaF2/Si(111) metal-insulator-semiconductor structures with thin (1.5–6 nm) pseudomorphic fluoride layer have been studied. It was found that CaF2 films in these structures are of better insulating quality than those in the devices reported previously. Typical breakdown field for the fluorite layers was about 8×106 V/cm and the tunnel current did not exceed the values predicted by simulations with realistic parameters. [ABSTRACT FROM AUTHOR]

Resonant tunneling diodes were implemented on Ge quantum dots fabricated using StranskiKrastanov growth mode on CaF[sub 2] matrix, lattice matched to Si(111) substrates. The negative differential conductance and conductance oscillations due to hole resonant tunneling through the zero-dimensional states of Ge quantum dots are clearly observed at room temperature. From the period of conductance oscillations, the energy separations between the states of the quantum dots with different sizes are estimated to be 40-50 meV (i.e., >kT=26meV at T=300 K). [ABSTRACT FROM AUTHOR]