Interpretation of acceleration measurements in inertial navigation

It is shown that, when the absolute and apparent accelerations are measured simultaneously, the problem of autonomous inertial navigation is reduced to the solvable inverse problem. Physical and geometrical (kinematic) conditions for solvability are formulated.     

Low frequency transport measurements in

Low frequency transport measurements are performed on GdSr₂RuCu₂O₈ pellets. The observed current-voltage curves are qualitatively explained in the framework of a simple phenomenological model accounting for coexistence in the sample of ferromagnetism and superconductivity. A Curie temperature T _cM = 133 K and a superconducting critical temperature T _cS = 18 K, with an onset temperature T _cO = 33 K, are extracted from the analysis of the current-voltage curves. Received 18 September 2002 Published online 4 February 2003 RID="a" ID="a"e-mail: canio@sa.infn.it     

Determination of thermal transport properties of thin metal films from pulsed thermoreflectance measurements in the picosecond regime

Picosecond transient thermoreflectance (PTTR) of metals is shown to depend strongly on the temperature coefficients of the complex dielectric constant. The properties of PTTR are studied for TE and TM waves as a function of the angle of incidence. A method is suggested for subtracting the thermal transport properties of thin films from PTTR measurements.     

Interpretation of excitation temperature measurements in a cesium plasma

Electron densities and temperatures have been measured by using a Langmuir probe, as well as spectroscopic observations of continuum radiation and of spectral lines, in a cesium plasma. It is shown that the excitation temperatures determined from relative intensities of spectral lines do not always agree with electron temperature determinations. An interpretation of this discrepancy is proposed and discussed.     

Direct evidence of high temperature superconductivity in one-unit-cell FeSe films on SrTiO_3 substrate by transport and magnetization measurements

Zero resistance and Meissner effect are two crucial experimental evidences of superconductivity in determining a new kind of superconductor, which can be detected by transport and diamagnetic measurements. In this paper, we briefly review the main transport and magnetization results on the one unit cell(1-UC) Fe Se films grown on SrTiO3(STO) substrates from our team in recent years, which identify the high temperature superconductivity in 1-UC FeSe films.     

Secondary electron transport in photoemission from films

Transport of electrons which have undergone scattering with formation of electronhole pairs is considered within the framework of a one-dimensional model. Analytical expressions are obtained for the probability of secondary electron output into a vacuum and the interference pattern of light absorption in the film for film illumination from the direction of the substrate and from the vacuum side, with consideration of multiple electron scattering on phonons and the boundary of the emission layer.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No, 6, pp, 89–93, June, 1985.     

Carrier transport in In-doped CuO thin films

Temperature-dependent conductivity and thermopower measurements are carried out for undoped and In-doped CuO thin films. We investigate the effects of In-doping on carrier transport properties of CuO thin films in the temperature range of 300?<?T?<?400?K. Carrier transport is dominated by simple thermally activated conduction in the undoped film. On the other hand, small polarons play an essential role in the carrier transport properties in the In-doped films. By increasing the In content, the conduction behaviour transits from adiabatic limit to the non-adiabatic limit, and the conductivity decreases.     

Electronic transport mechanisms in tetraphenyleprophyrin thin films

Thermally-evaporated thin films of tetraphenylporphyrin, TPP, with thickness range from (175 to 735) nm had been prepared. Annealing temperatures ranging from (273–473) K do not influence the amorphous structure of these films. The influence of environmental conditions: film thickness, temperature and frequency on the electrical properties of TPP thin films had been reported. It was found that dc conductivity increases with increasing temperature and film thickness. The extrinsic conduction mechanism is operating in temperature range of (293–380) K with activation energy of 0.13 eV. The intrinsic one is in temperatures >380 K via phonon assisted hopping of small polaron with activation energy of 0.855 eV. The ac electrical conductivity and dielectric relaxation in the temperature range (293–473) K and in frequency range (0.1–100) kHz had been also studied. It had been shown that theoretical curves generated from correlated barrier hopping (CBH) model gives the best fitting with experimental results. Analysis of these results proved that conduction occurs at low temperatures (300–370) K by phonon assisted hopping between localized states and it is performed by single polaron hopping process at higher temperatures. The temperature and frequency dependence of both the real and imaginary parts of dielectric constant had been reported.     

Electron transport in amorphous metal-carbon nanocomposite films

The electrical conductivity of amorphous silicon- and oxygen-containing W-, Nb-, and Cr-carbon nanocomposite films is studied. It is revealed that, at a metal concentration of 10–40 at. % and in the temperature range 80–400 K, the electrical conductivity of the films is a power function of temperature. In terms of inelastic electron tunneling, the average number of localized states in the intercluster potential barriers is calculated as a function of the metal concentration.     

Phonon spectroscopy measurements at amorphous films

Phonon spectroscopy measurements were used to examine the scattering of high frequency phonons (300 GHz-1 THz) in amorphous materials. The experiments were done with the use of time and frequency resolved measurements of the phonon transmission behaviour through amorphous single films of different thicknesses. The typical film thicknesses were of the order of 10 nm. In contrast to the pure amorphous semiconductors Si and Ge our experiments show inelastic phonon scattering processes in the case of SiO₂ and SiH. This inelastic phonon scattering also occurs when the pure semiconductors Si and Ge are prepared in an O₂ or H₂ atmosphere, but is missing when the preparation process is done in an N₂ atmosphere. In films of the pure semiconductors a-Si and a-Ge we only found evidence to elastic scattering processes. In further experiments at heated a-SiH samples we could examine the atomical bonded hydrogen to be the center of the inelastic phonon scattering.The measurements and investigations described in this work were done in time of preparing a thesis at: Physikalisches Institut Teil 1, Universität Stuttgart, Pfaffenwaldring 57, D-70569 Stuttgart, Germany     

Electrical measurements of nanoscale bismuth cluster films

A range of percolating atomic cluster films, with nanoscale overall dimensions, have been studied using a combination of in situ and ex situ electrical transport measurements, together with field emission electron microscopy and atomic force microscopy. Bismuth clusters with mean diameter 20 nm were deposited between electrical contacts defined by electron beam lithography. The morphology of the films can be understood within percolation theory, and the electrical measurements show complex behaviour characteristic of both percolation effects and modification of the cluster films by current flow and by oxidation.     

Optical measurements of oxide films on silicon

The optical constants of oxide films formed by heating single-crystal silicon specimens were measured. The measurements were carried out in a range of 300° to 1000°C. The thickness and refractive indices of the oxide films were determined by the polarimetric method. In the measured temperature interval the oxidation process can be divided into three groups. In the first range, from 300° to 560°C, no oxidation of the silicon surface was observed. In the second interval, from 560° to 950°C, the oxidation of silicon proceeded according to the linear oxidation law. At temperatures from 950° to 1000°C the thickness of the oxide films increased with the square root of the heating time according to the parabolic oxidation law.     

Ultrashort dephasing-time measurements in Nile Blue polymer films

Optical dephasing measurements using degenerate four-wave mixing (DFWM) were performed on thin dye-polymer films at room temperature. Incoherent light centered at 575 nm was used as a source for ultrafast measurements on the blue side of the inhomogeneous distribution of the oxazine dye Nile Blue. Under these conditions, a new form of interference was observed as a sinusoidal variation of the DFWM signal versus delay time. A measured interference period of 1.96+/-0.07 fs corresponds to the optical cycle time of the light source. Numerical solutions for the DFWM intensity confirm the oscillation effect and estimate a measured dephasing time of 2-3 fs.     

Potential distribution in probe measurements of anisotropic semiconductor films

The electric current distribution is studied for probe measurements performed on anisotropic wafers. The phenomena caused by anisotropy of conduction are explained using the laws of electrodynamics, which makes it possible to consider the results obtained to be physically general, independent of the nature of anisotropy of electrical conduction. The methods are proposed for determination of the components of specific electrical conductivity tensor in anisotropic films. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 51–57, January, 2009.